Sight Saver

The vitreous humor, the substance that fills two-thirds of the eyeball, is vital to vision. The clear, jelly-like material transmits light while maintaining the pressure that helps hold the retina in place. Hemorrhaging, which occurs often in severe diabetes, can cloud the vitreous and impair vision, and loss of its gel-like consistency can result in detachment of the retina. Both conditions can produce blindness.

Doctors now replace lost or damaged vitreous with either natural material taken from donors, saline solutions, air, silicone or other synthetics. None of those materials is completely satisfactory. The synthetics sometimes trigger toxic reactions that lead to further eye damage, the air is soon absorbed, and transplanted human vitreous may provide only short-term benefits. Now a research team at Cornell University Medical College's Rogosin Laboratories has developed a material that overcomes all these problems. According to Dr. Michael W. Dunn, he and his colleagues are using collagen, a natural body substance, to replace lost or damaged vitreous humor.

Holding the Retina. The choice is logical. A protein that helps to fill the spaces between cells of the body, collagen is already used experimentally to replace skin destroyed by burns. Extracted from animal tissue and further purified, the collagen gel is injected into the damaged eye by hypodermic. Once in place, it acts as both a light-transmitting substance and a source of pressure, filling the eye and holding the retina in place.

Experimentation with the collagen gel has been encouraging. In tests undertaken recently, no subject rejected the purified collagen as a foreign substance. Nor does the collagen liquefy. Instead, it is gradually absorbed as new ocular fluid appears naturally, usually within four weeks. Meanwhile, the gel promotes the return of vision. On one series of patients treated by Dr. Donald M. Shafer, the collagen gel was administered as part of a regular surgical procedure to seven people with eye hemorrhages. In three cases, there was a recurrence of the hemorrhaging, and the damage was too severe to be corrected. But four patients who had been blind regained the use of their eyes, one to the point where she was once again able to read.

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