Retrospective evaluation of pre-surgical electroretinography results in a mixed-breed canine population presented for cataract removal surgery

Objective: Electroretinography (ERG) is used prior to cataract removal surgery to assess retinal function. We aimed to replicate and improve upon previous studies by performing a full ECVO protocol and by examining the retina post-surgery in all patients. Animals studied: One hundred twenty-seven eyes from 67 dogs were included in the study. Procedures: A full ECVO protocol electroretinography, which includes extensive rod and cone analysis, was performed on all dogs presenting for cataract surgery. Results: Our main findings were that amplitudes, but not implicit times of rod responses decreased with advanced cataracts. Amplitudes of the single flash rod and rod flicker responses were significantly lower in eyes with mature cataracts, and the former also decreased in hypermature cataracts. Cone flicker amplitude responses were also significantly lower in eyes with mature and hypermature cataracts. However, mixed single flash rod-cone and cone responses, with the exception of the mixed rod-cone a-wave amplitude in eyes with hypermature cataracts, were unaffected by cataract stage. The b-wave amplitude of the scotopic, mixed rod-cone, and photopic cone responses were affected by age and decreased by an average of 2.9, 7.5, and 1.5 μV/year, retrospectively (p < 0.01). Conclusions: Lower ERG amplitudes in canine cataract patients may result from aging or the presence of advanced cataracts and may not indicate the presence of retinal disease.