Purpose: The objective of the study was to investigate the effect of glial cell line-derived neurotrophic factor (GDNF) on the multifocal electroretinogram (mfERG) following an induced branch retinal vein occlusion (BRVO) in pigs.
Methods: Electrophysiological examination of the retina was performed in 20 pigs with standard and four-frame mfERG 4 weeks after induced BRVO and intravitreal injection of GDNF or vehicle. BRVO was induced by intraocular diathermia of the superior retinal vein. Inner retinal function was measured by analysis of the four-frame mfERG (iN1) and outer retinal function with standard mfERG (P1).
Results: In GDNF-treated BRVO eyes, P1 and iN1 amplitudes (P = 0.51 and 0.78) or implicit times (P = 0.08 and 0.99) did not differ from those in healthy fellow eyes. After vehicle injection, P1 and iN1 amplitudes of BRVO eyes were significantly lower than in the healthy fellow eye (P = 0.022 and 0.013). The log ratios of mfERG amplitudes between experimental and healthy fellow eyes were calculated (BRVO/healthy). GDNF improved the ratios of the four-frame mfERG (1.29 [0.88-1.88]) compared with vehicle (0.32 [0.21-0.50], P < 0.001). Equally, GDNF improved the ratios of the standard mfERG; GDNF (0.75 [0.51-1.10]) and vehicle (0.42 [0.27-0.63], P = 0.048).
Conclusions: GDNF appears neuroprotective on retinal electrophysiological function after BRVO. The efficacy and safety of GDNF remain to be investigated in primate eyes.