Case studies: Soft lenses for keratoconus and the irregular cornea

Keratoconus (KC) is a progressive, localized thinning of the cornea that causes increasing irregular astigmatism resulting in distortion (1) and higher order aberrations, in particular, vertical coma (2). Consequently, visual quality with spectacles is often poor and patients rely on rigid contact lenses (CLs) to provide optical neutralisation of the irregular surface and thus be able to lead a normal life, including the ability to drive and work.

Historically, soft contact lenses (SCLs) have been considered inferior in the management of keratoconus as their tendency to drape the cornea – and therefore only minimally mask the surface irregularity – has given poorer visual performance (3). Studies have shown that RGP corneal lenses give enhanced reduction of higher order aberrations and better high and low contrast visual acuity in keratoconus than soft toric and soft spherical lenses respectively (4,5).