Prognostic value of subretinal fluid volume in patients with ranibizumab-resistant diabetic macular edema treated with intravitreal dexamethasone

Abstract

DESIGN. Retrospective, observational cohort study

PURPOSE. To investigate the prognostic effects of baseline Optical coherence tomography (OCT) parameters, especially subretinal fluid volume (SFV), in patients with ranibizumab (RNB) resistant diabetic macular edema (DME) who underwent an early switch to the dexamethasone (DEX) implant.

METHODS. Fifty-four eyes of 34 patients who underwent a loading dose of three-month RNB injection and then underwent a single dose of intravitreal DEX implantation were examined. Prior to RNB treatment, OCT scans were evaluated in terms of presence and volume of submacular fluid, size and localization of cystic changes, continuity of internal segment-external segment (IS-OS), number and localization of hyperreflective foci (HRF). Best corrected visual acuity (BCVA) and central macular thickness (CMT) were recorded at baseline RNB injection, at baseline DEX implant, at 1,2 and 4 months after DEX implant. Prognostic factors were evaluated by univariate and multivariate logistic regression analysis.

RESULTS. The mean age of 34 patients (21 females, 61.7%) was 64 years. Multivariate analysis showed a significant relationship between SRF (ß coefficient -5.615; 95%CI -10.96 to -0.27; p=0.04) increase and poor anatomical outcome (CMT reduction <20% of the baseline). As a result of multivariate analysis, the partially disrupted ISOS (ß coefficient -3.67; 95%CI -6.96 to -0.39; p=0.028), the number of HRF> 20 (ß coefficient -3.38; 95%CI -6.47 to -0.30; p=0.030), presence of a giant outer nuclear layer cyst (ß coefficient -3.56; 95%CI -6.22 to -0.89; p=0.009) and poor baseline BCVA (ß coefficient 4.82; 95%CI 0.20 to 9.45; p=0.041) are poor prognostic markers for visual change of <5 letters. According to the receiver operating characteristic analysis, 8.5 mm3 SRV was obtained as a cut-off value, as the best balance between sensitivity and specificity to predict anatomical failure. (75% sensitivity, 86% specificity, area under the curve 0.863, p<0.01)

CONCLUSIONS. SFV is a predictor in patients with RNB resistant DME who underwent an early switch to the DEX implant. Concomitant DEX implantation with anti-vegf instead of conventional anti-vegf therapy may be beneficial for prognosis in patients with high SFV.