Data extraction and reporting strategies of studies assessing non-central corneal thickness by Pentacam: a review

Purpose: To review data extraction strategies for the reporting of non-central corneal thickness with the Pentacam system. Methods: Using predefined search terms, the electronic National Institutes of Health database (PubMed) was searched for studies assessing non-central corneal thickness using the Pentacam instrument. The article titles of the search results were screened for relevance. The abstracts of papers with appropriate titles were retrieved and read. Articles with relevant abstracts were obtained and read in full. The reference list of each article was hand searched to identify further studies. Articles reporting central corneal thickness only were excluded. Results: Seventeen peer-reviewed studies were identified. Considerable differences in data extraction and reporting of non-central corneal thickness were noted, with non-central pachymetry being assessed at locations between 1.5 and 5.0. mm away from the centre. The terminology used to describe non-central pachymetry was inconsistent. Ring-averaged and single point pachymetry data have been reported. Ring-averaged pachymetry may obscure considerable regional variability in corneal thickness. Conclusions: The use of different data extraction and reporting strategies can obscure regional corneal thickness asymmetries. This may influence the monitoring of corneal crosslinking outcomes, the interpretation of corneal swelling in contact lens studies and the clinical decision-making in preoperative assessments of refractive surgery patients. For the reliable identification of regional corneal thickness variations point-pachymetry data appears to be preferable over ring-averaged pachymetry.