To the Editor:— The urgency of early diagnosis of chronic simple glaucoma stems from the fact that good therapeutic results are expected in early cases. By contrast, late cases invariably have sustained irreversible visual loss. The necessity for routine screening examinations is explained by the asymptomatic nature of chronic simple glaucoma. Aptly termed "the thief in the night," glaucoma stealthily encroaches on visual field and acuity, with this loss detected irrecoverably late by the victim. Many physicians have the misconception that glaucoma is an unimportant, rather rare, acute disease, readily recognized by the painful, hard, red eye. These are the characteristics of acute glaucoma. Far more common is chronic simple glaucoma. Thirteen per cent of all blindness reported in North America and Western Europe by Sorsby is due to glaucoma (Brit. J. Ophth., monograph supplement 16, 1950). Mass-screening procedures (J. A. M. A.56:933 [Nov. 6] 1954) indicate that