In a group of chickens studied after lid suture in the first month post hatching an unusually high myopia was found (n = 8 eyes; average: -21.87 Diopters). The non-operated eyes of these chicks had the same optical properties (n = 4; +0.93 Diopters) as the eyes of the normal control chicks (n = 12; +0.81 Diopters). Although enlargement of the whole eye occurred, the main determinant was an axial elongation (operated eyes, 18.0 mm; nonoperated, 13.7 mm; normal controls, 14.7 mm). The axial change involves an enlargement of the posterior as well as the anterior segments of the eye. Despite several structural characteristics specific to chicks, their eyes can serve as a model for myopia research.

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PubMedDate not supplied

Time course of electroretinographic recovery following argon laser photocoagulation in cats.

We wished to study in detail the time course of changes in the electroretinogram (ERG) that occur following lesioning of the cat retina by photocoagulation. The superior-temporal quadrant of one eye of 15 adult cats was photocoagulated by argon laser. The ERG was recorded at baseline and followed for up to 13 weeks postlaser. The retina was also observed ophthalmoscopically. Immediately after photocoagulation, the b-wave amplitude was markedly reduced. This was followed by a gradual recovery over the next 10 weeks. The ophthalmoscopic appearance of the lesions, however, appeared unchanged after 1 week. The ERG, which is reduced in amplitude immediately after retinal photocoagulation, shows recovery with time.

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PubMedDate not supplied

Processing of animated contours by single cells in visual cortex area 18 of the cat.

In view of previous evidence that area 17 and 18 cells in cats represent the first level contour abstraction, we decided to study the specific response pattern of these cells to shapes enriched with contours, such as animated objects (AO). AO (cat's body whole contours) and 4 levels of AO degraded patterns were presented monocularly and repeatedly to the same eye, within the cells' RF. The intact AO elicited stronger responses than degraded contours while the responses to various degradedAO were similar. We conclude that under monocular presentation of AO cells react mainly as "edge detectors": the best stimulus is closed, compared with open, contour.

Animals↗