Objective assessment of aberrations induced by multifocal contact lenses in vivo

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

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.

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.

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.