Spontaneous Vacuolar Cataract in Guinea Pigs-(2)

Abstract

The bilateral vacuolar cataract that has been previously reported in Crj: Hartley guinea pigs was further investigated. The incidence reached to 52% by ophthalmological examination. The onset of the vacuolar cataract was all within 28 weeks of age. The vacuoles were ophthalmoscopically first detected along the equator of the lens. Then, the vacuoles that developed only at a focal region disappeared within 12 weeks without any treatment, whereas those that developed throughout the equator progressed to prominent vacuoles extending from the equator toward the anterior pole of the lens. Histopathological examination of the lens with an advanced stage of the vacuolar cataract revealed vacuolation, degeneration and disarrangement of the cortical lens fibers.

High blood glucose levels were noted in all the guinea pigs that showed the vacuolar cataract, suggesting a relationship between the high blood glucose level and development of the vacuolar cataract. This assumption led us to conduct a diet restriction study where the blood glucose level was lowered by reducing a daily diet supply by approximately 50% of the standard consumption. As a result, the lens vacuoles were unequivocally reduced in number and size when animals with an advanced stage of the vacuolar cataract were maintained for 7 weeks under the restricted feeding regimen. And, the cataract was again progressed when these animals were returned to and kept on the ad libitum feeding regimen for 5 weeks. The decrease and increase in the blood glucose levels were well associated with the severity of the cataract, respectively. Thus, it can be concluded that high blood glucose levels are heavily involved in development of the vacuolar cataract. The vacuolar cataract found in Crj: Hartley guinea pigs that showed high blood glucose levels is regarded as a spontaneous diabetic cataract. Guinea pigs cannot synthesize ascorbic acid (vitamin C) de novo. Since ascorbic acid plays an important role in preventing diabetic cataract, Crj: Hartley guinea pigs can be a potential useful animal model for diabetic cataract in humans.