home Audience 1 Optical coherence tomography contraindications. How optical coherence tomography of the eyes is performed. Advantages of using optical coherence tomography

Optical coherence tomography contraindications. How optical coherence tomography of the eyes is performed. Advantages of using optical coherence tomography

If there are vision problems in one or both eyes, a comprehensive diagnosis is prescribed. Optical coherence tomography is a modern, high-precision diagnostic procedure that allows you to obtain clear cross-section images of the structures of the eyeball - the cornea and retina. The study is carried out according to indications so that the results are as accurate as possible. It is important to prepare properly for the procedure.

When is optical coherence tomography prescribed?

Modern ophthalmology has at its disposal a variety of diagnostic technologies and techniques that make it possible to accurately examine complex intraocular structures, making treatment and rehabilitation much more successful. Optical coherence tomography of the eye is an informative, non-contact and painless method with which it is possible to study in detail transparent ocular structures that are invisible in traditional studies in a cross section.

The procedure is carried out according to indications. OCT makes it possible to diagnose the following ophthalmological diseases:

macular edema and rupture;
optic disc deformation (OND);
glaucoma;
retinal vitreous dystrophy;
retinal dissection;
macular degeneration;
subretinal neovascular and epiretinal membrane;
senile macular degeneration.

The functionality of the device allows the doctor to examine the diseased organ in detail and obtain complete information about its condition.

There are 2 types of optical coherence tomograph - for scanning the anterior and posterior segment. Modern devices have both functions, so diagnostic results can be obtained more advanced. Ocular OCT is often performed on patients following glaucoma surgery. The method shows in detail the effectiveness of therapy in the postoperative period, while electrical tomography, ophthalmoscopy, biomicroscopy, MRI or CT of the eye are not able to provide data of such accuracy.

Pros of the procedure

OCT of the retina can be prescribed to patients at any age.

The procedure is non-contact, painless and at the same time as informative as possible. During scanning, the patient is not exposed to radiation, since the examination process uses the properties of infrared rays, which are absolutely harmless to the eyes. Tomography allows you to diagnose pathological changes in the retina even at the initial stages of development, which significantly increases the chances of successful treatment and rapid recovery.

How is the preparation going?

Some drugs are prohibited in the preparatory period.

There are no restrictions on eating and drinking before the procedure. On the eve of the study, you should not drink alcohol or other prohibited substances; your doctor may also ask you to stop using certain groups of medications. A few minutes before the examination, drops are instilled into the eyes to dilate the pupil. It is important for the patient to concentrate his gaze on the flashing dot located in the focus camera lens. Blinking, talking and moving your head is prohibited.

How is OCT done?

Optical coherence tomography of the retina lasts on average up to 10 minutes. The patient is placed in a sitting position, the tomograph with an optical camera is installed at a distance of 9 mm from the eye. When optimal visibility is achieved, the camera is fixed, then the doctor adjusts the image to get the most accurate image possible. Once the picture is accurate, a series of pictures are taken.

The finished survey result may look like a map.

the presence or absence of changes in the external ocular structures;
the relative position of the layers of the eyeball;
the presence of pathological formations and inclusions;
decreased or increased transparency of tissues;
thickness of the structures being studied;
dimensions and presence of deformations on the surface under study.

The interpretation of the tomogram is presented in the form of a table, map or protocol, which can most accurately show the state of the studied areas of the visual system and establish an accurate diagnosis even in the early stages. If necessary, the doctor can prescribe a repeat OCT study; this will allow tracking the dynamics of the progression of the pathology, as well as the effectiveness of the treatment process.

Method optical coherence tomography(optical coherence tomography, abbreviated as OST (eng.) or OCT (rus.)) is a modern, high-precision non-invasive study of various structures of the eye. OCT is a non-contact method that allows a specialist to visualize eye tissue with very high resolution (1 - 15 microns), the accuracy of which is comparable to microscopic examination.

The theoretical foundations of the OCT method were developed in 1995 by the American ophthalmologist K. Pulafito, and already in 1996 - 1997, the Carl Zeiss Meditec company introduced the first device for optical coherence tomography into clinical practice. Today, OCT devices are used to diagnose various diseases of the fundus and anterior segment of the eye.

Indications for OST

The optical coherence tomography method allows:

visualize morphological changes in the retina and the layer of nerve fibers, as well as assess their thickness;
assess the condition of the optic nerve head;
examine the structures of the anterior segment of the eye and their relative spatial arrangement.

The method can be used in ophthalmology to diagnose many pathologies of the posterior part of the eye, such as:

degenerative changes in the retina (congenital and acquired, AMD)
cystoid macular edema and macular hole
epiretinal membrane
changes in the optic nerve head (abnormalities, swelling, atrophy)
diabetic retinopathy
thrombosis of the central retinal vein
proliferative vitreoretinopathy.

Regarding pathologies of the anterior part of the eye, OST can be used:

to assess the angle of the anterior chamber of the eye and the functioning of drainage systems in patients with glaucoma
in case of deep keratitis and ulcers of the cornea
during examination of the cornea during preparation and after laser vision correction and keratoplasty
for control in patients with phakic IOLs or intrastromal rings.

Video of our specialist

How the research works

The patient is asked to fix the gaze of the eye being examined on a special mark, after which the doctor performs a series of scans and selects the most informative image to assess the condition of the organ of vision. Diagnosis is completely painless and takes minimal time.

This optical diagnostic method allows you to visualize the structure of tissues of a living organism in a cross section. Due to its high resolution, optical coherence tomography (OCT) allows one to obtain histological images intravitally, and not after preparing the section. The OCT method is based on low-coherence interferometry.

In modern medical practice, OCT is used as a non-invasive, non-contact technology to study the anterior and posterior segments of the eye at the morphological level in living patients. This technique allows you to evaluate and record a large number of parameters:

condition of the optic nerve;
thickness and transparency;
condition and angle of the anterior chamber.

Due to the fact that the diagnostic procedure can be repeated many times, while recording and saving the results, it is possible to evaluate the dynamics of the process during treatment.

When performing OCT, the depth and magnitude of the light beam, which is reflected from tissues with different optical properties, is assessed. An axial resolution of 10 µm provides the most optimal representation of structures. This technique allows you to determine the echo delay of a light beam, changes in its intensity and depth. When focusing on tissue, the light beam is scattered and partially reflected from microstructures located at different levels in the organ under study.

OCT of the retina (macula)

Optical coherence tomography of the retina is usually performed for diseases of the central parts of the eye - edema, dystrophies, hemorrhages, etc.

OCT of the optic nerve head (ONH)

The optic nerve (its visible part - the disc) is examined for such pathologies of the visual apparatus as swelling of the head of the nerve, etc.

The mechanism of action of OCT is similar to the principle of obtaining information from A-scanning. The essence of the latter is to measure the time interval required for the passage of an acoustic pulse from the source to the tissue being studied and back to the receiving sensor. Instead of a sound wave, OCT uses a beam of coherent light. The wavelength is 820 nm, that is, in the infrared range.

Performing OCT does not require special preparation, however, with medical expansion, you can obtain more information about the structure of the posterior segment of the eye.

Device structure

In ophthalmology, a tomograph is used in which the radiation source is a superluminescent diode. The coherence length of the latter is 5-20 µm. The hardware part of the device contains a Michelson interferometer, the object arm contains a confocal microscope (slit lamp or fundus camera), and the reference arm contains a time modulation unit.

Using a video camera, you can display the image and scanning trajectory of the area being studied. The received information is processed and recorded in the computer memory in the form of graphic files. The tomograms themselves are logarithmic two-color (black and white) scales. To make the result better perceived, using special programs, a black and white image is transformed into a pseudo-color one. Areas with high reflectivity are painted white and red, and areas with high transparency are painted black.

Indications for OCT

Based on OCT data, one can judge the structure of normal structures of the eyeball, as well as identify various pathological changes:

, in particular postoperative;
iridociliary dystrophic processes;
traction vitreomacular syndrome;
swelling, pre-tears and lacerations of the macula;
glaucoma;
pigmented.

Video about cataracts in diabetes

Contraindications

A limitation to the use of OCT is the reduced transparency of the tissues being examined. In addition, difficulties arise in cases where the subject is unable to fix his gaze motionless for at least 2-2.5 seconds. This is exactly how long it takes to scan.

Establishing diagnosis

To make an accurate diagnosis, it is necessary to evaluate the resulting graphs in detail and knowledgeably. In this case, special attention is paid to the study of the morphological structure of tissues (the interaction of various layers with each other and with surrounding tissues) and light reflection (changes in transparency or the appearance of pathological foci and inclusions).

With quantitative analysis, it is possible to detect changes in the thickness of a cell layer or the entire structure, measure its volume and obtain a surface map.

To obtain a reliable result, it is necessary that the surface of the eye is free of foreign liquids. Therefore, after performing the procedure with a panfundusscope, you should first thoroughly rinse the conjunctiva from contact gels.

The low power infrared radiation used in OCT is completely harmless and does not cause any damage to the eyes. Therefore, there are no restrictions on the somatic status of the patient for this study.

Cost of optical coherence tomography

The cost of the procedure in eye clinics in Moscow starts from 1,300 rubles. per eye and depends on the area being examined. You can see all prices for OCT in ophthalmology centers in the capital. Below we provide a list of institutions where you can do optical coherence tomography of the retina (macula) or optic nerve (ON).

Treatment of any eye pathology always begins with diagnostic measures. Optical coherence tomography is often performed for these purposes. This study involves high-frequency scanning of the fundus. This technique provides very accurate data, due to which it is widely used in ophthalmology. Optical coherence tomography of the eye allows an ophthalmologist to determine pathological changes in the visual organ that cannot be detected using other diagnostic procedures.

OCT allows you to scan and diagnose the condition of the fundus

In this article you will learn:

What is OCT

The technique of coherent tomographic examination of the eye was first used back in the 90s. Now this diagnostic method has become quite popular, since its accuracy is comparable to examination under a microscope. The OCT device uses infrared rays on the retina of the eye, which does not have a negative effect on the tissue. The diagnostic method allows you to examine the organ of vision not only with high accuracy, but also in a fairly short time. Doctors can examine and evaluate the condition of the retina in just one or two minutes.

The OCT mechanism actually combines the principles of such studies as X-ray CT and ultrasound. However, diagnostics are performed using optical rays of the infrared spectrum, the wavelength of which is 820–1310 nm.

A CT scan of the eye orbits shows any changes in the central parts of the organ. Tomography allows us to examine in detail both the shape and size, as well as the depth of pathological foci. In addition, doctors can see hidden manifestations: any form of edema, hemorrhage, scars, degenerative changes, inflammation and all kinds of pigment accumulations. Often, an examination is carried out to be able to monitor the progress of treatment. OCT is an indispensable diagnostic method for both the retina and the optic nerve.

Diagnostics is carried out due to the influence of infrared rays on the retina of the eye

What types of OCT are distinguished?

Currently, there are two types of OCT that are used to diagnose the orbit of the eye:

Michelson's technique. This method, using an interferometer named after the inventor of the method, was previously the most common. The resolution of the technique is about 10 microns. The light source is a superluminescent diode, which produces a beam with low coherence. However, when carrying out such a diagnosis, the medical worker had to manually move a special mirror on his own. Both the quality of the images and the speed of scanning depended on the speed and accuracy of movement. The device is quite sensitive to any eye movements, so its data has some errors.

Retinal OCT is prescribed for patients with macular degeneration

Spectral OCT. Unlike the first type, spectral research does not require constant manual movement of part of the device. This type of diagnosis is carried out using a broadband diode. The device is equipped with a spectrometer and a special camera, thanks to which almost all ranges of the reflected wave are simultaneously recorded. A spectral tomograph examines the eye much faster. During the time period required to form an image using a high-speed camera, the eye does not have time to make any movements. Therefore, this type of diagnosis allows you to obtain the most accurate information.

Common types of procedures include:

Optical coherence tomographic study of the state of the optic nerve head. It is carried out during the diagnosis or during the treatment of diseases such as glaucoma (caused by increased intraocular pressure), ischemic neuropathy (occurs due to impaired arterial circulation), neuritis (disease of peripheral nerve endings), hypoplasia (underdevelopment of an organ or tissue).

Spectral OCT allows for accurate diagnosis of the eye orbits in a short time

Optical CT of the retina. During the study, the central part of the retina and its neighboring sections are assessed. This diagnostic method is used for hemorrhages, retinopathy, chorioretinitis, macular degeneration, tumors and edema. Often, in addition to OCT of the retina, fluorescein angiography is also used.
OCT of the cornea. The study is carried out for dystrophies, as well as before and after operations on the cornea.

These diagnostic methods are completely painless and provide the doctor with a complete picture of the structure of the eye.

In what cases is the procedure indicated?

A retinal CT scan is performed in case of suspicion or in case of the presence of diseases such as:

If there are complaints of decreased vision and pain in the eyes, it is recommended that the patient undergo OCT of the eyes

In addition, patients undergo such testing in cases of retinal tears, detachments, before or after surgery, and in cases of corneal clouding of unknown origin.

The procedure is also performed if the patient complains of certain symptoms. This may be the appearance of spots before the eyes, pain in the organ, decreased visual acuity or its sudden disappearance.

How should a patient prepare?

No special preparation is required for computed tomography of the eyes. However, in order to obtain a better image, doctors recommend dilating the pupil. To do this, a special medication is instilled into the patient's eyes.

After diagnosis with contrast, redness and itching in the eyes may appear.

In some cases, MSCT of the eye orbit with contrast is required. For this procedure, an iodine-containing substance is used. Before such a study, the patient should not eat for four hours. If you have an allergy (even to anything), you should definitely inform your doctor about this, since sometimes performing a procedure with contrast causes a negative reaction in the form of redness and itching.

How is OCT performed?

The study is performed in a diagnostic room in which an OCT tomograph is located. The patient needs to look at a certain point. The device is equipped with an optical scanner. The infrared rays produced by the device are directed to the organ of vision. In this case, the patient needs to focus his gaze on these rays and try not to move his eyes.

At this time, the doctor moves the camera closer and closer to the patient’s face until an image appears on the computer monitor. The clearest pictures are formed when there is a distance of about 9 mm between the camera and the eye. After receiving the necessary images, the doctor compares the indicators and determines the presence or absence of diseases.

During diagnosis, the patient must look at the selected point and not move his eyes

What results does the doctor get?

An ophthalmologist interprets the results of the study. CT scan of the eye shows the data indicated in the table.

The doctor must study the location of the damage, its size, and the thickness of the cornea.

You can learn more about the OCT eye procedure by watching the video:

When to avoid the procedure

There are some contraindications to performing optical CT of the eye. These include:

Pregnancy, especially the first trimester. During the procedure, the human body is exposed to a small dose of radiation, and the fetus’s reaction to it has not been fully studied. Therefore, doctors do not advise pregnant women to take risks.
Children's age (up to age 14).
Renal failure and an allergy to the contrast agent (when performing a procedure with contrast). The drug is excreted through the kidneys, which can negatively affect the patient's health.
Mental disorders.

For people with claustrophobia, this procedure will not cause any harm, since only the patient’s head is in the scanned area. The presence of a pacemaker or any implants in the person being studied is not a contraindication for diagnosing the visual organ.

Optical coherence tomography of the retina of the eyeball is a modern research technique. The research technique is non-contact, and the specialist receives highly accurate information about the condition of the tissues.

The OCT technique was developed more than twenty years ago in America. In 1997, the company Karl Zeis Meditek introduced its first device that allows for optical tomography. Today, the device is used everywhere, and with its help ophthalmologists around the world diagnose various diseases of the eyeball.

Retinal tomography is a technology that allows an ophthalmologist to carefully examine the tissues of the eyeball without disturbing their rest. Using this technology, it becomes possible to evaluate not only the magnitude, but also the depth of all incoming signals. In addition, the doctor can determine the delay time for the penetration of the light wave.

Typically, the technique is used to study the anterior and posterior areas of the eye. Since the procedure does not cause any harm to the body, it can be used repeatedly, monitoring the dynamics of the development of certain processes. An OCT study can be performed several times, with a short time interval. The procedure is prescribed regardless of age, type of disease and its stage.

OCT is a modern non-invasive procedure for studying ocular tissues

Optical coherence tomography of the retina, what is it? OCT is a big step in medical progress. The research methodology today has the highest “resolution”. Also, there is no long list of contraindications for the use of this examination method, and the examination itself does not cause pain. A timely procedure can diagnose pathologies associated with retinal diseases in the early stages. This allows treatment to begin when vision can still be saved.

When is the procedure prescribed?

OCT of the retina is prescribed to diagnose almost all diseases associated with the visual organ and pathological changes in the center of the retina. The main reasons for performing a tomography procedure may be the presence of the following diseases:

retinal detachment;
spread of fibrous tissue along the retina;
glaucoma;
complications of diabetes;
the appearance of ulcers on the cornea;
rupture of molecules.

With the help of the procedure, the doctor receives a real picture of the processes taking place. Based on the data obtained, he can easily adjust the treatment. The uniqueness of the technique allows us to identify a huge percentage of the disease that is asymptomatic in the first stages, as well as evaluate the effect of the therapy and procedures. Tomography is used to diagnose the following diseases:

changes in the retina associated with heredity;
injury outcomes;
examination of neoplasms, edema, abnormalities and atrophy;
the appearance of ulcers on the cornea;
formation of blood clots, ruptures and swelling.

The method is similar to ultrasound technology, but infrared radiation is used instead of ultrasound waves to study the condition of tissues

Carrying out the procedure

Before starting the procedure, the patient’s data is entered into a special card and loaded into a computer database. This allows them to be used to monitor processes occurring in the retina of the eyeball. The process itself consists in the fact that when using the device, the time during which the light beam reaches the examination area is set.

During the procedure, the patient must focus his vision on a special area, in the form of a flashing static point. The camera gradually moves closer to the pupil until a picture of the required quality appears on the screen. Then, the doctor conducting the examination fixes the device and performs a scan. At the final stage, the resulting image is cleared of interference and leveled. Based on the data obtained, you can make a starting point when prescribing treatment and recommendations.

During treatment, the specialist takes into account changes in the outer shell of the retina, as well as the degree of its transparency. Using optical tomography, it is possible to identify cellular layers that have thinned or, conversely, increased their thickness. Collection of such data can prevent the development of severe consequences in the later stages of the disease.

The result obtained during the study may have the structure of a table, with the help of which you can assess the real state of the structure of the eyeball and its environment. The technique is somewhat similar to ultrasound diagnostics. Optical coherence tomography uses infrared radiation to detect pathologies that cannot be diagnosed using other means. All data obtained as a result of research is stored in a computer database.

Optical tomography demonstrates the greatest effectiveness in studying pathologies of the retina and optic nerve

Using the optical tomography procedure, the following data can be obtained:

analysis of the effectiveness of treatment of the internal organs of vision;
determination of the angle of the external chamber of the visual organs;
assess the condition of the cornea after surgery, for example, after keratoplasty;
exercise control over the operation of the drainage system, which is prescribed to stop attacks of glaucoma.

Very often, when the procedure is first prescribed, people wonder, OCT of the retina, what is it? Optical tomography is a procedure for examining the fundus of the eye, where a specialist uses a laser device of the same name to obtain information. This is the only measure that allows you to read information about distant areas of the eye shell that were previously inaccessible. The image obtained as a result of the examination is highly clear, and due to the fact that the technique does not require direct contact with the retinal tissue, the risk of damage is reduced to zero.