Refractive lens exchange in keratoconus

Purpose

To evaluate the visual results and complications of refractive lens exchange to correct myopia associated with early-stage keratoconus.

Setting

Private practice, Siena, Italy.

Methods

This prospective noncomparative interventional series comprised 34 consecutive eyes of 20 patients with stages I to II keratoconus. Mean patient age was 56.7 years ± 10.4 (SD). Preoperative mean spherical equivalent (SE) was −11.0 ± 4.65 diopters (D), (range −5.75 to −22). Ultrasound biometry was performed using videokeratographic central K-readings and the Holladay 2 formula. An intraoperative handheld autorefractor was used to check the power of implanted intraocular lenses.

Results

Intraocular lens exchange due to inaccurate power occurred in 11 eyes (32%; 9 eyes intraoperative, 2 eyes postoperative). At 12 months, mean SE was −1.31 ±1.08 D and mean defocus equivalent was 1.94 ± 1.57 D. Twenty-two eyes (65%) were within ±2 D of defocus equivalent, 16 eyes (47%) were within ±1 D, and 3 eyes (9%) were within ±0.5. Mean surgically induced astigmatism (vector analysis) was 0.54 ± 0.43 D. Preoperative mean best spectacle-corrected visual acuity (BSCVA) was 0.55 ± 0.20, and postoperative mean BSCVA was 0.76 ± 0.23; the difference was statistically significant (P<.05; 95% confidence interval, 0.19 to 0.25). Postoperative mean uncorrected visual acuity was 0.48 ± 0.25. The safety index was 1.38, and the efficacy index was 0.87. Complications were posterior vitreous detachment (9%) and dysphotopsia phenomena (15%). Corneal endothelial cell density at 12 months decreased by 6.3%.

Conclusion

Refractive lens exchange in keratoconic eyes predictably corrected myopia. However, ultrasound biometry was inaccurate in almost one third of eyes. Intraoperative autorefractometry is recommended to improve refractive outcome.