OPTIC ATROPHY


DESCRIPTION: Dysfunction of the optic nerve; may be congenital or acquired. If congenital, it is usually hereditary. The milder form is autosomal dominant and has a gradual onset of deterioration in childhood but little progression thereafter; the more severe form is autosomal recessive and is present at birth or within 2 years; this form is accompanied by nystagmus. Leber's Disease has an unclear mode of inheritance but is suspected of being X-linked, since it only rarely occurs in women; optic neuropathy occurs more commonly in 20-30 year old males; some vision is retained but there are varying degrees of impairment. The acquired type of optic atrophy may be due to vascular disturbances (occlusions of the central retinal vein or artery or arteriosclerotic changes within the optic nerve itself), may be secondary to degenerative retinal disease (e.g., papilledema or optic neuritis), may be a result of pressure against the optic nerve, or may be related to metabolic diseases (e.g., diabetes), trauma, glaucoma, or toxicity (to alcohol, tobacco, or other poisons). Loss of vision is the only symptom. Pale optic disk and loss of pupillary reaction are usually proportionate to the visual loss.

TREATMENT: There is no known treatment, since degeneration of optic nerve fibers is irreversible. Since changes in visual function occur gradually (over weeks or months), ophthalmoscopic observations are not reliable predictors of functioning until disk cupping and marked pallor are noted; these are unfavorable signs. Visual loss as a result of pressure against the optic nerve may be restored if the cause is identified and treated early. Optic atrophy secondary to vascular, traumatic, degenerative, and some toxic causes has a negative prognosis.

IMPLICATIONS: Enhancing visual function may require high levels of illumination and enlarged print with high contrast; magnification may be useful in some cases. Color perception may be impaired.

Since it is impossible to identify exactly which fibers of the optic nerve are involved, it should not be assumed that the optic nerve is not functioning at all; a better assumption might be that the visual stimulus is experiencing difficulty in getting to the brain; if and when it arrives, it may be in distorted or incomplete form. Thus, perceptual function may be greatly affected. Moreover, day-to-day classroom performance of a student with optic atrophy may fluctuate with no apparent reason. The child may not be aware of these fluctuations; the classroom teacher should be alerted to their possibility.

NOTE: Optic nerve hypoplasia should not be confused with optic atrophy. Optic nerve hypoplasia is an undeveloped optic nerve due to a neurological insult early in the prenatal developmental period; the optic nerve has started to develop, but regresses. Ophthalmologically, the nerve head appears unusually small, and is surrounded by a white "halo" of scleral tissue showing through. The anomaly appears to be related to chronic alcohol and drug abuse by the mother during the prenatal period. CAT scans of these children reveal defects in the septum pelucidum and posterior corpus callosum; those who lack the septum pellucidum have spatial orientation problems. At least one third of these children had low APGAR scores and end up to have endocrine problems. Most have some type of neurological problems. Visual acuity ranges from normal to severely impaired.


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