Abstract and Introduction
Uveitis is a challenging disease. It represents a major cause of ocular morbidity worldwide. More than half of all patients with uveitis develop sight threatening complications related to their disease, and up to 35% of patients suffer severe visual impairment.[1,2] Uveitis and its complications are responsible for 5% to 10% of all causes of legal blindness in developed countries.[1,3] The causes of uveitis are numerous, and include infectious conditions, autoimmune diseases, trauma, and tumors (masquerade syndrome). To develop an accurate differential diagnosis, clinicians must consider all available information, including the patient history, anatomic location of the inflammation (anterior or posterior), character (granulomatous vs. nongranulomatous), laterality, and chronicity of inflammation. Moreover, diagnostic tools, such as fluorescein angiography (FA), indocyanine green angiography, optical coherence tomography (OCT), and ultrasound, play an important role in the diagnosis and in the management of the uveitis.
Until recently, fluorescein FA was the primary imaging modality used to detect macular edema and other features related with uveitis like choroidal neovascularization and serous retinal detachment. Although FA is useful for determining the presence of vascular leakage, this technique does not provide any 3-dimensional anatomic information about the retinal layers, the retinal pigment epithelium (RPE), or the choroid. The development of OCT makes it possible to have high-resolution cross-sectional images of the retina or optic nerve.
OCT is now proven to be an effective noninvasive method in detecting pathologic features in uveitis and is rapidly gaining popularity as an ancillary exam. It may be used to assist in the diagnosis of uveitis and may be repeated safely during follow-up to monitor response to any intervention.[5,6]
Recently, the introduction of spectral domain optical coherence tomography (SDOCT) has improved image quality. Spectral domain, a type of Fourier domain detection, uses a high-speed spectrometer to measure light echoes from all time delays simultaneously enhancing OCT capabilities. The reference mirror does not require mechanical scanning. Improved sensitivity enables dramatic improvements in sampling speed and signal-to-noise ratio.[7,8] SD detection, coupled with improvements in light sources, achieves axial scanning speeds of >20,000 A-scan/s with an axial resolution of 3 to 7 μm in the eye. Consequently SDOCT has the advantage of detecting small changes in the morphology of the retinal layers and subretinal space, allowing for precise anatomic detection of microstructural changes that may correspond to progression or regression of chorioretinal lesions or complications secondary to uveitis. In addition, SDOCT is also used for anterior segment imaging where it may illustrate features of anterior uveitis and its complications.
This review focuses on SDOCT imaging in uveitis. It will first review OCT imaging in anterior uveitis; then, it will describe the image features observed in the posterior uveitis.
Int Ophthalmol Clin. 2012;52(4):33-43. © 2012 Lippincott Williams & Wilkins