Purpose: To analyze the axial distribution of intraretinal cystoid changes in patients with retinal vein occlusion (RVO), incorporating a new hypothesis about the optical coherence tomographic boundary between the outer nuclear layer and the outer plexiform layer.
Methods: Data were collected from patients with RVO who underwent spectral domain coherence tomography imaging. For each image set, certified graders evaluated each retinal layer for cystoid macular edema, defined as hyporeflective intraretinal cystoid spaces. Subretinal fluid, if present, was also noted.
Results: Forty-eight eyes were evaluated (24 branch RVO, 18 central RVO, 6 hemiretinal vein occlusion). Cystoid macular edema was present in 30.8% of eyes in outer nuclear layer, 77.9 % in outer plexiform layer, 77.9 % in inner nuclear layer, 36.9 % in inner plexiform layer, 48.8 % in ganglion cell layer, and 4.9% in nerve fiber layer. Subretinal fluid was assessed as present in 23.8% of patients. The presence of subretinal fluid correlated most strongly with cystoid changes in the outer nuclear layer (r = 0.514, P = 0.001) but was not significantly correlated with these changes in the superficial retina.
Conclusion: Use of spectral domain coherence tomography allows precise characterization of the axial location of cystoid spaces in RVO and highlights the frequency of fluid accumulation in the outer plexiform layer and inner nuclear layer. Using updated definitions, cystoid macular edema seems to occur less frequently in the outer nuclear layer, but when it does so, it is often associated with subretinal fluid. Future longitudinal studies, documenting the axial progression of such changes, and their response to treatment, may be of clinical relevance as pharmacotherapeutic options evolve.