Comparison of IOL power calculation methods and intraoperative wavefront aberrometer in eyes after refractive surgery

To compare preoperative methods for calculating intraocular lens (IOL) power versus the intraoperative wavefront aberrometer in eyes with a history of refractive surgery.

A retrospective study of 46 eyes (33 patients) with previous refractive surgery that underwent subsequent cataract surgery was conducted. Suggested IOL power predicted by ORange intraoperative wavefront aberrometer (WaveTec Vision Systems, Inc., Aliso Viejo, CA) was compared to power predicted by the (1) SRK-T formula using keratometry and axial length measurements from the IOLMaster (Carl Zeiss Meditec, Dublin, CA), (2) average central keratometry (Avg K) from corneal topography, and (3) average IOL power predicted by the American Society of Cataract and Refractive Surgery (ASCRS) web site. No historical information was used for the calculations. IOL power required for emmetropia was back-calculated using manifest refraction and implanted IOL power after cataract surgery.

Mean age was 60 ± 7.9 years. Fifteen percent had a history of myopic photorefractive keratectomy (n = 7), 57% myopic LASIK (n = 26), 13% hyperopic LASIK (n = 6), and 22% radial keratectomy (RK) (n = 10). In 37% of cases, ORange predicted IOL power to within ±0.50 diopters (D) of emmetropia, compared to 30% for IOLMaster keratometry, 26% for Avg K, and 17% for ASCRS web site. In eyes after myopic treatment, ORange, IOLMaster, Avg K, and ASCRS web site predicted within ±0.50 D of emmetropia in 39%, 27%, 24%, and 18%, respectively, and within ±1.0 D in 60%, 39%, 39%, and 51%, respectively. In eyes after RK, ORange, Avg K, and ASCRS web site predicted to within ±0.50 D of emmetropia in 14% and the IOLMaster in 43% cases.

Although the ORange most often predicted to within ±0.5 D of emmetropia, no method was able to achieve this accuracy more than 50% of the time. Predictions for eyes after RK were worse than for other types of refractive procedures.