There are many possible defects or diseases of the visual system , but, fortunately, many of them appear after the first few years of life. There are still many defects, diseases, infections, disorders and malformations that can affect the visual system in infants and toddlers. Only a few of the many visual disorders found in young children is described below:
Cataracts: defined as a clouding of the lens of the eye; can be congenital, caused by trauma, or associated with disease; when caused by maternal rubella, cataracts are not removed early, and acuity never develops well; if not caused by rubella, cataracts are surgically removed soon after birth (usually within the first two months), to allow the retina to be stimulated by light within the first 6-8 weeks of life; good acuity is possible if cataracts are removed early enough.
Glaucoma- (infantile): (also known as "buphthalmos") intraocular pressure build-up caused by an imbalance between the rate of production of the aqueous fluid and the rate of normal drainage; must be treated medically (often surgically).
Cortical Visual Impairment (CVI): apparent lack of or reduction in vision when eyes appear to be normal; cause of the visual reduction is in the visual cortex of the brain; there is no nystagmus; special intervention techniques are indicated (contact VI teacher).
Infections: many types, with a variety of symptoms; most common involve the conjunctiva (thin layer of tissue lining the eyelids and connected to top layer of sclera); require medical treatment (usually medication); other systemic infections (toxoplasmosis, herpes, cytomegalovirus) can also involve the visual system.
Malformations: many types; most common are clefts in the iris, dislocated lens, and syndrome-related abnormalities; may have prenatal causes
Ocular-muscle problems: most common is strabismus (one or both eyes out of alignment); can be outward, inward, upward, or downward, depending on which muscle(s) are affected; must be evaluated medically, for possible surgical treatment; if noticed after 6 months of age, child should be seen by an eye specialist; treatment can be before the child is a year old; every year of delay past age two lessens the chances for good prognosis in acuity; can cause loss of or diminished acuity in one eye (amblyopia) if not treated.
Nystagmus is another ocular-muscle anomaly; manifested by involuntary eye movements, usually noted as "jerky" or "jumpy" eye movement; occasionally occurs alone but most often accompanies other eye conditions; there is no cure; acuity may be reduced, but visual function may improve with age.
Ocular trauma: occurs when the eyeball is hit, lacerated, or punctured; always requires medical evaluation and treatment.
Optic nerve defects: Optic atrophy occurs when, for a number of possible reasons, the optic nerve does not function properly; may result in inconsistent visual functioning; often causes reduced acuity; there are usually no outward indicators - the eyes appear normal ; glasses will not improve acuity; must be medically diagnosed; the phrase pale optic disk(s) suggests the possibility of optic atrophy. Optic nerve hypoplasia (ONH) differs from optic atrophy; in ONH, the optic nerve has regressed in development (usually during the prenatal period, and usually caused by a prenatal insult to the neurological system); must be medically diagnose; may have accompanying brain malformation and/or endocrine problems; there is no treatment, and glasses will not help. Septo-optic dysplasia seem to be an extreme form of ONH.
Refractive errors: (nearsightedness, farsightedness, astigmatism) These are the only defects glasses will help, but, since the infant eye is still developing (and clear acuity is still poor), they are usually not identified as problems in the early months. If present to a marked degree after about 12 months, they may require a prescription for glasses but most toddlers will not need corrective lenses. If acuity seems to be reduced (not within normal ranges) after about age 2, medical evaluation is recommended. In the case of premature infants, an eye specialist should monitor vision periodically from birth.
Retinoblastoma: a tumor behind the eye which, if left untreated, can be both blinding and life-threatening; medical treatment (chemotherapy and/or enucleation) is essential, usually before age 2.
Retinopathy of Prematurity (ROP) : (formerly called retrolental fibroplasia, or RLF) a condition found primarily (but not exclusively) among premature infants; despite the suspected role of oxygen in this disease, prematurity seems to be the major factor; identified medically; cryotherapy appears to halt the progression of the disease; visual function can range from near normal acuity to total blindness, depending on the stage of the disease; about a fourth of children with ROP have severe visual impairment; many of these children are also myopic (nearsighted).