Purpose: To investigate the effect of primary selective laser trabeculoplasty (SLT) on outflow facility and aqueous flow rate in patients with primary open-angle glaucoma or ocular hypertension.
Methods: Eighteen eyes (9 with ocular hypertension and 9 with primary open-angle glaucoma) were included in this prospective noncontrolled study. Patients with intraocular pressures (IOPs)>21 to 35 mm Hg were treated with 360-degree SLT after a baseline measurement of IOP, tonographic outflow facility, and morning aqueous humor production. Electronic Schiøtz tonography was used to measure the outflow facility. The aqueous flow rate was measured by fluorophotometry, and a pneumotonometer was used to measure the IOP. All measurements were repeated at least 3 months after the laser therapy. Paired Student t tests were used to compare aqueous dynamics parameters before and after treatment.
Results: The mean age of the study population was 56.7 ± 12.4 years. The IOP decreased significantly (21%) from 24.0 ± 3.0 to 18.9 ± 2.7 mm Hg (P<0.001), whereas tonographic outflow facility increased significantly (55.5%) from 0.09 ± 0.05 to 0.14 ± 0.08 µL/min/mm Hg (P=0.003) 3 months after laser treatment. No statistically significant changes in the production of aqueous humor were found (P=0.46).
Conclusions: Our results show that SLT lowers the IOP by increasing the outflow through the trabecular meshwork, but it has no significant effect on the aqueous flow rate.