Age-related changes in anterior, posterior, and total corneal astigmatism.
OBJECTIVE
To evaluate age-related changes in anterior, posterior, and total corneal astigmatism by comparing simulated keratometric astigmatism to total corneal astigmatism.


METHODS
Corneal topography of the anterior and posterior surfaces was evaluated using three-dimensional optical coherence tomography in 419 patients with normal eyes (218 men and 201 women) with ages ranging from 8 to 93 years (mean ± standard deviation: 49.5 ± 23.1 years). Keratometric astigmatism was calculated using the keratometric index (1.3375) and radius of the anterior corneal curvature; anterior and posterior corneal curvature measurements were used to calculate total corneal astigmatism.


RESULTS
The keratometric and total astigmatism were 1.08 ± 0.71 diopters (D) and 1.03 ± 0.69 D, respectively. Vector analysis revealed a mean difference between keratometric and total astigmatism of 0.24 ± 0.09 D, which showed a significant correlation to age (P < .0001). In eyes with with-the-rule astigmatism, keratometric astigmatism overestimated total astigmatism. In eyes with against-the-rule astigmatism, keratometric astigmatism underestimated total astigmatism.


CONCLUSIONS
The anterior corneal surface shifts from with-the-rule to against-the-rule astigmatism with aging, whereas the posterior corneal surface remains as against-the-rule astigmatism in most cases. The variation in the anterior astigmatism is the most important factor contributing to this change. Total corneal astigmatism is a better predictor than keratometric astigmatism for selecting toric intraocular lenses.
Yuta
Y
Ueno
Takahiro
T
Hiraoka
Simone
S
Beheregaray
Maki
M
Miyazaki
Mutsuko
M
Ito
Tetsuro
T
Oshika
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001251:Astigmatism / Q000175:diagnosis / Q000503:physiopathology*; D002648:Child; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055815:Young Adult