The Effect of Intravitreal Bevacizumab Dose on Retinal Vascular Progression in Retinopathy of Prematurity

Introduction: In this study, we investigated the effect of drug dose on the progression of retinal vascularization in eyes treated with different doses of intravitreal bevacizumab (IVB). Methods: The patient charts of 259 eyes of 142 patients who were administered 0.3125 mg or 0.625 mg IVB as primary therapy for type 1 retinopathy of prematurity (ROP) or aggressive ROP (A-ROP) were retrospectively evaluated. Eighty-four eyes of 42 infants met all study inclusion criteria and underwent further morphological evaluation. Eyes treated with 0.3125 mg and 0.625 mg bevacizumab were grouped as the low dose and standard dose groups, respectively. Horizontal disc diameter (DD), optic disc-to-fovea distance (FD), and the length of temporal retinal vascularization (LTRV) were measured on pretreatment photographs (PPs) and final fluorescein angiography (FA) images. LTRV, measured in pixels, was converted to DD and FD units and analyzed. All PPs and FA images were captured with 130 degrees PanoCam Pro camera. The difference between final LTRV and pretreatment LTRV was defined as the difference of LTRV. The ratio of difference of LTRV to pretreatment LTRV was defined as the rate of increase of LTRV. Results: Of the 255 eyes, re-treatment rate before 55 weeks postmenstrual age (PMA) was 23% in the eyes treated with 0.3125 mg IVB and 19% in the eyes treated with 0.625 mg IVB (p = 0.362). Of the 42 infants included for further morphological evaluation, the median age at the time of treatment was 36 (35-38) weeks PMA, and the median age at the time of FA imaging was 66 (62-75) weeks PMA. While the difference of LTRV by unit of DD was higher in the low dose group (p = 0.017), this difference was similar between groups by unit of FD (p = 0.412). The ratio of the increase of the LTRV was similar between groups by units of DD and FD (p = 0.081, p = 0.390; respectively). The FD/DD ratio was 4.13 +/- 0.49 and 3.26 +/- 0.33 at the pretreatment and final sessions, respectively (p = 0.000). Conclusion: The ratio of FD to DD decreased significantly with increasing age. The additional treatment rate and progression of retinal vascularization by unit of FD were similar between the groups. The difference of LTRV by unit of DD was higher in the low dose group. The usage of dif-ferent formulas and methods may affect the evaluation of the progression of retinal vascularization.