Optical Coherence Tomography

Optical coherence tomography, as the name suggests, is a technique that is used to obtain the cross-sectional images of the eye based on the principle of reflection. Until a few years back, ultrasonography was the only available test to visualize the inner structures of the eye. Optical coherence tomography (OCT) was introduced 25 years ago as an alternative diagnostic tool that enables detailed visualization of the retina. 

Optical coherence tomography (OCT) is a diagnostic tool that produces high-resolution images of the eye. It provides images of different layers of the retina, which is the innermost light-sensitive covering of the eye. The color-coded images of the retinal layers help in qualitative and quantitative analysis, which in turn helps in establishing the diagnosis of various conditions affecting the posterior segment of the eyeball.  

Imagine your eye is a cake, and all we can see is its surface. When we cut a slice with a knife, we can see multiple layers of the cake. OCT is a non-invasive tool that takes multiple slice scans of the eye enabling visualization of all layers of the retina. Here in this article, we will discuss the details of optical coherence tomography, its indication, benefits, and limitations associated with it. 

Variations of OCT

In comparison to other ophthalmic investigative tools, OCT is a relatively new technology. Before OCT, diagnosis of conditions associated with the posterior segment of the eyeball was possible only if there was significant damage. In contrast, OCT can determine even minor changes in the retinal layer and disruptions of other structures within the posterior part of the eyeball, thereby allowing early diagnosis and timely intervention. Based on the image scanning speed and resolution, OCT is mainly of two types:

Time Domain OCT

Time domain OCT provides two-dimensional images of the retina using a fixed wavelength of light to produce cross-sectional images. It scans at a high speed providing hundreds of scanned cross-sections of the retina in one second.

Fourier Domain OCT

Fourier domain OCT is a widely used OCT in eye clinics that provides both two-dimensional and three-dimensional images of the retina using a broad wavelength spectrum of light to obtain multi-layered images. It can provide thousands of scanned cross-sections of the retina in just one second and with better resolution. Recent advances in optical coherence tomography have brought in additional features as well. Different types of available OCT systems include ultra-high resolution OCT, Doppler OCT, intraoperative OCT, and many more. OCT software takes hundreds of scans of the posterior segment of your eye and converts those scans into multi-layered images. This image can illustrate minute details regarding your eye health.

Conditions Diagnosed By OCT

OCT has brought a remarkable change in ophthalmic practice as a modern OCT machine helps obtain high-resolution two-dimensional and even three-dimensional scans. It is extremely useful in detecting early pathological changes in the retina by analyzing the minute differences in the anatomical cross-sections of the eyes. 

OCT is a highly recommended test for high-risk patients with glaucoma, diabetes, or other chronic eye conditions. Many eye conditions can be diagnosed by optical coherence tomography including: 

  • Cystoid Macular Edema (CME)
  • Central Serous Retinopathy (CRS)
  • Retinal detachment
  • Epiretinal membrane
  • Glaucoma
  • Foveal burn
  • Age-Related Macular Degeneration (ARMD)
  • Diabetic retinopathy
  • Macular hole
Wanna know your Optical Coherence Tomography options?
What Can You Expect While Undergoing Optical Coherence Tomography?

Like any other ophthalmic investigating tool, OCT is a machine with built-in software that converts eye images into virtual data. Usually, dilating eye drops are applied on both eyes prior to the procedure to enable better visualization. 

1. The patient will be asked to keep their chin on the chinrest and forehead against the forehead rest. The examiner then uses a knob to adjust and align the patient’s eye with the mark on the device. The patient will be asked to sit still and focus their eye on a laser light source emitted from the device. 
2. The examiner then takes hundreds of cross-sectional scans of the patient’s eye. The display unit shows software-assembled scans into a single, multi-layered image with red, green, and yellow color-coded structure. The whole process takes no more than ten minutes.
3. The vision may stay blurry for a few minutes after the test due to the remaining effect of dilating eye drops. 
Advantages of Optical Coherence Tomography

While there are no comparable alternatives to provide cross-sectional images of the eyes, there are other tests as well that can diagnose the conditions detected by OCT. OCT is superior to other tests due to its ability to detect subtle changes. Some advantages of optical coherence tomography over other diagnostic tests are:

Identifies earliest signs of diseases
Minimal patient compliance required
Real-time imaging of retinal layers
Provides qualitative and quantitative details
No direct eye contact
No radiation hazard

Limitations of Optical Coherence Tomography

There has been rapid development in many features of OCT since it was initially developed. Nevertheless, due to the principle by which it works, any hindrance between the device and the retina by cataracts, corneal opacities, corneal edema, and vitreous hemorrhage can hinder image quality.

The Takeaway

Optical coherence tomography or OCT is a diagnostic tool that provides cross-sectional images of the eye. It gives real-time images of the retina including details on the thickness and other pathologies. OCT scans can also help identify early signs of eye conditions associated with the posterior segment of the eyeball such as glaucoma and diabetic retinopathy. OCT is a convenient test for both examiner and patient to undergo. Currently, there are no other available non-invasive alternative tools with similar functions and quality of results as OCT. 

Wanna know your Optical Coherence Tomography options?

Our cataract surgeon in New York has extensive training and experience in laser cataract surgery to help you regain clearer vision and start your journey to a higher quality of life.
Contact Us