Conventional adaptive optics enables correction of high-order aberrations of the eye, but only for a single retinal point. When imaging extended regions of the retina, aberrations increase away from this point and degrade image quality. The zone over which aberrations do not change significantly is called the "isoplanatic patch." Literature concerning the human isoplanatic patch is incomplete. We determine foveal isoplanatic patch characteristics by performing Hartmann-Shack aberrometry in 1 deg increments in 8 directions on 7 human eyes. Using these measurements, we establish the correction quality required to yield at least 80% of the potential patch size for a given eye. Single-point correction systems (conventional adaptive optics) and multiple-point correction systems (multiconjugate adaptive optics) are simulated. Results are compared to a model eye. Using the Marechal criterion for 555-nm light, average isoplanatic patch diameter for our subjects is 0.80+/-0.10 deg. The required order of aberration correction depends on desired image quality over the patch. For the more realistically achievable criterion of 0.1 mum root mean square (rms) wavefront error over a 6.0-mm pupil, correction to at least sixth order is recommended for all adaptive optics systems. The most important aberrations to target for a multiconjugate correction are defocus, astigmatism, and coma.

To determine absorption coefficients for sodium chloride solution (saline) and balanced salt solution at the 193-and 213-nm laser wavelengths. Methods: Absorption coefficients were obtained for each of the component species found in balanced salt solution. This was achieved by measuring laser pulse transmission through solutions of varying concentration. The experiments were repeated using the 193-nm excimer and 213-nm solid-state laser wavelengths. Results for each species were then used to obtain an overall absorption coefficient and penetration depth for balanced salt solution and 0.9% sodium chloride solution. Results: Absorption coefficients in balanced salt solution for the 193-and 213-nm wavelengths were found to be 140 and 6.9 cm −1 , respectively. In 0.9% sodium chloride solution, the absorption coefficient was 81 cm −1 at 193 nm and 0.05 cm −1 at 213 nm. At 193 nm, absorption in balanced salt solution was dominated by sodium chloride. Sodium citrate emerged as the dominant species of absorption at 213 nm.

Subtle changes in cycloplegic refraction exist across the horizontal central 10 degrees of the retina. The results indicate the need for correct alignment when measuring objective refraction.

Aberrations of both astronomical telescopes and the human eye can be successfully corrected with conventional adaptive optics. This produces diffraction-limited imagery over a limited field of view called the isoplanatic patch. A new technique, known as multiconjugate adaptive optics, has been developed recently in astronomy to increase the size of this patch. The key is to model atmospheric turbulence as several flat, discrete layers. A human eye, however, has several curved, aspheric surfaces and a gradient index lens, complicating the task of correcting aberrations over a wide field of view. Here we utilize a computer model to determine the degree to which this technology may be applied to generate high resolution, wide-field retinal images, and discuss the considerations necessary for optimal use with the eye. The Liou and Brennan schematic eye simulates the aspheric surfaces and gradient index lens of real human eyes. We show that the size of the isoplanatic patch of the human eye is significantly increased through multiconjugate adaptive optics.

Our modeling is consistent with clinical findings that certain corneal aberrations almost balance those arising from the lens. Our calculations also support the general notion that, by optical sculpting, corneal aberrations can be adjusted to completely balance out those of the lens. This can effectively eliminate the eye's total monochromatic aberrations, but for only one retinal image point at a time. Centered on this point of minimal aberration is a region (the isoplanatic patch) within which the aberrations produce a point spread smaller than some tolerable limit. Also, using available evidence in the literature concerning changes in critical ocular parameters with age and accommodation, our modeling results parallel established clinical findings, and additionally indicate that the major source of aberration change can be attributed to the gradient index distribution in the lens.