What is Involved in Screening?
The first step in effective screening is to eliminate those individuals at low risk for Usher syndrome. A Low-risk Cause Form is available to assist you with this first step. The second step involves using the Behavioral Observations Form to note subtle changes that may signal vision loss. The next step is further screening followed by referral to an eye doctor if appropriate. *All forms can be requested from MaryAnn Demchak.
After the above forms are completed, a school nurse or teacher can carry out additional screening in the areas of dark adaptation and visual field loss. This screening can help to identify those individuals who should be referred for more in-depth evaluation by an eye specialist.
Please remember to follow district or agency procedures for obtaining parent/guardian permission for completing screenings and for evaluations. Any forms completed as a part of the screening process should be placed in the student's cumulative file.
Dark Adaptation Screening
Since RP usually begins to manifest itself as the inability to see well in dim lighting or darkness, a dark adaptation screening is the most basic preliminary screening. This screening should be done in a completely darkened room. Place a few items around the room. Ask the individual to sit in the dark room for about six minutes to allow his/her eyes to adjust to darkness. Then ask him or her to walk around the room. Observe if he/she bumps or stumbles into objects or walls. This is a crude test and does not necessarily indicate the individual has RP. The ophthalmologist or optometrist has a more sophisticated dark adaptation test.
The visual field loss associated with RP is a progressive condition which develops slowly. Screening should take place yearly since the loss may not be noticed until it becomes severe. The field loss might initially occur first as a circular or "doughnut" shaped area of loss. To test for a field loss, test one eye at a time (the loss may be different in each eye).
Facing the individual to be screened, a school nurse or teacher asks the individual to cover one eye with his or her hand. After giving the individual instructions to look straight ahead at the examiner's nose, the examiner holds one or two fingers up off to the side, just within his or her own visual field. Then the individual is asked whether he or she can see one or two fingers. These procedures are repeated on the other side.
IF the individual is able to discriminate between one or two finders, using the examiner's field of vision as a standard, it is evident that there is not a significant loss of visual field.
If any vision problem is observed during the use of the checklists and vision screening tests mentioned, the school nurse should refer the person to an ophthalmologist for further evaluation. Due to sensitive nature of sharing results that a vision problem is suspected for an individual with an already diagnosed hearing impairment, we suggest sharing, in person, the recommendation to see an ophthalmologist.
It is important to emphasize that following the procedures outlined here does not result in a diagnosis of RP or Usher syndrome. Such a diagnosis must be given by a qualified medical professional. The definitive test for RP, electroretinogram (ERG), may need to be repeated several times to confirm or disprove the diagnosis.
Retinitis pigmentosa develops gradually. Screening for children at risk should occur yearly until the child leaves school unless there is some other evidence, through ophthalmological testing, that the child does not have Usher syndrome. Even if it is determined that the individual does not have Usher syndrome, regular vision screening is extremely important for the individual identified as having a hearing impairment.
Vision difficulties can occur for a wide variety of reasons for all individuals. Because vision and hearing are the two senses relied upon most for learning, it is important that any vision difficulties be addressed for the individual with a hearing loss. Thus, yearly vision screenings are important for all children with hearing impairment.
If an individual is identified by a qualified medical professional as having Usher syndrome (or vision and hearing loss due to another reason), follow-up to that individual and hi/her family will be essential. Strategies are suggested below:
- Referral to a counselor with experience with individuals who have sensory impairments.
- Contact with other families who have a family member with Usher syndrome.
- Contact with an adult who has Usher syndrome.
- Referral to and involvement with the Nevada Dual Sensory Impairment Project.
- Referral to and involvement with the district or agency personnel knowledgeable about vision impairments.