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Tina Damarjian, Yang Sun, Vincent Gattone; Laser trabeculoplasty in primates: a morphometric analysis. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1870.
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Several mechanisms have been proposed to describe the modification of outflow facility and the contribution of this process to intraocular pressure (IOP) lowering in glaucomatous eyes treated with laser trabeculoplasty (LTP). Here we investigate the structural changes induced in the eyes of seven treated cynomolgus monkeys to examine the morphological changes in the trabecular meshwork.
Laser trabeculoplasty (LTP) was performed on one eye in each of seven cynomologus monkeys. The treatment was intended to duplicate the procedure as performed in humans. A median of 75 burns of 0.1 sec duration, 50 um size, 900-1400 mw power was applied to the entire circumference of the anterior trabecular meshwork (TM) of each animal. To assess a possible mechanism contributing to this process, analysis of linear and area measurements and calculated volume density changes in randomly selected areas of the filtration angle was done one month following treatment.
One eye of each of the monkeys was treated with LTP demonstrating a significant decrease in IOP (mean IOP reduction 3.5 mmHg p<0.001) and an increase in outflow facility (p<.001). This comparison was based on pretreatment levels measured with pneumotonometry. There was no significant change in outflow facility in the control eyes. Compared with controls, results demonstrate increased distance from the scleral-ciliary body junction to angle recess and increased thickness of the ciliary body (p<.05). While there was no change in the area of corneoscleral TM or Schlemm's canal, the area of the uveal TM also increased (p<.05). There was also an increase in interstitial space within the anterior ciliary body (p<.01) and the relative area of trabecular spaces within the uveal TM (p<.05).
This study shows that consistent IOP modification can be performed in a nonhuman primate model, and via this process demonstrates an increase in outflow facility maybe related to morphological changes. These quantifiable alterations may play a role in the IOP lowering effect of LTP.
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