Effect Of Eye Closure Research Articles

Various physical parameters which influence photosensitive epilepsy in the Papio papio

We have analyzed the influence of several physical parameters in photosensitive epilepsy in two baboons ( Papio papio), one very photosensitive and the other only slightly photosensitive. In order to describe average reactivity of the animals to intermittent light stimulation we chose 3 indices: I = mean intensity of the paroxysmal discharges, L = mean latency of these discharges, E = ratio of the number of effective stimulations to total number of stimulations. Comparing stimulations of different wavelengths, the most effective in revealing photosensitivity were the colours blue-green and dark green (487 and 538 nm); the least effective were green (544 nm) and red (676 nm). The paroxysmal discharges triggered by intermittent light stimulation were more intense, more frequent and of shorter latency when the distance between the light source and the animal was decreased, or when the surface area of the source was increased. With white light, increasing the pupil diameter increased the intensity of paroxysmal discharges in both animals, but to a greater extent in the more photosensitive animal. Closing the eyes also increased the response intensity but only when the pupils were dilated with homatropine. The effects of eye closure and pupillary dilatation, using coloured light stimulation, were not constant and seemed to depend upon the degree of photosensitivity of the baboon under study. These effects and the validity of the selected indices are discussed; the indices I and E are linked by a simple relation which we were able to evaluate, whereas L generally varies in the opposite direction to the other two indices.

The period of susceptibility to the physiological effects of unilateral eye closure in kittens.

1. Kittens were visually deprived by suturing the lids of the right eye for various periods of time at different ages. Recordings were subsequently made from the striate cortex, and responses from the two eyes compared. As previously reported, monocular eye closure during the first few months of life causes a sharp decline in the number of cells that can be influenced by the previously closed eye.2. Susceptibility to the effects of eye closure begins suddenly near the start of the fourth week, remains high until some time between the sixth and eighth weeks, and then declines, disappearing finally around the end of the third month. Monocular closure for over a year in an adult cat produces no detectable effects.3. During the period of high susceptibility in the fourth and fifth weeks eye closure for as little as 3-4 days leads to a sharp decline in the number of cells that can be driven from both eyes, as well as an over-all decline in the relative influence of the previously closed eye. A 6-day closure is enough to give a reduction in the number of cells that can be driven by the closed eye to a fraction of the normal. The physiological picture is similar to that following a 3-month monocular deprivation from birth, in which the proportion of cells the eye can influence drops from 85 to about 7%.4. Cells of the lateral geniculate receiving input from a deprived eye are noticeably smaller and paler to Nissl stain following 3 or 6 days' deprivation during the fourth week.5. Following 3 months of monocular deprivation, opening the eye for up to 5 yr produces only a very limited recovery in the cortical physiology, and no obvious recovery of the geniculate atrophy, even though behaviourally there is some return of vision in the deprived eye. Closing the normal eye, though necessary for behavioural recovery, has no detectable effect on the cortical physiology. The amount of possible recovery in the striate cortex is probably no greater if the period of eye closure is limited to weeks, but after a 5-week closure there is a definite enhancement of the recovery, even though it is far from complete.