Corneal Epithelial Thickness Intrasubject Repeatability and its Relation With Visual Limitation in Keratoconus

Area of Science:

• Ophthalmology
• Corneal Imaging
• Refractive Surgery

Background:

• Keratoconus is a progressive corneal ectasia affecting visual acuity.
• Accurate measurement of corneal epithelial thickness is crucial for diagnosis and management.
• Anterior Segment Optical Coherence Tomography (AS-OCT) offers high-resolution imaging of the cornea.

Purpose of the Study:

• To assess the intra-subject repeatability of epithelial thickness measurements obtained with AS-OCT combined with Placido disc MS-39.
• To correlate epithelial thickness variations with the degree of visual limitation in keratoconus patients.

Main Methods:

• A cross-sectional study involving 107 keratoconus eyes and 60 healthy eyes.
• Three consecutive epithelial thickness measurements were performed using MS-39 in central and peripheral corneal regions.
• Intrasubject repeatability was analyzed using the intraclass correlation coefficient (ICC).
• Correlation between epithelial indices and best-corrected visual acuity (BCVA) was evaluated.

Main Results:

• High repeatability (ICC ≥0.90) was observed for epithelial thickness measurements in both keratoconus and healthy eyes.
• Thinner central 3mm and thicker superior/thinner inferior 8mm epithelial zones were associated with worse BCVA.
• Decreased central 3mm thickness and increased superior-inferior ratios correlated with increased keratoconus severity.
• Multivariate analysis identified thinner central 3mm, superior-inferior ratios, and steeper K2 as significant predictors of keratoconus (AUC=0.92).

Conclusions:

• The MS-39 device demonstrates high repeatability for corneal epithelial thickness measurements.
• Epithelial thickness patterns are significantly correlated with visual acuity and keratoconus grading.
• These AS-OCT-derived epithelial measurements may aid in differentiating keratoconus from healthy eyes.