Strabismus is a misalignment of visual axis of the eyes in any direction – up, down, in, out. It affects 3-5% of children. Half are congenital or develop in the first 6 months of life. Strabismus can occur at any age and may indicate the presence of a serious eye disorder or a central nervous system problem. It may result from birth injuries, heredity, faulty eye muscle attachment, visual acuity abnormality or be associated with a neurodevelopmental disorder (strabismus is seen in 75% of children with cerebral palsy). Tests to examine for strabismus include corneal light reflex symmetry (Hirschberg test), unilateral cover test/cover-uncover test, Bruckner test and stereopsis testing (e.g.Random Dot E).
Pseudostrabismus is the appearance of strabismus without a true malalignment of the eyes. The illusion of eye crossing usually arises from a wide nasal bridge or an inner eyelid fold (epicanthal fold). It does not require treatment and may decrease or disappear as the child gets older. The corneal light reflex, cover-uncover test and random dot E stereo test are helpful in differentiating pseudostrabismus from true strabismus.
Amblyopia is reduced visual acuity in an eye resulting from lackof adequate visual stimulation during developmental period in childhood. The brain does not recognize visual stimuli from the affected eye. Amblyopia affects 2-5% of children. There is risk of permanent visual impairment or blindness if amblyopia is untreated until about age 6 years. The most direct way to evaluate for amblyopia is to test monocular visual acuity. Amblyopia can be caused by strabismus, anisometropia (differing visual acuity between eyes), ptosis, and cataracts.
Retinopathy of Prematurity (ROP)
ROP is an eye disorder that primarily affects immature vasculature in the eyes of premature infants, especially those weighing 1500 grams (about 2¾ pounds) or less. The resulting abnormal blood vessels are fragile and can leak, scarring the retina and pulling it out of position. The disorder usually develops in both eyes. The disorder may be mild with no resulting visual defects or it may become aggressive and progress to retinal detachment causing visual impairment or blindness.
Uncorrected refractive errors can cause amblyopia if severe or if there is a significant difference in the vision between the two eyes. Each of these is usually effectively treated with glasses/corrective lenses.
Myopia/Nearsightedness – Poor distance vision
Hyperopia/Farsightedness – Poor close vision
Astigmatism – Imperfect curvature of the lens causing distorted vision
High pressure inside the eye which can result in damage to the optic nerve and blindness if left untreated. Children may indicate discomfort, light sensitivity and tearing. Eventually there may be eye enlargement (increased corneal diameter) and cloudiness of the cornea. There is an increased risk of glaucoma in children who have had cataract surgery. Also at increased risk are children with neurofibromatosis or Sturge-Weber syndrome.
Color Vision Deficiency
Abnormal color perception ranging from inability to recognize certain colors to not being able to identify any color. Most color vision deficiencies are inherited and present at birth, but they can also occur with aging of the lens of the eye, medications, retinal and optic nerve disease. Color vision deficiency is estimated to affect 8% of males and 1% of females. Color vision deficiency is not sight-threatening.