Abstract
PurposeTo investigate the repeatability in corneal thickness (CT) and epithelial thickness (ET) measurements using spectral domain anterior segment optical coherence tomography (AS-OCT, REVO NX, Optopol) in keratoconus, and examine the effect of corneal crosslinking (CXL) on repeatability.MethodsA cross-sectional study of 259 eyes of 212 patients with keratoconus attending the corneal disease clinic at a university hospital tertiary referral center were enrolled. Two groups were analysed: eyes with no prior history of CXL (Group A) and eyes with prior CXL (Group B). Repeatability of measurements was assessed using the intraclass correlation coefficient (ICC) and coefficient of variation (CV).ResultsIn Group A, central corneal thickness (CCT) was 472.18 ± 45.41μm, and the ET was found to be the thinnest in the inferior-temporal aspect at 51.79 ± 5.97μm and thickest at the superior-nasal aspect at 56.07 ± 5.70μm. In Group B, CCT was 465.11± 42.28μm, and the ET was the thinnest at the inferior-temporal aspect at 50.63 ± 5.52μm and thickest at the superior aspect at 56.80 ± 6.39μm. When evaluating CT measurements, ICC was above 0.86 and 0.83 for Group A and Group B respectively. When evaluating ET measurements, ICC was above 0.82 for both groups. CXL had no statistically significant impact on the repeatability of measurements.ConclusionsAS-OCT provides repeatable CT and ET measurements in the central and peripheral cornea in patients with keratoconus. Repeatability is not affected by a history of CXL.
Highlights
Keratoconus is a progressive, non-inflammatory corneal degeneration that leads to corneal thinning, irregular astigmatism and reduced visual acuity [1]
This study aimed to investigate the repeatability of anterior segment optical coherence tomography (AS-OCT) derived corneal thickness (CT) and epithelial thickness (ET) measurements in patients with keratoconus with or without a prior history of CXL
Inferior-temporal thinning and superior-nasal thickening was observed in CT and ET measurements
Summary
Keratoconus is a progressive, non-inflammatory corneal degeneration that leads to corneal thinning, irregular astigmatism and reduced visual acuity [1]. The corneal epithelium is a non-keratinized, stratified layer with a thickness of 48–53μm in healthy eyes, which has previously been shown to be moldable [8]. The corneal epithelium undergoes localized thinning over the cone, the steepest part of the cornea, surrounded by an annulus of epithelial thickening over the flatter regions of the cornea [10]. This epithelial compensation has been shown to mask the underlying irregularities of the corneal topography in ectasia, and previous reports have suggested that ET mapping can be a sensitive test for the diagnosis of early keratoconus [11, 12]
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