Tuesday, April 8, 2014

What IS Optic Nerve Hypoplasia? - Everything I Know Part 1 -

It's come to my attention that everyone who reads the blog knows something's up with Hayes.  A little over half know that he has a neurological condition (a congenital birth defect) called optic nerve hypoplasia (ONH).  Less know, however, what that really means and entails.  And a few know there's some other stuff going on too; things that no one can really describe well or explain.

I think that sometimes even really, really close loved ones can feel uncomfortable when asking parents whose children have atypical development to explain, in detail, what's going on and why.  And so, they don't*.

I also know that I have read ... a lot... of information (printed and online) about optic nerve hypoplasia; I still Google it sometimes to see if anything new comes up.  I know how it feels to be a frightened mother looking to educate myself on something I'd never heard of until it affected my baby.

SO I want to do an exhaustive post (series) that covers everything that we know about ONH because of Hayes.  Please keep in mind that I am neither a doctor nor a pediatric therapist, and I am describing our family's experiences and decisions regarding this condition.  I'll post medical information, signs, and links I consider to be useful resources.

Optic nerve hypoplasia is a congenital (before birth) neurological (brain) condition resulting in varying degrees of vision loss and can be associated with other disorders and conditions.  Hypoplasia means 'under-developed', and so the name of the condition itself basically describes the fact that the optic nerves were malformed as the baby's brain developed during pregnancy.  The optic nerves are the nerves that connect the eyes to the brain.  There are no known causes of ONH, but studies have linked the usage of drugs, young maternal age, primaparity (first pregnancy), and low maternal weight gain to the condition.  It is not known to be a hereditary condition and is not currently linked specifically to any chromosomal malformations.

When a person has optic nerve hypoplasia, it can affect one (unilateral) or both (bilateral) eyes, and the development can be moderately to severely under-developed.  For example, one person with ONH may have optic nerves that are only slightly smaller than the typically developed person's, while another may have optic nerves that are almost completely diminished.  Obviously, this means that even with the same medical condition, vision loss can range from near to normal acuity (what we call "20/20") to no light perception, meaning that the brain does not perceive the image of light through the eyes.

Every ophthalmology appointment/MRI result has indicated to us that Hayes's optic nerves, while smaller than average, are not markedly underdeveloped.  Unfortunately, as he is still unable to talk, we are not sure of just how much/well he is able to see.

It is important to remember that even with a bilateral ONH diagnosis that the brain will adapt to the under-developed optic nerves.  And so while the optic nerves will not themselves repair or grow stronger, the brain can learn to read their signals better over time, often until the ages of three to five.

This is also why it is important to monitor the health and function of the eyes.  ONH is sometimes associated with strabismus (eye crossing) and nystagmus (eye shaking).  In the case of strabismus, if the eyes are crossed for a long period of time, the brain will eventually 'shut off' the signals it receives from one of the eyes to cancel the 'double vision' effect.  (This is called amblyopia.  Read more about it here.)  Treatment can be consulted with your ophthalmologist and generally consists of patching either eye or undergoing strabismus corrective surgery. (For more information on strabismus, talk to your child's ophthalmologist and click here.)

It was because of strabismus that we were initially referred to a pediatric ophthalmologist by our family physician after Hayes's four month check up, and in turn it was the ophthalmologist who first diagnosed Hayes with optic nerve hypoplasia.  Hayes had the strabismus corrective surgery in July.  His eyes have healed nicely and do not cross as frequently.  Because both of his eyes have always seemed to cross equally, rather than one or the other, our doctor has never recommended patching, and for this reason I am less comfortable giving extensive information on patching.  (For more information on patching as an aid for eye alignment and acuity, talk to your child's ophthalmologist and click here.)

Nystagmus often occurs in people with ONH, and it means that the eyes move quickly, or 'bounce' in different motions, like up and down or side to side.  Interestingly, people with ONH can find their 'null point, which is an angle at which they can look at things without having their eyes move constantly.  (For more information on nystagmus, talk to your child's ophthalmologist and click here.)

We have been on the watch to see if Hayes seems to prefer looking at objects or people from certain angles, which may indicate that he has found a 'null point'.  There is actually a surgical procedure that can 'move' a person's null point.  For example, it would be much more convenient if the null point could be found when the eyes were looking straight forward, instead of looking at things obliquely from a wide angle.  So far, we have not noticed Hayes preferring any such positioning.  

We have noticed him 'nodding' quite a bit, and at this last appointment, the ophthalmologist referenced a condition called spasmus nutans that is associated with nystagmus, although not necessarily with ONH.  Spasmus nutans is characterized by nystagmus and head movements, such as nodding.  It generally manifests during infancy and early childhood, but generally resolves itself by ages 3-4.  Because the signs can also be misread as spasmus nutans when they can actually be signs of problems such as brain tumors, doctors will often order MRI scans to be done.  Since Hayes has already had this done with no concerns coming up, our doctor felt comfortable ruling that out.  (For more information about spasmus nutans, talk to your child's ophthalmologist and click here.)


Because no one likes to scroll forever, this wraps up the first part of what I hope will be an informative, frequently updated series about optic nerve hypoplasia and hypotonia (in broad scope) and our journey with Hayes (in specific detail).  Stay tuned for: associated conditions, posts on early childhood intervention and how to get it, hypotonia, global developmental delay, genetics, and most likely more.


Everything I Know Series
What IS Optic Nerve Hypoplasia - Part 1 (you are here)

  • LEGEND
  • Medical information / New Terms
  • Personal Andrews information
  • Medical specialists
  • Therapy / Government Programs
  • Really important information
  • and links I think you should visit always look like this

But here's your reward for making it this far.  Hayes says, "I bet you thought she'd never stop talking!"


*It's okay to ask.  : )