advertisement
Abstract #6676 Published in IGR 4-1
Translimbal laser photocoagulation to the trabecular meshwork as a model of glaucoma in rats
Levkovitch-Verbin H; Quigley HA; Martin KRG; Valenta D; Baumrind LA; Pease MEInvestigative Ophthalmology and Visual Science 2002; 43: 402-410
PURPOSE: To develop and characterize a model of pressure-induced optic neuropathy in rats. METHODS: Experimental glaucoma was induced unilaterally in 174 Wistar rats, using a diode laser with wavelength of 532 nm aimed at the trabecular meshwork and episcleral veins (combination treatment group) or only at the trabecular meshwork (trabecular group) through the external limbus. Intraocular pressure (IOP) was measured by a tonometer in rats under ketamine-xylazine anesthesia. Possible retinal vascular compromise was evaluated by repeated fundus examinations and by histology. The degree of retinal ganglion cell (RGC) loss was assessed by a masked, semiautomated counting of optic nerve axons. Effects of laser treatment on anterior ocular structures and retina were judged by light microscopy. RESULTS: After the laser treatment, IOP was increased in all eyes to higher than the normal mean IOP of 19.4 ± 2.1 mmHg (270 eyes). Peak IOP was 49.0 ± 6.1 mmHg (n = 108) in the combination group that was treated by a laser setting of 0.7 seconds and 0.4 W and 34.0 ± 5.7 mmHg (n = 46) in the trabecular group. Mean IOP after six weeks was 25.5 ± 2.9 mmHg in glaucomatous eyes in the combination group compared with 22.0 ± 1.8 mmHg in the trabecular group. IOP in the glaucomatous eyes was typically higher than in the control eyes for at least three weeks. In the combination group, RGC loss was 16.1% ± 14.4% at one week (n = 8, p = 0.01), 59.7% ± 25.7% at six weeks (n = 88, p < 0.001), and 70.9% ± 23.6% at nine weeks (n = 12, p < 0.001). The trabecular group had mean axonal loss of 19.1% ± 14.0% at three weeks (n = 9, p = 0.004) and 24.3% ± 20.2% at six weeks (n = 25, p < 0.001), increasing to 48.4% ± 32.8% at nine weeks (n = 12, p < 0.001). Laser treatment led to closure of intertrabecular spaces and the major outflow channel. The retina and choroid were normal by ophthalmoscopy at all times after treatment. Light microscopic examination showed only loss of RGCs and their nerve fibers. CONCLUSIONS: Increased IOP caused by a laser injury to the trabecular meshwork represents a useful and efficient model of experimental glaucoma in rats.
Dr. H. Levkovitch Verbin, Glaucoma Research Laboratory, Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
Classification:
5 Experimental glaucoma; animal models