The purpose of the study was to identify corneal epithelial- and stromal-thickness distribution patterns in keratoconic eyes using spectral-domain-optical coherence tomography (SD-OCT).

Study Hypothesis: SD-OCT provides necessary details about the distribution of corneal epithelial and stromal thicknesses for identification of a pattern characteristic for early keratoconus.

Purpose of the study: To characterize epithelial and stromal thickness distribution in keratoconic eyes and to develop epithelial and stromal thickness-based variables for keratoconus detection.

Methodology: SD-OCT corneal scans of 20 eyes with keratoconus (group 1) and 20 healthy eyes with > 2 diopters (D) of corneal astigmatism as controls (group 2) are studied. Keratoconus patients referred to the Eye Dpt. of the University Hospital North Norway for CXL (Corneal collagen cross-linking)- treatment and healthy subjects seeking preoperative evaluation for refractive surgery at SynsLaser® Kirurgi AS Tromsø clinic are examined by corneal SD-OCT as a part of their routine examination. Analysis of their SD-OCT corneal scans is used for the purpose of this study.Two cross-sectional meridional corneal profiles (along steepest and flattest meridians, located by a Scheimpflug-based corneal topography) for each individual are obtained by using a RTVue100® (Optovue Inc. Fremont, California, USA), 26000-Hz SD-OCT across the central 6mm diameter of the cornea.

Inclusion Criteria:

• Keratoconus group: Confirmed diagnosis of keratoconus
• Astigmatism group: Healthy eyes with astigmatism of >2.0 D

Exclusion Criteria:

• Keratoconus group: Keratoconus > stage 3 on Krumeich scale
• Astigmatism group: No signs of keratoconus

20 eyes with diagnosed keratoconus and 20 healthy eyes with astigmatism >2.0 D