Effect of various agents on drug-induced opacities of the lens

Lenticular opacities, produced in mice and rats by the acute administration of morphine-like analgesic drugs, adrenaline or chlorpromazine, and cataracts induced by oxygen deprivation, were all shown to occur in the anterior portion of the lens below the capsule. Oxygen and respiratory stimulants significantly reduced the amount of opacity produced by analgesic drugs but did not alter that seen after the administration of adrenaline or chlorpromazine. Pre-treatment of mice 18 hr earlier with reserpine, only abolished opacities produced by analgesic drugs. This indicated that catecholamines are essential in the mediation of opacities induced by morphine and related drugs, but chlorpromazine could still cause opacities in the presence of reserpine. When excised lenses were incubated in a fluid having the approximate composition of aqueous humour, cataracts could be produced by raising the tonicity of the fluid by the addition of excess sodium chloride or glucose. Reducing the pH of the medium from 7·4 to 7·15, also caused the lenses to become opaque. These changes were completely reversible. It is suggested that lens opacities occur in vivo as a result of a temporary rise in the tonicity of the aqueous humour. This could be brought about by increased evaporation of water through the cornea and would occur when drugs are given which stimulate the sympathetic supply and cause the eyes to be kept open and reduce the blink rate.