Vascular architecture of the human optic chiasm and bitemporal field defects.

The system of blood supply of the optic chiasma was studied on 85 human fresh bodies by several methods. The optic chiasma is supplied by the Willis' circle, arterioles from which, after forming anastomosis at two levels, enter the chiasma and break into capillaries. The authors found that the median portion of chiasma is a weak point of microcirculation, as demonstrated by rarefied and transverse capillaries. When the blood supply of chiasma is compromised by lesions near the sella turcica, this weak point of microcirculation is apt to be disturbed first and becomes ischemic, causing disorders of the crossing optic nerve fibers in the median portion of chiasma, and the characteristic bitemporal visual field defects appear.

An epidemiologic survey of senile cataract in China.

This paper is based on data obtained in blindness screening in 7 rural areas throughout China and presented at the Second National Conference of the Chinese Ophthalmologic Society in 1979. This comparative study of the incidence of senile cataract in relation to geographic and meteorologic factors, with special reference to solar radiation, indicates that cataract incidence increases with decrease in latitude or increase in altitude due to increased solar radiation. Zedang in Tibet, with the highest altitude and low latitude (29 degrees N) has the highest incidence (1.32%) of the areas surveyed, followed by Aleitai 0.25% and Zhongshan (0.23%), whereas the incidences in lowland areas are between 0.12 and 0.14%, the lowest surveyed being in Zhongmou (0.066%). The differences in cataract incidence are apparently associated with solar radiation. Yu and coworkers in their research demonstrated the evidence for the solar UV-induced lowering of sulfhydryl level in the Tibet human lens nucleus. Therefore, these findings furnish some evidence supporting the theory that sunlight enhances cataract formation.