Evaluating the Global Consensus on Keratoconus and Ectatic Diseases Agreements Reached on Subclinical Keratoconus.

Purpose: To evaluate the consensus agreements reached in the Global Consensus on Keratoconus and Ectatic Diseases project for subclinical keratoconus, specifically that posterior corneal elevation abnormalities must be present to diagnose mild or subclinical keratoconus.

Design: Literature review.

Methods: Database review (PubMed) was performed on January 2, 2024, to identify studies evaluating the ability of posterior corneal surface metrics to identify subclinical keratoconus using the following search terms: posterior corneal elevation; keratoconus screening; corneal ectasia; subclinical keratoconus; keratoconus suspect; and asymmetric keratoconus. Articles were included for final analysis if they evaluated the ability of the posterior corneal surface to identify subclinical keratoconus compared to anterior corneal surface and/or thickness metrics and reported area under the receiver operating curve (AUROC) data for multiple variables to allow for metric comparison. Metrics evaluated in each manuscript were categorized as anterior surface, thickness, or posterior surface. The relative discriminative performance of anterior surface (A), thickness (T), posterior surface (P), and the multimetric D score (D) metrics were evaluated based on AUROC, sensitivity, and specificity in differentiating subclinical keratoconus from normal controls were evaluated.

Results: There were 29 articles identified that met the inclusion criteria and were evaluated. In intrastudy comparison, anterior surface metrics (37.9%) and thickness metrics (39.2%) performed best at differentiating subclinical keratoconus from normal corneas, while only 4 out of 29 studies (13.8%) reported posterior metrics outperforming all metrics. In the subgroup analysis including the multimetric D score (n = 15), anterior surface metrics performed best (33.3%), followed by the D score (26.7%). In this D subgroup, no paper reported superior posterior metric performance.

Conclusions: In aggregate, posterior corneal surface metrics performed worse than anterior corneal and thickness metrics in differentiating subclinical keratoconic eyes from normal controls. These results demonstrate a lack of evidence to support the consensus claim that posterior elevation abnormalities must be present to diagnose subclinical keratoconus.