Purpose: To compare retinal sensitivity and central retinal thickness in patients with focal diabetic macular edema (DME) and edema secondary to branch retinal vein occlusion (BRVO).
Methods: In this consecutive, cross-sectional, observational study, patients with either DME or BRVO underwent measurements for best-corrected visual acuity, microperimetry, and spectral domain optical coherence tomography. Retinal thickness and sensitivity were measured using Optos Spectral optical coherence tomography/scanning laser ophthalmoscopy (Optos plc, Dunfermline, Scotland, United Kingdom). Areas defined as abnormal demonstrated edema with clearly defined cystic spaces. Abnormal and control areas were compared in mean retinal sensitivity and mean retinal thickness for both conditions.
Results: Twenty eyes with focal DME and nine eyes with BRVO were included. In DME, mean retinal thickness was 413.6 ± 84.5 μm and 291.7 ± 36.7 μm in abnormal and control areas, respectively. Mean retinal sensitivity was 10.22 ± 4.23 dB and 12.25 ± 3.57 dB, respectively. In BRVO, mean retinal thickness was 491.4 ± 102.9 μm and 315.9 ± 29.9 μm in abnormal and control areas, respectively. Mean retinal sensitivity was 6.36 ± 5.47 dB and 13.05 ± 2.28 dB. In DME, a decrease in retinal thickness of 0.341 μm correlated with 1 dB reduction of retinal sensitivity, although this was not statistically significant (P = 0.717). In BRVO, however, an increase in retinal thickness of 9.702 μm correlated with 1 dB reduction of retinal sensitivity (P = 0.001).
Conclusion: In BRVO, an increase in retinal thickness corresponded with a significant reduction in retinal sensitivity; in DME, however, there was no significant correlation between retinal thickness and retinal sensitivity. Further study is required to assess why this is the case. The Optos Spectral optical coherence tomography/scanning laser ophthalmoscopy allows for a reliable point-to-point correlation, as microperimetry and spectral domain optical coherence tomography can be performed in the same device.