The Dr. Bill Takeshita Foundation

Last Modified: Sat, 18 Aug 2007

View other Common Causes of Vision Impairment

Optic nerve hypoplasia (ONH) is one of the leading causes of vision impairment among children today. The prevalence of ONH is increasing at a rapid rate but the cause of this disorder is not known. ONH affects the development of the optic nerve fibers of one or both eyes in the growing fetus, causing a wide range of vision problems. Some children may have near-normal sight while others may be totally blind. There is no medical treatment for ONH but many children respond very well to low vision aids, special glasses, magnifiers, and computer technology.

The optic nerve is the accumulation of hundreds of millions of nerves that transfer information from the rod and cone cells of the retina to the brain. The optic nerve develops in the growing fetus. Unfortunately, for some unknown reason, the fibers do not develop normally in children with ONH, resulting in blurred sight, color vision problems, reduced contrast vision, poor peripheral vision, and nystagmus (uncontrollable shaking of the eyes). The nystagmus does not cause them to perceive the world as moving or shaking. With time, they are often able to control the nystagmus or they may turn or tilt their head to reduce the nystagmus.

Children with ONH have a higher prevalence of significant hyperopia, astigmatism, and nearsightedness. Glasses should be prescribed as soon as possible to maximally stimulate the visual centers of the brain. Children with ONH also have a higher prevalence of strabismus, crossed or turned eyes. This often occurs when one eye has more optic nerve fibers than the other eye. Typically, the eye with more optic nerve fibers has better vision and the brain relies on the vision of that eye. Consequently, the other eye is ignored and the eye turns or deviates inward or outward. Strabismus eye muscle surgery is sometimes recommended to attempt to straighten the eye and improve the cosmetic alignment of the eyes.

Children with ONH often have visual areas of the brain that have not received maximal stimulation. Vision is a learned and developed skill that involves the stimulation of the visual cortex in the parietal lobe of the brain. As light enters the eyes, the retinal cells normally send information through the optic nerve to the visual cortex. In ONH, there are fewer and smaller optic nerve fibers and consequently the visual cortex does not receive maximal stimulation. In the 1970’s, Nobel prize winning scientists Hubel and Weisel determined that the brain requires stimulation for the development of vision and that patterned stimulation can promote the development of vision in kittens that were blind due to the absence of stimulation to the brain. The use of bright illumination, high contrast patterns, and low vision spectacles can provide higher than normal levels of stimulation to the visual cortex and potentially stimulate the visual cortex of children with ONH. This program of stimulation is called vision stimulation therapy.

Many children with ONH have associated developmental and medical conditions. Abnormal development of the midline structures of the brain may occur. The lack of development of the corpus collosum, absence of the septum pellucidum, and abnormal formation of the ventricles of the brain are common. Pituitary, thyroid, and other glandular abnormalities can affect growth, appetite, ability to quench thirst, regulate blood sugar, and secrete anti-diuretic hormones to regulate urination. Thus, it is very important that children with ONH are seen by an endocrinologist.

Recommendations

• Infants should have a complete neurological and endocrine workup as well as an assessment by a neurophthalmologist.
• Infants should be examined by the age of 6 months or younger. Glasses should be prescribed based on the visual developmental level of the children. For example, four-month-old infants should have their glasses prescribed to focus at their arms length rather than 20 feet.
• Infants will benefit from vision stimulation to maximally develop the visual cortex of the brain. For specific details, please see Developing Your Child’s Vision.
• Children with ONH will benefit from a consultation by a low vision specialist and low vision aids. Low vision aids such as bioptic glasses, hand held telescopes, and video magnification systems can improve distance sight to 20/20 while specialized reading glasses, hand magnifiers, and closed circuit televisions can allow patients to read small print, read medication labels, and see photographs. A consultation by a low vision specialist will be helpful for children and adults with ONH.
• Students with ONH should be positioned in the front portion of the room. The use of black dry erase markers or bold chalk will make it easier to read the chalkboard.
• Bold lined paper and felt pens will provide additional contrast to make it easier for students with ONH to see their writing.
• Students with ONH may have difficulty seeing red, orange, and magenta. These colors in the red spectrum should not be used for educational purposes of color-coding.
• Students will benefit from having copies of material normally written on the board or presented on overhead transparencies. If Powerpoint presentations are used, a dark background with white letters typed in Arial or Tahoma fonts will improve readability for students with low vision.
• Some students with ONH will have difficulty participating in sports such as baseball, softball, and tennis. Their blurred sight and peripheral vision defects will interfere with their ability to see the ball quickly.
• Computer users will benefit from changing the background of the display to a black or blue background with white letters. Enlargement of the font size will also increase readability. For information on how to modify the computer screen, see “Solutions to Help You User Your Computer.
• Students may benefit from using specialized computer software and technology such as Zoom Text magnification software, scanning programs such as Open Book and Kurzweil, and Video Magnification systems. For more information, see Computer and Assistive Technology.
• Potential drivers with ONH will benefit from having a low vision examination by an optometrist who specializes in fitting bioptic spectacles for driving.
• Specific low vision aids that are often helpful to patients with optic nerve hypoplasia include:
  • 4x to 6x bioptic spectacles
  • Ocutech bioptic auto focus spectacles can greatly improve distance and near sight for adults and teens with ONH.
  • DVI clear image aspheric reading glasses
  • Prescription CPF, Transitions, Melanin, and NoIR filters
  • 4x to 6x aspheric hand magnifiers for reading fine print.
  • Large print keyboards
• For more information, please see Low Vision Rehabilitation