Optical Coherence Tomography (OCT) is a non-invasive imaging tool that allows eye care professionals to see detailed, high-resolution cross-sections of the structures at the back of the eye. This technology has become a standard part of modern eye care, enabling a deeper view into the retina and optic nerve than traditional examination methods. The ability to visualize the eye’s delicate layers has transformed the early detection and management of numerous vision-threatening conditions.
How Optical Coherence Tomography Works
Optical Coherence Tomography uses low-coherence light waves, typically in the near-infrared spectrum, to generate detailed images of the eye’s internal structures. The mechanism is often compared to an ultrasound, but the OCT device uses light to scan the tissue and measure how the light reflects off the different layers. This light is split into two beams: one directed into the eye and another traveling a fixed reference path within the machine.
The light reflecting back from the eye’s tissues is recombined with the reference beam, creating an interference pattern. This pattern allows the machine to precisely measure the time delay of the light from various depths within the retina. By analyzing these subtle differences, the OCT system constructs a two-dimensional, cross-sectional image of the tissue at near-microscopic resolution. This process is repeated across a scan area, ultimately building a high-resolution, three-dimensional digital map of the retina and optic nerve.
What to Expect During the OCT Scan
The OCT scan is a fast, non-contact procedure easily integrated into a routine eye examination. The patient sits comfortably in front of the machine, placing their chin in a rest and their forehead against a support bar to keep their head steady. The technician asks the patient to focus on a target light inside the device, ensuring the eye is correctly aligned for the scan.
The device directs an invisible, low-powered beam of light into the eye to perform the scan. The entire process is painless and typically takes only a few seconds per eye, with the total duration often less than ten minutes. While many modern OCT devices can scan without preparation, the professional may use dilating eye drops to widen the pupil and improve image clarity. If dilation is necessary, vision may be blurry and light-sensitive for a few hours afterward.
Critical Eye Conditions Detected by OCT
The precise, layer-by-layer imaging provided by OCT is transformative for diagnosing and managing several serious eye conditions affecting the retina and optic nerve. For example, in cases of glaucoma, the OCT scan measures the thickness of the Retinal Nerve Fiber Layer (RNFL) and the optic nerve head. Thinning in these structures often signifies early nerve damage before noticeable vision loss occurs, allowing for earlier intervention.
The technology is also indispensable in the diagnosis of age-related macular degeneration (AMD). OCT can identify and map the presence of drusen and detect fluid accumulation or swelling, a hallmark of the more severe “wet” form of AMD. Furthermore, OCT is used to monitor diabetic retinopathy, a complication of diabetes that damages the blood vessels in the retina. It is highly effective at detecting macular edema, which is swelling in the macula caused by leaking blood vessels, facilitating timely treatment to preserve central vision.