Electroretinografic evaluation in diabetic dogs before and after facoemulsification

• Grant number: 09/07349-3
• Support Opportunities: Regular Research Grants
• Start date: July 01, 2009
• End date: December 31, 2011
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Clinics and Surgery
• Principal Investigator: Angélica de Mendonça Vaz Safatle
• Grantee: Angélica de Mendonça Vaz Safatle
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Diabetes mellitus (DM) is one of the most frequent disorder of endocrine pancreas in dogs and cats. DM induces several ophthalmic disorders, among them diabetic retinopathy and cataracts. Cataracts are the commonest ocular manifestation in diabetic dogs resulting blindness, while in human beings, blindness is mainly caused by diabetic retinopathy. Despite the presence of those fundoscopic alterations in DM dogs, its diagnosis is generally impossible by fundoscopic examination because of cataracts, making necessary the utilization of other exams like the full-field electroretinogram (ERG). ERG is a non-invasive objective diagnostic method and capable to evaluate retinal function, making possible an early detection of dysfunction at retinal external layers, even earlier than the appearance of clinical signs. Facoemulsification surgery is performed in diabetic dogs with good results. Studies in human beings suggest this tecnique could accelerate the evaluation of diabetic retinopathy. The aim of this study is to compare the ERG registration before and after facoemulsification. Twenty dogs with mature or hypermature cataracts, 10 diabetics and 10 non diabetics, male and female, will be submitted to full field ERG before and 180 days after facoemulsification according to the Bioethics Committee of the institution. The procedure was performed according to the ISCEV (International Society for Clinical Electrophysiology of Vision) human standard protocol, which is constituted of five responses: rod response; maximal response in the dark-adapted eye; oscillatory potentials; light adapted cone response; and responses to a 30-Hz flickering stimulus. ERG parameters were measured from peak-to-peak amplitudes differences, between negative a-wave and positive b-wave, in microvolts (¼V); and implicit times, times from the stimulus presentation to a- and b-waves peaks, in milliseconds (ms). For statistical analysis, registers will be compared and submitted to paired and non paired t-student test. (AU)