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Versión Español de este artículo (Spanish Version)
By Ann Adkins, Education Specialist, TSBVI Outreach
Abstract: This article examines Optic Nerve Hypoplasia (ONH) and describes some of the characteristics of students with ONH and related conditions such as Septo Optic Dysplasia (SOD).
Key Words: Programming, visually impaired, blind, optic nerve hypoplasia, septo optic dysplasia, sensory integration, autism
I recently had a fascinating conversation with Christopher Sabine who had contacted TSBVI Outreach about his business, ONH Consulting. I was excited to hear that there is a service available to support individuals with Optic Nerve Hypoplasia (ONH), which according to Mr. Sabine’s letter and his website <www.onhconsulting.com>, is the third most common cause of childhood blindness in the United States. I found the information and website particularly valuable since Christopher is an adult with ONH. In Texas, there are currently 313 students on the VI registration with ONH and 43 students with Septo Optic Dysplasia (2006 Annual VI Registration). There are additional students listed as having Optic Nerve Disorder and Optic Nerve Dysplasia. I know that many people consider these terms to be somewhat interchangeable and may use them to describe the same conditions. I have excerpted some information on ONH from Mr. Sabine’s website and his letter to Outreach, and hope that in the future I will be able to interview him about his personal experiences with ONH and his career as a social worker in Ohio. Be sure to look for more information on ONH in future issues of See/Hear.
Optic Nerve Hypoplasia is a congenital condition characterized by underdevelopment of the Optic Nerve and adjacent structures of the midline area of the brain. There is no known cause for ONH. While only a few cases of this condition were reported in the medical literature before 1970, the numbers of children born with ONH seem to be increasing dramatically.
For people with Optic Nerve Hypoplasia, the optic nerve is either nonexistent or did not develop properly. Many people with ONH also have malformation (dysplasia) or absence (agenesis) of other structures of the midline of the brain that are physically near the optic nerve. These might include:
Children with ONH can have abnormalities in the structure of the brain, its function, or both. These abnormalities can be minor and have little to no impact on a child’s functioning and development. In some children, however, these abnormalities can lead to developmental delays and other challenges. Many of these challenges include difficulties with sensory integration, motor planning, intelligence and academic skills, speech and language, and higher order communication and social skills. Children who are most severely impacted can have smaller than normal brains as well as cysts (fluid-filled sacks) in their brains which sometimes have to be drained with an implanted surgical device called a shunt. Children and adults with ONH demonstrate a full range of intellectual functioning from mental retardation to high intelligence.
Optic Nerve Hypoplasia is associated with a host of unique characteristics that distinguish it from blindness or visual impairment due to other causes. Children with ONH can exhibit a wide range of vision, from fairly good visual acuity to total blindness. They may have rapid, involuntary eye movements. This is called nystagmus. Since nystagmus is involuntary, it is impossible for the person to control.
Many children with ONH have sensory integration dysfunction and autistic behaviors and characteristics. Sensory integration is a term that describes how our bodies process the information we receive from our senses. In people with sensory integration difficulties, this process doesn’t work as it should. Children with ONH that have sensory integration difficulties might be highly sensitive to certain textures, sights, sounds, smells, or other features of the environment. They might demonstrate a high pain tolerance and run into dangerous situations with reduced consideration for their safety. Extreme food preferences are very common. They might exhibit inappropriate and stereotyped behaviors, including hand-flapping, body-rocking, head-banging, biting or hitting parts of the body, and eye-pressing. While these behaviors can occur in other children who are blind or visually impaired, they can be much more pervasive and difficult to extinguish in children with ONH. Distractibility, impulsivity, and trouble focusing and staying on task are also typical behaviors in children with ONH that have sensory integration dysfunction.
Many children with ONH demonstrate autistic characteristics and some have behaviors that qualify them for a diagnosis on the Autism Spectrum by a psychologist or another professional qualified to diagnose behavioral disorders. A child with ONH might have difficulty maintaining appropriate social interactions, rigid adherence to routines, and perseveration (talking excessively) on a specific and narrowly defined topic of interest, such as Rod Stuart or the sounds of telephone equipment. In many cases when perseveration occurs, it is on a topic related to music. Music is often a powerful motivator or even a primary means of communication for children with Optic Nerve Hypoplasia. Delays in areas such as adaptive functioning, social skills, and gross and fine motor skills are very typical, and global developmental delays are also prevalent.
Like some people with autism and related conditions, some children with ONH also demonstrate special narrowly-defined skills which are unique to them. These are called “splinter” or sometimes “savant” skills. (Christopher, for example, can multiply large numbers in his head and recite the names of the first 107 elements of the Periodic Table in numerical order). Some others are profoundly gifted musically.
Children with ONH can also face a host of secondary medical complications. In many cases, structures adjacent to the optic nerve are also underdeveloped, malformed, or even nonexistent. When structures such as the hypothalamus and the pituitary gland are impacted, children can have difficulty regulating their body temperature, metabolism, and other vital body functions properly. Some children are unable to produce adequate quantities of essential hormones, such as Cortisol, which the body needs toadapt to stress and regulate blood sugar and energy levels adequately. These children need to take synthetic hormones regularly. In particular, when the body’s level of Cortisol becomes too low, it can lead to a life-threatening condition known as an adrenal crisis. A person without enough Cortisol or growth hormone might have low blood sugar, called hypoglycemia. Hypoglycemia can also lead to serious medical complications, including unconsciousness and seizures in severe cases. If the pituitary gland is not functioning properly or at all, the person’s ability to produce hormones responsible for normal sexual development can be affected. Fortunately, a person who is unable to produce sex hormones can have normal sexual development with hormone replacements.
Children with ONH face a wide variety of challenges. They include blindness or visual impairment, medical complications such as hypopituitarism, sensory integration difficulties, developmental delays, and seizure disorders. They can require a full range of support from families and professionals from many disciplines in order to successfully navigate school and develop into productive and successful adults. ONH is a condition that impacts every child differently.
ONH Consulting, <www.onhconsulting.com>
Personal communication with Christopher Sabine, June 2006.
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