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Severity-Graded Repeatability of AS-OCT Including Epithelial and Stromal Metrics in Patients With Keratoconus Versus
Ramin Khoramnia1,2, Tadas Naujokaitis1,2, Maximilian Friedrich1
1International Vision Correction Research Centre, Department of Ophthalmology, University of Heidelberg, Heidelberg, Germany.
Purpose:
To compare the repeatability of corneal parameters measured by anterior segment optical coherence tomography (AS-OCT) in patients with keratoconus and healthy individuals.
Methods:
This monocentric cross-sectional study included 136 individuals in total: 95 patients with keratoconus and 41 healthy individuals. Three AS-OCT measurements were performed on the same day using the Anterion (Heidelberg Engineering). One eye per patient was randomly selected and repeatability coefficients (RCs) with two-sided 95% CIs were calculated for anterior and posterior keratometry, as well as corneal pachymetric, epithelial, and stromal parameters. The repeatability of measured parameters was compared between patients with keratoconus and healthy individuals and in different keratoconus severity groups using intra-subject variance.
Results:
The RC of maximum keratometry (Kmax) (two-sided 95% CI) was 0.33 diopters (D) (range: 0.29 to 0.39 D) in healthy eyes and 0.68 D (range: 0.62 to 0.76 D) in eyes with keratoconus. The RC of anterior Kmean was 0.19 D (range: 0.17 to 0.23 D) and 0.37 D (range: 0.33 to 0.41 D), the RC of anterior corneal astigmatism was 0.28 D (range: 0.24 to 0.33 D) and 0.43 D (range: 0.39 to 0.48 D), and the RC of minimum corneal thickness was 1.98 µm (range: 1.72 to 2.34 µm) and 2.15 µm (range: 1.96 to 2.39 µm) in healthy eyes and eyes with keratoconus, respectively. Patients with keratoconus had a lower measurement repeatability for most measured parameters, including Kmax (P < .001, Mann-Whitney U test, two-tailed) compared to the healthy individuals. Repeatability tended to worsen with increasing keratoconus severity.
Conclusions:
Although the AS-OCT demonstrated a high measurement repeatability in both healthy eyes and eyes with keratoconus, the repeatability of most evaluated parameters was slightly lower in patients with keratoconus and tended to worsen with increasing keratoconus severity.
