2.4. Systematic Review and Meta-Analysis

The review text was structured in accordance with guidelines from PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [16].

The aim of this review was to obtain the answer to the following PICO (patient, intervention, comparison, and outcome) question [17]: What effect do anesthetic eye drops have on CCT values?

An electronic literature search was conducted in several databases, including MEDLINE, EMBASE, and COCHRANE, and addressed articles published between January 1992 and June 2017 in the English language. MESH (for Medical Subject Headings) terms, keywords, and other free terms and Boolean operators (AND, OR) were used to combine searches based on the search strategy previously reported.

For the screening process in databases, the following terms were used: “topical anesthesia and corneal thickness”, “oxybuprocaine and corneal thickness”, “proparacaine and corneal thickness”, “tetracaine and corneal thickness”, “benoxinate and corneal thickness”, and “anesthetic eye drops and corneal thickness”. Two reviewers independently obtained the data from the studies (MM and MP-B). In the case of disagreement, consensus was reached by discussion with a third reviewer (JAS-G).

Articles were included in the systematic review if they met the following inclusion criteria: (1) articles published in Journals included in the Journal Citation Report Science Edition; (2) human study; (3) prospective; (4) studies that reported CCT values before and after oxybuprocaine eye drop instillation. Articles excluded from the systematic review were (1) animal studies; (2) case reports; (3) reviews; (4) studies that did not fulfill the above inclusion criteria; and (5) studies that reported information that was not clear enough or was inconsistent. The quality of such studies was assessed by two masked examiners using the Newcastle-Ottawa scale (NOS) [18]. The NOS assigns a maximum of nine stars; a minimum of six were required to be included in our study.