Predictability of Intraocular Lens Power Calculation for Cataract with Keratoconus: A Multicenter Study

Abstract

This study was aimed to assess the predictability of intraocular lens (IOL) power calculation after cataract surgery for keratoconus. We retrospectively reviewed the clinical charts of 102 eyes of 71 consecutive keratoconic patients who developed cataract. We determined manifest spherical equivalent, prediction errors, and absolute errors, 1 month postoperatively. The achieved refraction was significantly more hyperopic than the targeted refraction, when keratometric readings were used (p = 0.001). At 1 month, 36% and 63% of the eyes were within ±0.5 and ±1.0 D, respectively, of the targeted correction. We found a significant correlation between the prediction error and the mean keratometry (Pearson correlation coefficient r =-0.545, p < 0.001). No vision-threatening complications occurred in any case. The achieved refraction was significantly more myopic than the targeted refraction, when total corneal refractive power was used (p = 0.013). Phacoemulsification with IOL implantation appeared to be safe and effective, and the accuracy was also good in mild keratoconus, but not in severe keratoconus. It should be noted that that a large amount of hyperopic shift occurred especially in advanced keratoconic patients, when keratometric readings were used for IOL power calculation, and that a slight, but significant, myopic shift occurred, when total corneal refractive power was used.

Figure 1

A scatter plot of the attempted versus the achieved refraction (manifest spherical equivalent) 1 month postoperatively in eyes with cataract and keratoconus. Thirty seven (36%) and 64 (63%) of 102 eyes were within ±0.5 D and 1.0 D, respectively, of the targeted correction.

Figure 2

Scatter plots of the attempted versus the achieved refraction (sphere and cylinder) 1 month postoperatively in eyes with cataract and keratoconus.

Figure 3

A graph showing a significant association between the prediction error and the keratometric values (Pearson correlation coefficient r =−0.545, p < 0.001).

Figure 4

A graph showing no significant correlation between the prediction error and the axial length (Pearson correlation coefficient r = 0.163, p = 0.101).