Types & degrees of
visual impairment
Visual impairments in young children can result from a number of different
conditions which affect functioning of the eyes. Some of these conditions
can be improved or corrected with eye glasses or surgery while others
cannot.
Visual Acuity
Visual impairment may be due to a loss of visual
acuity. Visual acuity is the measurement of how clearly we see. A child's
acuity is measured in each eye and in both eyes working together. The loss
of acuity can range from mild to severe and can differ in each eye. The
child's eye doctor may prescribe eye glasses to help improve visual
acuity. If your child’s visual acuity is 20/200 or less in the better eye
after correction with conventional glasses, he/she is considered legally
blind.
Visual Field
Visual
impairment may also be due to a loss of visual field. Visual field is the
total area that can be seen without moving the head or eyes. Some children
experience a loss of visual field on one side (hemianopsia) while others
have a loss of the upper or lower field. Other children may experience
spots of poor vision (scotomas) within their visual field. A loss of
peripheral vision (tunnel vision) or a central visual field loss is
present with some eye conditions. If your child has a visual field of 20
degrees or less, he/she is considered legally blind.
Ocular Motor Impairment
Ocular motor impairment or difficulties with the motor
control in the eye can also impact a child's vision. The muscles of the
eye control how well a child is able to fixate, follow, search, and
converge with his eyes. When the muscles work together they allow the
child to see a three dimensional image. Difficulties with ocular skills
impact how effectively the eyes work. In some cases surgery may be
possible to help with ocular motor difficulties.
Various eye conditions can result in difficulties in
any one or more of the above areas.
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