Purpose: To review basic principles of optical coherence tomography, and to describe its use in the diagnosis and management of retinal diseases and glaucoma.
Methods: Literature review.
Results: Optical coherence tomography is a noninvasive imaging technique that has been used increasingly to diagnose and manage a variety of retinal diseases and glaucoma. Optical coherence tomography (OCT) is based on the principal of Michelson interferometry. Interference patterns produced by low coherence light reflected from retinal tissues and a reference mirror are processed into an "A-scan" signal. Multiple A-scan signals are aligned to produce a two-dimensional image that can be thought of as a form of "in vivo histology." Optical coherence tomography has been used to identify macular holes, to differentiate macular holes from simulating lesions, to identify lamellar macular holes, macular cysts, vitreomacular traction, subretinal fluid, pigment epithelial detachment, and choroidal neovascularization. It can be used to identify and quantify macular edema, and to measure retinal thickness changes in response to therapy. Macular thickness measurements determined by OCT correlate well with visual acuity and with leakage observed by fluorescein angiography. Optical coherence tomography is an accurate and reproducible method to measure retinal nerve fiber layer thickness. Particularly, when used in combination with other optic nerve imaging techniques, it can be used to differentiate glaucomatous eyes from normal eyes. Despite its usefulness, OCT has its limitations. Optical coherence tomography equipment is expensive, and not all insurance companies reimburse this procedure. Image quality is dependent on operator technique and can be degraded in the presence of media opacity. Change analysis software for glaucoma applications is not fully developed, and there is a scarcity of age, gender, and race-specific normative data upon which to compare eyes with retinal disease and glaucoma. In the next few years, it is likely that the role of OCT as a method to diagnose and manage retinal disease and glaucoma will be further defined, and many of the current limitations will be overcome.
Conclusions: Optical coherence tomography is a useful imaging technique to diagnose and manage a variety of retinal diseases and glaucoma. Care is needed to avoid artifacts and image misinterpretation.