April 18, 2017
Optical Coherence Tomography (OCT) is a non-invasive optical technology that is used to map the image of the retina and also determine its level of thickness. This is essentially done in order to understand the causal effects of many of the eye-related diseases, primarily Glaucoma, Age Related Macular Degeneration (AMD) and diabetes related eye problems. Optical Coherence Tomography is based on the principle of White Light or Low Coherence Interferometry. The ability of OCT technique to clearly deliver a retinal scan or retinal imaging is because it is based on light principle rather than sound or radio frequency. The production of live surface images at microscopic level and redundancy in preparation of sample before testing and non-ionizing radiation make OCT one of the most popular techniques for ophthalmologists. However, it also suffers from a certain drawback. Because OCT is based on interference of light, dense cataracts and bleeding in vitreous conditions render the effect of OCT ineffective.
There are two methods of OCT, namely Time-domain and Spectral Domain. In the case of time domain, the technique acquires around 400 A-scans per second using 6 radial slices pointed 30 degrees away from each other. In Spectral domain, OCT scans just about 20,000-40,000 scans each second. The elevated scan rate and number reduces the possibility of motion object, improves the resolution and reduces the possibility of missing lesions. OCT is gaining much recognition when assessing optic nerve disorders like glaucoma. OCT can precisely and consistently estimate the layer thickness of the nerve fiber.
The preparation before an OCT test is relatively simple. The ophthalmologist puts dilating eye drops in the eyes of the patient. These drops dilate the pupil and make it easier to examine the retina. The patient sits in front of the OCT machine and rests his head on the mouthpiece. The equipment then scans the eye without touching it. Scanning takes about 5- 10 minutes.
Disclaimer: The information given in this write-up is purely for educating the reader. It is not meant to be a substitute for any advice from a medical expert.