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Impressum
The Influence of Radiation, Corticosteroids and Vitamin E Deficiency on Cataract Onset in a Model for Bone Marrow Transplantation
1,2Junk A. K., 1Worgul B. V.
1ERERL, Dept. of Ophthalmology, Columbia University, New York; 2Dept. of Ophthalmology, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, USA
Objective: An experimental study was conducted to understand the
interaction of multiple risk factors for cataract formation associated
with bone marrow transplantation. The factors include ionizing radiation
(to model total body irradiation), corticosteroids, and the absence of
a potential free radical scavenger, Vitamin E. Various combinations of
the 3 were employed to study cataractogenesis.
Methods: The right eyes of seventy-two 4-week-old Brown-Norway
rats were irradiated with 6 Gy of 240 kV X-rays. The shielded left eyes
served as controls. Subgroups were maintained on a Vitamin E free diet
with or without dexamethasone. The initial daily steroid dose of 10 mg/kg
body weight injected subcutaneously was reduced to 0.5 mg/kg over the
course of 6 months. Cataract onset and development were followed over
6 months by weekly slit-lamp biomicroscopy.
Results: Irradiated eyes in all treatment subgroups showed an early
cataract onset [5 weeks versus 11 weeks in controls (p<0.0001)]. Corticosteroids
accounted for an accelerated cataract development in both irradiated (p<0.0005)
and non-irradiated eyes (p<0.0001) relative to the respective control
eyes. Vitamin E deficiency did not appear to affect cataract development
in combination with radiation or steroids alone. Unexpectedly, when compared
to irradiated controls, cataract development was inhibited when all
3 risk factors were combined (p<0.0005).
Conclusion: Radiation, at the applied dose, was the predominant
risk factor for early cataract onset in this study. Corticosteroids accelerated
cataract formation. The surprising protective influence of Vitamin E deficiency
may result from a stathmokinetic effect on mitosis - a possibility that
remains to be experimentally addressed.