Treatment of Astigmatism in Keratoconus and Other Corneal Ectasias
Clinical Scenario
This protocol addresses irregular astigmatism arising in conditions such as keratoconus, corneal ectasias, corneal dystrophies, corneal scarring, and postsurgical corneas — a population with correction needs that differ substantially from those with regular astigmatism.
Why Standard Correction Is Insufficient
In irregular corneal astigmatism, the magnitude and axis of astigmatism vary across different points of the cornea. Higher-order aberrations cannot be fully corrected by spherocylindrical corrective lenses, leaving significant uncorrected visual deficit in this group.
Approach Overview
Some patients in this setting achieve adequate visual function only with contact lenses. The protocol involves rigid gas-permeable contact lens options suited to the irregular corneal surface — the specific lens types, selection criteria, and management considerations for anisometropia are detailed in the full regimen.
Target: Corrected visual acuity of 20/25 or better
References
- In irregular corneal astigmatism, the magnitude and the axis of astigmatism vary in different points of the cornea, which can be clinically significant in conditions such as keratoconus and other corneal ectasias, corneal epithelial basement membrane and stromal dystrophies, corneal scarring, and postsurgical corneas.
- Higher order aberrations cannot be fully corrected by spherocylindrical corrective lenses.
- Some patients achieve adequate visual function only with contact lenses.
- This may include patients with high refractive errors, anisometropia, or an irregular corneal surface or shape.
- Rigid gas-permeable scleral lenses (diameter more than 17 mm) are an option for the correction of high and/or irregular astigmatism, particularly if combined with anisometropia.
- Although most normal eyes should have a corrected acuity of 20/25 or better, it may not be possible to achieve this level of acuity in patients with high refractive errors, even with optimal refraction.
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