Macular function following intravitreal ranibizumab for macular edema associated with branch retinal vein occlusion

To determine the physiology of the macula by the focal macular electroretinograms (fmERGs) in patients with branch retinal vein occlusion with macular edema (BRVOME) treated by intravitreal injections of ranibizumab (IVR).

We studied 17 eyes of 17 patients with BRVOME. The contralateral unaffected eyes served as controls. All patients were treated with an IVR at monthly intervals for 3 consecutive months. The baseline best-corrected visual acuity (BCVA), optical coherence tomographic (OCT) findings, and fmERGs were compared to the post-treatment values. The fmERGs were elicited by a 15° circular spot or a superior or inferior semicircular spot. The center of the spot was placed on the fovea. The amplitudes of the a- and b-waves, photopic negative response (PhNR), and sum of the oscillatory potentials (ΣOPs: sum of OP1, OP2, and OP3 amplitudes) were measured. In addition, the implicit times of the a- and b-waves were also measured.

The BCVA improved significantly from 0.39 ± 0.28 logMAR units to 0.17 ± 0.18 logMAR units after the resolution of the central macular edema (P < 0.01). All components of the fmERGs elicited by the semicircular stimulus spot placed on the occluded side were smaller than that elicited from the corresponding area of the control eyes. The b-wave amplitudes increased significantly from 0.49 ± 0.25 to 0.75 ± 0.36 µV following the IVR injections, but the amplitudes of the a-wave and PhNR remained reduced (P < 0.05). The amplitudes of the PhNR and ΣOPs elicited by stimulating the non-occluded side were reduced with relative preservation of the a- and b-waves (P < 0.05). They recovered after the treatment from 0.27 ± 0.15 to 0.50 ± 0.30 and 0.33 ± 0.15 to 0.53 ± 0.19 µV, respectively.

IVRs improved the macular function not only on the occluded side but also on the non-occluded side. On the occluded side, the BRVOME affects the function of all retinal layers of the macula. Even after the IVR, the function of the photoreceptors and retinal ganglion cells remained abnormal. On the non-occluded side, the inner retinal function improved after the IVR.