Abstract
Purpose :
XLRS is an inherited, early onset and progressively degenerative disease of the retina. The clinical hallmark of XLRS is the formation of cystic spaces in the plexiform and nuclear layers of the retina, predominantly within the macula. Studies in the mouse model of XLRS indicate that an additional, important element to the visual pathology in XLRS is an alteration in the function of the first synapse (photoreceptor to bipolar cell). Therefore, we used a clinical OCT system (Heidleberg Spectralis) and our custom adaptive optics (AO) OCT system to evaluate the schisis and structure of the outer plexiform layer (OPL).
Methods :
Clinical and AO OCTs were obtained from five subjects with XLRS. Repeat visits ranged from 1 to 9. One subject underwent carbonic anhydrase inhibitor treatment (dorzolamide) and has been followed for ~3.3 years with 9 OCTs at a median interval of ~4 months between tests. A range of clinical OCT scan densities were acquired, depending upon the cooperation of the subject: 49 to 241 B-scans consisting of 512 to 1,024 A-scans and covering 20°×20° to 30°×25° of central retina. An automated measure of central macular thickness was obtained. AO-OCTs included 512 B-scans consisting of 1,024 A-scans covering 8°×8° of central retina. The whole retina and the schisis therein were segmented from the volumetric OCTs using Materialise Interactive Medical Image Control System (MIMICS) software (Materialise USA, Ann Arbor, MI) and the total volume and other features were exported. In the AO-OCT images, the OPL was segmented, flattened, and displayed en face.
Results :
Retinal structures including schisis, connecting columns of retinal tissue, and the spoke-wheel pattern that is characteristic of XLRS, were well visualized using both AO-OCT and high-density clinical OCTs, but not more traditional OCTs. Measures of total schisis volume correlated well with clinical measures of central macular thickness. The OPL appeared mottled when viewed en face, suggesting disruption of the first synapse. In the patient who was treated with dorzolamide, schisis volume was markedly reduced after initiating treatment and persisted over time.
Conclusions :
Total retinal thickness by clinical OCT is a good measure of schisis volume. AO-OCT may be useful to monitor the status of the first synapse. The results from the dorzolamide treated patient show that dorzolamide can be effective in decreasing the volume of the schisis in XLRS.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.