CATARACT is an opacity of the lens of the eye, which causes reduction of vision in varying degrees. It is not a film or growth as is popularly supposed. For purposes of study we can divide cataract into the following types: 1. Senile: occurring in middle and later life. 2. Due to disease or toxic substances, e.g., diabetes, dinitrophenol poisoning, et cetera. 3. Traumatic: occurring as the result of an injury such as a blow to the eye. 4. Congenital: occurring in utero and present at birth. We are most concerned with the first type. Cataractous changes are often noted in the late fifties and increasingly so during the next two decades. They may be sufficient to cut down vision to the point where vision is uncomfortable or they may be so slight that the patient is unaware of any change. The first symptom is a lessening of vision. If the opacity is in the cortex of the lens, the patient will be most comfortable in bright light where the pupil is well contracted. If the opacity is in the nucleus, the patient will see best in dim light where the pupil dilates slightly, allowing better vision through the periphery of the lens. We do not know why senile cataract occurs. It appears to be a part of the general aging process in which tissues lose some of their elasticity and undergo the usual changes of age. The speed with which these changes come to the lens is quite unpredictable, and we have no way at present of arresting the process. Various theories have been offered as to the cause of cataract. Some think that diet plays a part, others feel that a change in the blood sugar level is a cause in all cases (even when diabetes is not present), still others look to a hormonal dysfunction. At present, we