Loss of vitreous gel during aging increases the risk of nuclear cataracts. Preservation or replacement of the vitreous gel may protect patients from nuclear cataract.

Total reaction cross sections R of (30-60)A MeV 4,6,8 He and 6,7,8,9,11 Li on Pb, and 2n-removal cross sections Ϫ2n of 6,8 He and 11 Li on Pb, were measured by injecting magnetically separated, focused, monoenergetic, secondary beams of those projectiles into a telescope containing Pb targets separated by thin Si detectors. All these R 's ͑except 4 He͒, and Ϫ2n for 6 He and 11 Li, are underpredicted by microscopic model calculations which include only nuclear forces. Better agreement is achieved by including electromagnetic dissociation in the model, for those projectiles for which either the electric dipole response functions or the dominant photodissociation cross sections were known. The cross sections Ϫ4n for 8 He, Ϫxn for 7,8,9 Li, and ( Ϫ3n ϩ Ϫ4n ) for 11 Li were found to be р0.7 b. All R 's were measured to better than 5% accuracy, showing that the method is usable for other target elements sandwiched into a Si telescope.

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