Macular function following intravitreal ranibizumab for macular edema associated with branch retinal vein occlusion: 12-month results

To evaluate the 12-month effects of intravitral ranibizumab (IVR) injections on the physiology and morphology of the macula in eyes with a branch retinal vein occlusion with macular edema (BRVOME).

We studied 13 eyes of 13 patients with a BRVOME. All patients were initially treated with IVR injections at 3 consecutive monthly intervals, the initiation phase. Additional treatments were done according to the pro re nata (PRN) regimen. The physiology of the macula was assessed by the focal macular electroretinograms (fmERGs) and the best-corrected visual acuity (BCVA). The morphology of the macular area was determined by spectral-domain optical coherence tomography. The retina was assessed at the baseline, and at 3, 6, and 12 months after beginning the IVR injections. The fmERGs were elicited by a 15° circular stimulus, and also by 15° semicircular stimuli placed on the occluded or non-occluded side of the macula. The amplitudes of the a- and b-waves, photopic negative response (PhNR), and sums of the oscillatory potentials (ΣOPs) were measured. In addition, the implicit times of the a- and b-waves were measured.

The BCVA was improved significantly relative to the baseline after the initiation phase (P < 0.01), and it was maintained with the PRN regimen for the 12-month experimental period. The foveal thickness was also significantly decreased after the initiation phase (P < 0.005) but was then worse at 12 months during the maintenance phase (P < 0.05). The fmERGs on the occluded side were significantly reduced at the baseline, and the b-waves and ΣOPs amplitudes improved after the initiation phase. However, they decreased during the PRN period. On the non-occluded side, the amplitudes and implicit times of the a- and b-waves remained unchanged after the initiation phase, the PhNR and ΣOPs amplitudes significantly increased at 3 months compared to the baseline (PhNR, P < 0.005; ΣOPs, P < 0.005), which was maintained throughout the 12 month study period.

The deterioration of the macular function on the occluded side during the maintenance phase suggests that there is a progression of the disease process during the PRN period in eyes with BRVOME.