Scheimpflug-Derived Keratometric, Pachymetric and Pachymetric Progression Indices in the Diagnosis of Keratoconus: A Systematic Review and Meta-Analysis
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Date
2023
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Publisher
Clinical Ophthalmology
Abstract
Scheimpflug Pentacam Tomography is becoming crucial in the diagnosis and monitoring of keratoconus, as well as in pre and post-corneal refractive care, but there are still some inconsistencies surrounding its evidence base diagnostic outcome. Therefore,
this study aimed at employing meta-analysis to systematically evaluate the keratometric, pachymetric, and pachymetric progression
indices used in the diagnosis of Keratoconus. The review protocol was registered with PROSPERO (Identifier: CRD4202310058) and
followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, MEDLINE, Web
of Science, and EMBASE were used for data search, followed by a quality appraisal of the included studies using the revised tool for
the quality assessment of diagnostic accuracy studies (QUADAS-2). Meta-analysis was conducted using the meta (6.5.0) and metafor
(4.2.0) packages in R version 4.3.0, as well as Stata. A total of 32 studies were included in the analysis. All keratometry (K) readings
(flattest meridian, K1; steepest meridian, K2, maximum, Kmax) were significantly steeper in keratoconic compared to normal eyes:
[MD (95% CI)], K1 [2.67 (1.81; 3.52)], K1-back [−0.71 (−1.03; −0.39)], K1-front [4.06 (2.48; 5.63)], K2 [4.32 (2.89; 5.75)], K2-back
[−1.25 (−1.68; −0.82)], K2-front [4.82 (1.88; 7.76)], Kmax [7.57 (4.80; 10.34)], and Kmean [2.80 (1.13; 4.47)]. Additionally, corneal
thickness at the center, CCT [−61.19 (−73.79; −48.60)] and apex, pachy-apex [−41.86 (−72.64; −11.08)] were significantly thinner in
keratoconic eyes compared to normal eyes. The pooled estimates for pachymetric progression index (PPI): PPImin [0.66 (0.43; 0.90)],
PPImax [1.26 (0.87; 1.64)], PPIavg [0.90 (0.68; 1.12)], and Ambrosio relational thickness (ART): ARTmax [−242.77 (−288.86;
−196.69)], and ARTavg [−251.08 (−308.76; −195.39)] revealed significantly more rapid pachymetric progression in keratoconic eyes
than in normal eyes. The Pentacam Scheimpflug-derived keratometric, pachymetric, and pachymetric progression indices are good
predictors in discriminating KC from normal eyes.
Description
Research Article
Keywords
corneal topography, keratometric readings, central corneal thickness