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We studied "steady-state" visual evoked potentials (VEPs) in 10 adult males (5 of whom were left-handed), using an alternating vertical-bar-pattern monocular stimulus in which the bar positions reversed at rates of 6,11, and 16 Hz. VEPs from electrodes over each hemisphere and midline were computer-averaged over 2 min and the average then subjected to spectral (Fourier) analyses. The stimulus reversals were square-wave regulated, and all subjects responded with near sine-wave spectral components (fundamental and some harmonics) at the corresponding reversal frequencies. Each subject developed larger responses at one of the stimulus frequencies (usually 6 Hz). Response magnitude at either the fundamental or harmonics of the stimulus frequency varied greatly across subjects. One of the specific hypotheses tested was that larger VEPs should develop after stimulation of the dominant eye; this could not be demonstrated. Two other hypotheses were verified: (1) VEPs should be lateralized and should correlate with handedness, and (2) some of the response received in a given hemisphere is physiologically relayed to the other hemisphere, and this occurs in both directions. Hemispheric lateralization occurred most clearly at each subject's optimum frequency. The "dominant" hemisphere for this kind of stimulus was always in the left hemisphere for the five right-handed subjects and in the right hemisphere for four of the left-handed subjects (the other left-hander had marked left-hemisphere dominance and also several right-handed behaviors).

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The eyes of rhesus monkeys were exposed to suprathreshold Q-switched laser pulses at wavelengths of 440, 530 and 694nm. The energy level which resulted in hemorrhaging following foveal exposure was determined for the different wavelengths. A comparison of the extent and type of retinal damage between foveal and extramacula exposure sites was obtained using both assessment with the fundus camera and histological evaluation of the lesions.