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Corneal power estimation for intraocular lens power calculation after corneal laser refractive surgery in Chinese
Haiying Jin1, Gerd U Auffarth, Haike Guo
1Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai, China.
Purpose:
To develop and evaluate an algorithm for corneal power estimation in intraocular lens (IOL) power calculation after corneal laser refractive surgery in Chinese eyes.
Setting:
Guangdong Eye Institute, Guangdong Academy of Medical Sciences, Guangzhou, China.
Design:
Prospective comparative case series.
Methods:
Corneal parameters in Chinese eyes and German eyes were measured using a rotating Scheimpflug camera. Corneal power was simplified as a corrective algorithm: K(C) = 1.114 × K(M) + K(2) (K(M) = measured K reading; K(2) = K(P) - K(A) × K(P) × CT/1.376; K(A) = anterior corneal power; K(P) = posterior corneal power; CCT = central corneal thickness). The variation and change in K(2) induced by refractive surgery were analyzed in Chinese eyes. The corrective algorithm was identified as K(C) = 1.114 × K(M) - 6.20. The method was evaluated in Chinese cataract cases after refractive surgery using the Haigis formula.
Results:
No difference in anterior corneal radius (R(A)) or CCT between Chinese eyes and German eyes were found; however, the posterior corneal radius (R(P)), R(A)/R(P) ratio, keratometric index, and K(2) were different. The mean K(2) was -6.23 diopters (D) ± 0.24 (SD) in Chinese eyes and -6.12 ± 0.23 D in German eyes (P<.01). The mean change in K(2) induced by refractive surgery was -0.02 ± 0.06 D. The median absolute prediction error in IOL power calculation was 0.43 D (range 0.01 to 1.80 D).
Conclusion:
The algorithm was a relatively reliable method in IOL power calculation after corneal refractive surgery in Chinese eyes.
