A Russian study has revealed factors contributing to the increased risk of long-term selective laser trabeculoplasty (SLT) failure after previously performed peripheral iridotomy (PI) in primary angle closure glaucoma (PACG) compared with primary open-angle glaucoma (POAG). The researchers also found that the high effectiveness rate of SLT (87% in both conditions) fell to just 6% in POAG patients and 4% in PACG patients after six years.

The retrospective study observed 68 eyes of PACG patients and 74 eyes of POAG patients and found SLT’s effectiveness—20% reduction of intraocular pressure (IOP)—on the two groups was equal (87%) one year post-op, but more POAG eyes experienced continued effectiveness at three years compared with PACG eyes (62% vs. 54%).

Predictive factors for SLT failure in the two conditions included corneal hysteresis and age. A smaller pre-SLT anterior chamber depth also factored into a poorer SLT outcome in PACG. The study found that, while pre-SLT IOP did not affect the outcome, the number of pre-SLT pressure-lowing medications was higher in the eyes with SLT failure in both POAG and PACG patients.

Researchers conclude that, despite some limiting factors, the results suggest that SLT is still a safe and effective method of reducing IOP in many eyes with primary chronic angle closure glaucoma.