Clinical associations between photoreceptor status and visual outcomes in diabetic macular edema

Abstract

Aim: to investigate morphological changes and visual acuity response to ranibizumab therapy in patients with different OCT-types of diabetic macular edema (DME) as well as different state of the inner and outer photoreceptor segments (IS and OS) and the outer limiting membrane (OLM); to study relationships between functional and morphological parameters before and after the treatment; to study the effect of glycated hemoglobin levels on morphological parameters and ME duration. Material and methods: The study included 113 patients (113 eyes) with DME, who underwent 3 once-monthly intravitreal injections of ranibizumab (the mean patient age, 63.5±2.2 years; men, 51.3%; type 2 diabetes, 81.4%). Basing on the results of OCT, 3 groups were formed: group 1 (40 patients) - intact IS and OS; group 2 (32 patients) - disturbed photoreceptor segments integrity, but intact OLM; group 3 (41 patients) - destruction of both layers. Results: Visual acuity at baseline and after the treatment was the highest in group 1 (p<0.05). In all groups, most parameters that indicated the state of photoreceptor segments and the OLM improved. Correlation analysis revealed a statistically significant negative correlation between visual acuity at baseline and after the treatment and morphological parameters (p<0.05). There was also a direct correlation between the morphometric parameters at baseline and after the treatment (p<0.05). The most favorable type of DME in terms of preserving the integrity of photoreceptor segments and the OLM was sponge-like edema, while DME with neuroepithelial detachment and mixed-type DME were prognostically unfavorable. Moreover, the state of photoreceptors and the OLM depended on the duration of ME and the level of glycated hemoglobin. Thus, the integrity of the inner and outer photoreceptor segments as well as the outer limiting membrane can contribute to prognosis for functional outcomes in DME patients that receive antiangiogenic therapy.