Researchers compare normal higher-order aberration values for different populations

A prospective study among young refractive surgery candidates has found that while normal values for higher-order aberrations in Indian eyes are similar to normal values for eyes in white populations, they are different from normative values for eyes in Asian Chinese populations.

Gaurav Prakash, MD, and colleagues at All India Institute of Medical Sciences in New Delhi used a Zywave workstation (Bausch & Lomb) to evaluate higher-order aberrations for 412 eyes of 206 Indian LASIK candidates who averaged 23.63 years of age.

The average spherical refractive error for these eyes was –2.97 D, and the average cylindrical refractive error was –1.73 D; the 6-mm higher-order root mean square value was 0.36 µm.

After summating the root mean square values of different modes to determine a combined value for respective orders, the investigators found that the third order was the most predominant, followed by the fourth order and the fifth order (P < .0001). Coma and trefoil were the most predominant third-order aberrations, the authors noted.

The ratio between summated root mean square average values was similar for the Indian and white populations; however, the ratio was different among Chinese populations.

In addition, third- and fourth-order aberrations in Chinese eyes were between 60% and 70% higher than in Indian or white eyes.

"These factors should be kept in mind when establishing nomograms for treatment specific to an Indian population," the authors said in the August issue of Journal of Cataract & Refractive Surgery.