OCT explained: the scan that changed eye care

Optical coherence tomography (OCT) is a noninvasive scan that creates cross sectional images of eye structures. It is widely used for retina care and for glaucoma monitoring. The scan is fast, does not touch the eye in most systems, and produces high resolution maps that are easy to compare over time.

OCT is sometimes described as an MRI like scan for the eye. The useful part of the analogy is that it reveals layers. The difference is that OCT is optical and uses light, which allows very fine detail of transparent tissues.

Retina disease often involves fluid, swelling, or subtle layer disruptions that are difficult to measure by symptoms alone. OCT makes these changes visible and quantifiable, which supports earlier detection and more precise monitoring.

A common pattern is that visual acuity can remain relatively stable while structure is changing. OCT helps detect that mismatch. It also helps distinguish between different causes of blur and distortion, which can alter the treatment plan.

A single scan is a snapshot. A series of scans creates a trend line. Many decisions in glaucoma and macular disease depend on whether change is occurring, how fast, and whether treatment is modifying the trajectory.

This is why clinics often emphasize follow up intervals and repeat imaging. The scan is not being repeated because the first scan was wasted. It is being repeated because progression detection is inherently a time series problem.

OCT is not a full diagnosis by itself. It is one input. Image artifacts, poor fixation, media opacity like cataract, and segmentation errors can create misleading outputs. That is why interpretation and correlation with the clinical exam still matter.

It is also common to over interpret small differences. Some scan to scan variability is normal. A good clinician looks for consistent change across time and across related measures, rather than reacting to one number.