Non-contact specular microscopy with Topcon instruments to assess central corneal thickness of healthy human eyes – A 20 year review

• Published in: Contact lens & anterior eye 2021-08, Vol.44 (4), p.101385-101385, Article 101385
• Main Author: Doughty, M.J.
• Format: Article
• Language: English
• Subjects: Cornea; Human; Non-contact specular microscopy; Pachymetry
• ISSN: 1367-0484; 1476-5411
• DOI: 10.1016/j.clae.2020.11.005

•The first objective review of the use of non-contact specular microscopy for measures of central corneal thickness.•An important and needed update to a review published 20 years ago on pachymetry in general.•A predictable outcome of use of this type of instrument can be expected. The purpose of this review was to evaluate the consistency of central corneal thickness (CCT) values reported with use of Topcon SP-2000 P and SP-3000 P non-contact specular microscopes since their introduction in 1999 with the two microscopes having been commonly used in a wide range of studies. As a primary resource, PubMed was used to search for peer-reviewed articles in any language that included CCT values obtained with non-contact specular microscopy reported for humans with nominally healthy corneas. Relevant articles were obtained and any cited publications also checked. A total of 76 articles were identified which reported CCT on different small-to-moderate sized groups of individuals, published between 1999 and 2019. From these, an overall group mean CCT value of 0.525 ± 0.013 mm (median 0.525 mm) can be calculated. An estimated 95 % confidence interval (CI, based on 1.96 SD) would be between 0.500 and 0.550 mm. For the two Topcon models, the group mean ± SD values were 0.529 ± 0.013 mm and 0.517 ± 010 mm respectively. An assessment of the CCT data sets in relation to the reported average age indicated no statistically significant effect (p = 0.289, r = −0.129). Very similar average CCT values were also encountered in 4 other reports where these microscopes were used in large-scale population studies as well as in 2 other reports using the newer Topcon SP-1 P model. The Topcon stand-alone non-contact specular microscopes have yielded consistent and predictable corneal thickness measures over many years.