The development of technology to measure and correct the eye's higher-order aberrations, i.e., those beyond defocus and astigmatism, raises the issue of how much visual benefit can be obtained by providing such correction. We demonstrate improvements in contrast sensitivity and visual acuity in white light and in monochromatic light when adaptive optics corrects the eye's higher-order monochromatic aberrations. In white light, the contrast sensitivity and visual acuity when most monochromatic aberrations are corrected with a deformable mirror are somewhat higher than when defocus and astigmatism alone are corrected. Moreover, viewing conditions in which monochromatic aberrations are corrected and chromatic aberrations are avoided provides an even larger improvement in contrast sensitivity and visual acuity. These results are in reasonable agreement with the theoretical improvement calculated from the eye's optical modulation transfer function.

We measured the improvement in retinal image quality provided by correcting the temporal variation in the eye's wave aberration with a closed-loop adaptive optics system. This system samples the eye's wave aberration at rates up to 30 Hz. Correction of the eye's aberrations can be completed in 0.25-0.5 seconds, resulting in residual rms wave-front errors as low as 0.1 microns for 6.8 mm pupils. Real-time wave-front measurements were used to determine how effectively the spatial and temporal components of the eye's wave aberration were corrected. The system provides dynamic correction of fluctuations in Zernike modes up to 5 th order with temporal frequency components up to 0.8 Hz. Temporal performance is in good agreement with predictions based on theory. Correction of the temporal variation in the eye's wave aberration increases the Strehl ratio of the point spread function nearly 3 times, and increases the contrast of images of cone photoreceptors by 33% compared with images taken with only static correction of the eye's higher order aberrations.

PURPOSE. To assess the suitability of corneal anterior and posterior surface aberrations and thickness profile data for discrimination between eyes with early keratoconus (KC), fellow eyes of eyes with early KC, and normal eyes. METHODS. Thirty-two eyes (group 1) of 25 patients were newly diagnosed with KC; 17 eyes of 17 patients (group 2) were asymptomatic fellow eyes without clinical signs of KC. One hundred twenty-three healthy eyes of 69 patients were negative control eyes (group 3). Zernike coefficients from anterior and posterior surfaces, data from corneal thickness spatial profiles, and output values of discriminant functions based on wavefront and pachymetry data were assessed by receiver operating characteristic (ROC) curve analysis for their usefulness in discriminating between KC (groups 1, 2) eyes and control eyes. RESULTS. Vertical coma (C(3)(-1)) from the anterior surface was the coefficient with the highest ability to discriminate between groups 2 and 3 (area under the ROC curve [A(z)ROC] = 0.980; cutoff, -0.2 microm). For posterior wavefront coefficients and pachymetry data, A(z)ROC values were lower. Constructing discriminant functions from Zernike coefficients increased A(z)ROC values. The function containing first-surface data reached an A(z)ROC of 0.993; the functions containing posterior surface or pachymetry data had lower A(z)ROC values (0.932 and 0.903, respectively). The function with anterior, posterior, and pachymetry data reached an A(z)ROC of 1.0. CONCLUSIONS. Corneal wavefront and pachymetry data enabled highly accurate distinction of eyes with subclinical keratoconus from normal eyes. Posterior aberrations and thickness spatial profile data did not markedly improve discriminative ability over that of anterior wavefront data alone.

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Higher-order aberration correction in abnormal eyes can result in significant vision improvement, especially in eyes with abnormal corneas. Customized optics such as phase plates and customized contact lenses are one of the most practical, nonsurgical ways to correct these ocular higher-order aberrations. We demonstrate the feasibility of correcting higher-order aberrations and improving visual performance with customized soft contact lenses in keratoconic eyes while compensating for the static decentration and rotation of the lens. A reduction of higher-order aberrations by a factor of 3 on average was obtained in these eyes. The higher-order aberration correction resulted in an average improvement of 2.1 lines in visual acuity over the conventional correction of defocus and astigmatism alone.