Optical coherence tomography (OCT) is one of the imaging modalities and is used in ophthalmology to examine the retina (retina), vitreous, and optic nerve (optic nerve). It is a noninvasive, noncontact method of producing optical, two-dimensional cross-sectional images that have high spatial resolution.
Indications (areas of application)
- Macular hole – sharply defined destruction of the retina in the fovea of the macula lutea (yellow spot – site of the sharpest vision).
- Macular edema – swelling of the central retina in the area of the macula lutea [cash benefit for macular edema due to diabetic retinopathy/retinal disease].
- Macular degeneration (group of eye diseases affecting the macula lutea (“the point of sharpest vision”) – also called “yellow spot” – of the retina) [health insurance benefit for neovascular age-related macular degeneration (nAMD)]
- Epiretinal gliosis (synonym: macular pucker) – membrane formation between the retina (retina) and vitreous mostly in the area of the macula lutea, which can occur after intraocular (eg, surgery on the eye) interventions; vision is reduced and it comes to distortion vision; prevalence (disease frequency): 2 – 20% in the group of 70-80 year olds.
- Retinopathia centralis serosa – disease of the macula lutea with subretinal (under the retina) fluid accumulation and sudden loss of visual acuity.
- Assessment of postoperative findings
- Follow-up of disease processes
- Progress monitoring in glaucoma
- Unclear vision impairments
- Vitreous traction (lifting of the vitreous to the retina with possible damage).
The procedure
Optical coherence tomography works on the same principle as an ultrasound, except that instead of sound waves, a beam of light is used. Using what is known as low-coherence interferometry (an interferometer measures interference – superposition of light waves – to precisely measure distances, for example), the propagation delay of a laser beam is measured and evaluated in comparison with a reference beam. The laser beam is in the infrared range at approx. 830 nm. The reflected and backscattered light is detected and an optical, two-dimensional sectional image is calculated from it. Optical coherence tomography accurately depicts the following structures of the retina and eye:
- Nerve fiber layer
- Photoreceptor layer
- Retinal pigment epithelium
- Choriocapillaris – part of the choroid (choroid), which is directly adjacent to the retina.
- Sclera (sclera; only very conditionally).
- Cornea (cornea) – determination of corneal thickness.
- Iris
- Lens
This dataset can be imaged in real time in a false color scale or in grayscale. Highly reflective structures such as the nerve fiber layer, vessels, or retinal pigment epithelium are displayed in bright colors (e.g., white or red). Structures with intermediate reflectivity appear green, and elements that reflect very little light are black or blue. Optical coherence tomography is able to determine parameters such as nerve fiber layer thickness, retinal thickness, anterior chamber volume, and chamber angle. It allows precise detection of pathological (disease-related) changes. Especially in the early detection and follow-up of glaucoma (glaucoma: increased intraocular pressure leading to damage of the optic nerve), the procedure promises an improvement. Optical coherence tomography allows highly precise imaging of the smallest structures of the retina and is thus a valuable diagnostic procedure in ophthalmology. Further notes
- The GBA (Federal Joint Committee) has decided to include OCT for patients diagnosed with diabetic retinopathy (retinal disease) and a resulting macular edema (swelling of the central retina in the area of the macula lutea) in the benefit catalog of the statutory health insurance funds; the same applies to neovascular age-related macular degeneration (nAMD).
- OCT as a health insurance benefit should be provided at the earliest three weeks after intravitreal (“into the vitreous”) drug administration into the respective eye; at most once within 26 days and at most six times within twelve months after the last intravitreal drug administration.
