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 phoropter.
While the phoropter may be faster and easier to use when quantifying vision
adjustment than using a manual lens frame, the restricted vision field of the
phoropter 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 phoropter 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 phoropter 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 mis-prescribed and misdiagnosed glasses? Your feedback would greatly be appreciated. |
