The Relationship between Foveal Ischemia and Spectral-Domain Optical Coherence Tomography Findings in Ischemic Diabetic Macular Edema

Abstract

PURPOSE. To investigate the relationship between enlargement of the foveal avascular zone (FAZ) and structural changes on spectral-domain optical coherence tomography (SD-OCT) in patients with ischemic diabetic macular edema (DME).METHODS. This was a retrospective, cross-sectional study including 35 eyes of 33 patients with ischemic DME as determined by irregular margins of the FAZ in fluorescein angiography. We measured the best-corrected visual acuity (BCVA), central subfield thickness (CST), subfield volume, subfoveal choroidal thickness, length of the photoreceptor outer segment (PR-OS), and the lateral extent of inner segment-outer segment (IS-OS) disruption on SD-OCT images, as well as the FAZ to optic nerve head (FAZ/ONH) area ratio by using the ImageJ program. RESULTS.The mean FAZ/ONH area ratio was 0.28 6 0.15. The FAZ/ONH area ratio was positively correlated with the logarithm of the minimum angle of resolution (LogMAR) BCVA (P ¼ 0.001, r ¼ 0.529). The mean CST was 391 6 110 lm, and the subfield volume was 0.31 6 0.09 mm 3 . The mean length of the PR-OS and the horizontal and vertical extent of IS-OS disruption were 40 6 8 lm, 169 6 294 lm, and 114 6 170 lm, respectively. The mean length of the PR-OS and the horizontal and vertical extent of IS-OS disruption were significantly correlated with FAZ/ONH area ratio (P ¼ 0.020, P ¼ 0.001, and P ¼ 0.049, respectively). The horizontal and vertical extent of IS-OS disruption showed a positive correlation with LogMAR BCVA (P ¼ 0.027 and P ¼ 0.049, respectively).CONCLUSIONS. Foveal ischemia in DME appears to cause PR-OS shortening and IS-OS disruption resulting in outer retinal layer atrophic changes and subsequent visual loss. (Invest Ophthalmol Vis Sci. 2013;54:1080-1085) DOI:10.1167/iovs.12-10503 D iabetic macular edema (DME) is a leading cause of visual loss in diabetes patients. 1 In diabetic retinopathy, enlargement of the foveal avascular zone (FAZ) is often detected by fluorescein angiography (FA). 2 FAZ enlargement is considered an indication of ischemia and may contribute to macular edema. 3 Macular ischemia is also known to be associated with poor visual outcome in diabetic patients regardless of their treatment. 4,5 Recent technological advances in imaging have made it possible to analyze morphological changes of the retina in various retinal diseases. Optical coherence tomography (OCT) is an important tool being used to evaluate the retinal status and to predict the visual outcome. Several studies have investigated the correlation between structural changes in OCT and the visual prognosis in diabetic patients with macular edema.6-8 Spectral-domain OCT (SD-OCT) is the most recently developed type of OCT and provides high-resolution images with an axial resolution of <5 lm. SD-OCT therefore provides clearer structural information regarding the retina and helps to identify the pathologic mechanisms in various retinal diseases. 9-10The purpose of this study was to investigate the relationship between enlargement of the FAZ and structural changes in SD-O...

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