home Folk remedies Optical tomography of the retina. OCT of the retina - what is it? What is OCT

Optical tomography of the retina. OCT of the retina - what is it? What is OCT

Today, such research is the most advanced technology for studying the structures of the organ of vision. This is an indispensable method for early diagnosis of diseases of the retina and other pathologies leading to blindness. Previously, such dangerous and serious diseases developed in patients largely due to the fact that they did not undergo a high-quality ophthalmological examination on time. Let's look at how eye tomography is performed, what this method is, and why it is becoming so popular.

Indications for diagnosis

Ophthalmologists use this type of examination to detect the following ailments.

Macular holes.
Eye damage due to diabetes.
Glaucoma.
Blockage of the central vein of the retina by a thrombus.
Detachment of this part of the organ of vision, which is one of the most dangerous conditions that contributes to the development of blindness.
Degenerative changes in the cavities of the eye.
Age-related macular degeneration.
The appearance of cystoid formations on the retina of the eye.
Swelling and other nerve abnormalities, leading to a significant decrease in visual acuity and even blindness.
Vitreoretinopathy.

In addition, eye tomography is also used to monitor the effectiveness of previously prescribed treatment. With its help, you can most fully determine the angle of the anterior chamber of the eye, the features of its drainage system (this is why tomography gives the most accurate results in cases of suspected glaucoma). It is also indispensable when installing an intraocular lens and performing keratoplasty.

This examination allows you to diagnose the condition of the cornea, optic nerve, iris, retina and anterior chamber of the eye. It should also be noted that all results are stored in the device’s memory, which allows the doctor to monitor the dynamics of the eye condition

How is the examination carried out?

This is a type of modern non-invasive procedure for diagnosing eye tissue. It is very similar to an ordinary ultrasound examination, with one difference - it uses infrared rays rather than sound. All information comes to the monitor after measuring the degree of delay of radiation from the tissue to be examined. This tomography makes it possible to detect changes that cannot be determined by other methods.

This study is most effective in relation to the retina and optic nerve. Despite the fact that this type of diagnostics has been used in medical practice for a little over 20 years, it has managed to gain popularity.

During the examination, the patient must focus on the highlighted mark. This must be done with the help of the eye that needs to be studied. At the same time, the tissues of the organ of vision are scanned. If a person cannot focus his gaze on the mark, he should use the other eye, which has better vision.

If there are hemorrhages, swelling, or clouding of the lens, then the information content of the procedure is sharply reduced. Other methods may be used to determine an accurate diagnosis.

Tomography results are provided in the form of summarized tables, pictures and detailed protocols. The doctor can analyze the condition of the eye using quantitative and visual data. They are compared with normal values, which makes it possible to make an accurate diagnosis.
Recently, three-dimensional examination has also been used. Thanks to layer-by-layer scanning of the membranes of the eye, the doctor identifies almost all possible abnormalities in it.

Advantages of this diagnostic method

Retinal tomography has the following advantages:

it allows you to accurately determine whether a person has glaucoma;
makes it possible to record the progression of the disease;
does not cause pain or discomfort;
most accurately diagnoses macular degeneration, that is, a condition in which a person sees a black spot in the field of vision;
combines perfectly with other methods for determining eye diseases that lead to blindness;
does not expose the body to harmful radiation (primarily X-rays).

What can such a study determine?

Tomography, used to study the structural features of the eye, allows you to see various diseases, processes and phenomena in this organ.

Any morphological changes in the retina or nerve fibers.
Any changes in the parameters of the nerve disc.
Features of the anatomical structures located in the anterior segment of the eye and their changes compared to the norm.
Any cases of degenerative changes in the retina leading to significant impairment of vision.
Disorders associated with the development of diabetic retinopathy, including its initial stages, which are difficult to diagnose using conventional ophthalmoscopy.
Lesions of the vitreous body and other areas of the eye associated with the development of glaucoma.
Changes in the retina resulting from venous thrombosis.
Various degrees of retinal detachment.
Various anomalies in the structure of the eye, optic nerve and other disorders that require detailed diagnosis.

Such examinations are carried out in specialized clinics with appropriate equipment. Of course, few diagnostic centers have such equipment. However, over time it becomes more accessible, and more and more clinics will accept patients to examine their eyes using the progressive method. Recently, OCT (optical coherence tomography) has become available in clinics in regional centers.

And although the cost of a CT scan is quite high, you should not refuse to perform it, especially if the ophthalmologist insists on such a diagnosis. It has much greater capabilities than a simple medical examination, even with the use of high-precision equipment. This way, it will be possible to detect dangerous eye pathologies even at a stage when the symptoms are not yet expressed.

OCT is used in various fields of medicine - for diseases of the gastrointestinal tract, respiratory system, in gynecology and for the diagnosis of arthritis and arthrosis. But optical coherence tomography was first used in ophthalmology.

The eyes are a very important organ whose main function is vision.

The human eye is a paired organ that performs the function of vision. Consists of the optic nerve, eyeball, and auxiliary organs, in particular muscles, eyelids.

Through the organs of vision, a person receives 80% (according to some sources more than 90%) of information from the outside. Loss of vision, even partial, negatively affects the life of a person and his relatives.

It is important to take care of your eyes - the visual organs are susceptible to many diseases. Some arise in the eye itself, called primary, these include:

retinal detachment;
color blindness;
conjunctivitis.

Optical coherence tomography - what is it and who is its author?

Ocular CT is performed using special equipment

People have many problems with their visual organs, and successfully combating them directly depends on the correctness of the chosen course of treatment. And this requires accurate and timely diagnosis.

In medicine, various types of studies are used - (visual acuity study), . One of the most reliable, accurate and painless methods is optical coherence tomography, what is it?

The idea of using light waves for diagnostics belongs to the American scientist Carmen Puliafito. The doctor gave a scientific basis for his theory - since the structure of living tissue has a non-uniform density, acoustic waves are reflected from them at different speeds.

The word coherent means “flowing in a consistent manner over time.” The device measures the time it takes for a beam of light to linger as it reflects off different layers of tissue. These readings are analyzed and information about the condition of the organs being examined is obtained.

The operation of the method is the same as with, where ultrasonic waves with a resolution measured in microns are used to study biological material. Optical coherence tomography uses infrared radiation.

The video will show how OCT of the eye is performed:

Advantages of the method

OCT eye - a modern type of diagnostics

A laser device is used, which allows you to obtain clear, high-resolution images. The device takes pictures of those layers of the retina (without damaging healthy tissue) that were inaccessible to previous diagnostic methods.

In what cases is it advisable to conduct this type of research:

in patients with almost all diseases - this is especially important if the patient has poor dilation or does not dilate (this can happen with diabetes mellitus), glaucoma;
at any age - in young children and elderly people;
the procedure does not take much time, it lasts only 5-7 minutes;
no contrast agents are required, as the method is non-invasive.
has a repeat scanning function, this is important for patients with gaze fixation problems.
It is possible to transmit information electronically to any medical institution at the request of the patient.

The equipment operates using the latest technology using a blue laser and allows diagnosing: the structure of the retina by layers, pathological changes, glaucoma and multiple sclerosis in the early stages, its progression, age-related macular degeneration of the eye.

Research process

To obtain a high-quality image, during the examination the patient must focus his gaze on a special mark. The operator scans the image, makes several copies, choosing the better one.

If for some reason this eye cannot be tested, the second eye is examined. Based on the test results in the form of tables, cards determine the condition of the tissues.

Indications and contraindications for the use of optical coherence tomography:

While safe, it has several contraindications:

In order to scan an image, the patient needs to fix his gaze at a certain point for 2.5 seconds. Some people cannot do this for various reasons, in which case it is not possible to conduct the study.
Severe mental illness of a person, in which it is impossible to contact doctors and the operator of the device.

Optical coherence tomography may be of poor quality if the environment of the eye has lost its transparency. But this cannot be a reason to refuse such a study, which is carried out in specialized clinics.

Diagnostic cost

Oct eyes: result

The optical coherence tomography procedure, which can be done without a doctor’s referral, is still paid for for all patients. Prices for examinations depend on the area of the eye in which the examination (scan) is required.

Types of method:

Study of the disc in glaucoma, neuritis. Diagnostic results help to establish or clarify the disease, as well as determine how effective the treatment is and whether it is chosen correctly.
With OCT of the retina, the central part of the eye is examined, the macula is examined in cases of hemorrhage, swelling and ruptures, retinopathy (the appearance of a veil or spots before the eyes), and in various inflammatory processes.
Scanning allows you to obtain information about all its layers (done before and after surgery on the cornea).

Prices for examinations vary; before enrolling in a particular medical institution, they must be clarified. The average cost of optical coherence tomography is as follows:

optic disc (one eye) - 1000 rubles;
retinal periphery with pupil dilation (2 eyes) - 2500 rubles;
OCT + angiography (1 eye) — 2000 rub.

The procedure is possible in eye clinics and ophthalmology centers in many cities. These can be both private and public institutions. Some offer patients a discount on services. For example, if diagnostics are carried out at night, the price can be reduced by 35-40%.

The eyes give us information about the world around us, making life colorful and interesting. But no one is immune from diseases and injuries; if this happens, there is no need to waste time, you should immediately contact a doctor, since an advanced disease is more difficult to cure.

Simple methods are not enough to fully diagnose most ophthalmological diseases. Optical coherence tomography allows you to visualize the structure of the visual organs and identify the smallest pathologies.

Benefits of OCT

Optical coherence tomography (OCT) is an innovative method of ophthalmological diagnostics, which consists of visualizing the structures of the eye in high resolution. It is possible to assess the condition of the fundus and elements of the anterior chamber of the eye at the microscopic level. Optical tomography allows you to study tissues without removing them, therefore it is considered a gentle analogue of a biopsy.

OCT can be compared with ultrasound and computed tomography. The resolution of coherence tomography is much higher than that of other high-precision diagnostic instruments. OCT allows you to detect the smallest damage down to 4 microns.

Optical tomography is the diagnostic method of choice in many cases because it is non-invasive and does not use contrast agents. The method does not require radiation exposure, and the images are more informative and clear.

Specifics of diagnostics using OCT method

Different body tissues reflect light waves differently. During tomography, the delay time and intensity of reflected light as it passes through the tissue of the eyeball are measured. The method is contactless, safe and highly informative.

Since the light wave travels at a very high speed, direct measurement is not possible. To decipher the results, a Michelson interferometer is used: the beam is divided into two beams, one of which is directed to the area being examined, and the second to a special mirror. A low-coherence beam of infrared light with a wavelength of 830 nm is used to examine the retina, and a wavelength of 1310 nm is used to examine the anterior segment of the eye.

Read also: – cancer arising from the immature retina.

When reflected, both beams enter the photodetector and an interference pattern is formed. The computer analyzes this picture and converts the information into a pseudo-image. In a pseudo-image, areas with high reflectance appear warmer, while areas with lower reflectance may appear almost black. Normally, nerve fibers and pigment epithelium appear “warm”. The plexiform and nuclear layers of the retina are moderately reflective, and the vitreous body appears black because it is optically transparent.

OCT capabilities:

assessment of morphological changes in the retina and nerve fiber layers;
determination of the thickness of eye structures;
measurement of optic nerve head parameters;
assessment of the state of the structures of the anterior chamber of the eye;
determination of the spatial relationship of the elements of the eyeball in the anterior segment.

To obtain a three-dimensional image, the eyeballs are scanned longitudinally and transversely. Optical tomography may be difficult due to corneal edema, opacities, and hemorrhage in the optical media.

What can be examined in the process of optical tomography

Optical tomography makes it possible to study all parts of the eye, but the condition of the retina, cornea, optic nerve, and elements of the anterior chamber can be most accurately assessed. A separate tomography of the retina is often performed to identify structural abnormalities. More accurate methods for studying the macular zone do not currently exist.

For what symptoms is OCT prescribed:

In the process of optical coherence tomography, it is possible to evaluate the angle of the anterior chamber and the degree of functioning of the drainage system of the eye in glaucoma. Similar studies are carried out before and after laser vision correction, keratoplasty, installation of intrastromal rings and phakic intraocular lenses.

Optical tomography is performed if the following diseases are suspected:

(congenital and acquired);
tumors of the organs of vision;
increased intraocular pressure;
proliferative vitreoretinopathy;
atrophy, swelling and other abnormalities of the optic nerve head;
epiretinal membrane;
thrombosis of the central retinal vein and other vascular diseases;
retinal disinsertion;
macular holes;
cystoid macular edema;
deep keratitis;
corneal ulcers;
progressive myopia.

Coherence tomography is absolutely safe. OCT allows you to identify minor defects in the structure of the retina and begin treatment on time.

For the purpose of prevention, OCT is performed for:

diabetes mellitus;
surgical intervention;
hypertension;
severe vascular pathologies.

Contraindications to optical coherence tomography

The presence of a pacemaker and other devices is not a contraindication. The procedure is not carried out in conditions where a person cannot fix his gaze, as well as in cases of mental disorders and confusion.

The contact environment in the organ of vision can also become an interference. By contact medium is meant the one that is used in other ophthalmic examinations. As a rule, several diagnostic procedures are not performed on the same day.

High-quality images can only be obtained in the presence of transparent optical media and a normal tear film. It can be difficult to perform OCT in patients with a high degree of myopia and optical opacities.

How is optical coherence tomography performed?

Optical coherence tomography is carried out in special medical institutions. Even in big cities it is not always possible to find an ophthalmology office with an OCT scanner. A retinal scan of one eye will cost approximately 800 rubles.

No special preparation for tomography is required; the study can be performed at any time. This procedure requires an OCT scanner, an optical scanner that sends beams of infrared light into the eye. The patient is seated and asked to fix his gaze on the mark. If it is not possible to do this with the examined eye, the gaze is fixed with the second one, which sees better. For a full scan, two minutes in a stationary position is enough.

During the process, several scans are made, and after that the operator selects the highest quality and most informative images. The result of the study is protocols, maps and tables, from which the doctor can determine the presence of changes in the visual system. The tomograph's memory contains a normative database that contains information about how many healthy people have similar indicators. The smaller the match, the greater the likelihood of pathology in a particular patient.

Morphological changes in the fundus, visible on OCT images:

high degree of myopia;
benign formations;
scleral staphyloma;
diffuse and focal edema;
swelling with subretinal neovascular membrane;
retinal folds;
vitreoretinal traction;
lamellar and macular hole;
through macular hole;
macular pseudohole;
detachment of the pigment epithelium;
serous detachment of the neuroepithelium;
Druze;
ruptures of the pigment epithelium;
diabetic macular edema;
macular cystoid edema;
myopic retinoschisis.

As can be seen, the diagnostic capabilities of OCT are extremely diverse. The results are displayed on the monitor as a layered image. The device independently converts signals that can be used to assess the functionality of the retina. It is possible to make a diagnosis based on OCT results within half an hour.

Interpretation of OCT images

To correctly interpret the results of optical coherence tomography, the ophthalmologist must have in-depth knowledge of retinal and choroidal histology. Even experienced specialists cannot always compare tomographic and histological structures, so it is advisable to have OCT images reviewed by several doctors.

Fluid accumulation

Optical tomography makes it possible to identify and evaluate the accumulation of fluid in the eyeball, as well as determine its nature. Intraretinal fluid collection may indicate retinal edema. It can be diffuse and cystic. Intraretinal fluid collections are called cysts, microcysts, and pseudocysts.

Subretinal accumulation indicates serous detachment of the neuroepithelium. The images show elevation of the neuroepithelium, and the angle of detachment from the pigment epithelium is less than 30°. Serous detachment, in turn, indicates CSC or choroidal neovascularization. In rare cases, detachment is a sign of choroiditis, choroidal formations, angioid bands.

The presence of subpigment fluid accumulation indicates detachment of the pigment epithelium. The photographs show elevation of the epithelium above Bruch's membrane.

Neoplasms in the eye

Optical tomography can show the epiretinal membranes (folds in the retina) and evaluate their density and thickness. With myopia and choroidal neovascularization, the membranes appear as fusiform thickenings. They are often combined with fluid accumulation.

Hidden neovascular membranes appear on imaging as irregular thickening of the pigment epithelium. Neovascular membranes are diagnosed in age-related macular degeneration, chronic CSC, complicated myopia, uveitis, iridocyclitis, choroiditis, osteoma, nevus, pseudovitelliform degeneration.

The OCT method allows you to determine the presence of intraretinal formations (cotton wool-like foci, hemorrhages, hard exudate). The presence of cotton wool-like foci on the retina is associated with ischemic nerve damage in diabetic or hypertensive retinopathy, toxicosis, anemia, leukemia, and Hodgkin's disease.

Hard exudates may be star-shaped or isolated. They are usually localized at the border of retinal edema. Such formations are found in diabetic, radiation and hypertensive retinopathy, as well as in Coats disease and wet macular degeneration.

Deep formations are observed with macular degeneration. Fibrous scars appear, which deform the retina and destroy the neuroepithelium. On OCT, such scars give a shadow effect.

Pathological structures with high reflectivity on OCT:

Pathological structures with low reflectivity:

cysts;
edema;
detachment of the neuroepithelium and pigment epithelium;
shading;
hypopigmentation.

Shadow effect

High optical density tissues can obscure other structures. Based on the shadow effect in OCT images, it is possible to determine the location and structure of pathological formations in the eye.

The shadow effect is given by:

dense preretinal hemorrhages;
cotton wool tricks;
hemorrhages;
hard exudates;
melanoma;
hyperplasia, hypertrophy of the pigment epithelium;
pigment formations;
neovascular membranes;
scarring.

Retinal characteristics on OCT

Swelling is the most common cause of retinal thickening. One of the advantages of optical tomography is the ability to evaluate and monitor the dynamics of different types of retinal edema. A decrease in thickness is observed with age-related macular degeneration with the formation of atrophy zones.

OCT allows you to evaluate the thickness of a certain layer of the retina. The thickness of individual layers can change with glaucoma and a number of other ophthalmological pathologies. The retinal volume parameter is very important in identifying edema and serous detachment, as well as in determining the dynamics of treatment.

Optical tomography can reveal:

Age-related macular degeneration. One of the main causes of visual impairment in people over 60 years of age. Although different methods are used in the diagnosis of dystrophy, optical coherence tomography remains the leading one. OCT allows you to determine the thickness of the choroid in macular degeneration; it can be used to make a differential diagnosis with central serous chorioretinopathy.
Central serous chorioretinopathy. The disease is characterized by detachment of the neurosensory layer from the pigment epithelium. In most cases, chorioretinopathy disappears spontaneously within 3-6 months, although in some cases fluid accumulates, causing permanent visual impairment. Chronic CSC requires special treatment. As a rule, these are intravitreal injections and laser coagulation.
Diabetic retinopathy. The pathogenesis of the disease is due to vascular damage. Diagnostics allows you to identify retinal edema and check the condition of the vitreous body (including identifying posterior detachment).
Macular hole, epiretinal fibrosis. Using OCT, you can determine the degree of retinal damage, plan surgical treatment tactics and evaluate the results.
Glaucoma. With increased intraocular pressure, tomography is an additional examination method. The method is very useful for normotensive glaucoma, when damage to the optic nerve is observed with normal intraocular pressure. OCT can confirm the disease and determine its stage.

Optical coherence tomography is the safest and most informative method for examining the visual system. OCT is allowed to be performed even in patients who have contraindications to other high-precision diagnostic methods.

Optical coherence tomography is a non-invasive (non-contact) method for studying tissue. It allows you to obtain higher resolution images compared to the results of ultrasound procedures. In essence, optical coherence tomography of the eye is a type of biopsy, only the first does not require taking a tissue sample.

A brief excursion into history

The concept on which modern optical coherence tomography is based was developed by researchers back in the 1980s. In turn, the idea of introducing a new principle into ophthalmology was proposed in 1995 by the American scientist Carmen Puliafito. A few years later, Carl Zeiss Meditec developed a corresponding device, which was called Stratus OCT.

Currently, using the latest model, it is possible not only to study retinal tissue, but also optical coherence tomography of the coronary arteries and optic nerve at the microscopic level.

Research principles

Optical coherence tomography consists of generating graphic images based on measuring the delay period when a light beam is reflected from the tissues being studied. The main element of devices in this category is a superluminescent diode, the use of which makes it possible to form light rays of low coherence. In other words, when the device is activated, the beam of charged electrons is divided into several parts. One stream is directed to the area of the tissue structure being studied, the other to a special mirror.

The rays reflected from objects are summed up. Subsequently, the data is recorded by a special photodetector. The information generated on the graph allows the diagnostician to draw conclusions about the reflectivity at individual points of the object under study. When assessing the next section of tissue, the support is moved to a different position.

Optical coherence tomography of the retina makes it possible to generate graphs on a computer monitor that are in many ways similar to the results of an ultrasound examination.

Indications for the procedure

Today, optical coherence tomography is recommended for diagnosing pathologies such as:

Glaucoma.
Macular tissue tears.
Thrombosis of the blood vessels of the retina.
Degenerative processes in the structure of the eye tissue.
Cystoid edema.
Anomalies in the functioning of the optic nerve.

In addition, optical coherence tomography is prescribed to evaluate the effectiveness of the therapeutic procedures used. In particular, the research method is indispensable in determining the quality of installation of a drainage device that is integrated into the eye tissue for glaucoma.

Features of diagnostics

Optical coherence tomography involves focusing the subject's vision on special marks. In this case, the operator of the device performs a series of sequential scans of tissues.

Such pathological processes as edema, heavy hemorrhages, and all kinds of opacities can significantly complicate the study and hinder effective diagnosis.

The results of coherence tomography are formed in the form of protocols that inform the researcher about the state of certain tissue areas, both visually and quantitatively. Since the obtained data is recorded in the device’s memory, they can subsequently be used to compare the condition of tissues before treatment and after the application of therapy methods.

3D visualization

Modern optical coherence tomography makes it possible to obtain not only two-dimensional graphs, but also to produce three-dimensional visualization of the objects under study. Scanning tissue areas at high speed allows you to generate more than 50,000 images of the diagnosed material within a few seconds. Based on the information received, special software reproduces the volumetric structure of the object on the monitor.

The generated 3D image serves as the basis for studying the internal topography of the eye tissue. This opens up the possibility of determining clear boundaries of pathological neoplasms, as well as recording the dynamics of their changes over time.

Benefits of Coherence Tomography

Coherence tomography devices demonstrate the greatest effectiveness in diagnosing glaucoma. When using devices of this category, specialists are able to accurately determine the development factors of pathology in the early stages and identify the degree of progression of the disease.

The research method is indispensable when diagnosing such a common disease as macular degeneration, in which, as a result of age-related characteristics of the body, the patient begins to see a black spot in the central part of the eye.

Coherence tomography is effective in combination with other diagnostic procedures, for example, with fluorescence retinal angiography. When combining procedures, the researcher receives especially valuable data that helps make the correct diagnosis, determine the complexity of the pathology and select effective treatment.

Where can optical coherence tomography be performed?

The procedure is possible only with a specialized OCT device. Diagnostics of this kind can be resorted to in modern research centers. Most often, vision correction rooms and private ophthalmology clinics have such equipment.

Price issue

Carrying out coherence tomography does not require a referral from the attending physician, but even if it is available, the diagnosis will always be paid for. The cost of the study determines the nature of the pathology that the diagnosis is aimed at identifying. For example, determining macular tissue holes is estimated at 600-700 rubles. While tomography of the tissue of the anterior part of the eye can cost a patient at a diagnostic center 800 rubles or more.

As for complex studies aimed at assessing the functioning of the optic nerve, the condition of the retinal fibers, and the formation of a three-dimensional model of the visual organ, the price for such services today starts from 1,800 rubles.

The capabilities of modern ophthalmology have been significantly expanded in comparison with the methods of diagnosing and treating diseases of the organs of vision some fifty years ago. Today, complex, high-tech devices and techniques are used to make an accurate diagnosis and identify the slightest changes in the structures of the eye. Optical coherence tomography (OCT), performed using a special scanner, is one such method. What is it, who and when should conduct such an examination, how to properly prepare for it, are there any contraindications and are there possible complications - the answers to all these questions are below.

Benefits and Features

Optical coherence tomography of the retina and other elements of the eye is an innovative ophthalmological study in which the surface and deep structures of the visual organs are visualized in high resolution quality. This method is relatively new; uninformed patients are prejudiced against it. And it is completely in vain, since today OCT is considered the best that exists in diagnostic ophthalmology.

Performing OCT takes only a few seconds, and the results will be ready within a maximum of an hour after the examination - you can stop by the clinic during your lunch break, perform OCT, immediately receive a diagnosis and begin treatment on the same day

The main advantages of OCT include:

the ability to examine both eyes at the same time;
speed of the procedure and efficiency of obtaining accurate results for diagnosis;
in one session, the doctor gets a clear picture of the condition of the macula, optic nerve, retina, cornea, arteries and capillaries of the eye at the microscopic level;
the tissues of the eye elements can be thoroughly studied without a biopsy;
the resolution of OCT is many times higher than that of conventional computed tomography or ultrasound - tissue damage no larger than 4 microns in size and pathological changes are detected at the earliest stages;
no need to administer intravenous contrast dyes;
The procedure is non-invasive, therefore it has almost no contraindications and does not require special preparation or recovery period.

When performing coherence tomography, the patient does not receive any radiation exposure, which is also a great advantage considering the harmful effects of external factors that every modern person is already exposed to.

What is the essence of the procedure

If light waves are passed through the human body, they will be reflected from different organs in different ways. The delay time of light waves and the time of their passage through the elements of the eye, the intensity of reflection is measured using special instruments during tomography. Then they are transferred to the screen, after which the data obtained is deciphered and analyzed.

Retinal OCTA is an absolutely safe and painless method, since the devices do not contact the organs of vision and nothing is injected subcutaneously or inside the ocular structures. But at the same time, it provides much higher information content than standard CT or MRI.

This is what the image on a computer monitor looks like, obtained by scanning with OCT; special knowledge and skills of a specialist will be required to decipher it

It is in the method of deciphering the resulting reflection that the main feature of OCT lies. The fact is that light waves move at a very high speed, which does not allow direct measurements of the necessary indicators. For these purposes, a special device is used - the Mekelson interferometer. It splits the light wave into two beams, then one beam is passed through the ocular structures that need to be examined. And the other is directed to the mirror surface.

If it is necessary to examine the retina and macular area of the eye, a low-coherence infrared beam with a length of 830 nm is used. If you need to do OCT of the anterior chamber of the eye, you will need a wavelength of 1310 nm.

Both beams combine and enter the photodetector. There they are transformed into an interference pattern, which is then analyzed by a computer program and displayed on the monitor as a pseudo-image. What will it show? Areas with a high degree of reflection will be painted in warmer shades, and those that reflect light waves weakly will appear almost black in the picture. Nerve fibers and pigment epithelium are displayed as “warm” in the picture. The nuclear and plexiform layers of the retina have an average degree of reflectivity. And the vitreous body looks black, since it is almost transparent and transmits light waves well, almost without reflecting them.

To obtain a complete, informative picture, it is necessary to pass light waves through the eyeball in two directions: transverse and longitudinal. Distortions in the resulting image may occur if the cornea is swollen, there are vitreous opacities, hemorrhages, and foreign particles.

One procedure lasting less than a minute is enough to obtain the most complete information about the state of the eye structures without invasive intervention, to identify developing pathologies, their forms and stages

What can be done with optical tomography:

Determine the thickness of the ocular structures.
Determine the size of the optic nerve head.
Identify and evaluate changes in the structure of the retina and nerve fibers.
Assess the condition of the elements of the anterior part of the eyeball.

Thus, when performing OCT, the ophthalmologist has the opportunity to study all components of the eye in one session. But the most informative and accurate is the examination of the retina. Today, optical coherence tomography is the most optimal and informative way to assess the condition of the macular zone of the visual organs.

Indications for use

Optical tomography, in principle, can be prescribed to every patient who contacts an ophthalmologist with any complaints. But in some cases this procedure cannot be avoided; it replaces CT and MRI and even surpasses them in terms of information content. Indications for OCT are the following symptoms and complaints from patients:

"Floaters", cobwebs, lightning and flashes before the eyes.
Blurred vision.
Sudden and severe loss of vision in one or both eyes.
Severe pain in the organs of vision.
Significant increase in intraocular pressure due to glaucoma or other reasons.
Exophthalmos is protrusion of the eyeball from the orbit spontaneously or after injury.

Glaucoma, increased intraocular pressure, changes in the optic nerve head, suspicion of retinal detachment, as well as preparation for eye surgery are all indications for optical coherence tomography

If vision correction using a laser is to be performed, then a similar study is carried out before and after surgery to accurately determine the angle of the anterior chamber of the eye and assess the degree of drainage of intraocular fluid (if glaucoma is diagnosed). OCT is also necessary when performing keratoplasty, implantation of intrastromal rings or intraocular lenses.

What can be determined and detected using coherence tomography:

changes in intraocular pressure;
congenital or acquired degenerative changes in retinal tissue;
malignant and benign neoplasms in the structures of the eye;
symptoms and severity of diabetic retinopathy;
various pathologies of the optic nerve head;
proliferative vitreoretinopathy;
epiretinal membrane;
thrombi of the coronary arteries or central vein of the eye and other vascular changes;
macular tears or detachment;
macular edema, accompanied by the formation of cysts;
corneal ulcers;
deep penetrating keratitis;
progressive myopia.

Thanks to such a diagnostic study, it is possible to identify even minor changes and anomalies of the visual organs, make a correct diagnosis, determine the extent of damage and the optimal method of treatment. OCT actually helps maintain or restore the patient's visual function. And since the procedure is completely safe and painless, it is often performed for preventive purposes in diseases that may be complicated by eye pathologies - diabetes, hypertension, cerebrovascular accidents, after injuries or surgery.

When not to perform OCT

The presence of a pacemaker and other implants, conditions in which the patient is unable to focus, is unconscious, or is unable to control his emotions and movements, most diagnostic tests are not performed. In the case of coherence tomography, everything is different. A procedure of this kind can be performed when the patient is confused and has an unstable psycho-emotional state.

Unlike MRI and CT, which, although informative, have a number of contraindications, OCT can be used to examine children without any fear - the child will not be afraid of the procedure and will not suffer any complications

The main and, in fact, the only obstacle to performing OCT is the simultaneous conduct of other diagnostic studies. On the day on which OCT is prescribed, no other diagnostic methods for examining the visual organs can be used. If the patient has already undergone other procedures, then OCT is postponed to another day.

Also, high myopia or severe clouding of the cornea and other elements of the eyeball can become an obstacle to obtaining a clear, informative image. In this case, light waves will be poorly reflected and produce a distorted image.

OCT technique

It must be said right away that optical coherence tomography is usually not carried out in district clinics, since ophthalmology offices do not have the necessary equipment. OCT can only be done in specialized private medical institutions. In large cities, it will not be difficult to find a trustworthy ophthalmology office with an OCT scanner. It is advisable to agree on the procedure in advance; the cost of coherence tomography for one eye starts from 800 rubles.

No preparation is required for OCT; all you need is a functioning OCT scanner and the patient himself. The subject will be asked to sit on a chair and focus his gaze on the indicated mark. If the eye whose structure needs to be examined is unable to focus, then the gaze is fixed as much as possible by the other, healthy eye. It takes no more than two minutes to remain motionless - this is enough to pass beams of infrared radiation through the eyeball.

During this period, several pictures are taken in different planes, after which the medical officer selects the clearest and highest quality ones. Their computer system checks them against an existing database compiled from examinations of other patients. The database is presented with various tables and diagrams. The fewer matches are found, the higher the likelihood that the structures of the eye of the patient being examined are pathologically altered. Since all analytical actions and transformations of the obtained data are performed automatically by computer programs, it will take no more than half an hour to obtain the results.

The OCT scanner produces perfectly accurate measurements and processes them quickly and efficiently. But to make a correct diagnosis, it is still necessary to correctly decipher the results obtained. And this requires high professionalism and deep knowledge in the field of histology of the retina and choroid of an ophthalmologist. For this reason, interpretation of research results and diagnosis are carried out by several specialists.

Summary: most ophthalmological diseases are extremely difficult to recognize and diagnose in the early stages, much less to establish the real extent of damage to the ocular structures. For suspicious symptoms, ophthalmoscopy is usually prescribed, but this method is not enough to get the most accurate picture of the condition of the eyes. Computed tomography and magnetic resonance imaging provide more complete information, but these diagnostic measures have a number of contraindications. Optical coherence tomography is completely safe and harmless; it can be performed even in cases where other methods of examining the visual organs are contraindicated. Today, this is the only non-invasive way to obtain the most complete information about the condition of the eyes. The only difficulty that may arise is that not all ophthalmology offices have the equipment necessary to carry out the procedure.