Predictors of Response to Intravitreal Bevacizumab in Diabetic Macular Edema: A Prospective Study in Tanzania

Abstract

Purpose: To assess the clinical outcomes and predictors of response to intravitreal bevacizumab injections (IVB) in patients with diabetic macular edema (DME) at Muhimbili National Hospital (MNH).

Methodology: A prospective longitudinal study was conducted at MNH for six months. Patients received monthly IVB (1.25 mg/0.05 mL) for three consecutive months. Baseline and post-treatment assessments included ocular examination, spectral-domain optical coherence tomography (OCT), and laboratory investigations. Main outcome measures were changes in best-corrected visual acuity (BCVA, logMAR) and central macular thickness (CMT, µm) at 12 weeks. Data were analyzed using SPSS v25 with paired t-test and linear regression, and p < 0.05 was considered statistically significant.

Results: Of the 60 patients, 58.3% were male, with a median age of 60.5 years (IQR 44). More than half (56.7%) had diabetes for 11–20 years, and 83.3% had HbA1c >7%. Baseline mean BCVA was 0.876 ± 0.592 logMAR, and mean CMT was 453.02 ± 71.94 µm. At 12 weeks, mean BCVA improved by 0.216 ± 0.523 logMAR (p = 0.002), equivalent to a >10-letter gain, and mean CMT decreased by 95.78 ± 57.65 µm (p < 0.001). Longer diabetes duration was significantly associated with less CMT reduction, with each additional year corresponding to a 0.434 µm increase in CMT (p = 0.003).  Elevated HbA1c also predicted poor anatomical response, with each 1% increase associated with a 0.434 µm increase in CMT (p = 0.003).

Conclusion: Three intravitreal bevacizumab injections (IVB) resulted in a significant reduction in diabetic macular edema, marked by a decrease in central macular thickness and accompanied by a significant improvement in mean best-corrected visual acuity. Longer diabetes duration and poor glycemic control predict poor anatomical response, highlighting the importance of integrated diabetes management and structured treatment protocols in resource-limited settings.