Characterization of the biological antioxidant potential in the vitreous fluid from patients with rhegmatogenous retinal detachment

Abstract

Editor, Oxidative stress has been reported to cause cellular damage and play a role in triggering programmed cell death. In many vitreoretinal disorders, including proliferative diabetic retinopathy (PDR) (Yokoi et al. 2007), age‐related macular degeneration (Rattner & Nathans 2006) and retinitis pigmentosa (Berson 1996), oxidative stress has been implicated in the development of retinal cellular damages (Carmody et al. 1999). Cederlund et al. (2013) previously reported an elevated vitreous level of oxidative stress biomarkers in their small group of patients with rhegmatogenous retinal detachment (RRD), in addition to showing that oxidative stress was related to the RRD severity. Research has also shown that antioxidant treatments can reduce photoreceptor cell death in experimental retinal detachment in animal models (Rostein et al. 2003). The results of these studies indicated that oxidative stress may play an important role in photoreceptor cell death in RRD. Our current study attempted to characterize the biological antioxidant potential (BAP) in the vitreous fluid of RRD by comparing the BAP in the vitreous fluid collected from patients with various vitreoretinal disorders including RRD and then statistically analysing the BAP in relation to the clinical features of RRD. This study was approved by the Institutional Review Board of Hirosaki University Graduate School of Medicine. Undiluted vitreous fluid was obtained at the time of vitrectomy from RRD (n = 45), PDR (n = 93), retinal vein occlusion (RVO, n = 14), epiretinal membrane (ERM, n = 18) and macular hole (MH, n = 24) patients. Biological antioxidant potential (BAP) values were determined by measuring the reducing potential determined by the conversion of Fe3+ to Fe2+ in thiocyanate solution (FREE™, Wismerll, Tokyo). Clinical features of RRD were analysed by examining medical records for the extent of the detachment, duration of symptoms, presence of proliferative vitreoretinopathy (PVR) or vitreous haemorrhage (VH), macular status (on or off), and patient age. Biological antioxidant potential values (μM) were 1860.50 ± 470.50 in RRD, 1647.76 ± 460.53 in PDR, 1863.14 ± 413.76 in RVO, 2169.23 ± 594.01 in ERM and 2258.83 ± 450.79 in MH, respectively. Rhegmatogenous retinal detachment (RRD) exhibited a significantly lower BAP value than MH (anova with post hoc Dunnett's T3 test, p =0.012), while PDR had a significantly smaller BAP than ERM (p = 0.019) and MH (p < 0.001). There were no statistically significant differences in the BAP values between RRD, PDR, RVO and ERM. For the clinical features, BAP values for the detached areas confined within 2 quadrants (2006.59 ± 401.17) were significantly greater than that extended over 3 quadrants (1568.33 ± 474.82, Student's t‐test, p = 0.002). In addition, there was a statistically significant negative correlation between the BAP values and the extent of the detached area, with a Pearson's correlation coefficient of −0.384 (p = 0.008, R1 in Fig. 1). Furthermore, when the BAP values of the MH group were used as the controls (0 quadrant), there was an even stronger correlation, with a Pearson's correlation coefficient of −0.484 (p < 0.001, R2 in Fig. 1). There were no significant correlations noted between BAP and any other features examined. Figure 1 Correlation between BAP and the extent of detachment. BAP is significantly correlated with the extent of the detachment in the RRD group (closed circle, R1 = −0.384, p = 0.008, Pearson's correlation coefficient). When BAP in the MH group is used as the control (= 0 quadrant, open circle), there is a significantly greater correlation between the BAP and the extent of the detachment (R2 = −0.484, p < 0.001). Current results suggest that significantly increased oxidative stress was present in RRD compared to MH. Of the possible clinical features that could influence BAP in RRD, only the extent of the detachment was significantly correlated to the BAP with no significant relationships found for the duration, presence of PVR or VH, macular status and patient age. These results suggest that a detached retina by itself has a much greater influence on intravitreal BAP versus that of the presence of free haemoglobin. Thus, antioxidant treatments may be of benefit in retarding photoreceptor cell death during RRD.