Optical Coherence Tomography

Optical Coherence Tomography (OCT) is a non-invasive, advanced medical imaging technique that provides high-resolution, cross-sectional images of biological tissues. Since its introduction in the 1990s, OCT has been widely adopted in various medical fields, with ophthalmology being the most prominent. The technology has revolutionized eye care, allowing for the early detection, diagnosis, and monitoring of eye diseases. For example, age-related macular degeneration (AMD), glaucoma, and diabetic retinopathy.

The fundamental principle behind OCT is based on interferometry, which combines two or more light waves to produce an interference pattern. OCT employs low-coherence light with a broad spectral bandwidth to create high-resolution images of tissues. The technique involves sending a light beam into the tissue and measuring the reflected light’s echo time delay and intensity. The light is combined with a reference light to create an interference pattern. By analyzing these patterns, OCT generates detailed, three-dimensional images of the target tissue’s microstructure with a resolution of up to a few micrometres.

One of the main advantages of OCT is its non-invasive nature, as it does not require any contact with the tissue being examined. This is particularly beneficial in ophthalmology, where the delicate structures of the eye must be preserved. Additionally, OCT can image tissue in real-time, providing instant feedback to healthcare professionals and enabling prompt intervention if necessary.

In ophthalmology, OCT is commonly used to assess the retina’s structure, a critical part of the eye responsible for converting light into neural signals. The high-resolution images generated by OCT can reveal subtle changes in retinal layers, allowing for early detection and management of various eye conditions. For instance, OCT can help detect the presence of fluid or abnormal blood vessels in the retina, indicative of wet AMD, a condition that can lead to severe vision loss if left untreated.

Another application of OCT in ophthalmology is evaluating the optic nerve head, which is essential for diagnosing and monitoring glaucoma. By measuring the thickness of the retinal nerve fibre layer (RNFL), OCT can detect subtle changes in the optic nerve head structure, providing essential information for assessing glaucoma progression and the effectiveness of treatment.

In recent years, Optical Coherence Tomography has also been employed in other medical fields, such as cardiology, dermatology, and gastroenterology. For example, in cardiology, intravascular OCT (IV-OCT) can be used to visualize coronary artery walls, evaluate stent placement, and assess plaque morphology. In dermatology, OCT can aid in the early detection of skin cancers by providing detailed images of skin layers. Finally, in gastroenterology, OCT can be utilised to diagnose and monitor gastrointestinal conditions, such as Barrett’s oesophagus and inflammatory bowel diseases.