Effect of intravitreal dexamethasone implant on retinal and choroidal thickness in refractory diabetic macular oedema after multiple anti-VEGF injections

Abstract

AimsTo investigate the effect of intravitreal dexamethasone implant (IVD) on central foveal thickness (CFT), choroidal thickness (CT) and its correlation with visual acuity in eyes with refractory diabetic macular oedema (DMO).MethodsThis was a retrospective interventional case-series. Thirty-five eyes of 35 patients were treated with a single injection of IVD because of refractory DMO with CFT over 300 μm, and persistent intraretinal and subretinal fluid despite of multiple intravitreal bevacizumab injections. Patients were followed-up for 6 months for the evaluation of CFT and subfoveal CT by spectral-domain optical coherence tomography.ResultsAll eyes (mean age: 59.4±12.35 years; 18 males, 17 females) had been previously treated with multiple bevacizumab injections and showed persistent DMO (mean number of injections 4.08±2.98) The preoperative logMAR BCVA was 0.49±0.24, which gradually improved to 0.46±0.32 at 6 months (P=0.652) and 26% gained two or more lines of Snellen visual acuity. At baseline, the mean CFT was 526.29±123.48 μm, which significantly improved to 316.15±100.09 μm at 3 months (P<0.001). However, CFT deteriorated to 457.07±136.53 μm at 6 months (P=0.051). Similarly, the mean preoperative subfoveal CT was 288.91±36.47 μm and it decreased to 266.85±30.93 μm at 3 months (P<0.01), but increased to 278.63±32.55 μm at 6 months (P=0.137). The reduction of CFT from baseline showed significant correlation with that of subfoveal CT at 3 months (P=0.041) and at 6 months (P=0.008).ConclusionsIn DMO refractory to multiple bevacizumab injections, IVD significantly reduced CFT and subfoveal CT, with BCVA improvement in one-fourth of the patients. The reduction of CFT showed significant correlation with reduction of subfoveal CT.

Figure 1

EDI-OCT images of a patient with refractory DMO treated with IVD implant. CFT and subfoveal CT at (a) baseline, (b) 1 month, (c) 3 months, and (d) 6 months after IVD treatment. CFT was measured on the 1 mm Early Treatment Diabetic Retinopathy Study (ETDRS) circle centered on the fovea, with the mapping protocol of the OCT software. Subfoveal CT (double-headed arrow) was measured from the hyper-reflective line of the Bruch's membrane to the chorioscleral interface (arrowheads).

Figure 2

Chronological changes of (a) CFT, (b) mean subfoveal CT, and (c) mean BCVA in logarithm of the minimal angle of resolution (logMAR), in refractory DMO eyes during 6 months follow-up. There was a significant reduction of subfoveal CT at 1 and 3 months, but not at 6 months. The mean CFT significantly decreased at 1 month, and significant improvement in CFT was maintained until 3 months, but the mean CFT increased after 6 months of follow-up. Although BCVA tended to improve gradually until 3 months and decreased after 6 months, the changes in BCVA from baseline were not statistically significant. *Statistically significant difference (P<0.05).

Figure 3

The reduction (%) of CFT from baseline showed significant correlation with that of subfoveal CT at 3 months (P=0.041) and at 6 months (P=0.008), whereas the correlation was not statistically significant at 1 month (P=0.053).