Subretinal fluid correlates with increased macular volume in diabetic macular edema

To determine the prevalence and clinical phenotype of subretinal fluid (SRF) in eyes with diabetic macular edema (DME).

A retrospective study was conducted in treatment-naive patients with DME. The presence of SRF, hard exudates, and cystoid spaces with hyperreflective material (HRM) on OCT B-scans, along with central macular thickness (CMT) in the 1-mm, 3-mm, and 6-mm central areas, were assessed, and the correlation between the presence of SRF and macular thickness was estimated using linear mixed-effects models.

Of 101 eyes from 63 patients (49% men, mean age 61.31 ± 9.45 years), 36% had SRF. SRF was significantly and independently associated with macular thickness, with higher 1-mm, 3-mm and 6-mm CMT compared to eyes without SRF (β = 104.7 [95% CI, 53.5; 156] µm, p<0.001; β = 80.5 [95% CI, 45.9; 115.2] µm, p<0.001); β = 55.1 [95% CI, 30.1; 80] µm, p<0.001, respectively). Even though macular thickness was significantly associated with visual acuity, SRF was not associated (β = 0.127 [95% CI, -0.034; 0.287]; p = 0.12). However, in eyes with SRF, width (but not height) of the subretinal fluid was independently associated with lower visual acuity (β = 0.00017; [95% CI: 0.00003 - 0.00031]; p = 0.028).

DME patients with SRF exhibited higher macular thickness compared to those without SRF, suggesting SRF is an anatomical marker of a more severe exudative process. However, SRF independent impact on visual acuity was limited and modest in magnitude, suggesting further studies could improve our understanding of the pathophysiological and clinical significance of SRF in DME.