10. Use of good clear-cut pictorial materials, such as pictures, posters, graphs, etc., will often give a child more exacting information than he can derive from reading several pages.

11. Keep a card catalog or a bibliography of all available reading materials in the clear-type, large-print books.

THE

Appendix 21

Causes and frequency of visual handicaps

HE UNDERLYING CAUSES of blindness can be readily understood even by the average layman, since the terminology in which they are described is already familiar. It is in description of the topographical factors (i. e., the location and nature of the eye affection) that the examining ophthalmologist uses the technical vocabulary of his specialty. It is desirable that the teacher, nurse, or social worker wishing to help a child know the significance of terms used in diagnosis in order to understand better the nature of visual handicaps. If one knows each of the main parts of the eye by name, where it is situated, and its basic characteristics and functions, one can more easily understand why and how a condition of that part will affect vision.

2

For example, an essential feature of the cornea, which covers the front portion of the eye (over the iris), and of the lens, situated just behind the iris, is that they shall remain crystalline clear and transparent so that light rays may pass through them. Hence any diagnosis implying infection or injury of the cornea might be expected to result in opacities of the cornea, and an injury or disturbance of normal metabolism of the lens would cause opacity (cataract) of the lens. These opacities would therefore obstruct vision in proportion to their density and extent.

Similarly, if one recognizes the retina as the innermost of the three layers forming the eyeball and knows that it contains nerve tissue which registers visual images, a diagnosis of central retinitis or macular degeneration of the retina would imply a loss in central visual acuity, but most of the other

1 Appendix 2 was prepared by C. Edith Kerby. Refer to pp. 7–10.

2 For a simple text on eyes see: Sidney A. Fox, M. D., Your Eyes. New York, Alfred A. Knopf, 1944, 191 pp. A mimeographed list of definitions of eye terms is available on request from the National Society for the Prevention of Blindness, 1790 Broadway, New York 19, N. Y.

terms (retinal detachment, retinal hemorrhage, retinitis pigmentosa, etc.) imply impairment of sight in other areas of the field of vision.

Nutrition of the eye is provided by the middle layer (uvea) which contains blood vessels and consists of the choroid (the portion under the retina) and the ciliary body and iris toward the front of the eyeball. It is therefore easy to understand that when one part of the eye becomes diseased the other parts are frequently affected. For example, areas of choroidal atrophy or degeneration would impair vision in the portions of the retina above these

areas.

SITE AND TYPE OF AFFECTION

In the table on page 43 in which causes of blindness are shown by site and type of eye affection, it will be noted that cases are classified by part of eye affected. The largest group is the 36.1 percent affecting the eyeball in general. These include the various structural anomalies of the eye. In the order of their frequency these anomalies are: The eye with several structural defects, the excessively large (buphthalmic) eye which is the congenital type of glaucoma, the albinotic eye which lacks pigment, the excessively small or microphthalmic eye, the eye with a cleft (coloboma) in one or more of its parts, the eye without an iris (aniridia), finally the eye which fails to develop at all (anophthalmos). These defects are often inherited, but may be due to other prenatal factors.

The entire eyeball may be affected also by a general inflammation because of infection (panophthalmitis or endophthalmitis) or to a serious penetrating injury which may cause degeneration of the eyeball. Refractive errors, if extreme, may cause blindness. This is especially true of myopia (nearsightedness) of the progressive malignant type which is invariably associated with pathological affection of the choroid and retina. The amountof blindness from myopia in the school-age group is not large (2.6 percent of the total). Fortunately, much of the myopia in school children is not of this serious type. While it may tend to increase somewhat during the period of growth, it finally becomes static while still moderate in degree and can be fully compensated by eyeglasses.

Blindness involving the crystalline lens accounts for 17.8 percent of the total. These are chiefly the cataracts which are prenatal, sometimes hereditary in origin, but cataracts may also be caused by injury or disease. Dislocated lenses, although much less frequent (0.7 percent), are usually prenatal in origin. The recently identified retrolental fibroplasia is also classified here. The numbers included in the 1947-48 tabulations do not reflect the true frequency, since few of the children known to be affected had not then reached school age.

Affections of the optic nerve are involved in 14.9 percent of the blindness

Causes of Blindness Among Pupils in Residential Schools for the Blind and Braille Day Classes, by Site and Type of Affections, 1947-48

Optic Nerve, Visual Pathway, and Visual Cortical Centers-

14.9

in school children. They may be present at birth, or due to an infectious disease, chiefly syphilis or meningitis, or to an injury or brain tumor.

Affections of the choroid and/or retina account for 12.3 percent of the total cases. They are largely of prenatal or infectious origin, but the cause in many cases is unknown.

Affections of the iris and ciliary body (5.8 percent) occur most often in injuries, but may also be due to infectious disease or to unknown cause. The corneal affections (8.6 percent) are due chiefly to infections, especially ophthalmia neonatorum and syphilis, but may be due to other causes such as injury.

CAUSES OF BLINDNESS

Of the known causes of blindness the most important are the infectious diseases, which in 1947-48 accounted for 16.8 percent of the total cases. Ophthalmia neonatorum (infection of the eyes of newborn) with 7.5 percent and syphilis with 3.2 percent still head the list. The figure for percentage of blindness because of syphilis is believed to be higher than this, since many cases of a type which might have been caused by syphilis are diagnosed as "unknown." However, blindness from both ophthalmia neonatorum and syphilis is decreasing. For example, among new pupils entering the schools for the blind in 1947-48, the percentage due to ophthalmia neonatorum was only 2.2 percent. Because of public health control measures, blindness from diseases such as smallpox, diphtheria, and typhoid fever is no longer a problem.

Trauma, or injury, ranks second on the list of known causes, with 7.6 percent of the total. Eye accidents incurred in play or sport are responsible for most of these cases, or 4.8 percent of the total. Blindness from trauma is decreasing, because of the success of safety measures, such as legislation to control the use of fireworks and air rifles and of safety education directed to parents and children, stressing the hazards of sharp or pointed objects, of explosives, and of blows or falls. Blindness from trauma is decreasing also because of prompt ophthalmological care. This is sometimes necessary in order to save the uninjured eye.

The third cause, neoplasms, although not large in numbers (3.8 percent of the total) is increasing. It is believed that the reason for this increase is not so much an increase in cancer as the fact that surgical removal of brain tumors located near the optic nerve often saves the life of a child but not his vision.

Other causes of blindness are general disease (1.2 percent) and poisonings (0.2 percent). Reported cases are relatively few in available data, but their actual frequency may be greater than the figures indicate, since in the ophthalmological examinations made at the school for the blind, usually long after blindness has occurred, it would be quite difficult to determine the cause. The presence in data of even a few cases attributed to toxic poisoning or to some systemic disease provides proof of the importance of good general health in the protection of eye health.

selected readings

BUELL, CHARLES G. Sports for the Blind. Ann Arbor, Mich., Edward Bros., Inc., 1947. 239 p.

CUTSFORTH, THOMAS D. The Blind in School and Society: A Psychological Study. New York, D. Appleton & Co., 1935. 263 p.

FOX, SIDNEY A. Your Eyes. New York, N. Y., Alfred A. Knopf, 1944. 191 p.

GALISDORFER, LORRAINE. A New Annotated Reading Guide for Children with Partial Vision. Buffalo, N. Y., Foster and Stewart Publishing Co.

HATHAWAY, WINIFRED. Education of the Partially Seeing Child. New York, Columbia University Press, 1947 (Rev. Ed.). 216 p.

ILLINOIS STATE Department of PUBLIC INSTRUCTION. The Visually Defective. Springfield, Ill., The Department. 66 p. (Circular Series "D", No. 12.)

LENDE, HELGA, ed. What of the Blind? New York, The American Foundation for the Blind, 1938 (Volume One) and 1941 (Volume Two). 214 and 206 p.

Lowenfeld, BERTHOLD, ed. The Blind Pre-School Child. New York, The American Foundation for the Blind, 1947. 148 p.

An Eye Health Program (Publication 141.)

NATIONAL SOCIETY FOR THE PREVENTION OF BLINDNESS, INC. for Schools. New York, The Society. 7 p.

Suggested Equipment for Partially Seeing Pupils. New York, The Society, 1948. 10 p. NATIONAL SOCIety for Study OF EDUCATION. The Education of Exceptional Children, 49th Yearbook, Part II. Chicago, The Society, 1950. 350 p. (Chapter VIII, “Teaching the Visually Handicapped" by Winifred Hathaway and Berthold Lowenfeld, pp. 135-151.)

OFFICE OF VOCATIONAL REHABILITATION, FEDERAL SECURITY AGENCY. Psychological Tests for Use with Blind Adults in Vocational Rehabilitation. Washington, U. S. Government Printing Office, 1947. 14 p.

SOMMERS, VITA STEIN. The Influence of Parental Attitudes and Social Environment on the Personality Development of the Adolescent Blind. New York, American Foundation for the Blind, 1944. 124 p.