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S.M. Ali, M.A. R. Awan, S. Murthy, P.G. J. Corridan; Argon Laser Trabeculoplasty: Is ALT1 IOP Response a Good Predictor of ALT2 IOP Response? . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5459.
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Argon Laser Trabeculoplasty (ALT) is considered as an important adjunct treatment option for Primary Open Angle Glaucoma (POAG), Pigmentary Glaucoma (PG), Pseudo Exfoliative Glaucoma (PEXG) and normal tension glaucoma (NTG) for last three decades. Some Ophthalmologists also tried it as a primary treatment modality for POAG and other sub types of secondary open angle glaucoma. Most often it is delivered in two sessions (ALT 1 and ALT2) to prevent the acute transient rise in Intra Ocular Pressure (IOP) following the trabeculoplasty.
The purpose of this study was to look at the correlation between ALT 1 and ALT2 IOP responses and to determine whether the IOP response to ALT1 could predict the IOP response to ALT2.
We retrospectively reviewed the case notes of the patients who had ALT in two sessions between 2000 and 2005. We used Pearson correlation test to look at the correlation between ALT1 and ALT2 IOP responses.
46 eyes of 30 patients were included. Mean age was 73 years (range: 46– 93). 14 were males and 16 were females. 27 patients had POAG, 2 had NTG and 1 had PG. Mean time interval between ALT1 and ALT2 was 7.56 months (range 1–55 months). Mean pre ALT1 IOP was 21.19 ± 4.3 mm Hg which dropped to 18.76 ± 3.6 mm Hg, after mean duration of 11.6 weeks (range: 6–16 weeks) following ALT1. Mean pre ALT2 IOP was 19.91 ± 4.2 mm Hg which dropped to 17.74 ± 3.7 mm Hg after mean duration of 13.7 weeks (range: 6–16 weeks) following ALT2. Mean IOP drop of ALT1 was 2.3 ± 3.0 mm Hg and that of ALT2 was 2.19 ± 3.7 mm Hg. The correlation analysis showed weakly positive correlation between ALT1 and ALT 2 IOP responses, the correlation coefficient being 0.12. Our results also showed that 40% of the patients who did not respond well to ALT1 (IOP drop less than 2 mm Hg) did well with ALT2 with the IOP drop being greater than 2mm Hg. Mean IOP drop was 0.41 mm Hg after ALT1 and 2.47mm Hg after ALT2 in these patients.
IOP response to ALT1 is not good predictor of the IOP response to ALT2. A significant proportion of the patients who have poor IOP response to ALT1 can achieve a significant IOP drop with ALT2.
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