Abstract

Volume.117 Number.8

Original article : Clinical science

Simulation of Toric Intraocular Lens Results: the Effect of Repeatability and Increments of Automated Keratometry
Yoshihiko Ninomiya1, Yayoi Kanazawa1, Yoshinao Kojima1, Naoyuki Maeda2
1 Department of Ophthalmology, Yukioka Hospital
2 Department of Vision Informatics, Osaka University Graduate School of Medicine

Objective: To study the repeatability and scale increments of automated keratometry and their influence on the use of the toric intraocular lens (IOL) and on astigmatism correction.
Method: The study enrolled 131 eyes of 82 patients. Preoperative corneal astigmatism was measured in the different (0.01 D and 0.25 D) scale increment setting of automated keratometer on separate days. An arithmetic astigmatism in 0.25 D scale increment was also calculated from that of 0.01 D scale increment. These three types of corneal astigmatism were comparatively appraised with a web-based calculator, evaluating indication and style selection of the toric IOL and simulated residual astigmatism.
Results: Different scale increments caused no significant difference in simulated residual astigmatism. The repeatability of calculated IOL style selection and axis location was low in eyes with mild astigmatism. True standard deviation of test-retest discrepancy in the size of corneal astigmatism was 0.293 D.
Conclusion: In mild astigmatism, the effectuation of the toric IOL, such as IOL style selection and axis location, was ineffective. However, the scale increment of 0.25 D presented moderate sensitivity. The refinement of corneal astigmatism measurement and development of algorithm would be the key to more accurate astigmatism correction with a toric IOL implantation.
Nippon Ganka Gakkai Zasshi (J Jpn Ophthalmol Soc) 117: 621-628, 2013.

Key words
Astigmatism correction, Toric intraocular lens, Automated keratometry, Repeatability, Scale increment
Reprint requests to
Yoshihiko Ninomiya, M.D. Department of Ophthalmology, Yukioka Hospital. 2-2-3 Ukida, Kita-ku, Osaka 530-0021, Japan