Guidelines for Vision Screening in Missouri Schools

Children who are born deaf or who have a profound hearing loss should be screened for the possibility of a genetic disorder, Usher Syndrome. This condition is of very low incidence, but a young person with Usher Syndrome develops retinitis pigmentosa (RP), usually in adolescence. RP is a condition that results in progressive loss of vision and ultimately, total blindness. It is important to identify these students as soon as possible in order to prepare them for the future.

Deaf students may function well using sign language or lip reading, but when they lose their vision, they must have other means of communication. Students identified with Usher Syndrome are often referred to special centers where they learn communication skills and mobility before they totally become blind.

The first screening is done by completing a screening checklist on any student who has a history of congenital deafness or has a significant hearing loss. This will rule out more than 99 percent of the students who should be screened further for vestibular dysfunction, or balance, dark adaptation, and loss of peripheral vision (see page 32).

Screening for Balance

Screening for balance is easy to do. Ask the student to stand with feet together, arms outstretched to the side, and then close their eyes. In this position, younger students may have problems maintaining balance, but older students may only wobble a little.

Next, ask the student to stand with the heel of one foot immediately in front of the other foot, with arms outstretched. They may have some problem with their eyes open, but when asked to close their eyes, they will fall over immediately. It is important to support the sides of their torso until they get their balance, and be ready to catch them if they fall.

If the student fails the balance screening, parents should be contacted to get further history and to ask questions about their observations of the student’s balance and vision. Look particularly for signs of night blindness. The student may have excellent central visual acuity in well-lighted conditions but have difficulty in dim light, twilight or at night.

Screening for Dark Adaptation

Put some red, white and blue objects (poker chips work well) in a jumbled heap on a dark table or carpet. Ask several students to participate. Turn out the lights, leaving just a tiny amount of light in the room. Ask the students to pick up a white object and note how long it takes each one to do it. Next, ask one student to sort the red and blue objects. After the first one completes the task, mix them up again and ask the next student to sort them. Use yourself as a comparison, but be aware that older people may have a longer adaptation time.

Some students with RP may not show any clinical signs of vision loss at night or during the day until mid- adolescence, so night vision should be checked periodically.

Screening Visual Fields

In students over age eight, screen for visual fields. In the early stages of cone dysfunction (a result of retinitis pigmentosa), students can see well at the extreme periphery but then lose sight of the object closer-in while maintaining normal vision centrally. Face the student, asking him to keep looking at your nose. Hold your hands out at three and nine o’clock, then at six and 12 o’clock and in between these two positions. Keep your arms completely still and wiggle just the fingers on one or the other hand, varying the side in an unpredictable pattern. Ask the student to point to the one which is wiggling. If the student is unable to see the wiggling fingers, he may be losing peripheral vision.

Referral

Students who meet the referral criteria should be referred to a pediatric ophthalmologist or retinal specialist. The provider should be given any history that indicates the possibility of Usher Syndrome, results of observations, balance screening, dark adaptation and visual fields.

If a student is identified as having Usher Syndrome, please call the Missouri Deafblind Project (see page 33 for a description of services).

What is Usher Syndrome?

Usher Syndrome is a genetic disorder involving the loss of both sight and hearing. Hearing loss occurs at birth or shortly thereafter. A progressive loss of vision due to retinitis pigmentosa (degeneration of the eye’s retinas) begins later in life, but usually before adolescence. There is no way of knowing the time of onset or rapidity of vision loss, but in almost all cases, the result is legal blindness.

A person with Usher Syndrome has inherited the Usher gene from both parents. Usher Syndrome is an autosomal recessive gene, and both parents must pass the gene to their child in order for the child to have the condition. When both parents have the gene, the chances each child will have Usher Syndrome is one in four. While only approximately three per 100,000 people will have Usher Syndrome, it is estimated that three percent to six percent of people who are congenitally deaf have the condition.

Usher Syndrome accounts for over 50 percent of all cases of deaf-blindness, with approximately 10,000 known cases in the United States. In the general population, anywhere from one in 100 to one in 300 carry the Usher gene.

The two major types of Usher Syndrome are Type I and Type II. The most common is Type I (almost 90 percent of all Usher Syndrome cases) and is deafness with retinitis pigmentosa (RP) symptoms before adolescence. In Type II (almost 10 percent of cases), moderate to severe congenital hearing loss is paired with RP symptoms after adolescence.

Why Is It Important to Diagnose Usher Syndrome as Soon as Possible?

Identifying Usher Syndrome as early as possible is important because:

• The gradual decrease in vision may go unnoticed by an individual who may continue activities, e.g., driving or working in hazardous conditions that cannot be safely done anymore.
• The individual, parents and teachers can plan for educational and vocational experiences and guidance that take into account the eventual visual difficulties. Resources are available for experiences such as mobility training, use of Braille and tactual communication.
• A diagnosis of Usher Syndrome in an older child allows parents to consider genetic counseling.
• People who have Usher Syndrome may also want to consider genetic counseling.

How Is an Individual Identified as Having Usher Syndrome?

Several screenings are used to determine whether a person has retinitis pigmentosa, and that is how a person who has a hearing loss is identified as having Usher Syndrome. These screenings include a visual field screening to assess peripheral vision and screening to evaluate color vision and dark adaptation. However, the definitive screening of retinitis pigmentosa is electroretinography (ERG), which has been found to be 95 percent accurate. ERG is the measurement of the electricity given off by nerve impulses in the retina. This painless screening is done by having the patient wear special contact lenses while looking at flashing lights.

The following is provided by the Missouri Deafblind Project in cooperation with the Missouri School for the Blind and the Missouri School for the Deaf.

Missouri Deafblind Project

Purpose

The purpose of the Missouri Deafblind Project is to develop partnerships, coordinate service networking and provide systematic training. Technical assistance, training and resources are available for the students identified as deaf and blind on the Missouri Deafblind Census, their families and service providers. Leadership and support is provided by the Missouri School for the Blind Outreach Team. Services are coordinated with local education agencies, adult service providers and Deafblind task forces to enhance networking and build expertise in the community.

Services

• On-site technical assistance and consultation from the outreach team
• In-service training on specific content areas
• Active state and local Deafblind task forces
• Transition assistance including personal futures planning
• Missouri Deafblind Census
• Parent training including a home program for children, birth through five years
• Family workshops including Family Learning Vacation and Families Together, Inc.
• Early childhood training, such as VIISA and INSITE workshops
• Deafblind coursework, such as Hand-in-Hand
• Mentor program
• Usher screening resources
• Loan library of resources on effective practices
• Deafblind newsletter

All services are free. For additional information regarding the Missouri Deafblind Project, contact:

Director, Outreach Services
Missouri School for the Blind3815 Magnolia Avenue
St. Louis, MO 63110

314-776-4320, ext. 250
https://msb.dese.mo.gov/