Association between photoreceptor integrity and visual outcome in diabetic macular edema

To investigate the correlation between foveal photoreceptor integrity and final visual acuity (VA) after treatment of eyes with diabetic macular edema (DME), and to determine the visual prognostic factors.

We retrospectively studied 61 eyes of 52 patients with DME who were treated successfully with intravitreal triamcinolone injection (IVTA). Using spectral domain optical coherence tomography (SD-OCT), the eyes were categorized into three groups at the final visit according to restoration of the photoreceptor inner and outer segment junction (IS/OS) and the external limiting membrane (ELM): (1) the A group, with a completely visible IS/OS and ELM, (2) the B group, with a disrupted IS/OS and intact ELM, and (3) the C group, with a disrupted or loss of the IS/OS and ELM. Disrupted IS/OS length (DIL), disrupted ELM length (DEL), and mean disrupted IS/OS and ELM length (DIEL) were measured at the initial and final visits. Foveal thickness (FT), macular center thickness (MCT), and outer nuclear layer (ONL) thickness were also measured at the initial and final visits. Multivariate analysis testing was performed over the measured SD OCT variables.

Final VA was closely associated with IS/OS integrity at the final visit; final VA (logMAR) in the A group (0.21 ± 0.14; 31 eyes) or B group (0.31 ± 0.21; 15 eyes) was significantly better than that in the C group (0.45 ± 0.33; 15 eyes) (p < 0.001). Shorter DIL, DEL, and DIEL at the final visit were associated with better final VA. Multivariate analysis showed that DIEL (r = 0.564) have the greatest correlation coefficient with final VA compared to DIL (r = 0.561) and DEL (r = 0.540). Better VA, preservation of the IS/OS and ELM at the initial visit were associated with intact photoreceptor integrity after resolution of DME. However, MCT, FT, and ONL thickness had no significant correlation with photoreceptor integrity.

IS/OS and ELM are useful hallmarks for use in evaluation of foveal photoreceptor layer integrity, and are closely associated with final VA in DME. Pretreatment VA and photoreceptor status can predict potential restoration of photoreceptor integrity and subsequent visual recovery in DME.