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Yotam Weiner, Asher Weiner; The Relationships between Immediate and Short-term Intra-ocular Pressure (IOP) Following Selective Laser Trabeculoplasty (SLT), Trabecular Meshwork Pigmentation (TMP), and Laser Power Used. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1859.
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To study the relationships between immediate and early post-SLT IOP, TMP and laser power used.
A retrospective interventional non-randomized comparative chart review. Main outcome measures were 1-hour IOP elevations and 8-week post-SLT IOP, and their relations to TMP and laser power used. Eyes with primary open angle or normal-tension glaucoma, and ocular hypertension were included. Eyes with pigment dispersion were excluded.
We identified 189 eyes of 189 patients with no previous trabeculoplasty in either eye. Age was 72±12 (mean±SD, range: 28-97) years. Central corneal thickness was 552.4±39.41 (range: 460-669) micron. TMP was 1.3±0.7 (range: 0-4), and SLT power used was 0.82±0.13 (range: 0.5-1.2) mJ. Mean pre-SLT IOP was 18.7±4.7 (range: 11-37) mmHg, reduced to 14.7±3.7 (range: 8-26) mmHg at 8 weeks (p<0.0001). The latter IOP was directly correlated with pre-SLT IOP (p<0.0001, r2=0.389). Neither TMP nor power used alone were correlated with 8-week IOP reduction (%), but the latter was directly correlated with pre-SLT IOP (p<0.0001, r2=0.096), and inversely correlated with TMP/power ratio (p=0.012, r2=0.037). Multiple regression analysis also showed the significant correlation between IOP reduction at 8 weeks, and both pre-SLT IOP (p<0.0001, r2=0.0012) and TMP/power ratio (p=0.0192, r2=0.0012). IOP 1 hour post SLT and Brimonidine 0.1% treatment was 14.5±4.2, (range: 4-30) mmHg. It was significantly lower than pre-SLT IOP (p<0.0001), and directly correlated with it (p<0.0001, r2=0.1749). IOP elevations of >5 mmHg at 1 hour occurred in 4 (2.1%) eyes despite Brimonidine 0.1% treatment. In all 4 eyes, the power used was >0.8 mJ, TMP was <2, and the TMP/power ratio was ≤1.5.
The TMP/power ratio was inversely correlated with SLT efficacy at 8 weeks, that is, we found higher efficacy with higher powers used for a given TMP. Acute IOP elevations were more common with higher powers used, lower TMP, and a lower TMP/power ratio, suggesting that the power used and not the degree of trabecular pigmentation was related to acute IOP elevations. These results may contrast previously published treatment parameters recommendations, and our findings may not apply to eyes with pigment dispersion as these were excluded from our study.
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