Unilateral cerebral ischemia inhibits optomotor responses of the ipsilateral eye in mice.

A reduction in blood flow to the brain causes stroke and damage to neuronal networks. Cerebral ischemia is frequently associated with loss of visual functions. Because retinal and small cerebral vessels are vulnerable to similar risk factors, the loss of vision could result from concurrent retinal ischemia, and it is not clear if visual functions may be inhibited by cerebral ischemia directly. In this study, the distal middle cerebral artery in the right hemisphere of mice was occluded to produce unilateral cerebral ischemia and subsequent infarction. The layer V neurons expressing YFP in transgenic yellow fluorescent protein in transgenic B6.Cg-Tg(Thy1-YFPH)2Jrs/J mice disappeared in the motor and somatosensory cortex, but not in the visual area. The latencies of flash visual evoked potential recorded from two hemispheres were imbalanced, but did not differ markedly from the latencies recorded in controls. However, the optomotor responses of the ipsilateral eye were significantly reduced by 48 h after occlusion. Our results suggest that focused cerebral ischemia may inhibit ipsilateral eye movement in the absence of damage to the visual cortex. This study may provide a platform for further investigation of the relationship between cortical ischemia and visual function.

[Susceptibility of guinea pig eyes to form deprivation myopia and its age-related recovery].

OBJECTIVE: Young guinea pigs are susceptible to become myopic during form deprivation. They can also quickly recover from the myopia after removal of the form deprivation. This study investigated whether mature guinea pigs are sensitive to form deprivation and its refractive recovery from deprivation myopia. METHODS: It was an experimental study. Thirty-nine guinea pigs were arranged to 3 groups according to age. Group 1: 9-week old (n = 18). Group 2: 12-week old (n = 10). Group 3: 15-week old (n = 11). All the animals were performed refraction measurement prior to the experiment, then wore a facemask that covered one randomly assigned eye for three weeks. The masks were then removed and refraction was measured in both eyes immediately, 2 and 7 days after. RESULTS: After form deprivation, the refraction of the MFD (monocular form deprivation) eyes shifted to myopia, which had significant difference compared to the unmasked eye in all the groups (t = -5.691, -2.203, -2.760; P < 0.05), the relative myopia compared to the unmasked eye in 9 weeks old animals were (-2.53 ± 1.89) D, 12 weeks old (-1.43 ± 1.57) D, 15 weeks old (-0.60 ± 1.48) D. There was significant difference between 9 weeks old animals and 15 weeks old animal in the refractive error right after the form deprivation (F = 2.823, P < 0.05). And the distribution of refractive error tended to lower degree of myopia as the guinea pigs grew older. None of the three groups showed significant reduction in relative refractive error during the recovery, but a trend of recovery was found in 9 weeks old animals. CONCLUSIONS: The guinea pigs are sensitive to the form deprivation even when they are sexual mature, but both the susceptibility and the ability of recovery decrease as they grow older but in different patterns. The ability of recovery in short term (7 days) diminishes when guinea pig is older than 12 weeks while the sensitivity to form deprivation last until 15 w.