Selective laser trabeculoplasty: adverse effects of prior topical anti-glaucoma medication

To determine the long-term effect of the administration of topical anti-glaucoma medications on Selective Laser Trabeculoplasty (SLT) efficacy and to identify other potential risk factors for failure of SLT.

A single-centre, observational cohort study of 264 SLT procedures performed on 127 patients over a 10-year period. Data collected included the absolute number of anti-glaucoma drops administered, intraocular pressure (IOP) and the number of anti-glaucoma medications at each visit. A Cox's proportional hazards regression analysis was performed to analyse various risk factors. A multivariate logistic regression model for failure in the first 12 months was constructed to adjust for potential confounders, including age, pre-SLT IOP, treatment duration, disease duration, total number of pre-SLT drops administered and SLT energy delivered.

A greater number of pre-SLT drop administrations was identified as a risk factor for failure of SLT. At 12 months, the complete success rate of SLT for eyes unexposed to drops was 62%, for those to a moderate number of drops, 36-41% and for those to a high number of drops, only 2%. Other statistically significant risk factors included duration of drop therapy, exposure to drop preservatives, disease duration, age, previous cataract surgery, lower pre-SLT IOP and a lower SLT energy level.

Long-term exposure to topical anti-glaucoma medication (especially if preserved), longer duration of disease and therapy, together with older age and prior cataract surgery, may all have a significant adverse effect on SLT outcome.