Abstract
Purpose :
Limited information is available on the influence of diabetic macular ischemia on photoreceptor cone (CP) morphology and function. This cross-sectional, observational study assessed CP density and retinal sensitivity (RS) in ischemic and non-ischemic areas in eyes with diabetic ischemic retinopathy using adaptive optics OCT (AO-OCT) and microperimetry (MP).
Methods :
Ischemic and non-ischemic areas in 4 eyes of 4 patients (35 year old, male, type 1 diabetes; 38yo, female, type 1; 58yo, m, type 2; 60yo, m, type 2) were detected by analysis of the superficial and deep vascular plexus in 6x6mm SS-OCTA volumes (Plex Elite, Zeiss). CP morphology at height of the inner and outer photoreceptor segment junction (IS/OS) and at height of the cone outer segment tips (COST) was assessed with AO-OCT. CP density was assessed on 2x2 degree en face images by manual counting of 4 regions (150x150µm) per ischemic area and 4 regions (150x150µm) per non-ischemic area of same foveal eccentricity. Retinal sensitivity (RS) of ischemic and non-ischemic areas was then compared with MP (MP-3, Nidek) using custom grids. Paired t-test and Mann-Whitney U-Test was used for statistical analysis.
Results :
In AO-OCT, ischemic areas were sharply demarcated and showed severe alterations of the cone mosaic, including reduced reflectivity and distorted photoreceptor signals. In ischemic areas, mean photoreceptor density at IS/OS (9 000 ± 3 400/mm2) and COST (7 850 ± 3 200/mm2) was significantly lower than in non-ischemic areas of same foveal eccentricity (IS/OS 15 400 ±1 780/mm2; COST 13 900 ±1 700/mm2)(p-values <.001). Regarding retinal function, mean RS in ischemic areas (9,34 ±1,62 dB) was significantly lower than in non-ischemic areas (27,03 ±0,45 dB) (p-values<.001).
Conclusions :
Cone density and morphology are severely affected in regions of diabetic macular ischemia. These structural changes are accompanied by a significant reduction of retinal sensitivity, indicating the importance of preventing impaired capillary circulation in patients with diabetic retinopathy.
This is a 2020 ARVO Annual Meeting abstract.