The relationship between central retinal thickness relative change and visual prognosis in diabetic macular edema patients following intravitreal injection of ranibizumab

Abstract

Background The studies on intravitreal ranibizumab for diabetic macular edema (DME) primarily focuses on the absolute change of central retinal thickness, while the affection of the relative change of central retinal thickness (RCRT) or relative change of central retinal thickening (RCRTing) on visual prognosis has not been elucidated completely. Objective This study aimed to evaluate the effect of RCRT and RCRTing in assessing visual prognosis in DME patients following intravitreal injection of ranibizumab. Methods A self-controlled observational study was designed.Thirty eyes of thirty patients with clinically significant DME (CSDME) were recruited in Beijing 401 Hospital of China Nuclear Industry from November 2013 to October 2014.Ranibizumab of 0.05 ml (10 mg/ml) was intravitreally injected by 30G syringe needle at 3.5 mm posterior corneal limbus.Best corrected visual acuity (BCVA) far 2.5 meters away modified ETDRs visual chart was examined before injection and 3 and 6 months after injection, and the BCVA difference value between before injection and 6 months after injection was calculated as the absolusion BCVA (ABCVA). Spectral domian optical coherence tomography (SD-OCT) system was employed to measure the central retinal thickness (CRT) and to calculate the RCRT and RCRTing value.The correlations of RCRT or RCRTing with ABCVA was analyzed. Results The LogMAR values were (0.66±0.20), (0.40±0.25)BCVA and (0.37±0.25) before injection and 3, 6 months after injection respectively in the CSDME patients, with a significant difference among them (F=36.79, P<0.05). The values were obviously improved 3 and 6 months after injection compared with before injection (both at P<0.05). The mean ABCVA (LogMar) of the patients was (0.30±0.21). The CRT 3, 6 , pmyjd sgyrt omkrvyopm values were (508.63±130.44), (331.07±71.84) and (311.77±64.47)μm before injection and respectively in the CSDME patients, showing a significant difference among them (F=49.78, P<0.05). The CRT values were evidently reduced 3 and 6 months after injection in comparison with before injection (both at P<0.05), and the mean ACRT value was (196.87±140.59)μm.The ABCVA values were (0.13±0.13), (0.44±0.14), (0.07±0.09) and (0.41±0.15)LogMAR in the RCRT<35% group, RCRT≥35% group, RCRTing<69% group and RCRTing≥69% group, respectively.Significant differences were found in ABCVA between the RCRT<35% group and RCRT≥35% group (t=-6.27, -8.65, both at P<0.05). RCRT and RCRTing showed the positive correlations with ABCVA in the CSDME patients (r=0.86, 0.79, P<0.05). Conclusions RCRT and RCRTing can identify well the optimal responders to intravitreal ranibizumab and predict BCVA improvement after treatment.RCRT has better association with ABCVA than RCRTing.RCRTing may be preferable when retinal thickening is more severe. Key words: Diabetes retinopathy/drug therapy; Macular edema/therapy; Central retinal thickness; Vision; Antibodies, monoclonal, humanized; Tomography, optical coherence; Vitreous body