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F. Gil-Carrasco, M. Turati, A. Morales-Gonzalez, H. Quiroz-Mercado, M. George, G. Schuele, D. Palanker; Semi-Automated Patterned Laser Trabeculoplasty. Invest. Ophthalmol. Vis. Sci. 2009;50(13):164.
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Argon laser trabeculoplasty (ALT) with 100 ms pulses is an effective therapy for lowering intraocular pressure (IOP). Similar reductions in IOP have been achieved using ns (SLT) and microsecond (MLT) pulses, which produce less thermal damage to trabecular meshwork (TM). Lack of clinically visible changes may make the accurate alignment of subsequent pulses difficult. We describe a novel technique - Patterned Laser Trabeculoplasty (PLT) using the PASCAL Photocoagulator system, and its preliminary evaluation in patients with open angle glaucoma.
In this prospective case series 24 patients (47 eyes) with uncontrolled and untreated open angle glaucoma received patterned laser treatment (180 degree, 532nm, 5ms, 100 µm spot). The laser was first titrated for TM blanching at 10 ms, and using the same power sub-visible PTL was applied with 5 ms pulses. The arc patterns of 24 spots covering 22.5o of TM rotated automatically after each laser application by 22.5o, so that the new pattern is applied at the untreated position, and no visibility of the previously treated area is required for alignment. Pre- and post-treatment IOP was monitored up to 9 months with a Goldmann tonometer.
192 laser lesions were placed per eye in 8 steps. The IOP decreased from pre-treatment level of 21.5 (3.5 STDV) mmHg to 15.3 (2.2 STDV) at 1 day (n=44), to 17.7 (3.7 STDV) (n= 42) at 1 week and stabilized at 16.0 (2.7 STDV) beyond 2 weeks (n=45) up to 9 months (n=7). This highly statistically significant result (all p-values <0.007) corresponds to a 25% IOP reduction.
Single administration of PLT with 5 ms exposures provided an approximate 25% reduction in IOP during the follow-up of 4 to 9 months. Total therapeutic energy with PLT protocol decreased by a factor of 5 on average, compared to ALT. PLT provides for rapid and precise semi-automated treatment with exact abutment of invisible lesions.
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