Biomicroscopy of the eye. Biomicroscopy: an informative diagnostic method. Indications for ultrasound examination
Thanks to B. g., early trachoma, glaucoma, cataracts and other eye diseases, as well as neoplasms, are possible. B. g. allows you to determine the perforation of the eyeball, to detect the smallest particles not detected by x-ray examination in the conjunctiva, cornea, anterior chamber of the eye and lens (particles of glass, aluminum, coal, etc.).
Biomicroscopy of the eye is carried out using a slit lamp (stationary or manual), the main parts of which are an illuminator and a magnifying device (stereoscopic or magnifying glass). In the path of the light beam there is a slot, which makes it possible to obtain vertical and horizontal lighting slits. Using the measuring eyepiece of a stereoscopic microscope, the depth of the anterior chamber of the eye is determined; additional dispersive power of about 60 diopter, neutralizing the positive effect of the optical system of the eye, makes it possible to examine the fundus of the eye .
The study is carried out in a dark room to create a sharp difference between the darkened and lamp-lit areas of the eyeball. The maximally opened slit of the diaphragm provides diffuse light, allowing one to examine all areas of the anterior part of the eye; a narrow slit provides a luminous optical ““. When a beam of light is combined with the observed area of the eye, direct focal illumination is obtained, which is most often used in B. and makes it possible to establish the localization of the pathological process. By focusing light on the cornea, an optical lens is obtained that has the shape of a convex-concave prism, on which the anterior and posterior surfaces of the cornea itself are clearly distinguished. When inflammation or clouding is detected in the cornea, B. g. allows one to determine the location of the pathological focus and the depth of tissue damage; in the presence of a foreign body, determine whether it is located in the corneal tissue or partially penetrates into the eye cavity, which allows the doctor to choose the right treatment tactics.
When light is focused on the lens, its optical section is determined in the form of a biconvex transparent body. In the section, the surfaces of the lens are clearly visible, as well as grayish oval stripes - the so-called interface zones, caused by different densities of the lens substance. Studying an optical section of the lens allows us to establish the exact localization of the beginning clouding of its substance and assess the condition of the capsule.
Biomicroscopy of the vitreous body reveals fibrillar structures (the skeleton of the vitreous body) that are not distinguishable by other research methods, changes in which indicate inflammatory or dystrophic processes in the eyeball. Focusing light on the fundus makes it possible to examine the retina and (size and depth of excavation) in an optical section, which is important in the diagnosis of glaucoma, for the early detection of optic neuritis, congestive nipple, and centrally located retinal breaks.
For B., other types of lighting are also used. Indirect illumination (dark field examination), in which the observed area is illuminated by rays reflected from the deeper tissues of the eye, allows for a good view of the vessels, areas of atrophy and tissue. To examine transparent media, illumination with transmitted light and is used, which helps to identify minor irregularities in the cornea, a detailed examination of the surface of the lens capsule, etc. Examination of the fundus is also carried out in the rays of the spectrum (). Biomicroscopy of translucent and opaque tissues of the eyeball (for example, conjunctiva, iris) is less informative.
Bibliography: Shulpina N.B. Biomicroscopy of the eye, M., 1974
II Biomicroscopy of the eye (Bio-+)a method of visual examination of optical media and eye tissues, based on creating a sharp contrast between illuminated and unlit areas and magnifying the image by 5-60 times; carried out using a slit lamp.
1. Small medical encyclopedia. - M.: Medical encyclopedia. 1991-96 2. First aid. - M.: Great Russian Encyclopedia. 1994 3. Encyclopedic Dictionary of Medical Terms. - M.: Soviet Encyclopedia. - 1982-1984.
See what “Biomicroscopy of the eye” is in other dictionaries:
biomicroscopy of the eye- rus biomicroscopy (f) eyes eng slit lamp examination fra examen (m) à la lampe à fente deu Linsenuntersuchung (f) mit der Spaltlampe spa examen (m) con lámpara de hendidura … Occupational safety and health. Translation into English, French, German, Spanish
- (bio + microscopy) a method of visual examination of optical media and eye tissues, based on creating a sharp contrast between illuminated and unlit areas and magnifying the image by 5-60 times; carried out using a slit lamp... Large medical dictionary
CHEMICAL EYE BURNS- honey Chemical burns of the eye are one of the emergency conditions in ophthalmology that can cause impaired or complete loss of vision. Frequency 300 cases/100,000 population (burns with alkalis account for 40% of all cases of eye burns, with acids 10%).… … Directory of diseases
PENETRATING EYE WOUNDS- honey Penetrating wounds of the eye are characterized by disruption of the integrity of its fibrous membrane (cornea and sclera). Clinical picture Presence of a wound channel Loss or pinching of the inner membranes of the eye (iris, vascular tissue itself) in the wound… Directory of diseases
MELANOMA OF THE OCULUS PROPER- honey Melanoma of the choroid proper is a malignant pigmented tumor. Frequency 0.02 0.08% of patients observed by ophthalmologists on an outpatient basis Most often diagnosed in men aged 31 60 years (75%) Peak incidence (57%) 50... ... Directory of diseases
I Foreign bodies Foreign bodies (corpora aliena) are objects foreign to the body that have penetrated into its tissues, organs or cavities through damaged integuments or through natural openings. Foreign bodies are also those introduced into the body with... ... Medical encyclopedia
I Cataract (cataracta; Greek: katarrhaktēs waterfall) is an eye disease characterized by clouding of the lens. There are primary (congenital and acquired) and secondary cataracts. Congenital K. (Fig. 1) can be hereditary (dominant ... Medical encyclopedia
I (oculus) organ of vision that perceives light stimulation; is part of the visual analyzer, which also includes the optic nerve and visual centers located in the cerebral cortex. The eye consists of the eyeball and... Medical encyclopedia
- (Gonio + biomicroscopy (Biomicroscopy of the eye); synonym microgonioscopy) a method of examining the iridocorneal angle of the eye (anterior chamber angle) by examining it with a gonioscope and a slit lamp... Medical encyclopedia
Extrapulmonary tuberculosis is a conditional concept that unites forms of tuberculosis of any localization, except for the lungs and other respiratory organs. In accordance with the clinical classification of tuberculosis (TB), adopted in our country, to T.v. include... ... Medical encyclopedia
The eyes are the most important sense organ. With its help, a person perceives 70% of information coming from outside. The matter concerns not just the formation of images, but also adaptation to the terrain, reducing the risk of injury, and the organization of social life.
Therefore, when the eyes are affected due to injury, age-related changes or general diseases, the question is about disability and a noticeable decrease in the quality of life. It is for the purpose of early and accurate diagnosis of diseases of the organ of vision in ophthalmology that there is a fast and informative method of biomicroscopy.
What is the biomicroscopy method?
Biomicroscopy is a microscopic examination of the structures of the visual organ in vivo (in a living organism) using a slit lamp (biomicroscope).
The slit lamp is an optical device consisting of:
- Binocular (for two eyes) microscope - a device for obtaining images magnified up to 60 times.
- Light source: halogen or LED lamps with a power of 25W.
- Slit diaphragm - to create thin vertical or horizontal beams of light.
- Supports for the patient's face (support under the chin and forehead).
- Aspheric Grud lens - for biomicroophthalmoscopy (examination of the fundus using a slit lamp).
The image acquisition method is based on the optical Tyndall effect. A thin beam of light is passed through an optically inhomogeneous medium (cornea - lens - vitreous body). The examination is carried out perpendicular to the direction of the rays. The resulting image appears in the form of a thin, cloudy light strip, the analysis of which is the conclusion of biomicroscopy.
Types of biomicroscopy
Examination of the eyes using a slit lamp is the standard technique, however, for studying individual structures of the eye, there are different methods of illuminating the biomicroscope, described below.
- Diffuse lighting. Most often, this method is used as the initial stage of research. With its help, at a slight magnification, a general examination of the structures of the eye is carried out.
- Direct focal illumination. The most used method, since it provides the opportunity to examine all the superficial structures of the eye: cornea, iris, lens. When directing the light beam, a wider area is first illuminated, then the aperture is narrowed for a more detailed study. The method is useful for early diagnosis of keratitis (inflammatory process in the cornea) and cataracts (clouding of the lens).
- Indirect focal illumination (dark field examination). The doctor's attention is drawn to areas located next to the illuminated area. Under such conditions, empty vessels, folds of Descemet's membrane, and small precipitates (sedimentary complexes) are clearly visualized. In addition, the method is used for the differential diagnosis of iris tumors.
- Variable (oscillatory) lighting is a method that combines the previous two methods. With a rapid change of bright light and darkness, the reaction of the pupil is studied, as well as small foreign bodies, which in such conditions give a characteristic shine.
- Mirror field method: a study of reflective zones is carried out. Technically, this method is considered the most difficult, but its use makes it possible to identify the smallest changes in the surface of the eye structures.
- Transmitted (reflected) lighting. The elements are studied through a beam of light reflected from another structure (for example, the iris in light reflected from the lens). The value of the method lies in the study of structures that are inaccessible under other lighting conditions. In reflected light, thin scars and swelling of the cornea, thinning of the pigment layers of the iris, and small cysts under the anterior and posterior capsules of the lens are visible.
Important! When examining the structures of the eye in reflected light, the areas under study acquire the color of the structures from which the light beam came. For example, when light is reflected from a blue iris, the lens under study acquires a gray-blue color
Due to the widespread use of ultrasound diagnostic methods, a new research option has emerged - ultrasound biomicroscopy. It can be used to identify pathological changes in the lateral parts of the lens, on the posterior surface of the iris and in the ciliary body.
Indications for the study
Taking into account the capabilities of the method and the wide field of view, the list of indications for biomicroscopy is quite large:
- Conjunctivitis (inflammation of the conjunctiva).
- Pathologies of the cornea: erosions, keratitis (inflammation of the cornea).
- Foreign body.
- Cataract (clouding of the lens).
- Glaucoma (a condition characterized by increased intraocular pressure).
- Anomalies in the development of the iris.
- Neoplasms (cysts and tumors).
- Dystrophic changes in the lens and cornea.
The additional use of a Grud lens makes it possible to diagnose pathologies of the retina, optic nerve head and vessels located in the fundus.
Contraindications to biomicroscopy
There are no absolute contraindications for diagnostic manipulation. However, biomicroscopy is not performed on people with mental illness and patients under the influence of drugs or alcohol.
How the research works
Biomicroscopy does not require prior preparation of the patient.
Doctor's advice! Biomicroscopy is recommended for children under 3 years of age in a horizontal position or in a state of deep sleep.
The patient is examined in a dark room (for greater contrast between illuminated and darkened areas) of the ophthalmology office of a clinic or hospital.
Important! If you plan to examine the vitreous body and structures in the fundus, mydriatics (medicines that dilate the pupils) are dripped immediately before the procedure.
Fluorescein drops are used to detect violations of the integrity of the cornea
The patient sits in front of the slit lamp, places his chin on a special stand, and presses his forehead against the bar. It is recommended not to move during the examination and to blink as little as possible.
Using a control joystick, the doctor determines the size of the slit in the diaphragm and directs a beam of light to the area being examined. Using different lighting methods, all structures of the eye are examined. The duration of the procedure is 15 minutes.
Possible complications after biomicroscopy
Biomicroscopy does not cause discomfort or pain. The only undesirable consequence may be an allergic reaction to the drugs used.
Important! If a foreign body is detected during the examination, lidocaine eye drops are used before removing it. Therefore, you need to notify your doctor if you are allergic to the drug.
Advantages of the method
The ability to study the state of the superficial and deep structures of the visual organ makes biomicroscopy the method of choice for diagnosing most ophthalmological diseases. To objectively assess the benefits of this study, comparison with other diagnostic methods is necessary.
|
Criterion |
Biomicroscopy |
Ophthalmoscopy |
|
Invasiveness of the study |
Non-invasive, non-contact |
Non-invasive, non-contact |
|
Duration of the procedure |
10-15 minutes |
|
|
Structures studied |
|
|
|
Field width |
360 degrees |
270 degrees |
|
Image Resolution |
Depends on the vision of the ophthalmologist and the distance from which the examination is carried out |
|
|
Possibility of storing objective data |
On digital media |
Examination of the eye using a slit lamp and changing lighting allows you to see the smallest signs of pathologies of all structures. A separate advantage of the method is its low cost when using new biomicroscopes with aspherical lenses and tonometers, replacing traditional tonometry and ophthalmoscopy.
How to decipher the results of biomicroscopy
When examining a healthy eye, the following is determined:
- Cornea: convex-concave prism with a slight bluish glow. Nerves and blood vessels are visible in the thickness of the cornea.
- Iris: the pigment layer is represented by a colored (depending on the color of the eyes) fringe around the pupil, and in the ciliary zone zones of contraction of the ciliary muscle are visible.
- Lens: A transparent body that changes shape when focused. It consists of an embryonic nucleus covered with a cortex, anterior and posterior capsule.
Variants of possible pathologies and the corresponding biomicroscopic picture are presented in the table.
|
Disease |
Biomicroscopic picture |
|
Glaucoma |
|
|
Cataract |
|
|
Foreign body and eye injuries |
|
|
|
|
Coloboma of the iris (a congenital anomaly where part of the iris is missing) |
|
|
Eye tumors |
|
Due to its diagnostic value, ease of performance and safety, biomicroscopy has become a standard procedure for examining ophthalmic patients, along with measuring visual acuity and examining the fundus.
The video below describes the technique of biomicroscopy.
is an examination method in ophthalmology that allows intravital microscopy of the conjunctiva, anterior chamber of the eyeball, lens, vitreous body, cornea and iris. Visualization of the fundus is only possible using a special three-mirror Goldmann lens. The technique makes it possible to identify pathological changes of inflammatory, dystrophic and post-traumatic origin, areas of neovascularization, structural anomalies, clouding of the optical media of the eye, and areas of hemorrhage. The non-invasive procedure is performed natively after preliminary preparation of the patient. Biomicroscopy of the eye is not accompanied by pain and can be performed alone or in combination with other diagnostic studies.
A slit lamp is used to perform biomicroscopy of the eye. This device was created in 1911 by the Swedish ophthalmologist A. Gullstrand. For the development of a device for microscopy of the living eye, the scientist was awarded the Nobel Prize. Today, eye biomicroscopy is one of the most accurate diagnostic methods in ophthalmology, allowing one to evaluate microscopic changes in the structures of the eyeball that are not visible when using other diagnostic procedures. However, compared to optical coherence tomography, the study does not make it possible to so clearly determine the localization and extent of the pathological process.
A slit lamp for eye biomicroscopy is a binocular microscope with a special lighting system, which includes an adjustable slit diaphragm and light filters. When a linear beam of light passes through the optical media of the eyeball, they are accessible to visualization using a microscope. During eye biomicroscopy, lighting options can be adjusted, which makes the various structures of the eyeball more accessible for viewing. The main method of lighting is diffuse. In this case, the ophthalmologist focuses a beam of light through a wide slit on a specific area, and then directs the axis of the microscope towards it.
The first stage of eye biomicroscopy is an indicative examination. Next, the gap must be narrowed to 1 mm and targeted diagnostics must be carried out. The surrounding tissues are darkened, which underlies the Tyndall phenomenon (light contrast). The direction of the light beam at the boundary of the optical media of the eyeball changes sharply, which is associated with a different refractive index. Partial reflection of light provokes an increase in brightness at the interface. Thanks to the law of reflection, it is possible not only to examine surface structures, but also to assess the depth of the pathological process.
Indications
Biomicroscopy of the eye is a standard ophthalmological examination, which is often carried out in combination with visometry and ophthalmoscopy both for diseases of the organ of vision itself and to identify reactive changes in the eyeball in systemic pathologies. The procedure is recommended for patients with traumatic injuries, benign or malignant neoplasms of the conjunctiva, viral or bacterial conjunctivitis. Indications for this study on the part of the iris are developmental anomalies, uveitis, and iridocyclitis.
Biomicroscopy of the eye allows you to visualize swelling, erosion and folds of Bowman's membrane with keratitis. This method is recommended for the differential diagnosis of superficial and deep keratitis. Biomicroscopy of the anterior chamber of the eye is performed to identify signs of the inflammatory process. This technique is informative for the study of congenital and acquired cataracts, as well as the diagnosis of anterior and posterior polar opacities of the lens and the zonular form of the disease.
Biomicroscopy of the eye is a necessary examination in patients with Sturge-Weber disease, diabetes mellitus, and hypertension. A slit lamp examination is indicated for a foreign body of the eyeball, regardless of its location. This procedure is also carried out at the stage of preparation for surgery on the organ of vision. In the early and late postoperative period, eye biomicroscopy is recommended to assess treatment results. Twice a year it must be prescribed to patients who are under dispensary registration in connection with cataracts and glaucoma. There are no contraindications to the procedure.
Preparation for biomicroscopy
Before the examination, the ophthalmologist uses special drops to dilate the pupils for further examination of the lens and vitreous body. To diagnose erosive lesions of the cornea, a dye is used before the examination. The next stage of preparation is the instillation of saline or other drops to remove the dye from the intact structures of the cornea. If the pathological process of the organ of vision is accompanied by pain or the reason for eye biomicroscopy is a foreign body, the use of local anesthetics before the procedure is indicated.
Methodology
Biomicroscopy of the eye is performed by an ophthalmologist in an outpatient clinic or ophthalmology hospital using a slit lamp. The study is carried out in a darkened room. The patient sits in such a way as to fix the forehead and chin on a special support. If there is a disease accompanied by photophobia, the ophthalmologist uses light filters to reduce the brightness of the light. Next, the base of the coordinated table is brought closer to the frontal-mental support, placing its movable part in the center. The illuminator is installed on the lateral side of the eye at an angle of 30-45°.
During eye biomicroscopy, the upper part of the table is moved until the clearest image is achieved. Next, the doctor looks for the illuminated area under a microscope. To correct the clarity of the biomicroscopic picture, the specialist smoothly rotates the microscope screw. In order to examine all structures of the eyeball in a certain plane, the upper part of the apparatus should be moved from the lateral to the medial side. The ability to move the coordinated table in the anteroposterior direction during eye biomicroscopy makes it possible to identify pathological changes in the organ of vision at different depths. The posterior parts of the eye are accessible to visualization only when using a negative lens (58.0 diopters).
When biomicroscopy of the eye in a dark field, indirect illumination is used, with the help of which the ophthalmologist can assess the state of the vasculature and Descemet's membrane, and detect precipitates in the area located near the illuminated zone. When examining in diaphanoscopic (reflected) light, the angle between the lighting system and the microscope is increased, then when light is reflected from one structure of the eye, the adjacent membrane, lens or vitreous body become more accessible for visualization. This eye biomicroscopy technique makes it possible to detect swelling of the epithelial and endothelial layers of the cornea, scars, pathological neoplasms, and atrophy of the posterior pigment layer of the iris.
The ophthalmologist begins the examination with low magnifications. If necessary, stronger lenses are also used during eye biomicroscopy. This technique makes it possible to obtain an image magnified by 10, 18 and 35 times. The examination does not cause discomfort or pain. Its average duration is 10-15 minutes. The duration of eye biomicroscopy increases if the patient blinks frequently. The non-invasive diagnostic method does not cause adverse reactions or complications. The result of eye biomicroscopy is issued in the form of a conclusion on paper.
Interpretation of results
Normally, the vascular pattern at the junction of the cornea and the sclera can be divided into the following zones: palisade, vascular loops and marginal loop network. The area of Vogt's palisade during eye biomicroscopy has the appearance of parallel-directed vessels. Anastomoses are not determined. The average width of this zone is 1 mm. In the middle part of the limbus, the diameter of which is 0.5 mm, a large number of anastomoses are detected. The width in the area of the edge loop reaches 0.2 mm. With inflammation, the diameter of the limbus is expanded and slightly elevated. Vascular dementia and encephalotrigeminal angiomatosis are accompanied by ampulla-shaped vascular dilatation and the appearance of multiple aneurysms.
Normally, during biomicroscopy of the eyes, Bowman's and Descemet's membranes are not visualized. The stromal part is opalescent. With inflammation or traumatic injury, the epithelium is swollen. Its detachment may be accompanied by the formation of multiple erosions. With deep keratitis, in contrast to superficial keratitis, infiltrates and cicatricial changes in the stroma are visualized. Biomicroscopy of the eye reveals a specific symptom of the superficial form - the formation of multiple folds on Bowman's membrane. The reaction of the stroma to the course of the pathological process is manifested by swelling, tissue infiltration, increased angiogenesis and the formation of folds on Descemet's membrane. During the inflammatory process, protein is detected in the moisture of the anterior chamber, which leads to opalescence.
Violation of the trophism of the iris during eye biomicroscopy is manifested by the destruction of the pigment border and the formation of posterior synechiae. At a young age, when examining the lens, the embryonic nucleus and sutures are visualized. After 60 years, an aged surface of the core with a younger crust is formed. The capsule is identified on optical sections. Biomicroscopy of the eye reveals ectopia or cataracts. Based on the localization of the turbidity, the variant of the disease course is determined (cataract of embryonic sutures, zonular, anterior and posterior polar).
Cost of eye biomicroscopy in Moscow
The cost of a diagnostic study depends on the technical characteristics of the slit lamp (stationary, manual, 3-, 5-position) and the manufacturer. Pricing is also influenced by the nature of the doctor's opinion. In private medical centers, the procedure is more expensive than in a public clinic. Often the cost is determined by the category of the ophthalmologist and the urgency of the examination. A slight increase in the price of eye biomicroscopy in Moscow is possible if additional funds are used at the preparation stage (analgesics, dye, saline solution).
24-07-2012, 19:53
Description
Microscopy of the living eye is an addition to other well-known methods of examining the eye. Therefore, biomicroscopy, as a rule, should be preceded by a routine ophthalmological examination of the patient. After collecting an anamnesis, the patient is examined in daylight, using the lateral focal illumination method, a study is performed in transmitted light, and ophthalmoscopy is performed. Functional studies of the eye (determining visual acuity, perimetry) should also precede biomicroscopy. If the study of eye functions is carried out after biomicroscopy, this leads to erroneous data, since after exposure to strong light from a slit lamp, even for a short time, the readings of visual functions will be underestimated.Intraocular pressure examination should, as a rule, be performed after biomicroscopy; otherwise, traces of dye remaining on the cornea after tonometry will interfere with a detailed slit-lamp examination of the eye. Even thorough washing of the eye after tonometry and instillation of disinfectant drops do not allow the paint to be completely removed, and it is revealed under a microscope on the anterior surface of the cornea in the form of a brown coating.
During a preliminary examination of a patient, the doctor usually has a number of questions regarding the depth of localization of the pathological focus in the tissues of the eye, the duration of the disease process, etc. These questions are resolved through further biomicroscopic examination.
In the process of teaching a biomicroscopy course, we usually focus the attention of doctors on microscopy of the living eye was to a certain extent targeted, i.e., for the researcher to pose certain questions and resolve them during slit-lamp research. This approach to the biomicroscopy method makes it more meaningful and significantly shortens the patient’s examination time. The latter is especially necessary in cases where the patient suffers from pain, photophobia and lacrimation. In this condition of the patient, in the process of biomicroscopy it is necessary to resort to the help of another person, whose role is to hold the patient’s head, since the latter, suffering from photophobia, sometimes involuntarily strives to move away from the source of bright light, as well as to open and hold the eyelids. In acute inflammatory processes, unpleasant subjective sensations can be significantly reduced by preliminary instillation of a 0.5% dicaine solution into the conjunctival sac two or three times. A calmer patient behavior will also reduce the time of the slit lamp examination.
Biomicroscopy must be performed in a darkened room, but not in complete darkness. It is advisable to place a regular table lamp behind the observer at some distance from him. To prevent the lighting from being too bright, it is recommended to turn it towards the wall or lower it downwards. Moderate light falling from behind does not interfere with the doctor’s work. He can observe the patient and guide him during the examination process. However, when biomicroscopy of very thin structures that reflect little light (vitreous body), complete darkness is necessary.
During biomicriscopy, both the patient and the doctor are under some tension, since for some period of time they must be very concentrated and completely motionless. Considering this, it is necessary before conducting the study create certain conveniences for the patient and the doctor. The patient is seated on a swivel chair in front of an instrument table on which a slit lamp is installed. The table should be raised up or down according to the height of the patient. The patient should not be allowed to sharply stretch his neck while placing his head in the headrest. In this case, the contact of the forehead with the headrest will be incomplete, which will affect the quality of the examination. When the headrest is low, the patient is forced to bend, which causes, especially in older people, difficulty breathing and rapid fatigue. After fixing the head, the patient is asked to calmly place his arms bent at the elbows on the instrument table and lean on it. The doctor is placed on the other side of the instrument table on a movable chair that corresponds to the height of the instrument.
During the examination, in order to avoid overworking the patient, as well as overheating of the lamp need to take breaks. Overheating of the lamp is accompanied by significant overheating of the surrounding parts of the illuminator (especially in the ShchL lamp), which can lead to the appearance of cracks in the condenser and a decrease in the quality of the lighting slit, in which, according to the location of the cracks, a darkened area (defect) appears. During the biomicroscopy process, after a 3-4-minute examination, the patient is asked to turn his head from the front and sit up straight in a chair. At the same time, the slit lamp illuminator is turned off from the electrical network. After a short rest, research can continue.
For doctors who are little familiar with the biomicriscopy technique, in the process of mastering the research methodology it is advisable to use a certain, preferably low, microscope magnification. Only as skills about the work develop can the degree of magnification of the microscope be varied more widely. Beginning ophthalmologists can be recommended to first examine each other: this shortens the training period for the biomicroscopy technique and, in addition, allows them to get an idea of the sensations that the patient experiences during the process of biomicroscopy.
Technique for working with the slit lamp
Biomicroscopic examination can only begin in the presence of a well-adjusted lighting slit. The quality of the slit is usually checked on a white screen (a sheet of white paper).
Depending on which eye is intended to be examined, the position of the head rest must be different. When examining the patient's right eye, the head rest is moved to the left (relative to the patient) side, and when examining the left eye - to the right. The head rest is moved by hand to the end, that is, until it comes into contact with the flywheel, which ensures smooth movement of the head rest horizontally. The illuminator is placed on the temporal side of the eye being examined. The illuminator can only be moved to the appropriate side when the microscope head is tilted back. After moving the illuminator, the microscope head is returned to its normal position.
The patient places his head in a headrest. In this case, it is necessary to ensure that the chin and forehead fit tightly to the chinrest and frontal ridges and do not move during the examination, when it is necessary to move the headrest in the vertical and horizontal directions.
Microscope being installed at zero scale mark, indicating the biomicriscopy angle (i.e., perpendicular to the eye being examined), the illuminator is placed on the side (outside) at a certain angle to the microscope column. The revolving disk of the microscope is turned so that a pair of lenses with a magnification of 2X is in front of the patient’s eye, and the first magnification option, equal to 4X, is inserted into the eyepiece sockets. In this case, the eyepiece tubes should be placed in accordance with the distance between the centers of the examiner’s pupils. After such preparation, you can begin biomicriscopy.
The light beam must be directed to one or another part of the eyeball by moving both the illuminator itself and the head support. For novice ophthalmologists, in the process of aiming, which, as experience shows, is very slow at first, it can be recommended to place in the path of the light beam neutral density filter. This relieves patients from the glare of light. To avoid excessive fatigue of the patient with bright singing, another technique can be recommended. You can reduce the brightness of the lamp filament by moving the rheostat knob in the direction of the “darker” indicator.
After the illumination slit is aimed at the eye, it is necessary to focusing light. This is achieved by moving the lighting magnifier, as well as rotating the tilt screw located on the head rest. After focusing the light on a certain area of the eye, an image of the biomicroscopic picture is found under a microscope.
To quickly find an image of the eye under a microscope It is recommended to check the location of the microscope lenses in relation to the focal lens of the illuminator. They must be at the same level (at the same height). Failure to comply with this seemingly elementary condition leads to the fact that the novice researcher spends a lot of time searching for an image of the eye, since the microscope lens turns out to be located not against the illuminated eyeball, but below or above it. When determining an image of the eye under a microscope, a novice researcher can also be helped by slight lateral movements of the microscope head, made directly by hand.
After the image of the eye is found under the microscope, it is necessary to achieve clarity of biomicroscopic picture by rotating the microscope's focus screw. Leaving the illuminator and microscope motionless, you can examine the surface of the eyeball, eyelids, and conjunctiva. This is done by moving the head rest in vertical and horizontal directions. In this case, the image of the fissure is placed in various parts of the eye and its appendages. visible at the same time under a microscope, and biomicroscopic images of various parts of the eye pass before the observer.
It is recommended to start an eye examination at low microscope magnification levels(8X, I6X) and only if a more detailed examination of the eye membranes is necessary, switch to higher magnifications. This is achieved by moving lenses and changing eyepieces.
It should be noted that when switching lenses, the sharpness of the focus on the eye image does not change. When starting to examine the deeper parts of the eyeball, it is necessary to change the focal setting of both the illuminator and the microscope accordingly, which is achieved by moving the illuminating loupe forward and rotating the microscope's focus screw. Some help (especially if the ability to focus the magnifying glass and microscope is exhausted) is provided by moving the headrest forward or backward using the tilt screw. According to B. Polyak and A.I. Gorban (1962), such movement of the subject’s head is the main methodological technique in the process of biomicroscopic examination. In this case, the patient’s eye is, as it were, strung on the spatially combined focuses of the illuminator and microscope. Before carrying out the specified movement, you must ensure that there is spatial combination of the foci of the illuminator and microscope. According to B.L. Polyak, their foci coincide only when the optical section of the cornea is located in the center of the microscope field of view, has clear boundaries and does not mix along the cornea when the illuminator is rotated (i.e., when the angle of bonomicroscopy changes). If, when rocking the illuminator, the optical section of the cornea moves in the same direction as the illuminator, then the head support should be moved slightly posteriorly. When the optical section of the cornea moves in the direction opposite to the movement of the illuminator, it is necessary to bring the head rest closer to the microscope. The head rest should be moved until the optical section of the cornea becomes stationary (when the position of the illuminator changes). Fulfilling the remaining requirements to ensure that the focuses of the illuminator and the microscope are aligned is not particularly difficult. To do this, you need to set the image of the optical section of the cornea in the center of the microscope field of view and, by moving the focal magnifier, achieve maximum clarity of cut edges.
The specified addition of B. L. Polyak to the biomicroscopy technique is of practical value, but can be used mainly when examining the eye in direct focal illumination.
Biomicriscopy using a ShchL lamp performed at different angles of biomicroscopy, but more often at an angle of 30-45°. The deeper located parts of the eyeball are examined with a smaller angle of biomicriscopy. It is useful to remember the rule: the deeper into the eye, the smaller (narrower) the biomicroscopy angle. Sometimes, for example, during examination of the vitreous body, the illuminator and microscope move closely.
Some optometrists use a slit lamp when removing small foreign bodies from the conjunctiva and cornea. In this case, only one illuminator can be used. The head of the microscope is usually folded back and moved to the side, making room for manipulation. A beam of light is focused at the location of the foreign body, after which it is removed using special needles. The doctor's hand holding the needle can be fixed on a special bracket, which is attached to the headrest frame on the right side.
Technique of working with the slit lamp ShchL-56
At the beginning of the study using the ShchL-56 lamp
- The patient's head is conveniently fixed on the facial support, the chin part of which should be placed in the middle position. The base of the coordinate table must be moved close to the face unit. The presence of even a small gap between them makes research extremely difficult.
- It is also necessary to ensure that the coordinate table is located in the middle of the tool table.
- After this, the movable part of the coordinate table is placed in the middle position by moving the handle, which is installed vertically.
- The illuminator is placed on the outside of the eye being examined at one or another angle of bioncroscopy, depending on which part of the eye is to be examined and what type of lighting is intended to be used.
- It is necessary to ensure that the illuminator head (head prism) is in the middle position and located opposite the patient’s eye.
By moving the upper plateau of the coordinate table, establish a clear image of the lighting slit on the area of the eye that needs to be examined. After this, an image of the illuminated area is found under a microscope. By rotating the focal screw of the microscope, maximum clarity of the biomicroscopic picture is achieved.
Sometimes the image of the slit does not coincide with the field of view of the microscope and the unilluminated part of the eye is visible through the microscope. In this case it is necessary slightly rotate the head prism of the illuminator to the right or left; in this case, the beam of light falls into the field of view of the microscope, i.e., it is combined with it.
Moving the top of the X-Y table and (and with it the lighting slit) horizontally, you can examine all the tissues of the eye located in a given plane, at a given depth. Moving the plateau anteroposteriorly, you can examine areas of the eye located at different depths, with the exception of the posterior parts of the vitreous body and the fundus. To examine these parts of the eyeball, it is necessary to lower the ophthalmoscopic lens down by turning the lens handle clockwise, and place the illuminator in front of the lens of the binocular microscope (the biomicroscopy angle approaches zero). If these conditions are met, the image of the illuminated slit appears on the fundus.
When examining with a ShchL-56 lamp, biomicroscopy of the anterior segment of the eyeball, deeper tissues, as well as the fundus performed under different microscope magnifications. In everyday practical work, low and medium magnifications are preferred - 10x, 18x, 35x. The examination should begin at a lower magnification, moving to a higher magnification as needed.
Some doctors, when working with the ShchL-56 microscope, note persistent double vision and the inability to merge images seen separately by the right and left eyes. In such cases you should carefully set the microscope eyepieces according to your distance between the centers of the pupils. This is achieved by bringing together or spreading the eyepiece tubes. If this technique fails to achieve a single, clear, stereoscopic image, another technique can be used. Eyepieces are installed in strict accordance with the distance between the centers of their pupils. After this, by moving the upper plateau of the coordinate table, the sharpness of the image of the illuminated slit on the eyeball is established. The focal screw of the microscope is moved all the way forward, and then gradually (under the control of vision through the microscope) it is moved back towards you until a single, clear image of the eye being examined appears in the field of view of the microscope.
Infrared slit lamp technique
Infrared slit lamp examination produced in a dark room. It is recommended that this study be preceded by biomicroscopy in a conventional slit lamp, which makes it possible to get a certain idea of the nature of the disease and raise a number of questions to resolve them when examining using infrared rays. The patient's eye is directed rays from an infrared illuminator, after which, through a slit-lamp binocular microscope, the tissues of the eye hidden behind a cloudy cornea or clouded lens become visible on a fluorescent screen. Microscopy is performed in the same way as biomicroscopy with a conventional slit lamp. By moving the handle of the coordinate table, the image is sharpened. More precise focusing carried out by rotating the focus screw of the microscope. The study is carried out under various microscope magnifications, but mainly small ones. During operation, an infrared illuminator with a slit can be used. A slit illuminator, by projecting an image of a slit onto the eye, allows one to obtain an optical section of the eye tissue in infrared rays. This further expands the possibilities of examining the eyeball with an infrared slit lamp.
Types of lighting
Used for biomicroscopy several lighting options. This is due to different types of light projection onto the eye and different properties of its optical media and shells. However, it must be emphasized that all illumination methods currently used in biomicroscopy arose and developed on the basis of the lateral focal illumination method.
1. Diffuse lighting- the simplest lighting method for biomicroscopy. This is the same side focal light that is used in normal examination of the patient, but more intense and homogeneous, devoid of spherical and chromatic aberration.
Diffuse lighting is created by pointing the image of a luminous slit at the eyeball. The slit must be wide enough, which is achieved by maximizing the opening of the slit diaphragm. The possibilities of research in diffuse light are expanded thanks to the presence of a binocular microscope. This type of lighting, especially when using small degrees of microscope magnification, allows you to simultaneously examine almost the entire surface of the cornea, iris, and lens. This may be necessary to determine the extent of the folds of Descemet's membrane or corneal scar, the condition of the lens capsule, lenticular star, and the surface of the senile nucleus. Using this type of lighting, you can to a certain extent orient yourself in relation to the location of the pathological focus in the membranes of the eye in order to then begin a more thorough study of this focus using other types of lighting necessary for this purpose. Biomicroscopy angle when using diffuse lighting, it can be anything.
2. Direct focal illumination is the main one, leading in biomicroscopic examination of almost all parts of the eyeball. With direct focal illumination, the image of the luminous slit is focused on any specific area of the eyeball, which, as a result, clearly stands out, as if delimited from the surrounding darkened tissues. The axis of the microscope is also directed into this focally illuminated area. Thus, under direct focal illumination, the foci of the illuminator and the microscope coincide (Fig. 9).
Rice. 9. Direct focal illumination.
Study in direct focal illumination start with a gap of 2-3 mm. to get a general idea of the tissue to be biomicroscopy. After an indicative examination, the gap is narrowed in some cases to 1 mm. This provides even brighter illumination necessary for examining a certain area of the eye, and highlights it more prominently.
During normal examination, the optical media of the eye are visible only when they lose transparency. However, during biomicroscopy, when a narrow focused beam of light passes through transparent optical media, in particular through the cornea or lens, you can see the path of the light beam, and the optical medium itself that transmits light becomes visible. This is due to the fact that a focused beam of light, encountering colloidal structures and tissue cellular elements of the optical media of the eye on its path, undergoes partial reflection, refraction and polarization upon contact with them. A peculiar optical phenomenon occurs, known as Tyndall phenomenon.
If a beam of light from a slit lamp is passed through distilled water or a solution of table salt, it will be invisible because it will not encounter particles in its path that can reflect the light. For the same reason the beam of light from the slit lamp is not visible in the moisture of the anterior chamber. During biomicroscopy, the chamber space appears completely black and optically empty.
If any colloidal substance (protein, gelatin) is added to distilled water, then the light beam from the slit lamp becomes visible in the same way as colloidal particles suspended in distilled water become visible, since they reflect and refract the light incident on them. Something similar is observed in the eye during the passage of a light beam through optical media.
At the border of various optical media of the eye (the anterior surface of the cornea and air, the posterior surface of the cornea and chamber humor, the anterior surface of the lens and chamber fluid, the posterior surface of the lens and the liquid filling the retrolenticular space), the density of the tissue changes quite sharply, and therefore changes And refractive index of light. This leads to the fact that the focused beam of light from the slit lamp, directed at the interface between any two optical media, changes its direction quite sharply. This circumstance makes it possible to clearly distinguish between dividing surfaces - boundary zones, or interface zones, between different optical environments of the eye. When a thin slit-like beam of light passes through these media, it appears as if the eyeball is being cut into pieces. Such a thin, focused light beam can be called a light knife, since it provides an optical section of the transparent tissues of the living eye. The thickness of the optical section with the maximum narrowed slit of the illuminator is about 50 μm.
Thus, a section of living eye tissue during biomicriscopy is close in thickness to a histological one. Just as histologists prepare serial sections of eye tissue, during biomicroscopy by moving the illumination slit or the head of the subject it is possible to obtain an infinite number (series) of optical sections. Moreover, the thinner the optical section, the higher the quality of the biomicroscopic examination. However, the concepts of “optical” and “histological” section should not be identified. The optical section reveals mainly the optical structure of the refractive medium. More dense elements and clusters of cells appear as gray areas; optically inactive or slightly active zones have a less saturated gray or dark color. In an optical section, in contrast to a stained histological section, the complex architecture of cellular structures is less visible.
When examining in direct focal illumination, a beam of light from a slit lamp can be concentrated in isolation in a specific optical medium(cornea, lens). This makes it possible to obtain an isolated optical section of a given medium and to carry out more accurate focusing inside the carrier. This research method is used to determine the localization (depth) of a pathological focus or foreign body in the tissues of the eye. This method greatly facilitates the diagnosis of a number of diseases, allowing one to answer the question about the nature of keratitis (superficial, median or deep), cataract (cortical or nuclear).
For deep localization of the pathological focus under a microscope good binocular vision required. The biomicroscopy angle when using the direct focal illumination method can vary widely depending on need; often examined at an angle of 10-50°.
3. Indirect lighting(dark field examination) is used quite widely in eye biomicroscopy. If you concentrate the light on any part of the eyeball, then this brightly lit area itself becomes a source of illumination, albeit weaker. Scattered rays of light reflected from the focal zone fall on the tissue lying nearby and illuminate it. This tissue is located in a zone of parafocal illumination, or dark field. The axis of the microscope is also directed here.
With indirect illumination: the focus of the illuminator is directed towards the zone of focal illumination, the focus of the microscope is directed towards the zone of the darkened field (Fig. 10).
Rice. 10. Indirect lighting.
Since light rays from a focally illuminated area propagate not only over the surface of the tissue, but also into depth, the indirect illumination method is sometimes called diaphanoscopic.
Indirect lighting method has a number of advantages in front of others. Using it, you can examine changes in the deep parts of the opaque media of the eye, as well as identify some normal tissue formations.
For example, in a dark field on lightly colored irises, the sphincter of the pupil and its contractions are clearly visible. Normal vessels of the iris and accumulations of chromatophores in its tissue are clearly visible.
Study in indirect, diaphanoscopic illumination is of great importance in differential diagnosis between true iris tumors and cystic formations. The tumor, which retains and reflects light, usually stands out in the form of a dark, opaque mass, in contrast to the cystic cavity, which is translucent like a lantern.
During biomicroscopy of patients with eye trauma, examination in a dark field helps to identify a tear (or rupture) of the sphincter of the pupil, hemorrhages in the tissue of the iris. The latter, when examined in direct focal lighting, are almost invisible, but when indirect lighting is used, they are revealed in the form of limited areas painted dark red.
Indirect illumination is an indispensable research method to detect atrophic areas in iris tissue. Places devoid of posterior pigment epithelium are visible in a dark field in the form of translucent slits and holes. With pronounced atrophy, the iris, when biomicroscopy in a dark field, resembles a sieve or sieve in appearance.
4. Variable lighting, oscillating, or oscillatory, is a combination of direct focal illumination with indirect. The tissue being examined is either brightly illuminated or darkened. Changing lighting should be fairly quick. Observation of variablely illuminated tissue is carried out through a binocular microscope.
When working with a ShchL lamp, variable illumination can be obtained either by moving the illuminator, that is, by changing the angle of biomicroscopy, or by moving the head support. In this case, the area under study sequentially moves from the focally illuminated zone to the dark field. When examining with a ShchL-56 lamp, variable illumination is created by displacing the entire illuminator or only its head prism. Variable lighting can also be obtained regardless of the lamp model. changing the degree of opening of the slit diaphragm.
In the process of research the microscope must always be at the zero scale division.
Variable lighting for biomicroscopy used to determine the reaction of the pupil to light. Such a study is of undoubted importance if the patient has hemianopic pupil immobility. A narrow beam of light allows isolated illumination of one of the halves of the retina, which cannot be achieved when examining with a conventional magnifying glass. To obtain more accurate data, it is necessary to use a very narrow slit, sometimes turning it into a pinhole. The latter is necessary in the presence of quadrant hemianopia. When examining patients with hemianopsia, the light source is placed, depending on the need, on the temporal or nasal side of the eye being examined. It is advisable to observe the reaction of the pupil to light at low magnification of the microscope.
Variable lighting also used to detect small foreign bodies in eye tissues, not diagnosed by radiography. Metallic foreign bodies with rapid changes in lighting appear as a kind of shine. The shine of glass fragments found in liquid media, the lens and membranes of the eye is even more pronounced.
Variable lighting can be applied to detect detachment or rupture of Descemet's membrane, which is observed after cyclodialysis surgery, perforation injury. The vitreous Descemst's membrane, which sometimes forms bizarre curls during spontaneous or surgical trauma, gives a peculiar changing shine when examined under oscillatory lighting.
5. Transmitted light It is used mainly for examining the transparent media of the eye, which transmit light rays well, most often when examining the cornea and lens.
To conduct a study in transmitted light, it is necessary to obtain behind the tissue being examined bright lighting if possible. This lighting must be created on some kind of screen capable of reflecting as many rays of light incident on it as possible.
The denser the screen, i.e., the higher its reflectivity, the higher the quality of research in transmitted light.
The reflected rays illuminate the tissue being examined from behind. Thus, transmitted light research is examination of tissue for transillumination, transparency. If there are very subtle opacities in the tissue, the latter retain the light falling from behind, change its direction and, as a result, become visible.
When examined in transmitted light The foci of the illuminator and the microscope do not coincide. If there is a sufficiently wide slit, the focus of the illuminator is set on an opaque screen, and the focus of the microscope is set on a transparent tissue located in front of the illuminated screen (Fig. 11).
Rice. eleven. Transmitted light.
- When examining the cornea, the screen is the iris,
- for atrophic areas of the iris - the lens, especially if it is cataractically modified;
- for the anterior parts of the lens - its posterior surface,
- for the posterior parts of the vitreous body - the fundus.
Transmitted light examination can be implemented in two versions. Transparent fabric can be viewed against the background of a brightly lit screen, where the focus of the light beam is directed - research in direct transmitted light. The tissue under study can also be examined against the background of a slightly darkened section of the screen - a section located in the parafocal zone of illumination, i.e., in a dark field. In this case, the inspected transparent tissue is illuminated less intensely - examination in an indirect passing light.
Novice ophthalmologists are not immediately successful in examining in transmitted light. The following procedure can be recommended. After mastering the direct focal illumination technique, the focal light is placed on the iris. The axis of the microscope is also directed here, as required by the focal illumination technique. After finding the focally illuminated area under the microscope, rotating the focal screw of the microscope back, i.e. towards you, place it on the image of the cornea. The latter in this case will be visible in direct transmitted light. To examine the cornea in indirect transmitted light, the focus of the microscope must first be placed on the dark field zone of the iris, and then transferred to the image of the cornea.
A normal cornea, when biomicroscopy in transmitted light, has the appearance of a barely noticeable, completely transparent, glassy, structureless shell. Transmitted light examination often reveals changes undetectable under other types of lighting. Usually, swelling of the epithelium and endothelium of the cornea, subtle cicatricial changes in its stroma, and newly formed ones are clearly visible. in particular, already deserted vessels, atrophy of the posterior pigment layer of the iris, vacuoles under the anterior and posterior capsule of the lens. When examined in transmitted light, the bullous degenerated epithelium of the cornea and lens vacuoles appear bordered by a dark line, as if inserted into a frame.
When examining in transmitted light, one must take into account that the color of the examined tissues does not appear to be the same as when examined under direct focal illumination. Opacities in optical media appear darker, just as they do when examined in transmitted light using an ophthalmoscope. In addition, in the tissue studied, it is often unusual color shades appear. This is due to the fact that the rays reflected from the screen receive the color of this screen and impart it to the tissue through which they then pass. Therefore, opacification of the cornea. having a whitish tint when examined in direct focal illumination, when biomicroscopy in transmitted light appears yellowish against the background of a brown iris, and gray-bluish against the background of a blue iris. Lens opacities, which have a gray color when examined in direct focal illumination, acquire a dark or yellowish tint in transmitted light. After detecting certain changes during examination in transmitted light, it is advisable to examine in direct focal illumination to determine the true color of the changes and identify their deep localization in the tissues of the eye.
6. Sliding beam- illumination method introduced into ophthalmology by Z. A. Kaminskaya-Pavlova in 1939. The essence of the method is that the light from the slit lamp is directed to the eye being examined perpendicular to its visual line (Fig. 12).
Rice. 12. Sliding beam.
To do this, the illuminator must be moved as far as possible to the side, towards the temple of the subject. It is advisable to open the illumination slit aperture quite wide. The patient should look straight ahead. This creates the possibility of almost parallel sliding of light rays along the surface of the eyeball.
If parallel direction of light rays does not occur, the patient's head is slightly turned in the direction opposite to the incident rays. When examining with this type of illumination, the axis of the microscope can be directed to any zone.
Sliding beam lighting used to examine the relief of the membranes of the eye. By giving different directions to the beam, you can make it slide along the surface of the cornea, iris and that part of the lens that is located in the lumen of the pupil.
Since one of the most prominent membranes of the eye is rainbow, in practical work it should most often be used specifically for its inspection. A beam of light sliding along the front surface of the iris illuminates all its protruding parts and leaves the recesses darkened. Therefore, with the help of this type of lighting, the smallest changes in the relief of the iris are well revealed, for example, its smoothing during tissue atrophy.
Glancing beam examination is advisable used in difficult cases of diagnosing neoplasms of the iris, especially in the differential diagnosis between a neoplasm and a pigment spot. A dense tumor formation usually delays the grazing beam. The tumor surface facing the incident beam is brightly illuminated, the opposite surface is darkened. The tumor, which delays the sliding beam, casts a shadow from itself, which sharply emphasizes its distance above the surrounding unchanged tissue of the iris.
With a pigment spot (nevus), the indicated contrast phenomena in the illumination of the tissue under study are not observed, which indicates the absence of its persistence.
Sliding beam method also allows you to identify small irregularities on the surface of the anterior lens capsule. This is important when diagnosing detachment of the zonular plate.
A sliding beam can also be used to inspect surface topography. senile lens nucleus, on which protruding warty seals form with age.
When a beam of light slides over the surface of the nucleus, these changes are usually easily detected.
7. Mirror field method(research in reflective zones) - the most difficult type of lighting used in biomicroscopy; accessible only to ophthalmologists who already know the basic methods of illumination. It is used to inspect and study the interface zones of the optical media of the eye.
When a focused beam of light passes through the interface between optical media, more or less reflection of the rays occurs. In this case, each reflective zone turns into a kind of mirror and gives a light reflex. Such reflective mirrors are the surfaces of the cornea and lens.
According to the law of optics, when a ray of light falls on a spherical mirror, the angle of its incidence is equal to the angle of reflection and both of them lie in the same plane. This is the correct reflection of light. The area where the correct reflection of light occurs is quite difficult to see, since it shines brightly and blinds the researcher. The smoother the surface, the more pronounced its light reflex.
If the smoothness of the mirror surface (reflective zone) is disrupted, when depressions and protrusions appear on it, the incident rays are reflected incorrectly and become diffuse. This - incorrect reflection of light. Incorrectly reflected rays are perceived by the researcher more easily than correctly reflected rays. The reflective surface itself becomes better visible; recesses and protrusions on it appear in the form of dark areas.
To see the rays reflected from a mirror surface and perceive all its smallest irregularities, the observer must place his eye in the path of the reflected rays. Therefore, when examining in a mirror field, the axis of the microscope is directed not to the focus of the light coming from the slit lamp illuminator, as is done when examining in direct focal illumination, but to the reflected beam (Fig. 13).
Fig. 13. Research in a mirror field.
This is not entirely easy, since when studying in the field of reflection, it is necessary to catch in the microscope not a wide beam of diverging rays, as with other types of illumination, but a very narrow beam of light having a certain direction.
During the first exercises, to make it easier to see the reflected rays, The illuminator and microscope should be positioned at right angles. The visual axis of the eye should bisect this angle. Focused light is directed onto the cornea, making the gap more or less wide. It should fall at approximately 45° to the visual axis of the eye. This beam is clearly visible.
To see the reflected beam(it will also be reflected at an angle of 45°), you must first get it on the screen. To do this, place a sheet of white paper along the reflected beam. Having received the reflected beam, the screen is removed and the axis of the microscope is set in the same direction. At the same time, under the microscope, the mirror-like surface of the cornea becomes visible - bright, shiny, very small areas.
To facilitate the study in order to reduce the brightness of the reflective areas, it is recommended to use narrower lighting slit.
The technical difficulty of research in reflective zones is rewarded by the great opportunities that this type of lighting provides for the diagnosis of eye diseases. When examining the anterior surface of the cornea in a mirror field a very blinding reflection area is visible. Such a strong reflection of rays is associated with a large difference in the refractive indices of the cornea and air. In the reflective zone, the smallest irregularities of the epithelium, its swelling, as well as dust particles and mucus located in the tear are revealed. The reflex from the posterior surface of the cornea is weaker, since this surface has a smaller radius of curvature compared to the anterior one. It has a golden-yellowish tint and is shiny. This can be explained by the fact that part of the rays reflected from the posterior surface of the cornea, when returning to the external environment, are absorbed by the cornea’s own tissue and reflected back by its anterior surface.
The mirror field method makes it possible to detect on the posterior surface of the cornea mosaic structure of the layer of endothelial cells. In pathological conditions, in the reflex zone one can see folds of Descemet's membrane, its warty thickenings, swelling of endothelial cells, and various deposits on the endothelium. In cases where it is difficult to distinguish the anterior surface of the cornea from the posterior one in the reflex zone, it can be recommended to use a larger biomicroscopy angle. In this case, the mirror surfaces will separate and move away from one another.
Specular zones from the surfaces of the lens are much easier to obtain. The anterior surface is larger in size than the posterior one. The latter is visible much better in a mirror field, since it reflects less. Therefore, when mastering the research methodology in reflective zones, you need to start your exercises from obtaining a mirror field on the posterior surface of the lens. When examining the reflective zones of the lens, the irregularities of its capsule are clearly visible, the so-called shagreen, caused by the peculiar arrangement of the lens fibers and the presence of a layer of epithelial cells under the anterior capsule. When examined in a mirror field, the interface zones of the lens are not clearly visible, which is due to their insufficiently sharp delineation from one another and a relatively small difference in the refractive index.
8. Fluorescent lighting introduced into domestic ophthalmology by Z. T. Larina in 1962. The author used fluorescent lighting, while examining the affected eye tissues through a binocular slit lamp microscope. This type of lighting is used for the purpose of intravital differential diagnosis of tumors of the anterior segment of the eyeball and ocular appendages.
Luminescence- a special type of glow of an object when illuminated by ultraviolet rays. The glow can occur due to the presence of inherent fluorescent substances in the tissue (the so-called primary luminescence) or can be caused by the introduction of fluorescent dyes into the patient’s body (secondary luminescence). For this purpose, a 2% solution of fluorescein is used, 10 ml of which the patient is asked to drink before the study.
For research under fluorescent lighting you can use a mercury-quartz lamp PRK-4 with a uviol filter that transmits ultraviolet radiation and blocks heat rays. A quartz loupe can be used to concentrate ultraviolet rays on tumor tissue.
During the examination, a mercury-quartz lamp is placed on the temporal side of the eye being examined. The microscope is placed directly in front of the eye being examined.
Primary luminescence of tissue arising from ultraviolet irradiation allows you to determine the true boundaries of the tumor. They are revealed more clearly and in some cases are wider than when examined with a slit lamp with conventional lighting. The color of pigmented tumors changes during primary luminescence, and in some cases it becomes more saturated. According to the observations of Z. T. Larina, the more the color of the tumor changes, the more malignant it turns out to be. The degree of malignancy of the tumor can also be judged by the speed of appearance of the fluorescein solution drunk by the patient in its tissue, the presence of which is easily detected by the appearance of secondary luminescence.
Article from the book: .
Biomicroscopy of the eye is an objective method of studying the structures of the eye, which is carried out with a special device - a biomicroscope (slit lamp). Using this method, you can examine the elements of the anterior and posterior sections of the eyeball (learn about the eyeball).
Device structure
The biomicroscope consists of a lighting system, which is a light source, and a microscope for two eyes.
The light from the lamp passes through a slit-shaped diaphragm, after which it is projected onto the cornea or sclera in the form of an oblong rectangle. The resulting optical section is examined under a microscope. The doctor can move the light slit to those elements that need to be examined.
Indications and contraindications
For the pathology of what eye structures is biomicroscopy indicated?
- Conjunctiva (conjunctivitis, formations)
- Corneas (inflammation, dystrophic changes).
- Sclera.
- Irises (inflammation, structural abnormalities).
- Lens.
- Vitreous body.
These techniques are also used for cataracts, glaucoma, the presence of foreign bodies in the eye, at the stage of preparation for eye surgery and in the postoperative period.
There are no absolute contraindications to this diagnostic procedure. The procedure should be rescheduled if the patient has an exacerbation of mental disorders or is intoxicated.
Methodology
First, the patient is prepared - drops are instilled into the eyes to dilate the pupil (if it is necessary to examine deep structures), or special dyes (in cases where it is necessary to diagnose corneal pathology).
The patient places his head on a special stand that has supports for the forehead and chin. The doctor stands opposite the patient and moves the microscope and lamp to the patient’s eye level. Using diaphragms, the size and shape of the light slit is adjusted (usually in the form of a rectangle, less often in the form of a small circle). Light rays are directed to the eye structures being examined, after which they are examined in detail.
By examining the cornea, you can detect foci of opacities, infiltrates, and newly formed vessels. The biomicroscopy procedure allows you to clearly examine the lens, as well as identify the localization of pathological changes. This method allows you to examine the blood vessels of the conjunctiva.
Also, using a biomicroscope, you can evaluate the sphericity and specularity of the cornea, determine its thickness, as well as the depth of the anterior chamber of the eyeball.
There are several lighting options during this diagnostic procedure:
- direct focused illumination - light is directed to the area of the eye being examined. This is how the transparency of the optical media of the eyeball is assessed;
- indirect focused light - light rays are directed near the area under study, as a result of which it is possible to better examine pathological changes due to the contrast of the illuminated and unlit area;
- reflected light - this is how certain structures (for example, the cornea) are examined by light reflected from other elements (the iris), as from a mirror.
Recently, ultrasound biomicroscopy of the eye has become increasingly popular, thanks to which it is possible to examine the lateral sections of the lens, the posterior surface and section of the iris, and the ciliary body.
Also find out how other examinations are carried out by an ophthalmologist, for example, measuring pressure in the eyes and is it scary? Read
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