Abstract
Background: Early diagnosis and management of diabetes mellitus is an important factor in limiting visual and physical complications of the disease. Globally, diabetic retinopathy has been identified as the most common cause of blindness amongst adults with Type 1 (TIDM) and Type 2 (T2DM) diabetes. The presence of vascular endothelial growth factor, which has been identified as the cause of macular oedema, has led to the use of anti-vascular endothelial growth factor injections, such as Bevacizumab (Avastin) in the management of cystoid macular oedema in participants with diabetes (DM).
Aim: To investigate the efficacy of Avastin in improving visual acuity (VA) and reducing central foveal thickness (CFT) and parafoveal thickness (PFT) in participants with diabetic retinopathy at a tertiary hospital in Gauteng.
Methods and Materials The cross-sectional observational study was conducted at a tertiary hospital in Gauteng Province (South Africa). The study collected both retrospective and prospective data from participants diagnosed with diabetic retinopathy (DR). A total of 55 eyes from 49 participants aged between 24 and 86 years old were included in the study. Retrospective data was collected from record cards of 37 participants that had received at least three cycles of Avastin injections and prospective data was collected from 18 participants who had been diagnosed with diabetic retinopathy and were receiving Avastin injections. Participants included in the study were those with VAs that were less than 0.5 LogMAR units and CFTs greater than 300 microns (μm). Participants with cystic spaces in the PFT were also included in the study. Excluded from the study were those participants who had recent cataract surgery and were diagnosed with wet age-related macular degeneration, retinal vein occlusion, epiretinal membrane, and Irvin Gass syndrome for both the retrospective and prospective phases. Measurements of VA’s (LogMAR units), CFT (μm) and PFT (μm) were done at baseline after three months and six months of receiving Avastin treatment. These measurements were captured on Microsoft Excel Version 2021 spread sheet and data analysis was done using BM SPSS Version 28. The study was conducted over six months from July 2022 to December 2022.
Results: A total of 55 eyes from 49 participants were included in the study. The age of the participants ranged from 24 to 86 years. Of the 55 participants, 37 were Africans, 9 were Caucasians, 4 were Coloured and 5 were Asians. Most of the participants had T1DM (n=42) and 13 had TDM1. The mean VA was to have improved from 1.00±0.71 LogMAR at baseline to 0.66±0.51 LogMar at three months and 0.57±0.48 LogMAR at 6 months, p < .001. The
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mean CFT was found to be improved from 441.22±142.35 μm at baseline to 355.58±129.38 μm at 3 months and 308.40±137.60 μm at six months, p <.001. The superior parafoveal thickness (SPFT) showed the highest decrease from a mean baseline of 379.04 μm to a mean baseline of 317.36 μm at three months. Our study showed that Avastin effectively improved VA and CFT from baseline, at 3 and 6 months which was statistically significant (p < .001). The Wilcoxon Signed-Rank non-parametric test was used to investigate the relationship between VA, the dependent variable, and the independent variables (CFT and SPFT, IPFT, NPFT and TPFT). A p-value of less than 0.05 was considered statistically significant. A Spearman’s ρ correlation coefficient of .628 was found between VA and CFT after 3 months of treatment with Avastin, (p <.001). The CFT was the one variable that predicted the improvement in VA, p < .001. A decrease in CFT resulted in an improvement in VA. We found a Spearman’s ρ correlation coefficient of .463 between VA and CFT after 6 months of treatment with Avastin, which was statistically significant (p <.001), while the correlation coefficients for SPFT, IPFT, NPFT and TPFT were relatively strong at three months and moderate at six months. The results of a multiple linear regression model showed that at both 3 Months and 6 Months the CFT predicted an improvement in VA, p < .001 while the other independent variables had no significant influence on VA (.663, .666, .291 and .084) respectively. At 6 Months, however, the NPFT was statistically significant in improving VA, p <.025.
Conclusion: The results of the study showed that after treatment with Avastin there was a reduction in mean CFT which resulted in an improvement in the mean VA at 3 months and at 6 months. The independent variable, CFT, was found to predict an improvement in VA while the PFT independent variables had no significant contribution in improving VA. On the other hand, at 6 the NPFT was statistically significant in improving VA.