Higher-order aberrations from the internal optics of the eye.
OBJECTIVE
To analyze the distribution of human higher-order wavefront aberrations (3rd- to 6th-order) from the internal optics (WA(internal)) and the variations with age and to evaluate the degree of compensation that the internal optics provide for anterior corneal aberrations (WA(cornea)).


METHODS
Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.


METHODS
With assumption of a simple model for the eye, the WA(internal) were obtained by direct subtraction of the WA(cornea) from the ocular aberrations (WA(eye)). The WA(eye) were measured using the WaveScan system (Visx, Inc.), and the WA(cornea) were computed from the topographic data (Humphrey Atlas) using the CTView program (Sarver and Associates, Inc.). In 144 eyes of 114 normal patients (age 20 to 69 years), WA(internal) were calculated for a 6.0 mm pupil and a compensation factor (CF) was computed, with positive values representing compensation of WA(cornea) by WA(internal) and negative values indicating that the internal surfaces add aberrations to those of the cornea.


RESULTS
There was wide individual variation in WA(internal). The mean coefficient for 4th-order spherical aberration (Z(4)(0)) was -0.145 microm +/-0.094 (SD) (95% confidence interval [CI], -0.160 to -0.130 microm); 95.1% of eyes had negative values. The mean root-mean-square value for HOAs was 0.334 +/- 0.096 microm (95% CI, 0.319 to 0.350 microm). Moderate to high correlations were found between the right and left eyes in HOAs, 4th-order and 6th-order spherical aberration coefficients (Z(4)(0) and Z(6)(0)). With increasing age, the HOAs did not change, whereas the negative coefficients for Z(4)(0) tended to become less negative. Only the term Z(4)(0) had a CF significantly correlated with increasing age (r=-0.338, P<.05 with Bonferroni correction).


CONCLUSIONS
WA(internal) varied widely among patients, and a moderate to high degree of mirror symmetry existed between the right and left eyes. Internal surfaces compensated at least partially for the HOA and Z(4)(0) in most eyes, and this compensation decreased only mildly with increasing age.
Wang
Li
L
Department of Ophthalmology, Baylor College of Medicine, Houston, Texas 77030, USA.
Santaella
Ricardo M
RM
Booth
Marc
M
Koch
Douglas D
DD
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D003315:Cornea / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009799:Ocular Physiological Phenomena; D012030:Refractive Errors / Q000503:physiopathology*