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The sufficient component cause model can be used as a framework to explain the role of individual mechanisms of causation and treatment of primary angle closure disease. It also aids understanding of the proportion of disease due to specific causes.

Phacoemulsification as treatment for primary open-angle glaucoma (POAG) remains more controversial than for primary angle-closure glaucoma (PACG). If the objective of glaucoma surgery is an additional greater than or equal to 5 to 6 mm Hg reduction of intraocular pressure (IOP), the role of phacoemulsification should be based on the probability of achieving this. A Bayesian analysis of available data was performed to calculate the change in IOP after phacoemulsification in POAG and PACG. Standard meta-analysis formulation with prephacoemulsification and postphacoemulsification IOP-assumed to have normal distributions, with study-specific means and SDs-was used. Absolute and relative change in IOP was calculated using different priors, and sensitivity analyses were performed. The prior that just included a decrease of greater than or equal to 6 mm Hg in the 95% credible interval was identified. The probability of achieving greater than or equal to 5 to 6 mm Hg decrease in IOP (and other levels) was calculated. Depending on the prior, the probability of achieving a greater than or equal to 5 mm Hg reduction in IOP in POAG varied from 0.1% to 3%. Confidence in a greater than or equal to 6 mm Hg decrease required a prior belief that phacoemulsification produces a mean decrease of 7 mm Hg. The probability of a decrease in IOP was greater in PACG: approximately 50% probability of a greater than or equal to 5 mm Hg decrease in PACG uncontrolled on medications. Phacoemulsification in POAG has a high probability of producing a small decrease in IOP that may be useful in early, well-controlled disease. The probability of a clinically significant decrease of greater than or equal to 5 to 6 mm Hg-required for advanced/uncontrolled disease-is low. Results support the role of phacoemulsification in PACG.

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