Customised aberration-controlling contact lenses for keratoconus: the story so far

Purpose: Technological advances have led to the design of customised, aberration-controlling soft contact lenses for keratoconic patients. These lenses are designed to reduce the magnitudes of higher-order aberrations induced through corneal apical protrusion, such as coma, trefoil and spherical aberration. This presentation reviews the limitations of such customised soft contact lens corrections. Methods: Mathematical computations were used to model the magnitude of superfluous aberrations induced through typical ‘on-eye’ rotations or translations of customised soft lenses, specifically designed for patients with mild, moderate and severe keratoconus. Results: The tolerances for on-eye lens displacements were found to be very restrictive. For optimal optical performance, lens rotations should be minimised to less than 8 degrees for patients with mild to moderate keratoconus, yet ideally less than 4 degrees for patients with severe keratoconus. Equally, vertical lens displacements ought to be minimised to 0.10 mm, or less. Conclusions: Compared to conventional, flat-fitting rigid gas-permeable (RGP) contact lenses, customised soft lenses may offer keratoconic patients improved comfort and a reduced risk of developing RGP lens-induced apical scarring. However, the typical on-eye movements of customised soft lenses are likely to hinder their optimal optical performance, thereby limiting their use to patients with early to mild keratoconus only.