Repeat-selective laser trabeculoplasty (SLT) administered during the LIGHT Trial lowered intraocular pressure (IOP) in eyes with IOP increases during 1.5 years after the initial SLT application. The decrease lasted longer than the initial lowering.
This article was reviewed by Prof Gus Gazzard, FRCOpthMA, MBBCHIR, MD
Repeat-selective laser trabeculoplasty (SLT), a protocol explored in a subset of patients in the SLT Laser in Glaucoma and Ocular Hypertension (LIGHT Trial), successfully lowered the IOP in eyes in which the IOP increased after 1.5 years after the initial SLT application.
The IOP decrease resulting from repeat-SLT lasted longer than the first round of IOP lowering.
The three-year LIGHT Trial evaluated the initial treatments using SLT laser or medications in patients with glaucoma and ocular hypertension; treatments were increased as required, according to Gus Gazzard, FRCOpthMA, MBBCHIR, MD, professor of ophthalmology at UCL-University College and consultant ophthalmic surgeon, Moorfields Eye Hospital, London.
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The study included only treatment-naÃ¯ve patients with newly diagnosed primary open-angle glaucoma (POAG) or ocular hypertension in one or both eyes. Patients with advanced disease who could not be treated with laser or medication were excluded from the trial.
A total of 718 patients ultimately were randomly selected to either SLT laser or medication at the beginning of the LIGHT Trial.
At the end of the three years, 91% of patients remained in the study.
The initial standardized SLT protocol included 360º of treatment in which 100 laser shots were applied using a Latina SLT contact lens.
The clinical endpoint was that at least 50% of the shots had visible bubble formation without free streams of bubbles. The SLT could be repeated once, Dr. Gazzard explained.
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The criteria for undergoing repeat-SLT were failure within 18 months after the initial SLT and eyes in which retreatment was triggered at a pre-defined criteria using eye-specific, severity-dependent target IOP, and/or disease progression based on a custom-designed clinical decision-support algorithm.
That software also guided the follow-up intervals and time to reintervention.
In selecting the eyes to undergo repeat-SLT, the investigators also considered the degree of IOP lowering at two months; this value at that time point is strongly predictive of the three-year outcome.
The two-month time point was the first time point at which treatment increases were allowed.
The investigators also looked at the duration of the effect after the initial and the repeated applications of SLT to determine how long the target IOP remained controlled, Dr. Gazzard explained.
In the initial LIGHT Trial, 611 eyes underwent SLT. Of those, 158 eyes failed during the first 18 months and 115 eyes (90 patients) underwent repeat-SLT.
The other 43 eyes that were not at the target IOP did not undergo repeat-SLT.
“The total repeat-SLT power used was slightly greater,” Dr. Gazzard reported.
The initial value was 89.1 mJ versus 100.5 mJ, which was a significant increase (p < 0.001).
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Dr. Gazzard reported that the mean IOP was higher before the initial SLT compared with the repeat-SLT (24.5 versis 21.0 mm Hg, p < 0.001).
“We did not allow the patients to return to the baseline IOPs before we re-intervened, to mirror normal clinical practice,” he pointed out.
At that important two-month time point, the absolute IOP reduction was greater after the initial SLT, that is 5.3 versus 4.6 mm Hg (p = 0.02).
Dr. Gazzard also explained that if the two-month IOP adjusted for the starting IOP immediately before laser treatment was used, there was a greater adjusted effect after the repeat-SLT.
“The adjusted difference between the primary laser and the repeat laser showed that the latter seemed to be producing a greater proportional effect,” he said.
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The adjusted mean difference was -1.1 mm Hg (P = 0.001).
The results also showed that the targeted IOP after the repeat-SLT was maintained better than the IOP after the initial SLT.
A comparison of the early failures with the later failures who were not included in the Repeated-SLT subgroup was undertaken to determine a bias.
Thirty-four eyes were retreated at two months because they had not achieved the target IOP and compared with 81 eyes that failed after two months. There was no difference in effect in the early versus later failures; the mean difference in the IOP reduction was 0.3 mmHg, Dr. Gazzard explained.
“The early failures tended to more often have moderate to more severe POAG, and, therefore, the IOP target was more stringent,” he said.
Dr. Gazzard concluded that repeat-SLT successfully reduced IOP in eyes that failed within 1.5 years of the start of the LIGHT Trial.
“The adjusted absolute IOP reduction, controlling for the pre-treatment IOP, seemed to be greater than after the first laser treatment,” he said. “The IOP lowering in these eyes seemed to last longer after repeat-SLT. The response did not seem to be linked to the time of the first failure.”
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Gus Gazzard, FRCOpthMA, MBBCHIR, MDE: firstname.lastname@example.org
Dr. Gazzard is supported by a grant from the National Institute for Health Research-Health Technology Assessment. He reports that he has no financial interest in any ophthalmic products, company, or related stocks.