By Michael Fischer, OD, FAAO
Every child should have a regular general eye examination as early as six months of age to evaluate the health of the eye and visual system. A child with a visual impairment may experience a variety of difficulties, depending to some extent on the age at which the impairment develops. For example, a child who experiences vision loss before age five can have trouble with physical, cognitive, and social development. An older child may have additional difficulties learning in school or interacting with others. That's why it's important to determine vision problems early on.
If a vision problem is diagnosed, the next step should be a low vision examination performed by an ophthalmologist or optometrist specially trained in low vision. This differs from a general eye examination in that much of the testing centers around function. Once a child's visual needs have been determined and his or her visual abilities have been quantified, appropriate interventions will be recommended by the doctor. These may range from glasses or special optical devices to visual stimulation or mobility training. The goal of the low vision examination, for people of all ages, is to improve function through the use of devices and/or adaptive skills.
The age factor
The pediatric low vision examination varies depending on the age of the child, both in terms of the testing techniques used and the ultimate recommendations. In the infant and toddler group, for example, the primary concern is to gather as much information as possible about the child's visual function so that the doctor, and other professionals who will be working with the child, can decide on an appropriate program to assist and enhance the child's overall development. The aspects of visual function that are assessed will depend to a degree on the child's age and the cause of the vision loss. These functions often include visual acuity (a measure of how small an object the eye is capable of distinguishing), refractive error (the type of prescription needed to optimize vision), visual field (the extent of side vision), eye muscle function (the ability to move the eyes in all directions), eye hand coordination, and color vision.
While it is often difficult to get accurate data on the very young child, some aspects of visual function can still be estimated using special or modified techniques. One such technique, used to estimate visual acuity, is known as preferential looking. In this test, cards are presented that have grating patterns (stripes) on one half of the card. If a child can see the stripes, he or she will prefer to look in their direction. A child who has very good visual acuity will recognize and pay more attention to even small stripes. Other tests (like visual field testing) can also be tailored specifically to children by using familiar toys or objects or by using symbols that are easy for a child to identify. As a child with low vision gets older, the doctor can use more accurate testing techniques to better quantify visual function.
Maximizing use of vision
Different recommendations may arise from the exam, based on a child's age and abilities. Glasses may be prescribed even for a very young child if there is a significant refractive error. Absorptive lenses (sunglasses) may be recommended if a child's condition produces significant light sensitivity. Various types of low vision devices may be used to help an older child maximize the use of his or her vision. High powered spectacles or hand-held magnifiers may assist a child with reading or writing. A telescope may be prescribed to help a child see the blackboard in school. Teenagers may use more sophisticated devices, such as a spectacle mounted telescope.
If a child has a significant peripheral field loss (or decreased side vision), a doctor may recommend presenting toys or other objects in a specific area of his or her visual field to permit easier detection and recognition. Children with peripheral losses may have to be taught to scan with their head and eyes to gain more awareness of their environment. Recommendations may be made to a teacher to provide a school age child with a preferred seat in class or to supply larger print materials. Both parents and teachers may have to be educated to expect and encourage the child to hold reading materials close enough to see them.
Perhaps the most important thing that a parent of a child with a visual impairment can do is to ask questions of their child's eye doctor. Each child is unique, but there are very few who cannot be evaluated. Understanding how the child sees and what can be done to improve his or her visual performance can only help the child in their growth and development.
Adapted from The Lighthouse International's EnVision newsletter.