Selective laser trabeculoplasty (SLT) may do more than lower mean intraocular pressure (IOP)—it may also reduce short-term diurnal pressure fluctuation for up to 18 months after treatment, according to data presented at the American Glaucoma Society’s annual meeting in Rancho Mirage, California.
In a prospective study using home tonometry, Catherine Johnson, MD, MPH, reported that eyes treated with SLT showed sustained reductions not only in mean and maximum intraocular pressure but also in measures of variability, including IOP range and standard deviation. The findings may help clarify how SLT influences pressure control beyond what is captured during routine clinic visits.
“Short-term IOP fluctuation over the course of the day is a significant risk factor for glaucoma progression,” said Dr. Johnson, a PGY-2 resident at the University of Buffalo, who presented on behalf of researchers from the John A. Moran Eye Center of the University of Utah, Salt Lake City. “However, there are limited prospective studies evaluating how SLT affects diurnal IOP fluctuation, which was the primary motivation for this study.”
The study enrolled patients with open-angle glaucoma or ocular hypertension who were scheduled to undergo SLT and were able to reliably use a home tonometer (iCare Home2; iCare USA). Participants measured their IOP at home at 6 standardized time points—6 am, 9 am, noon, 3 pm, 6 pm, and 9 pm—for 7 consecutive days at baseline and again at 6 weeks and 3, 6, 12, and 18 months after SLT. The study ultimately included 52 eyes of 32 patients, with a mean age of approximately 65 years.
Using mixed-effects regression models, investigators found that SLT produced sustained reductions in multiple IOP parameters—including mean and maximum IOP, IOP range, and standard deviation—at all posttreatment time points through 18 months. “These differences were statistically significant across all measured time points,” Dr. Johnson said.
The reductions in IOP variability persisted even as the number of eyes available for analysis declined over time, which investigators attributed to loss to follow-up, medication changes, or repeat SLT. Dr. Johnson noted that “attrition of participants is a notable limitation of our study,” adding that several eyes required additional intervention before reaching the 18-month endpoint.
The study also examined whether patient or disease characteristics predicted IOP fluctuation reduction after SLT. Age, sex, glaucoma subtype, baseline IOP, medication burden, and prior SLT exposure were not significant predictors, Dr. Johnson noted.
One of the more clinically relevant findings involved the timing of peak IOP values. “A large proportion of maximum IOP values occurred outside typical clinic hours,” defined as 8 am to 5 pm, Dr. Johnson said, suggesting that office-based measurements may underestimate true IOP variability. The greatest reduction in mean IOP compared with baseline was observed in the early morning hours, roughly between 4:30 and 7:30 am, a period when IOP is known to peak in many patients.
Taken together, the findings suggest that SLT may provide more comprehensive pressure stabilization than is apparent from single clinic measurements. “Overall, we found that measures of IOP fluctuation were significantly reduced through 18 months after SLT,” Dr. Johnson said. “The IOP-lowering effect of SLT was durable over this time period.” Another takeaway is that home tonometry is an effective tool to assess patients’ response to treatment, she noted.
She mentioned that future research is planned, including a similar prospective study to assess IOP response to the direct SLT procedure (Voyager DSLT; Alcon), a study to examine the IOP response to SLT in the untreated fellow eye, and a similar assessment of IOP fluctuation before and after MIGS procedures. GP