Investigation On The Regularity Of Elevated Intraocular Pressure Of Glaucoma Rat Model By Photocoagulation To The Trabecular Meshwork With A Laser

Purpose:To characterize the regularity of elevated intraocular pressure of glaucoma model induced in Wistar rats by a diode laser with wavelength of 532nm.Methods : Experimental elevated intraocular pressure ( IOP ) was performed unilaterally by a diode laser with wavelength of 532 nm irradiating trabecular meshwork via external limbus without lens in 30 Wistar rats aging 2 and 4 months, respectively, alternating right and left eyes. That was altogether for 4 times at a 7-day interval. In each treated animal, the contralateral eye served as the own control. Another untreated 10 rats served as the blank group only measured IOP. After the fourth laser treatment for 7 days, randomly chose half of the survival as the experimental group and each enucleated the two eye balls with the aid of general anesthetics, the other as the continue observational group measured IOP for one more month and then enucleated the both eye balls with the same method. The blank group enucleated the both eyeballs on the same day with the experimental group. Approximately 150 laser burns were delivered around the trabecular band 360°at laser settings of 200 um, 0.5w, and 0.2 seconds. IOP was measured by an applanometer called tonolab in both eyes before laser coagulation,the moment of accomplished photocoagulation and the same time of 6 days weekly for 4 weeks. 6 consecutive readings were obtained in each eye and recorded the average. The protomerite of both eyeballs were observed carefully daily.Results:IOP in the 2 aging months was 15±3.8mmHg and 13±2.8mmHg in the aging 4 months before first laser treatment, and increased to 24±6.3mmHg and 26±10.8 mmHg at the moment of accomplished photocoagulation, respectively. The peak IOP was separately 60 mmHg and 54mmHg at the moment of accomplished photocoagulation. Both groups using the simple pared t-test presented significant differences (P<0.001). There was no variability between the 2 groups(t=-1.623, P>0.05). The highest mean IOP was available on the first day after photocoagulation, then began to decrease in succession and be normal on the sixth day. Peak IOP was 66 mmHg in the aging 2 months and 74 mmHg in the aging 4 months in the next 6 days. About 63% animals gained elevated IOP immediately after first laser coagulation in the aging 2 months and 60% in the aging 4 months. The maximum amount appeared on the first day after laser coagulation and most animals returned to baseline on the sixth day in the 2 groups. On the first day after the fourth laser treatment, there were separately 77% and 88% animals gained elevated IOP in the aging 2 months and aging 4 months. 4 laser treatments showed the same regularity.Conclusion:It is of possibility that translimbal laser photocoagulation to the trabecular meshwork leads to transient elevated IOP in glaucoma rats model. Chronic glaucoma animal model can be produced by repeated photocoagulation of trabecular meshwork with a laser.