Jose L. Guzman III
Optic Nerve Hypoplasia:
Description/Etiology:
Optic nerve hypoplasia is the underdevelopment of the optic nerve. It
is a congenitally small optic disk, usually surrounded by a light halo, having
regression in growth during the prenatal period. Optic nerve hypoplasia
may result in visual acuity. The optic nerve is underdeveloped during
pregnancy. It is more common bilaterally (both eyes) than unilaterally
(one eye). Optic nerve hypoplasia (OPH) is not progressive, and has no
cure. OPH is one of the three most common causes of visual impairment in
children.
As visual acuity can vary from 20/20 to no light perception and is nonprogressive. repeatedBecause of this, visual prognosis in an infant is
uncertain. OPH is frequently associated with a variety of central nervous
system and endocrine abnormalities. Hormonal problems may not show
until later in life.
Facts & Figures:
OPH is not inherited. Visual acuity can vary from 20/20 to no light
perception repeated and is not deteriorate with time. It is a stable
condition. A mild improvement in visual function may occur as a result of
maturation of the brain.
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Jose L. Guzman III
A percentage of OPH patients have nystagmus (involuntary oscillation
of the eyes, rhythmic). This is usually associated with severe bilateral
reduced visual acuity. In some cases, reduced nystagmus may occur.
Risk Factors:
There is no known cause of ONH. It has been associated with
environmental factors, including maternal diabetes, maternal alcohol
abuse, maternal use of anti-seizure medications, and young maternal age
below 20years of age. Research shows these factors account for few of
the total number of cases.
ONH has been associated with other systemic and ocular disorders like
aniridia, Klippel-Trenauney-Weber syndrome, Trisomy 18 and 13. All races
and socioeconomic groups can be affected by ONH.
Clinical Presentation/Signs & Symptoms:
Children with ONH have a wide range of visual function ranging from
normal visual acuity to no light perception repeated again. Effects of the
visual field may range from generalized loss of detailed vision in both
central and peripheral fields (depressed visual fields) to subtle peripheral
field loss.
On physical exam the optic disc is small, pale, and surrounded by
yellowish halo bordered by a ring of pigmentation (double ring sign).
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Many children present with nystagmus (involuntary movement of the
eyes). Depth perception may be worse if vision loss is great. Mild
photophobia (light sensitivity) may occur.
Some patients present with feeding problems due to hormonal
problems. They may have lack of interest in eating due to decreased
sense of smell and taste. Some present with behavioral problems like
inability to pay attention and irritability due to hypoglycemia (low blood
sugar). If the patient has central nervous system problems, they may be
easily distracted and act unorganized and impulsive.
Diagnosis:
ONH is diagnosed by examination of the eye by an ophthalmologist.
There are no laboratory or x-ray tests to confirm diagnosis. Visual acuity is
difficult to predict at an early age. Visual functioning can be determined
by the appearance of the optic discs. Again, visual prognosis in an infant
is uncertain.
Children found to have ONH need MRI to identify midline brain
anomalies. Hormonal insufficiencies require examination by
endocrinologist.
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Treatment:
ONH is not progressive, but it has no cure. Management of these
patients should include a medical team consisting of a primary doctor, an
ophthalmologist, an endocrinologist, a psychologist, a neurologist, and
perhaps a social worker to help the parents or family member obtain
special visual impairment services. The primary doctor will manage the
ongoing assessment of the patient. The hormonal insufficiencies
(hypoglycemia, prolonged jaundice, failure to grow, maintaining
temperatures, will be managed by the endocrinologist. Feeding issues
may be managed with dieticians and or speech therapists.
Many children require placement in programs for children with poor
sight (visually handicapped). As a child gets older, he or she may benefit
from visual aids such as an enlarger (to increase the size of print) and/or a
special computer for the visually impaired (e.g., a scanner that takes
written words and turns them into spoken words).
Children diagnosed with ONH can benefit from other services like
language therapy (provided by a speech/ language pathologist), and
vision therapy. Some children will benefit from instruction from instructors
of Orientation and Mobility and Visually Impaired Specialist.
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References:
Bernas-Pierce, J., Jacob, N., Hoyt, C. et, al. (2005), Blind Babies
Foundation. The pediatric visual diagnosis fact sheet. Accessed on
6/30/009 on www. Tsbvi.edu/Outreach/seehear/spring99/opticnerve.htm
Karl, C. (1998): Congenital optic nerve anomalies. Current Opinion in
Ophthalmology, 9:VI 18-26.
Lueck, A. (2004): Functional Vision: A Practitioner’s Guide to Evaluation
and Intervention. New York, NY: AFB Press, American Foundation for the
Blind.
Marsh-Tootle, W. (1994). Congenital optic nerve hypoplasia: a symposium
paper. Optometry & Vision Science, 71 (3), 174-180.
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