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no way reduces the value they have for the partially sighted.
In
general, most fully sighted persons would have no use for aids listed in the 200 and 300 series since these aids are specifically designed
for the partially sighted. is more complex.
The situation with aids in the 100 series
The problem is to distinguish between conventional
lens prescriptions for fully sighted persons and unconventional
lens prescriptions for the partially sighted.
Since our interviewers
were not ophthalmologists or optometrists, and were sometimes not able to determine whether ordinary appearing spectacles or contact lenses
were conventional or unconventional, many aids listed in the 100 series
may in fact be designed for the partially sighted. Robert L. Gordon, O.D., low vision consultant to the Center for the Partially Sighted, has devised and suggested a set of parameters that would allow us to distinguish conventional from unconventional
spectacles and contact lenses.
Spectacles or contact lenses are con-
sidered to be unconventional if they satisfy one of the following
seven conditions: 1.
Single vision spectacles with lenses that, in absolute value, are greater than eight diopters.
2.
Bifocal spectacles whose distant viewing segment, in
absolute value, is greater than eight diopters, or whose distant viewing and near viewing segments differ from one another, in absolute value, by more than four diopters. 3.
Multifocal spectacles with distant viewing segments that, in absolute value, are greater than eight diopters.
4.
Glasses with astigmatic corrections that, in absolute value, are greater than four diopters.
5.
Spectacles with prismatic correction that is greater than six diopters.
6.
Occluding contact lenses; pinhole contact lenses; stenopaic *
slit contact lenses; cosmetic contact lenses.
*
To conceal scarred corneas or other ocular disfigurements.