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Optic Nerve Hypoplasia: A Major Cause of Childhood Blindness

by | Mar 1, 2024 | Manuscripts | 0 comments

Keya Chakrabarty, B. Optom Student

NSHM Knowledge Campus, Kolkata, India

 

Have you ever seen a child facing problems in understanding, speaking, or seeing objects clearly? Or maybe their eyes are moving in an uncontrolled way when they try to focus on some object? Be careful! It can lead to total blindness or Optic Nerve Hypoplasia.

Now you may think, what is optic nerve hypoplasia?

The optic nerve is a bundle of millions of nerve fibers sending visual signals to our brain. Any issues in this pathway can disrupt the visual system and brain function. Optic Nerve Hypoplasia (ONH) is a birth defect affecting the optic nerve, causing partial or total vision loss in children. It can affect one or both eyes, with a significant decrease in the number of optic nerves. Improper development of axons may make the optic disc appear very small.(1)

Bilateral ONH is more common. Patients with ONH may have ocular issues (nystagmus, strabismus), facial abnormalities, and central nervous system anomalies. Other observations include hypothalamus problems, cerebral palsy, sleep issues, gastric problems, and neurological development problems with undeveloped white or grey matter.(2)

Maternal behaviors such as alcohol consumption, diabetes, smoking, being a young mother, and premature birth can contribute to this occurrence.(3)

The most common and rare associations for ONH are as follows: Aniridia, Albinism, High Myopia, Chorioretinal coloboma, Microphthalmos, etc. The rarer associations are Klippel-Trenaunay-Weber, Goldenhar-Gorlin, Diane’s, Hemifacial, Meckel, Blepharophimosis, Chondrodysplasia, Osteogenesis, etc.(4)

ONH, or optic nerve hypertrophy, is a condition characterised by nystagmus, strabismus, visual impairment, photophobia, brain abnormalities, neurological issues, obesity, and sleep cycle problems. It is mainly caused by genetic variation and maternal behavior, with genetic variations like Netrin, POUF1, PROP1, SF-1, PITX2, NeuroD1, GATA-2, LHX3, TPIT, SOX3, SOX2, and HESX1 being major risk factors.(5)

Generally, three types of ONH can be seen:

  1. Simplex ONH
    • Diffuse
    • Segmental
    • Tilt segmental
  2. Septo-optic dysplasia
  3. Septo-optic-pituitary dysplasia (6)

ONH affects both males and females, affecting visual acuity and optic nerve development. It can cause field defects and pupillary light reflex. Ophthalmoscopic diagnosis is crucial for fundus evaluation, revealing a white, pale, small optic disc with anatomical variations, double-ring structures, and tortuous retinal blood vessels. Double-ring structures may be due to the retina and pigmented epithelium.(7)

Figure 1:  Severe Optic Nerve Hypoplasia (Optic Disc is denoted by white arrow and Double-ring structure is denoted by black arrow)
Image courtesy- https://entokey.com/optic-nerve-hypoplasia-2/

In most cases, ONH is bilateral, and unilateral ONH is found in late age when the vision is fully developed. An optometrist should check the child’s visual acuity, especially central visual acuity, which can vary from normal to no light perception.

When optometrists encounter such babies, Optical Coherence Tomography for retina assessment, fundus examination, visual field testing, color vision evaluation, and visual electrophysiology should be performed. Typically, we should look for a small optic disc size, narrow nerve fiber layer, and peripapillary double-ring sign. Visual field testing by Humphrey field analyser can be done. It is very necessary to follow up on the children’s looking behavior such as nystagmus, strabismus, etc., checking visual acuity, and analysing the situation of the Optic disc as early as possible, to treat the disease.(8)

A physician should examine hypothalamic problems, vision problems, and brain functioning using MRIs. Regular tests for growth and development are necessary for babies and children. Various therapies, medications, and food habits are needed for ONH. If an optometrist notices by examining that 1-3-month-old patients have strabismus, photophobia, aniridia, albinism, then the child should be suggested to have regular follow-up and further treatment. Early diagnosis is crucial, and genetic counseling and awareness of maternal behavior are also important.

 

References:

  1. Kanski, J. J. (2007). Clinical ophthalmology: a systematic approach. Elsevier Brasil.
  2. Vickers, A., Zhou, A., & Vickers, A. Superior Segmental Optic Nerve Hypoplasia (SSONH).
  3. Garcia-Filion, P., & Borchert, M. (2013). Optic nerve hypoplasia syndrome: a review of the epidemiology and clinical associations. Current treatment options in neurology, 15, 78-89.
  4. Kaur, S., Jain, S., Sodhi, H. B., & Rastogi, A. (2013). Optic nerve hypoplasia. Oman Journal of Ophthalmology, 6(2), 77.
  5. Altyar, A. E., El-Sayed, A., Abdeen, A., Piscopo, M., Mousa, S. A., Najda, A., & Abdel-Daim, M. M. (2023). Future regenerative medicine developments and their therapeutic applications. Biomedicine & Pharmacotherapy, 158, 114131.
  6. Scott, D. A., Wang, M. T., Danesh-Meyer, H. V., & Hull, S. (2023). Optic atrophy in prematurity: pathophysiology and clinical features. Clinical and Experimental Optometry, 1-10.
  7. Kaur, S., Jain, S., Sodhi, H. B., & Rastogi, A. (2013). Optic nerve hypoplasia. Oman Journal of Ophthalmology, 6(2), 77.
  8. Kahn, A. L. R. (2021). Families’ Experiences Raising a Child with Optic Nerve Hypoplasia. University of Northern Colorado.

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