Impact of Anatomically Defined Retinal Zones on Ultrawide-Field Fluorescein Angiography Nonperfusion Measurements in Diabetic Retinopathy.

INTRODUCTION

The aims of the study were to determine the effect of retinal zone placement on nonperfusion index (NPI) measurements using ultrawide-field fluorescein angiography (FA) in eyes with diabetic retinopathy (DR) and assess its association with disease progression.

METHODS

The study analyzed retinal periphery zones based on FA findings in 18 eyes without DR to standardize anatomical boundaries. NPI measurements were then conducted on a separate set of 285 eyes with DR. Eyes were grouped by NPI levels, and Cox regression was used to examine the association between nonperfusion in the mid-peripheral and far peripheral retina and progression to proliferative diabetic retinopathy (PDR).

RESULTS

The retinal zones defined by FA (FA-defined zones) were similar in size to a standard 15-mm radius circle centered on the optic disk (14.98 ± 1.40 mm). However, when compared to circles centered on the fovea, the fovea-centered circles were displaced temporally by an average of 3.94 mm, leading to a significant overestimation of the anatomic nasal far periphery (79.10 ± 13.60 mm2 vs. 36.91 ± 10.52 mm2, p < 0.001). Among the eyes with at least 1 year of follow-up (N = 121, 42.5%), those with medium and high mid-peripheral NPI had a significantly higher risk of progression to PDR (HR, 3.44; 95% CI, 1.36-8.70; p = 0.009) when using FA-defined zones. No significant association was found when using fovea-centered zones (HR, 1.39; 95% CI, 0.56-3.46; p = 0.476).

CONCLUSION

While the diameter of the retinal measurement zones did not differ significantly, the location of the zone center had a substantial impact on NPI measurements. Using FA-defined zones centered on the optic disk led to lower mid-peripheral and higher far peripheral NPI measurements, providing a more accurate prediction of progression to PDR compared to fovea-centered zone.