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The confocal principle was applied to double pass method to measure the point spread function (PSF) of the human eye and an artificial eye, and to improve the ratio of signal to noise of retinal images. The double-pass PSFs of four human eyes on and off the optical axis of the eyes were measured. The off-axis double pass PSF in the human eye along vertical and horizontal direction is asymmetrical. When the subject looks left on the horizontal off axis, the PSF appears right of the optical axis of the subject eye. When the subject looks right the PSF is located left of the optical axis. The location of the PSF on the vertical off axis appears above the optical axis when the subject looks up. When the subject looks down the double pass PSF is located below the axis. The PSFs of the human eye recorded at varying off-axis angles are presented. Asymmetrical results suggest a more dynamic process in the optical system of the eye perhaps driven by the complicated outer or inner ocular structure.

In the future, aviation aircrews will likely operate in an environment that is saturated with electromagnetic energy emitted from a variety of sources. Lasers serving many applications, such as rangefinding and guidance, will be included in this environment. Eye damage from laser sources is possible, but laser irradiation below levels necessary to produce eye damage may still degrade visually guided human performance. It is important to understand how, and to what extent, visually mediated human performance is affected by low-level laser glare. To this end, we have conducted some initial laboratory studies in which we have systematically varied level of glare and cockpit windscreen characteristics while subjects, who were seated in a cockpit familiarization trainer, performed a visual search task. The search task required subjects to scan a complex visual scene projected on a screen and report the location of one small target disk randomly placed among larger background disks. In a series of studies, we have shown that windscreen characteristics and ambient illumination can interact with laser- induced glare to disrupt visual search performance. We have also shown that lens opacity, an opaqueness of the lens that increases with age, may interact with laser glare and degrade visual search performance more in older individuals. Laser light intensities well below the eye injury threshold may effectively disrupt visually guided performance.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Sixty-six college students read two chapters from a contemporary novel while their eye movements were monitored. The eye movement data were analyzed to identify factors that influence the location of a reader's initial eye fixation on a word. When the data were partitioned according to the location of the prior fixation (i.e. launch site), the distribution of fixation locations on the word (i.e. landing site distribution) was highly constrained, normal in shape, and not influenced by word length. The locations of initial fixations on words can be accounted for on the basis of five principles of perceptuo-oculomotor control: a word-object has a specific functional target location, a saccadic range error occurs that produces a systematic deviation of landing sites from the functional target location, the saccadic range error is reduced somewhat for saccades that follow longer eye fixations, there exists perceptuo-oculomotor variability that is a second, nonsystematic source of variation in landing sites, and the perceptuo-oculomotor variability increases with distance of the launch site from the target.