A person’s visual
field is the most important single factor affecting visual function.
There is an increased number of patients with visual impairment, secondary
to visual field loss alone or in conjunction with decreased visual acuity.
This is mainly due to the increased survival rate of head trauma and
stroke patients. A
problem exists only when the field loss involves both eyes. If the field
loss is in one eye only, it will be covered by the other eye. These
patients need a combination of optical intervention along with mobility
instruction.
There are two
general types of field defects:
Overall constriction
Usually caused by advanced ocular disease such as retinal
degeneration’s (retinitis pigmentosa) and optic nerve disease (glaucoma).
Hemispheric
field loss
Usually due to a stroke or head injury.
While a person
with a visual field loss may have near normal visual acuity, the visual
field loss may make walking in a crowd difficult because the ground
cannot be seen. A visual field loss may also make reading difficult
because the beginning or end of a sentence cannot be seen. Special
glasses with prisms can be made to help a patient become more aware
of their lost visual field, making navigation and reading easier.
A low vision optometrist prescribes this type of eyeglasses.
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to Low Vision Aids