All potential studies required measurement of IOP to be made with the Tono-Pen XL (TP) or Tono-Pen AVIA (TP) applanation tonometers and the Goldmann applanation tonometer (GAT), in the same subject, in a single session, with the subject sitting in an upright position, in accordance with standardized measurement instructions provided by each instruments’ manufacturer. All IOP measurements were required to be reported in mm Hg. Summary statistics which contained the means and standard deviations of TP and GAT IOP measurements were required, for each primary study.
All primary studies were required to report the number of individuals participating, the number of eyes included in the statistical summaries, whether only 1 eye or 2 eyes were reported for each subject, the mean age of subjects (all subjects must have been 17 years of age or older), the country in which the study was completed, and the setting in which the IOP measurements were made (hospital, out-patient clinic, clinician’s office, research laboratory).
All primary studies were required to provide a clear statement, that all subjects reported in the “healthy” or “control” groups were free from eye pathologies, for example, glaucoma, suspected glaucoma, ocular hypertension, corneal edema, inflammation, which would potentially effect IOP measurements. Eye health was assessed by patient history in combination with ophthalmological examination. Primary studies were not required to investigate IOP in healthy adult, as the study’s primary research objective; only that IOP measurements and associated required information could be extracted from the primary study.
In the event mean CCT and associated standard deviations from the means were reported in the primary study, in addition to TP and GAT IOP, this information was recorded and included in the database for descriptive purposes and subsequent secondary analyses. CCT measurements were not required for primary study inclusion in the meta-analysis of IOP.
All primary studies were required to provide a clear statement, the study had been preapproved by the facility’s Institutional Review Board or local Ethics Committee and conducted in accordance with the tenets of the World Medical Association Declaration of Helsinki-Ethical Principles for Medical Research Involving Human Subjects.