One such condition is glaucoma. In this disease, eased pressure within the eyeball seriously injures the vision. In the acute type of glaucoma, dimming of the vision may be sudden: the eye- ball becomes painful, and the affected person feels quite ill. However, the insidious type of glaucoma doesn't cause pain, and injures the vision very slowly. Sometimes it may make itself known by the appearance of colored rings and halos about bright objects, or by the fact that the vision in front remains good while that on the sides becomes dim. About half of the blindness occurring in adults in this country-is due to glaucoma, which occurs most frequently in people over forty. There is a great deal that can be done to preserve the vision in most cases, provided the disease is caught in time. It is easily recognized by a doc tor specializing in the eyes (an ophthalmologist). Isn't it foolhardy not to have your eyes examined once a year after you have reached the age of forty? Once every three years is sufficient if you are between twenty-five and forty.