Orthokeratology effect on the corneoscleral profile: Beyond the bull's eye

To assess the impact of 3 months of orthokeratology (ortho-k) contact lenses (CLs) for myopia correction on the corneoscleral profile, as changes in scleral geometry could serve as indirect evidence of alteration in the corneal biomechanical properties.

Twenty subjects (40 eyes) were recruited to wear ortho-k lenses overnight; however, after discontinuation (two CL fractures, one under-correction and two non-serious adverse events), 16 subjects (31 eyes) finished a 3-month follow-up. Corneoscleral topographies were acquired using the Eye Surface Profiler (ESP) system before and after 3 months of lens wear. Steep (SimKs) and flat (SimKf) simulated keratometry and scleral sagittal height measurements for 13-, 14- and 15-mm chord lengths were automatically calculated by the ESP software. Additionally, sagittal height and slope were calculated in polar format from 21 radii (0–10 mm from the corneal apex) at 12 angles (0–330°). Linear mixed models were fitted to determine the differences between visits.

SimKs and SimKf were increased significantly (p ≤ 0.02). The sagittal height in polar format increased significantly (p = 0.046) at a radius of 2.5 mm for 150°, 180°, 210° and 240° orientations and at a radius of 3.0 mm for 210°. Additionally, the slope in polar format significantly decreased (p ≤ 0.04) at radii ranges of 0.0–0.5, 0.5–1.0 and 1.0–1.5 mm for multiple angles and at a radii range of 5.0–5.5 mm for 90°. It also increased significantly (p ≤ 0.045) at a radii range of 1.5–2.0 mm for 30° and at radii ranges of 2.0–2.5, 2.5–3.0 and 3.0–3.5 mm for multiple angles. No significant changes were found for any parameter measured from the scleral area.

Three months of overnight ortho-k lens wear changed the central and mid-peripheral corneal geometry as expected, maintaining the peripheral cornea and the surrounding sclera stability.