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N. Y. Gan, L. W. Yip; Correlating Pre-Operative Axial Lengths With Phacotrabeculectomy Outcomes - A Retrospective Analysis of Primary Angle Closure and Primary Open Angle Glaucoma Patients in an Asian Population. Invest. Ophthalmol. Vis. Sci. 2010;51(13):630.
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To determine if there is an association between pre-operative axial lengths (AL) and outcomes of combined cataract and glaucoma surgery in primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG) patients; based on the hypothesis that shorter eyes might benefit from an extra IOP-lowering effect due to lens extraction facilitating angle opening.
Inclusion criteria were all patients who had undergone phaco-trabeculectomies with the use of anti-metabolites at Tan Tock Seng Hospital from 2004-06. Retrospective data collection was done for the first, third, sixth month and subsequent half-yearly follow-ups, for a total of 24 months.Regression analyses were used to describe the relationships between pre-operative ALs and IOPs at 1 month, complete success at 24 months. The latter taken as failure if IOP >15 mmHg or if glaucoma drops were initiated. Further analyses were performed comparing PACG and POAG eyes and within each group.
294 eyes (263 patients) fulfilled the inclusion criteria. Single eye was used for analysis by randomisation. POAG formed the majority with 134 eyes (51.0%), while PACG comprised 35.7% with 94 eyes.PACG eyes have a shorter mean AL of (22.96 ± 0.88) mm, compared to POAG eyes (23.79 ± 1.21) mm, p<0.05; and have a statistically significant reduced odds of failure at 24 months (OR: 0.463; p=0.022).However, within each glaucoma subtype, shorter eyes did not have a statistically significant difference in survival compared to longer eyes. Also, no significant correlation was found between ALs and IOP outcomes at 1 and 24 months, after adjusting for glaucoma subtype and IOP-susceptibility factors.
Our findings did not support our hypothesis. Although PACG eyes were found to have reduced odds of failure at 24 months, no significant relationship was found between shorter ALs and better outcomes, suggesting that shorter eyes do not seem to benefit from an additional IOP-lowering effect from lens removal in phaco-trabeculectomy, as compared to longer eyes. We postulate that this could be due to bleb function taking over the major IOP-lowering role in the long run.
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