Correlation Between Visual Function and Photoreceptor Integrity in Diabetic Macular Edema: Spectral-Domain Optical Coherence Tomography

Purpose: To evaluate the relationship between visual function and (i) microstructural changes in the fovea of the inner segment-outer segment junction (IS/OS) and (ii) external limiting membrane (ELM) in diabetic macular edema (DME). Methods: We conducted a retrospective, observational, cross-sectional study of 40 DME patients (61 eyes), all of whom had been treated at Shanghai First People's Hospital. Patients were divided into groups based on integrity of the IS/OS or ELM: IS/OS (+, +/- and ) and ELM (+, +/- and ). We performed best-corrected visual acuity (BCVA), MP1 microperimetry and spectral-domain optical coherence tomography (SD-OCT) on all patients. Several variables, including IS/OS and ELM integrity, central macular thickness (CMT) and central macular volume (CMV), were evaluated by two observers, each masked to patients' BCVA. Main outcome measures included determination of the association of visual function with SD-OCT results. Results: Significant differences were found between IS/OS (+), IS/OS (+/-) and IS/OS (-) groups in BCVA (66.88 +/- 7.89, 51.60 +/- 9.39, 32.64 +/- 17.93 letters, p<0.001); macular sensitivity (MS; 8.21 +/- 2.91, 3.55 +/- 2.75, 2.72 +/- 1.86 dB, p<0.001); fixation stability within 2 degrees (82.09 +/- 12.76, 66.43 +/- 29.54, 33.73 +/- 29.51%, p<0.001); and % central fixation (74.87 +/- 16.88, 61.39 +/- 31.38, 31.64 +/- 31.89%, p<0.001); but no differences were found for CMT (p = 0.069) or CMV (p = 0.069). Results were similar for ELM groups. There were significant differences between ELM (+), ELM (+/-) and ELM (-) groups in BCVA (64.16 +/- 9.49, 50.44 +/- 9.83, 32.73 +/- 17.98 letters, p<0.001); MS (7.54 +/- 3.22, 3.38 +/- 2.38, 2.20 +/- 1.72 dB, p<0.001); fixation stability within 2 degrees (81.48 +/- 15.26, 61.12 +/- 31.63, 35.00 +/- 29.07%, p<0.001); and % central fixation (75.90 +/- 17.33, 55.88 +/- 30.94, 30.09 +/- 33.00%, p<0.001); but not for CMT (p = 0.216) or CMV (p = 0.202). There was a strong correlation (r = 0.881, p<0.001) between ELM and IS/OS integrity for the same patient. Categories of IS/OS showed more severe changes than did those of ELM. Conclusions: Both IS/OS and ELM integrity correlated positively with visual function in DME patients. Further studies are needed to confirm and validate this relationship.