Background To review the refractive outcome of cataract surgery in eyes with keratoconus.

Methods We retrospectively reviewed the medical records of 64 consecutive patients (92 eyes) who underwent cataract surgery with implantation of a spherical intraocular lens (IOL). We recorded the method of refractive correction and the effect of the keratometry (K) on the biometry prediction error (BPE).

Results 35 eyes had mild keratoconus (mean K<48 dioptres (D)), 40 had moderate keratoconus (mean K 48 D to 55 D) and 17 had severe keratoconus (mean K>55 D). Actual K values were used in all eyes with mild or moderate keratoconus with a target refraction of approximately −1.0 D in mild keratoconus and −1.5 D in moderate keratoconus that resulted in a mean BPE of 0.0 D and +0.3 D, respectively. The actual K values were used in eight of the 17 eyes with severe keratoconus with a mean target refraction of −5.4 D, which resulted in a mean BPE of +6.8 D. In the remaining nine eyes, a standard K value of 43.25 D was used with a mean target refraction of −1.8 D, which resulted in a mean BPE of +0.6 D.

Conclusions Using the actual K values with a target of low myopia is a suitable option for spherical IOL selection for eyes with a mean K of ≤55 D. When there is severe keratoconus, the use of actual K values can result in a large hyperopic error and the use of standard K value in these eyes should be considered.