The human body is complex, and many things can go wrong while a baby is developing. Sometimes, genetic mutations occur, or things don’t form quite right.
One condition that can result from developmental errors is optic nerve hypoplasia.
What Is Optic Nerve Hypoplasia?
Optic nerve hypoplasia is a condition in which the optic nerve is underdeveloped. This often results in a small optic nerve. This is due to a problem with the development of the eyes in utero.
The optic nerve is the nerve that connects your eyes to your brain. It sends light signals to your brain, allowing you to see.
Those with optic nerve hypoplasia may experience symptoms ranging from mild visual impairment to blindness. A condition called nystagmus, or uncontrollable shaking of the eyes, commonly accompanies optic nerve hypoplasia, as does a misalignment of the eyes called strabismus.
90% of patients with optic nerve hypoplasia have central nervous system abnormalities, and 70% have neuro-developmental handicaps. Optic nerve hypoplasia may also occur alongside brain structure abnormalities such as:
- Absence of septum pellucidum. A condition in which the septum pellucidum, a thin membrane in the middle of the brain, is absent.
- Agenesis of corpus callosum. A condition in which the area of the brain that connects the two hemispheres is missing.
- Abnormalities in one of the cerebral hemispheres. The brain has two cerebral hemispheres within the cerebrum, which ordinarily control muscle function, speech, emotions, thoughts, learning, reading, and writing.
- Abnormalities in the pituitary gland. The pituitary gland is a small, pea-shaped gland at the top of the spinal cord that controls many hormones.
Optic Nerve Hypoplasia Causes
Scientists currently do not know what causes optic nerve hypoplasia. In most cases, it appears at random.
There is evidence, though, that certain gene mutations may be associated with optic nerve hypoplasia. However, the correlation seems to be small, as the majority of those with optic nerve hyposplasia do not have these gene mutations.
Some researchers hypothesize that optic nerve hypoplasia could be the result of vascular disruption. Vascular disruption refers to something temporarily disrupting blood flow to an unborn baby, which then can cause developmental delays and birth defects.
Risk factors that have been associated with optic nerve hypoplasia include:
- First trimester bleeding
- Maternal smoking
- Young maternal age
- Maternal diabetes
- Preterm labor
- First pregnancy
- Low maternal weight gain or maternal weight loss
- Use of recreational drugs during pregnancy
- Use of some medications during pregnancy
Optic Nerve Hypoplasia Symptoms
Optic nerve hypoplasia is present at birth, but since newborns don’t have great eyesight anyway, symptoms may not emerge until childhood. In some cases, newborns may have nystagmus, uncontrollable shaking of the eyes.
In many cases, the only symptom of optic nerve hypoplasia is vision loss. However, in situations in which the optic nerve hypoplasia also accompanies neurodevelopmental abnormalities, young children may experience developmental delays and behavioral difficulties.
Occasionally, children born with an underdeveloped optic nerve also have an underdeveloped hypothalamus. The hypothalamus is a part of the brain that coordinates the endocrine system, which monitors hormones, with the nervous system. It’s responsible for keeping the body in homeostasis, managing things like blood pressure, body temperature, hunger, thirst, and sleep. Children who have both an underdeveloped optic nerve and hypothalamus often experience trouble with regulating these things.
Children with optic nerve hypoplasia may have issues with their pituitary gland. This can lead to a range of symptoms, including:
- Intellectual disability
- Delayed maturation
- Obesity
- Hypothyroidism
- Low blood sugar (hypoglycemia)
- Diabetes
Optic Nerve Hypoplasia Diagnosis
If your ophthalmologist suspects that your child may have optic nerve hypoplasia, they will likely perform an examination followed by several other tests.
During the exam, your doctor will look for signs of optic nerve hypoplasia, such as:
- A smaller-than-normal optic disc, the structure where the optic nerve meets the rest of the eye
- A pale or gray optic disc
- A ring around the optic disc
- Thinning layers of the retina, the cells that line the back wall of the eye
- An eye shape that causes vision problems
Magnetic resonance imaging (MRI) studies are commonly used to help diagnose optic nerve hypoplasia. MRIs create detailed images of soft tissue by using a magnetic field and radio waves. With an MRI, the ophthalmologist will be able to see the size of the optic nerve and view the optic chiasm. The optic chiasm is the place within the brain where some of the nerves from each eye cross. An MRI can also show any other brain abnormalities that may be present.
Another tool used to diagnose optic nerve hypoplasia is optical coherence tomography. Optical coherence tomography, or OCT, is a non-invasive method of recording images of the back of the eye.
If hormonal or pituitary problems are suspected along with optic nerve hypoplasia, your doctor may run blood tests to check hormone levels.
Optic Nerve Hypoplasia Treatment
Optic nerve hypoplasia has no cure. Instead, treatment involves managing and alleviating the symptoms of hypoplasia and its associated conditions. Children with optic nerve hypoplasia may need to work with a team of doctors, including endocrinologists and neurologists.
Vision problems are usually not treatable, but depending on its severity and type, a vision problem may be manageable with vision aids. Hormonal imbalances may require hormone replacement therapy. In some cases, surgery may be necessary for accompanying conditions like strabismus.
Optic Nerve Hypoplasia Prognosis
While there is no cure for optic nerve hypoplasia, it is not a degenerative condition, and vision usually does not get worse.
The prognosis for each patient will be different, though, depending on what other conditions they have alongside their optic nerve hypoplasia. Some may need hormonal therapy for the rest of their lives, while others will only have slight vision problems.
Early intervention is the best way to set your child up for success. This can give kids access to services like vision therapy, occupational therapy, and physical therapy. If you’re concerned that your child may have optic nerve hypoplasia, schedule an appointment with an ophthalmologist right away.
