We read with interest the systematic review and meta-analysis on the effect of statins on intraocular pressure (IOP) and glaucoma incidence and progression by McCann et al. 1 We would like to discuss the appropriateness of inclusion of studies in the systematic review, placement of studies in the metaanalysis, and the process of appraising the quality of evidence of the included studies.
APPROPRIATENESS OF INCLUSION OF STUDIES IN THE SYSTEMATIC REVIEWThe authors claim that the systematic review was to evaluate the effect of statins on glaucoma; the inclusion of studies with nonglaucoma cases could lead to erroneous conclusions. The authors included the case-control study by Owen et al., 2 which defined cases based on a combination of diagnostic codes for glaucoma or ocular hypertension and codes for prescription specific to glaucoma treatment. In the definition of glaucoma, ocular hypertension is not a subtype of glaucoma. There was also a lack of information on the proportion of cases with a diagnostic code of ocular hypertension in the study. With the large uncertainty on the proportion of cases with glaucoma, this case-control study must be excluded from both the systematic review and meta-analysis.In addition, one of the purposes of the systematic review was to