Association of Retinal Sensitivity to Integrity of Photoreceptor Inner/Outer Segment Junction in Patients with Diabetic Macular Edema

Purpose: To evaluate the relationship between retinal sensitivity and the photoreceptor inner segment/outer segment (IS/OS) layer status in patients with diabetic macular edema (DME). Design: Cross-sectional study. Participants: Twenty-five adult patients (37 eyes) diagnosed with DME and managed at the Wilmer Eye Institute, Johns Hopkins University (Baltimore, MD). Methods: We obtained simultaneous fundus microperimetry (MP) and optical coherence tomography (OCT) of patients with DME using a combined MP/OCT system. The device recorded retinal sensitivity and retinal thickness on a 3-dimensional tomography map, and we performed a point-by-point analysis of the IS/OS layer integrity at every MP point. We also reviewed OCT scans to determine the type of DME, cystoid macular edema, or diffuse macular edema (absence of any cysts). In addition, fixation stability and fixation location were analyzed. Main Outcome Measures: Retinal point sensitivity measured by MP. Results: Twenty-five patients (37 eyes: 29 male and 8 female; mean age, 64.16 years) with DME were enrolled. Fixation was centric in 30 eyes (81%), paracentric in 3 eyes (8%), and eccentric in 4 eyes (11%). Twenty-seven eyes had cystoid macular edema, and 10 eyes had diffuse macular edema. Mean central subfield thickness was 325 mu m. We analyzed a total of 1036 individual MP points. Mean point sensitivity was 10.51 dB. A total of 793 points (76.5%) had IS/OS layer present, and 243 points (23.5%) had IS/OS layer disrupted. A mixed linear model, constructed to adjust for potential confounders and account for dependence between retinal points, revealed that the absence of the IS/OS junction was significantly associated with a 3.28-dB decrease in retinal point sensitivity (P < 0.001). Conclusions: This novel index study demonstrates that disruption of the IS/OS junction is correlated with a significant decrease in point sensitivity in eyes with DME. Further studies are indicated to confirm and validate this relationship. (C) 2013 by the American Academy of Ophthalmology.