The eye is a very sensitive and complex organ that consists of several different intricate structures. Spectral-domain optical coherence tomography, often abbreviated to SD-OCT, therefore provides a unique method for ophthalmologists to observe retinal structure that is key to the diagnosis of injury and disease during eye examinations.
Key advantages of SD-OCT include the non-contact and non-destructive approach to observing the eye, a very high imaging resolution, and its ability to be performed quickly, without any special patient prep. It is perhaps the easiest medical imaging test that a patient can take and it only lasts about 5 minutes.
Ophthalmologists commonly divide the eye into two parts: the front of the eye, known as the anterior segment, and the area behind the lens, the posterior segment. Imaging these two segments with spectral-domain optical coherence tomography requires different wavelengths in the infrared region to probe the eye perfectly. For example, the cornea, part of the anterior segment, is examined with 800 nm wavelength in proximity to the surface while 1300 nm wavelength is suitable for deeper anterior structures such as the lens. Examination of the anterior segment is crucial for treatments of diseases such as glaucoma and cataracts. The main parts of the posterior segment are the retina, macula, and optic nerve. By means of spectral-domain optical coherence tomography, high resolution details of the retina may also be obtained with 800 nm wavelength, while a wavelength of 1050 nm is suitable for examinations of the optic nerve. Examining the posterior region is relevant in the diagnostic of age-related macular degeneration (AMD) which is a leading cause of vision loss in elderly people.
Although spectral-domain optical coherence tomography is already a common instrument in ophthalmology, recent approaches aim at even higher resolution and higher imaging speed for better diagnostics, monitoring, and treatment of eye conditions. Ultra-high resolution ophthalmic imaging on the cellular level is already on the way. It would mark a major step forward in ophthalmology when it comes to clinical use for the detection of early-stage ocular disease.
Ultra hi-resolution SD-OCT imaging of the cornea is being explored by Dr. Kostadinka Bizheva at the University of Waterloo as a future method to advance disease diagnosis & treatment.