Purchase this article with an account.
Vikas Gulati, Shan Fan, Donna G Neely, Bret J Gardner, Marie T Schaaf, Shane Havens, Carol B Toris; Mechanism of Action of Selective Laser Trabeculoplasty. Invest. Ophthalmol. Vis. Sci. 2014;55(13):820.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To determine the mechanism by which intraocular pressure(IOP) decreases following selective laser trabeculoplasty(SLT) in patients with ocular hypertension(OH) and primary open angle glaucoma(POAG).
Thirty one subjects with OH or POAG undergoing SLT as primary IOP lowering therapy were enrolled in this prospective study. All subjects underwent a baseline assessment of aqueous humor dynamics(AHD) in both eyes. The primary outcomes assessed were IOPs at 9AM and 12 noon (pneumatonometry), daytime(9AM-noon) aqueous flow (fluorophotometry), episcleral venous pressure (venomanometry), outflow facility (pneumatonography and fluorophotometry after oral acetazolamide) and uveoscleral outflow (Goldmann equation). All subjects underwent 360 degrees SLT (80 spots) within a week after baseline measurements. Subjects underwent a repeat assessment of AHD in both eyes at 3 months following SLT. Subjects were not on any IOP lowering medications at the time of either assessment.
In the 29 subjects that completed all study visits the IOPs at 3 months after SLT were significantly lower at 9AM(19.5±3.1mmHg vs. 22.9±5.0mmHg at baseline; p=0.001) and 12 noon (19.9±3.4mmHg vs. 23.4±4.5mmHg at baseline; p<0.001). Outflow facility by fluorophotometry was significantly increased from 0.17±0.11 µl/min/mmHg at baseline to 0.24±0.14 µl/min/mmHg at 3 months(p=0.012). The changes in outflow facility by tonography (baseline:0.17±0.09 µl/min/mmHg vs. 3-months:0.21±0.12 µl/min/mmHg; p=0.14) did not reach statistical significance. There was no change in aqueous flow, episcleral venous pressure or uveoscleral outflow at 3 months after SLT. There were no changes in IOP or AHD in the untreated eye. A comparison of AHD was made between 16 subjects with >10% IOP reduction after SLT treatment (responders), and those without an IOP change (non-responders). Responders had a significant increase in fluorophotometric outflow facility from 0.16±0.13 µl/min/mmHg at baseline to 0.28±0.14 µl/min/mmHg at 3 months after SLT(p<0.001). Non responders did not have any change in outflow facility (baseline:0.19±0.09 µl/min/mmHg; 3 months:0.19±0.12 µl/min/mmHg, p=0.84). The only predictor of response was higher baseline IOP in the responder group (25.3±5.5mmHg vs. 20.3±2.8mmHg, p=0.004).
The IOP lowering effect of SLT appears to be mediated through an increase in trabecular outflow facility. Higher baseline IOP is associated with a better response to SLT laser.
This PDF is available to Subscribers Only