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Michael Belkin, Noa Geffen, Shay Ofir, Audrey Kaplan Messas, yaniv barkana, Avner Belkin, Ehud Assia; Trans-scleral Selective Laser Trabeculoplasty (SLT) Without a Gonioscopy Lens. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1863.
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To evaluate whether direct application of SLT irradiation to the perilimbal area is effective in reducing Intraocular Pressure (IOP), eliminating the need for gonioscopy during the procedure.
A randomized, masked, controlled trial was performed on open angle and pseudoexfoliation glaucoma patients. The control group underwent conventional SLT, delivering 100 laser spots through a gonioscope for 360 degrees of the trabecular meshwork(TM). The trial group underwent irradiation by the same laser at the same irradiation parameters, but instead of delivering the energy through a gonioscopy lens, a similar number of applications were administered all around the limbus on the sclera overlying the TM. IOP was measured and side effects evaluated 1, 7, 30, 60 and 180 days after treatment. No changes were made in the medical regimen.
In the trial group (N=11), IOP decrease from an average of 20.90 mmHg before treatment to 15.89 at 2 months and 15.00 at 6 months. The corresponding numbers for the control group (n=10), were 20.50mmHg, 14.71 and 7 (one patient) respectively. There was no statistical difference between the two groups in IOP reduction [P = 0.863, 1, 0.387, 0.529, 0.918 for the IOP on recruitment, 1, 7, 30, 60 and 180 days post SLT respectively, Mann Whitney]. Success, defined as >20% IOP reduction, was attained in 7 patients of either group. There was no statistically significant difference between the groups [P= 0.757, Fisher]. One patient in each group showed mild transient inflammatory response.
The effectiveness of trans-scleral SLT depends on the laser energy penetrating a few millimeters into tissues to impact the TM.Laser coherency, lost in tissue transmission, is not required. The mechanism of action of the external laser irradiation studied is probably similar to that of the conventional one. It seems that SLT applied directly to the perilimbal sclera is as efficacious as the conventional procedure and that the use of a gonioscopy lens is not necessary. As the long-term IOP reduction of SLT can be discerned within a few days after treatment, it is likely that the new technique will be as effective as the conventional one. If so, the novel method will simplify and shorten the SLT procedure considerably and eliminate the corneal and gonioscopy-induced side effects.
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