Optic Nerve Hypoplasia (ONH)

The following is from the Chicago Lighthouse convention I attended with Dr. Lawrence Kaufman, M.D., Ph.D.

ONH is the leading cause of blindness.

hypoplasia means underdevelopment of a body structure, so optic nerve hypoplasia means underdevlopment of the optic nerve

ONH is non progressive, meaning it doesn't get any worse than what it already is, and the optic nerve is 25% the normal size (it is smaller)

ONH can be bilateral or unilateral

Bilateral ONH
-"blind infant" means that the child seemed to be blind as an infant
-nystagmus the child may have nystagmus
-strabismus the child may have strabismus
-usually diagnosed at 3-4 months of age

Unilateral ONH
-variable age of diagnosis
-strabismus child may have this
-fail vision screen if the child is older they detect it when the child fails a vision screen at school
-infrequent nystagmus

There can be different groups for ONH. The groups are as follows; *note the children don't usually fall into just one of these catagories, but it helps the doctors for a better understanding.

1) Isolated ONH
-visual deficit
-normal growth, development, behavior (these children have nothing else diagnosed except for ONH)

2) Absent septum pellucidum
- visual deficit
-otherwise normal growth, development, intellegince and behavior (these children have ONH and are missing the septum pellucidum but are otherwise doing great)

3) Posterior pituitary
-visual deficit
-endocrine deficits
-+/- developmental delays
- missing pituitary star (these children have endocrine problems, may or may not have developmental delays and are missing the pituitary star.

4) Hemispheric migration
- visual deficit
-developmental delays
- mental retardation
- focal neurologic deficits
- seizures (theses children are developmentaly delayed, have mental retardation, seizures, and neurological deficits)

5) Intra-uterine/perinatal/hemispherci injury
-profuondly affected
-very impaired
-developmentally delayed
-visual deficit
-mental retardation
-cerbal palsy
- hempligia
- quadripleigia
- focal nurological ( these children are profoundly affected. They have lots more problems. They may have cerbral palsy, mental retardation, they may be quadriplegic)

Septo-Optic Dysplasia

septo means absence of
the septum is hypoplastic
the optic is hypoplastic

Endo deficiency

There may be some endo glands that are not working properly

SOD means ONH plus - you have ONH plus any endocrine anomalitly or any brain anomality

It is rare to have ONH and no septum pellucidum only (meaning nothing else, no developmental delays, endo problems, etc)

The first case of ONH was diagnosed in 1864
prior to 1970 it was rarely diagnosed
1970-1980 there were 350 cases reported
1990 15% cause of childhood blindness

Causes.......
usually the first born child
usually a young mother
has no racial preference
familial cases are extrmely rare (usually won't have another child born with SOD)
intra-uterine infection (may have had an infection while pregnant)
ingested-quinie, dilantin, alcohol, phencyclidine,LSD (the mother may have ingested one of these)

In most cases the mom was healthy, it was a normal pregnancy, was seen by OB regularly, was on prenatal vitamins and they have no idea as to why it happened.

Everything happens in the embryo, it doesn't happen once the child is born --the child is born with ONH

Why does it happen?

1) agenesis
it was never formed in the first place
agenesis means missing

2) developmental
cells were there but never sent out the fibers

3) apoptosis
cells were there, the fibers were sent out, then the cells died (almost as if they committed suicide) no one knows why?

4) destructure
cells were there, the fibers sent out, then there was an injury, inflamation or indigestion

So, all in all they know how, but they don't know why?

Is it getting more common?

They don't know for sure. There are more and more cases reported now but they are unsure if it is due to it occuring more often or if it is because ONH is now easier to diagnosis and wasn't diagnosed alot before.

The above are notes taken by Sheryl Trowbridge from the Chicago Lighthouse Convention in 1997 presented by Lawrence Kaufman, M.D., Ph.D.

We welcome your comments:
trow6@mchsi.com

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