Topographic Correlation of Microperimetry With Structural Characteristics in Diabetic Macular Ischemia

This study aimed to determine the threshold for defining abnormal retinal sensitivity (RS) that correlates with structural changes in diabetic macular ischemia (DMI) patients with stable treated proliferative diabetic retinopathy (PDR).

Prospective cross-sectional study.

In a single center, we recruited 85 eyes (67 patients) with stable treated PDR with best-corrected visual acuity (BCVA) ≥54 Early Treatment Diabetic Retinopathy Study (ETDRS) letters (Snellen equivalent 20/80) and optical coherence tomography angiography evidence of DMI. The function-function and function-structure correlation were assessed. Two preselected thresholds in overall RS (oRS), 25 decibels (dB) and age-matched normative data (AMND), were tested on their ability to reflect abnormal anatomy in DMI. Finally, a multivariable regression model was established to depict the relationship between the oRS and various parameters.

The oRS showed only a modest correlation with BCVA and low-luminance visual acuity (LLVA). The whole-image deep vessel density (wiDVD) was the most reliable vascular metric correlated with RS. For every 1% decline in the wiDVD, the oRS decreased by 0.37 dB (P < .001) after multivariable adjustment. Furthermore, both a reduction of oRS to <25 dB or below AMND could differentiate eyes with FAZ ≥0.5 mm², whole image superficial vessel density (wiSVD) <37.7%, wiDVD <41.9%, and the presence of disorganization of the retinal inner layers (DRIL) from their counterparts.

The absolute value of 25 dB in oRS is worth considering as a trial endpoint, because it does not require complex calculation and closely reflects the structural abnormalities in DMI.