Objective assessment of aberrations induced by multifocal contact lenses in vivo.

PURPOSE: This study examined the effects of a soft multifocal progressive contact lens on individual Zernike coefficients describing the aberrations of the eye.

METHODS

Ocular wavefront aberrations (OWA) of 10 subjects not wearing contact lenses were quantified using a Shack-Hartmann aberrometer and were repeated after lens insertion (two lenses,+2 diopters [D], and -2D distance power, order of insertion was randomized). All data were captured and stored on computer. Each coefficient of the Zernike polynomials representing, coma, spherical aberration (SA), and the fifth-order aberrations were evaluated for each OWA. Pupil size was monitored using an infrared device.

RESULTS

After subjecting the data to various permutations, the following relationships and chief findings were detected: (1) Comparing coefficients with and without lenses, significant correlations for coma (Z(1)3 [rho,theta], P=0.0056; -2D and P=0.0399, +2D); SA (Z(0)4 [rho,theta], P=0.0006; -2D; and P=0.0061,+2D). Fifth-order aberration (Z(-1)5 [rho,theta], P= 0.0029,+2D). (2) With the -2D lens, the average root-mean-square (RMS) value for the SA coefficient Z(4)4 (rho,theta) and fifth-order Z(-3)5 (rho,theta) increased (P=0.045 and 0.0392, respectively). (3) With the +2D lens, the average RMS value for fifth-order coefficient Z(1)5(rho,theta) increased (P=0.0278). (4) Coma (Z(1)3 [rho,theta] coefficient) correlated with pupil size (P<0.05). Initial mean (+/-SD) pupil size (mm) was 3.05 (0.499), and this did not change significantly.

CONCLUSIONS

Z(1)3(rho,theta) and Z(0)4(rho,theta) coefficients may be useful objective markers of success or failure for such contact lenses. The -2D lens had a more predictable effect on SA compared with the +2D lens design. The opposite occurs when considering the effects on the higher fifth-order order aberrations.