Characteristics of Electroretinograms in Canine Eyes with Cataracts

Abstract

Pre-operative electroretinographic (ERG) data from 203 dogs with cataracts at the National Taiwan University Veterinary Hospital (NTUVH) were analyzed. Retinal function of the catatact dogs was examined by a RetinoGraphics ERG system with a white flash stimulus delivered to mydriatic canine eyes under general anesthesia. ERG was recorded by a contact-lens type of recording electrode referenced to a needle electrode inserted subcutaneously 3 cm posterior to the lateral can-thus. Abnormal ERG results with a wave amplitude less than 70 micorvolts were measured in 27% (109/402) of the eyes examined, including 9% (37/402) of eyes with absent responses and 18% (72/402) of eyes with decreased responses to light stimuli. Miniature schnauzer, Miniature poodle, Pomenarian, and Cocker spaniel showed significantly lower ERG b-wave amplitudes when compared to mix-breed dogs. There were no remarkable changes in the implicit time of ERG wave. There was a big difference in b-wave amplitudes between different age among dogs lost of retinal function, whereas there was no difference in gender among dogs lost of retinal function. In 73% of the dogs, ERG results were normal and cataract surgery was performed with good post-op visual prognosis achieved. As retinal diseases commonly affect dogs and the diseases greatly affect post-op visual outcome and success rate of surgery performed in cataract patients, ERG is an essential procedure before cataract surgery to select suitable candidates for surgical treatment of cataracts in animals.