Macular ischemia predicts the resolution pattern of disorganization of retinal inner layers (DRIL) in patients with center involved diabetic macular edema (ci-DME)

Abstract

Purpose: Previous studies have shown that both FAZ/ON ratio and DRIL length measured on spectral domain optical coherence tomography (SDOCT) were highly associated with visual acuity (VA) in eyes with ci-DME. The purpose of this study was to investigate the relationship between foveal avascular zone (FAZ) size, as a measure of macular perfusion, using fluorescein angiography (FA) and the resolution pattern of DRIL in patients with ci-DME.

Methods: This was a longitudinal study in which patients underwent serial BCVA testing, SDOCT (Spectralis, Heidelberg, Germany) and FA imaging over an 8 month period. Both FA and SDOCT images were graded in a masked fashion. Using Adobe photoshop, the FAZ area was measured and referenced to the size of the optic nerve to account for the patient’s refractive error. The length of DRIL (defined as the inability to distinguish the boundaries between the inner retinal layers in the central 1500 microns) was measured in the corresponding SDOCT image.

Results: 36 eyes of 25 study participants were evaluated. 25% of the eyes (n=9) had no baseline DRIL. Out of the remaining 75% of eyes with baseline DRIL (n= 27), 19 eyes showed no resolution of DRIL over time (non resolvers), DRIL resolved in 8 eyes (resolvers). Mean FAZ/ON ratio [95%CI] in eyes with no baseline DRIL was 0.2 ± 0.05 [0.1, 0.3]; vs. 1.2 ± 0.6 [0.3, 2.4] in non resolvers (p=0.01); and vs. 0.7 ± 0.5 [0.3, 1.8] in resolvers (p=0.4). Mean logmar VA at the end of the study [95%CI] in eyes with no baseline DRIL was 0.1 ± 0.09 [0, 0.3]; vs. 0.5 ± 0.2 [0.1, 1] in non resolvers (p<0.001); and vs. 0.3 ± 0.2 [0.1, 0.9] in resolvers (p=0.05). There was no significant difference in central retinal subfield thickness (CST) among resolvers and non-resolvers. Regression analysis showed a high association between FAZ/ON ratio and logmar VA both at baseline and at the end of the study (R² = 0.6, P < 0.0002) and (R² = 0.5,P < 0.0001), respectively. There was also a high association between FAZ/ON ratio and the extent of DRIL both at baseline and at the end of the study (R² = 0.4, P < 0.0001) and (R² = 0.4, P < 0.0001), respectively.

Conclusions: The extent of foveal ischemia appears to influence the resolution pattern of DRIL in patients with ci-DME. Thus, DRIL resolution pattern could have potential prognostic implications if validated in larger prospective studies.