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Masking of irregular corneal topography with contact lenses
M Griffiths1, K Zahner, M Collins
1Centre for Eye Research, School of Optometry, Queensland University of Technology, Australia.
Purpose:
We examined the effectiveness of various types of contact lenses in masking irregular corneal topography using videokeratoscopy, residual aberrations, and measurement of visual acuity.
Methods:
Thirteen subjects with differing degrees of keratoconus were recruited. Four types of soft lenses were used that varied in both thickness and water content, along with a rigid gas permeable (RGP) and a flexible gas permeable contact lens.
Results:
RGP contact lenses provided the best visual acuity and the least residual aberrations. Flexible gas permeable lenses showed a reasonable masking of corneal distortion but did not provide the expected improvement in visual acuity. Soft contact lenses provided marginally better visual acuity than spectacle correction, but the level of residual aberrations was still high, even for relatively thick soft lenses (up to 0.2 mm). A significant correlation existed between the regularity of the front surface of the contact lenses on the eye and visual acuity in low illumination.
Conclusions:
Among the currently available contact lens materials, RGP lenses provide the best visual performance for subjects with keratoconus.