Complete cataract causes blindness to patients and prevents the visual evaluation of the retina by the examiner. Hence, prior to surgery, the retina is routinely evaluated by electroretinography (ERG) to ensure the functional integrity of the retina. However, there is a paucity of data regarding the correlation between the pre-operative ERG and the post-operative visual function. This gap of knowledge prevents the formation of clear guidelines for patients screening for cataract surgery. Our goal is to evaluate the correlation between the pre-operative ERG results and the visual outcome following cataract surgery in canine patients.

At least 36 canine patients with at least 90% cataract involvement of each lens, will be recruited for this study. Within seven days prior to surgery, ERG will be performed for each dog under dark-adapted (scotopic) and light-adapted (photopic) conditions to evaluate rod and cone function, respectively. The visual function of each patient will be evaluated at the same time by means of an obstacle-avoidance course (OAC), under scotopic and photopic conditions, to evaluate night and day vision, respectively. Each dog will perform 3 runs through the OAC for each light condition; each run with a random, predetermined obstacle pattern, will be videotaped. Evaluation of TTC will be determined based on the video recording by an observer who is masked of the ERG result. The 3 runs for each time point and light condition will be averaged for further analysis. Four weeks and six months post-operatively, the OAC testing will be repeated. Electroretinography will also be re-evaluated at the 6-month time point. Linear regression will be performed to assess the correlation between the pre-operative ERG recording and the visual function test (OAC) for each light condition.

We expect the visual function of dogs following cataract surgery to correlate with the pre-operative ERG recording results.

The results of this study will help develop and strengthen clinical guidelines for the selection of cataract surgery patients based on pre-operative ERG evaluation and may change the way we interpret the routine pre-operative ERG test results for cataract surgery patients screening.