Retinal thickness fluctuations in patients receiving fluocinolone acetonide implant for diabetic macular edema

Objectives: To evaluate central foveal thickness (CFT) variability and accompanying changes in visual acuity (VA) 12 months before and after treatment with the 190 mcg fluocinolone acetonide (FAc) intravitreal implant for diabetic macular edema (DME).Methods: The Iluvien Clinical Evidence cohort study in the United Kingdom (ICE-UK) investigated the effectiveness of the FAc implant in people treated at 13 hospitals from April 2013 to April 2015. The following parameters were calculated for CFT for each patient: mean, standard deviation (SD), retinal thickness amplitude (RTA, the difference between maximum and minimum values), and coefficient of variation (CV).Results: In 149 eyes with ≥2 CFT observations both before and after FAc implantation, the median VA was 50 ETDRS letters at implantation. Mean CFT was 487 µm at implantation and 135 µm at 12 months post-implant. Before implantation, the mean CV and mean SD for CFT were 24.6% and 112 µm, respectively; the mean RTA was 254 µm. A statistically significant (p < .001) decrease in all three parameters was observed after implantation (18.3%, 68.2 μm and 146 μm, respectively). There was an association between CFT change between extremes and the corresponding change in VA (Pearson's correlation coefficient, r = -0.292, p < .001, prior to the implant; r = -0.379, p < .001, post-implant).Conclusions: After accounting for the reduction in CFT, retinal thickness stabilized following FAc implantation. There might be VA benefits in reducing variability in CFT over time. This merits further exploration but would require more frequent CFT observations in order to properly determine patterns of retinal thickness variability.