In the valley of the blind, the
one-eyed man is king.
|
Discussion The following is only opinion. If you can help document my supposition, or refute it,
I would greatly appreciate your comments. Presbyopia is associated with the inability to have the
muscles of the eye properly adjust to close distances and is typical in
people over 45 years of age. Because of presbyopia, people who do a lot
of close visual work (such as reading or using a computer) frequently need
either "reading glasses" or "computer glasses" or
alternative glasses such as bifocals or progressive glasses. Vision, however, is subjective. Only the patient can
tell the doctor when their vision is clear, and sometimes even the patient
cannot tell. ("Which is clearer, ONE or
TWO.") The most frequently used device for measuring corrective
vision is the phoroptor.
While the phoroptor may be faster and easier to use when quantifying vision
adjustment than using a manual lens frame, the restricted vision field of the
phoroptor may give an INHERENTLY INACCURATE prescription
with older eyes than the less-restricted visual field of a lens frame.
(This is similar to "pin hole vision" in which
an image becomes clearer when viewed through a screen or a viewer with
multiple pin holes. While the disclaimer on "pin hole
glasses" may question their validity, the concept as applied to the
phoroptor may be valid even if the glasses are not.) The "standard" Snellen vision test requires the
interpretation of barely legible letters at a simulated 20 foot
distance. The Snellen test also inadvertently encourages
over-refraction since the benchmark for correct refraction is 60% letter
recognition (i.e. clearly identify 3 of 5 letters). In a highly
assertive literate society, that 60% score may subconsciously be viewed as
"failing the test" whereas a 100% "passing" score
inadvertently causes excess-refraction. Such excess-refraction from using a phoroptor may be as much as
1 diopter in each eye. Unless the patient is aware that their
progressive glasses are too strong, that effect on their ability to read will
lead to a loss of reading
comprehension or an assumption of increased
stupidity. Our "high tech" culture, and the unintentional
misdiagnosis by Optometrists and Ophthalmologists, creates a "technical
disability" for older people with presbyopia similar to starvation from
an inability to chew that killed many Native Americans by age 45. While a loss of comprehension and mental function likely
is associated with old age, the question that needs to be re-evaluated is
"How much of dementia is caused by "old age" versus how much of
it is caused by habituation to misprescribed and misdiagnosed glasses? Your feedback would greatly be appreciated. |
