Cornea and Retina: What Optical Coherence Tomography is for
Eye health is essential for a complete and fulfilling life at any age. The eye functions like a camera, and two of its components, the cornea – the most important ocular lens- and the retina – the tissue involved in the perception and initial image processing – are essential.
Properly preserving the health of the cornea and retina, therefore, is a critical step in ensuring a person’s well-being.
One diagnostic test has become crucial in the last decade to learn about and maintain healthy cornea and retina – Optical Coherence Tomography (OCT).
What is OCT?
Optical Coherence Tomography (OCT) is a non-invasive, well-tolerated, laser light-based diagnostic examination that allows the creation of virtual sections, and thus the study of the anatomy in micrometer detail, of essential eye structures. In particular, it helps evaluate the retina, cornea, and optic nerve.
What is OCT used for?
A highly reliable, safe, and extremely accurate examination, Optical Coherence Tomography has become an everyday and indispensable tool for obtaining scans—that is, cross-sectional images—of the cornea and retina. These allow detailed analysis (shape, thickness, and condition) of the cornea, retina, and optic nerve. This approach has revolutionized the diagnosis and monitoring of multiple retinal diseases.
OCT finds particular application in the study of diseases involving the macula, the central region of the retina that enables fine vision – reading and face recognition – and the optic nerve, the “electrical cable” that carries images from the eye to the brain. Digitizing the images allows OCT to study changes in these structures over time, building differential maps and time trend graphs of tissue thickness values.
When is OCT performed?
OCT is a key examination for the recognition of many diseases affecting the cornea, retina, and optic nerve, such as:
- Keratoconus is a genetic disorder in which the cornea spontaneously changes curvature and thins, with progressive deterioration of its function as the lens of the eye system.
- The epiretinal membrane (macular pucker), which is the presence of fibrous-scar tissue on the surface of the macula. This scar, as it contracts, results in distortion of the macula with, as a result, impaired vision. Specifically, patients report distortion of images, particularly straight lines, and/or loss of the ability to distinguish details of an object; blurred and distorted vision, which generates progressive difficulty in reading and vision in the distance. In the early stages, pucker is often asymptomatic, and over time the complaints may remain stable or gradually worsen. Once diagnosed, it is therefore important to keep the epiretinal membrane under control, with eye examinations and OCT performed at regular intervals. OCT digitization allows the creation of differential maps that immediately detect whether the disease is progressing or stable. If symptoms worsen, impacting the patient’s quality of life, an ophthalmologist can surgically remove the membrane.
- Diabetic retinopathy. Diabetes is essentially a vessel-altering disease, so richly vascularized organs, such as the eye and kidney, are most heavily affected. Diabetic retinopathy is among the most frequent illnesses that can cause significant vision loss in Western countries. Damage to the walls of the small retinal blood vessels leads to losing their ability to retain fluids, resulting in extravasation of fluid, protein, and fat into the retinal tissue.
- Age-related macular degeneration (AMD), which is the deterioration of the macula seen in some patients due to the natural aging process, affects everyone over sixty. This disease can present in mild form, without affecting vision, or very severe forms, resulting in the loss of central vision in one or both eyes. AMD can present with features of atrophy (“dry” form), characterized by the disappearance of visual tissue and intraretinal accumulation of small deposits called drusen, with disruption and thinning of the retinal layers. These cause a progressive and nonreversible reduction in visual function, usually over many years. The patient perceives a central area in the visual field where vision is not possible. Alternatively, AMD may be exudative (“wet” form), characterized by the emergence at the macula of reticulations of new and abnormal blood vessels, which are more fragile than usual, leading to an overflow of fluid or actual hemorrhages within the retina with consequent damage to its tissue. The dry form can progress into the wet form, which is more aggressive and rapid in terms of progressive loss of central vision.
Why is a collaboration between an orthoptist and an ophthalmologist important?
The incredible diagnostic potential of OCT has expanded its applications in ophthalmology, increasing the number of examinations performed. Collaboration between an orthoptist technician and an ophthalmic physician makes it possible to take full advantage of the possibilities offered by OCT.
The orthoptist is responsible for performing the examination and selecting the most appropriate images for understanding the patient’s disease, while the ophthalmologist evaluates the images and proceeds with the reporting.