Optical coherence tomography (OCT for short) is a non-contact and precise method for examining the eyes. What sets OCT apart is its ability to provide a detailed image of the individual layers of the retina.
Below you will find further information as well as a selection of specialists in optical coherence tomography.
This laser-assisted procedure plays a very important role in the diagnosis of retinal diseases.
It is used in the following areas:
- Examinations of the macula (the area of sharpest vision)
- Optic nerve disorders such as glaucoma
Sections of the central retina: fovea, choroid, sclera, retina, macula @ rob3000 /AdobeStock
How optical coherence tomography works
Optical coherence tomography uses laser light to visually map tissue layers. Different layers reflect the incoming light in different ways. This principle of interferometry—that is, the analysis of the interference of light waves—makes it possible to calculate and visualize a cross-section of the tissue. This type of reconstruction is called tomography. Technically, the light beams in the OCT device are split into two paths by a beam splitter: one part is directed onto the retina, where the tissue is scanned point by point, and the other onto a reference path. The device uses the returning interference signal from both paths to calculate the deep structure of the tissue.
Unlike ultrasound diagnostics, which uses sound waves, OCT uses light and is therefore non-invasive.
The different tissue layers produce reflections at the interfaces because they differ in their refractive indices. The coherence length of the light source used determines the axial resolution, while the penetration depth depends on the wavelength. Modern high-resolution OCT devices thus achieve imaging resolution in the micrometer range. Image quality can be limited by highly scattering materials in the beam path, such as in the case of lens opacity.
Fundus examination and fluorescein angiography provide a “top-down view” of the retina and its structures. However, they do not show the three-dimensional structure of the tissue being examined.
This is where OCT comes into play. Coherence tomography does not strain the eye, and measurements through the vitreous humor are not impaired.
Advantages of Optical Coherence Tomography
Optical coherence tomography is suitable for visualizing the structures of the posterior segment of the eye and is therefore ideal for examining the fundus. It enables a microscopically precise imaging of the thin layers of the retina. It also allows for the exact measurement of the individual layers.
Thanks to its high sensitivity and measurement accuracy, the layered imaging of the retina enables the physician to detect even minor changes in the tissue at an early stage.
This enables the physician to take early action to prevent or slow irreversible damage to nerve cells.
Due to its high precision, ultra-high-resolution optical coherence tomography has revolutionized ophthalmology. Ophthalmologists can now examine tissue layers in vivo that they previously knew only from textbooks.
Compared to a confocal microscope, OCT—as a high-resolution imaging modality—offers the advantage of deeper tissue visualization combined with non-contact application.
Another distinctive feature of the procedure is its ability to visualize the anterior segment of the eye. This is particularly useful for the cornea (thickness measurement, placement of corneal grafts) and the anterior chamber angle (obstruction during a glaucoma attack).
Conducting the Examination
The examination is similar to a slit-lamp examination: The patient sits in front of the device with their head stabilized so that small movements do not distort the image. Since this is a non-contact examination, anesthesia is not necessary.
The doctor captures images, which he then reviews and evaluates.
Conclusion
Optical coherence tomography is an unrivaled procedure in ophthalmology. It enables the early diagnosis of serious conditions without causing any stress to the eye.
If age-related macular degeneration is diagnosed, health insurance covers the cost of the examination. OCT is also an important tool for the early detection of retinal damage in patients with diabetes. Otherwise, it is considered an IGEL service (individual health service), which the patient must pay for out of pocket.
Due to its significant benefits, the procedure has become indispensable in the diagnosis of retinal and optic nerve diseases. Furthermore, OCT has established itself as one of the most important imaging techniques in other medical fields as well.
In cardiology, intravascular optical coherence tomography is used to produce high-resolution images of the walls of coronary arteries. This allows for the assessment of plaques and verification of proper stent placement following coronary interventions.
OCT is also increasingly used as a complementary diagnostic method in dermatology, oncology, and angiology.
FAQ
How does OCT work?
In OCT, light waves are directed onto the retina. The reflected light is analyzed using an interferometer and reconstructed into a high-resolution cross-sectional image—a tomogram.
What is OCT used for?
OCT is used to examine the back of the eye and is particularly suitable for diagnosing retinal diseases and macular degeneration, as well as for monitoring the progression of glaucoma.
Is the examination uncomfortable?
No. OCT is a non-contact, high-resolution procedure that does not require anesthesia and does not cause any discomfort to the eye. The imaging takes only a few seconds.
Are the costs covered?
If age-related macular degeneration has been diagnosed, health insurance covers the costs. In all other cases, it is considered an individual health service (IGeL), which the patient must pay for out of pocket.
