Characterization of a rat model of glaucoma induced by laser

Abstract

Abstract Purpose: To characterize a rat model on which glaucoma was induced by laser photocoagulation of episcleral veins, trabeculum and limbal veins. The characterization of the model was based on the evaluation of the intraocular pressure (IOP), the retinal function and the number of functional retinal ganglion cells (RGCs). Methods: Male Sprague Dawley rats were used at 6 weeks of age. Three of the episcleral veins, the trabeculum and the limbal veins were photocoagulated with a laser (532nm) in one eye. IOP (using a Tonolab®) and electroretinogram (ERG) were recorded every 2 weeks during 11 weeks. Three months after photocoagulation, RGCs were retrogradely labelled with a 5% Fluorogold solution applied to both superior colliculi. Seven days after labelling, retinas were flatmounted and were examined under a confocal fluorescence microscope equipped with a motorized stage. Functional RGCs were counted using an image analysis software (Image Pro Plus®). Results: Treated eyes displayed a significant increase in IOP as soon as the first week after the procedure (32 mmHg versus 18 mm Hg in control eyes) and lasting for 7 weeks. The retinal function of treated eyes was altered since the ERG b‐wave amplitude was significantly decreased when compared to control eyes (50% after 11 weeks). No differences were observed in the b‐wave latencies. A reduction of 50% of the number of RGCs was observed in treated eyes when compared to control eyes Conclusions: These results show that in the rat, eyes treated by laser photocoagulation are a valuable model of glaucoma since they display typical characteristics, namely elevated IOP, followed by an alteration of the inner retinal function and retinal ganglion cell death.