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Innovative Techniques
for Studying Damage to the Eye Lens by Hypericin (St. John's Wort).
Wahlman, Judit1,
Trevithick, John 2, Hirst, Maurice1
and Roberts, Joan3
Dept. Biochemistry, University of Western Ontario1
Dept. Pharmacology & Toxicology, U. of W. Ontario 2
Fordham University, New York, N.Y.3
Abstract-
Some herbal medications have photosensitizing properties that may lead
to damage to the eyes when the patient is exposed to sunlight. Hypericin,
the active principle of the antidepressant herbal remedy for depression
(St. John's Wort) has been shown to be taken up by the lens and
to produce reactive oxygen species when irradiated by light. To model
the damage which can occur to light exposed ocular tissues, bovine lenses
can be used in a new apparatus named 'SCANTOX' which quantifies
the fuzziness of focus associated with cataract by calculating the variability
of focal length measured at 20 different positions in a straight line
scanned across the lens diameter. This is correlated with accumulated
protein leakage integrated over the period of 8 days of incubation in
tissue culture media for each lens. The SCANTOX software generates ray
diagrams of the focal lengths measured for each lens, along with a plot
of focal lengths and their variance, a measure of the fuzziness of the
focused image. Correlation with protein leakage, an independent measure
of lens damage, has been performed for model diabetic cataract and hypericin-light-induced
cataract. Combining a physical technique, SCANTOX, with a biological
technique for measuring damage to the lens by protein leakage into the
medium results in a superior method for estimating damage to the lens.
This technique,developed by Sivak, may be used to test the potential
ocular damage induced by other herbal medications and as well as used
as an alternative to the Draize test for chemical irritancy. Acknowledgements:
Cognis Corporation for financial help.
Keywords: cataract,
focal length variability of lens, organ culture, hypericin
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