Comparison of objective and subjective refraction before and after laser in situ keratomileusis

Abstract

Purpose To compare the accuracy and reliability of objective and subjective refractions before and after laser in situ keratomileusis (LASIK) for myopia, hyperopia, and astigmatism. Setting Augenchirurgie und Laserzentrum Hochrum, Innsbruck, Austria. Methods In this prospective study, the objective refraction obtained with the Nidek AR-K 900 autorefractor was compared with the subjective refraction in 159 eyes (125 with myopia and 34 with hyperopia) operated on with 2 different lasers. Refractions were done before and 6 months after LASIK. Results Preoperatively, the objective and subjective refractions correlated better in eyes with low myopia than in those with high myopia ( P < .01). Postoperatively, objective refraction was less accurate and reliable than preoperatively. The difference between the objective and subjective spherical refractions was statistically significant ( P < .0001) after LASIK in eyes with hyperopia. The correlation between the objective and subjective cylindrical refractions was stronger preoperatively. Especially after LASIK for hyperopia, the objective refraction did not reliably assess the magnitude and axis of the cylinder. The preoperative refractive error did not significantly affect the preoperative and postoperative difference between the objective and subjective refractions or the change between the preoperative and postoperative mean differences. The type of excimer laser used significantly affected the difference between the objective and subjective refractions. Conclusions Especially after LASIK for hyperopia, the objective refraction determined with the Nidek AR-K 900 autorefractor delivered erroneous results, which have implications for postoperative care and preoperative measurements for ocular surgery such as enhancement procedures or cataract surgery.