Optical Coherence Tomography (OCT) in ophthalmology is an emerging technology and is used to obtain high-resolution cross-sectional images of the nerve layer on the inside of the eye, the retina. It is a non-invasive imaging technology. This technology provides images on the micron scale in real time. The retinal layers can be differentiated, and the thickness of the retina can be measured with optical coherence tomography.

With the help of such sharper and clearer results, an ophthalmologist can detect and diagnose various retinal diseases and also emerging problems early. With the latest swept-source technology faster images can be obtained and even the structures behind the retina, ie. choroid (vascular layer of the eye) can be visualised.

Very few centres in the country have acquired OCT angiography, which is a no dye, no injection technology used to analyse blood flow in the retina and choroid. Since this technology does not involve injection of a dye, complications related to dye injection like anaphylaxis (severe allergic reaction), vomiting etc are totally obviated. This technology is especially useful in  evaluation of patients with kidney disease who are not suitable for fluorescein dye injection.

Swept source OCT with OCT angiography machine

Swept source OCT with OCT angiography machine

Today, optical coherence tomography has become the most comfortable and standard procedure for the assessment, diagnosis, and treatment of several retinal and uveal  conditions and glaucoma. This technology uses light rays to measure the thickness of the retinal tissues. In the OCT scan, no X-rays or radiations are used. It is a non-contact scan and therefore it does not hurt nor does it make patients uncomfortable. It can be acquired in less than a minute.

Optical Coherence Tomography during an Eye Examination

Optical Coherence Tomography helps ophthalmologists to view the anatomical structures of the back of the eye. With this technology, an eye professional can take clear and detailed images of the various structures situated at the back of the eye including retina, optic nerve, macula, and choroid. It works by using interferometry which enables an ophthalmologist to image the tissue with the help of a beam of light directed into the eye. Some part of this shining light is reflected by different eye tissues. On the basis of this, images are built.

OCT scan in progress

OCT scan in progress

Uses of Optical Coherence Tomography

Your eye doctor may advise you for an Optical Coherence Tomography scan for a plethora of reasons which include:

  • Diagnosis of various eye conditions like a macular hole, macular oedema, macular pucker, glaucoma, age-related macular degeneration, central serous retinopathy, vitreous traction, diabetic retinopathy, etc.

  • Monitoring of eye diseases like uveitis.

  • Discounting or verifying suspected retinal swelling.

  • To check the effectiveness of the given medication regime.

  • To check or compare OCT results against visual acuity.

  • In recent times, Optic Coherence Tomography is used in graft assessment after corneal surgery.

  • OCT is also used to evaluate the conditions related to the optic nerve as a scan to observe changes to the fibres of the optic nerve.

Indications of Optic Coherence Tomography

The indications of Optic Coherence Tomography have increased during the past few decades. Recently, OCT is widely used in various ophthalmic diseases which affect retina of the eye, the angle of the eye, uvea (vascular middle layer of the eye) and cornea. The non-contact nature and high acquisition speeds of this new technology offer a wide range of quantitative and qualitative information. With Optical Coherence Tomography imaging clear and detailed images of in-vivo examination of human eyes can be obtained.

For Optical Coherence Tomography, the dimension of the cataract along with its shape, the intraocular lens position, the posterior capsular bag, and the incision healing have become the new potential targets. Also, OCT and OCT angiography have given insights into the study of natural history of diseases of the retina and pathophysiologic mechanisms of healing in diseases of the choroid. Thus, OCT is a promising technology which can help ophthalmic research as well as clinical practice.

Dr. Raja Rami Reddy P

Dr. Raja Rami Reddy P

MD FRCS (Glasg), Chief Retina Surgeon, Founder & Medical Director at Neoretina
Dr. Reddy is a renowned specialist in retinal surgery with more than 20 years’ experience in the field. He is the Founder, Director and Chief Retinal Surgeon at NEORETINA Eyecare Institute, Hyderabad, which is a foremost referral centre for diseases of the Retina. His areas of expertise include Surgical Retina especially complicated vitreo-retinal surgeries for retinal detachment, vitreous hemorrhage, advanced diabetic retinopathy, macular holes and epiretinal membranes. He studied MBBS and MD at the prestigious All India Institute of Medical Sciences, New Delhi and was a Specialist Registrar at the Vitreo-Retina Department of the reputed Dr. Rajendra Prasad Centre for Ophthalmic Sciences, AIIMS, New Delhi. He is a member of the American Society of Retinal Surgeons and is an active member of the state and national academic societies.
Dr. Raja Rami Reddy P