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Study: Age does not factor into higher-order aberration increases
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SAN FRANCISCO — The magnitude of higher-order aberrations varies greatly among patients in the general population and increases only slightly with age, according to a surgeon speaking here.
Douglas D. Koch, MD, examined higher-order aberrations, using the Visx WaveScan system, across a 6 mm pupil in 532 eyes of 306 patients ranging in age from 20 years to 71 years (mean age of 41 years). He presented his findings here at the American Society of Cataract and Refractive Surgery annual meeting.
Patients in the study had a mean spherical equivalent of –3.39 D, and none of the eyes had had previous refractive surgery. No eyes were pharmacologically dilated.
Dr. Koch said the average of the Zernike coefficients centered around zero for the overall population. The main exception was the third-order terms of trefoil and spherical aberration.
“There’s a big standard deviation. But the mean tends to be relatively low,” Dr. Koch said. “On the other hand, if you look at the mean absolute values, you get a much different sense of things. And as you might anticipate, the third-order terms are the greatest, and the fourth order, the spherical aberration term, had a tendency to diminish.”
The mean RMS values for the higher-order aberrations was 0.305 ± 0.095 mm, 0.128 ± 0.074 for spherical aberrations and 0.17 ± 0.089 for coma.
In addition to higher-order aberration, Dr. Koch also looked at mirror symmetry between the right and left eyes of the individual patients.
He noted that significant correlations were found between the right and left eyes (P < .001), with a Pearson correlation coefficient of r = 0.601 for higher-order aberrations, r = 0.776 for spherical aberrations and r = 0.511 for coma.
The strongest correlation was for fourth-order spherical correlation, r = 0.836 between the eyes.