Impact of serous retinal detachment on the efficacy of ranibizumab in diabetic macular oedema

In diabetes mellitus, diabetic macular oedema (DME) has been reported in 4.8–7.8% of patients. Recent studies have shown that DME is associated with serous retinal detachment (SRD) in 13–36% of cases (Otani et al. 1999; Shereef et al. 2014). The natural course (Gaucher et al. 2008), pathogenesis and visual outcome of SRD associated with DME have previously been described. However, in patients treated with ranibizumab for DME, the impact of SRD remains unclear. The aim of this study was to assess the functional and anatomical outcome in DME patients with and without SRD. All diabetic patients treated with ranibizumab for DME in our department from November 2012 to November 2013 were retrospectively included. In case of bilateral DME, we included the first affected eye. Exclusion criteria were proliferative diabetic retinopathy with no history of panretinal laser photocoagulation, intravitreal haemorrhage, diabetic tractional retinal detachment, ischaemic maculopathy, previous use of intravitreal steroids or bevacizumab injections <3 months before inclusion, thromboembolic arterial event <3 months before inclusion, pregnancy, uncontrolled glaucoma (intra-ocular pressure > 24 mmHg on medication OR neovascular glaucoma), uveitis or another condition which could contribute to the visual decrease. Patients were divided into two groups: DME with SRD (SRD+ group) and DME without SRD (SRD− group). The diagnosis of SRD was reviewed independently by two ophthalmologists (AGA, LQ), and in the absence of consensus, one of the investigators (FF) adjudicated the disagreement. All patients received a loading dose of three monthly injections of ranibizumab, followed by retreatments on an as-needed basis (PRN regimen). The primary end-point was to assess the difference in mean change in best-corrected visual acuity (BCVA) between SRD+ and SRD− groups from baseline to month 6. Secondary end-points were to determine the difference in mean change in central retinal thickness (CRT) between SRD+ and SRD− groups and the number of intravitreal injections. Forty eyes of 40 patients were included: 18 (45%) eyes in the SRD+ group and 22 (55%) eyes in the SRD− group. Patient characteristics are presented in Table 1. The mean change in BCVA score from baseline to month 6 was significantly higher in the SRD+ group (+20.11 ± 12.2 letters) than in the SRD− group (+8.23 ± 8.22 letters) (p = 0.004). The mean change in CRT from baseline to month 6 decreased significantly in the SRD+ group (−332 ± 218 μm) compared to the SRD− group (−153.5 ± 87 μm) (p = 0.015). Sixteen of the 18 (88.9%) SRD resolved at month 6. The mean number of ranibizumab injections was similar in both groups: 4.2 (range: 3–6). Our study suggests that a more favourable visual acuity gain may be observed in patients with SRD compared to patients without SRD. At baseline, the BCVA in the SRD+ group was lower than in the SRD− group, probably due to the impact of subretinal fluid present beneath the fovea. However, at the end of the follow-up, the BCVA was similar in both groups and the SRD had resolved in almost all cases. Previous studies have shown a visual acuity gain ranged from +6 to +9.9 (Mitchell et al. 2011; Diabetic Retinopathy Clinical Research Network et al. 2015) at month 6. Our study suggests that a better gain may be expected in patients with SRD. The presence of a SRD seems to be an important feature to consider at baseline in future studies and attention should be paid on a well-balanced proportion of patients with SRD in different groups. Indeed, in a large number of patients, the presence of a SRD could significantly impact visual gains.