can you accomodate one eye only?

hi i have a cousin he is farsighted in one eye only. his other eye is
plano. his doc says he can accomodate to see clearly far away. he was
given contact lens in one eye only. now if his farsighted eye can
accomodate to see clearly then why would he need contact in that eye?
can't his good eye stay normal and his farsighted eye accomodate at
the same time? TIA

dam

 

Hey Same,

It is simple, when your cousin accomodate,both eyes are getting the plus
addition in the same amount ( in normal circumstances)
The error in the far sighted eye can be corrected that way but in the same
time you are getting a too much plus correction in the emmetropic eye (the
plano one).
In other words, when not accomodating the emmetropic eye sees sharp in the
distance and the hyperopic (far sighted) blurred.
When accomodating in the right amount, the hypermetropic sees sharp and the
emmetropic eye (with the plus addition) sees blurred at distance.
Further more, it is a good thing to see sharp at distance without having to
accomodate and to have a simultaniously good and sharp vision with both eyes
at the same time.
The doc is right!
All this is said for normal conditions BTW.

Jan (normally Dutch spoken)

 

it is extremely difficult for the eyes to accommodate differentially. That
is, the human body isn't "wired" very well for 1 eye to accommodate a lot
while the other doesn't. It's a good idea to wear a contact in the
farsighted eye as your cousins doctor suggested.

 

I know people that are doing research on wearable computers. With this, they
use a tiny screen just in front of one eye. They claiim they can accomodate
with their left eye for screen viewing and their other eye in the distance
at the same time. They claim that the images blend together. This way they
get 1 image of the one eye with the image of the screen blended in. I don't
know if it's true but these guys are people that are very known in the
academic world.

kind regards

Chris

 

Dear Dam,

Can your cousin read the eye-chart at 20/20?

If so, it is difficult to understand why a plus (or minus)
would be used.

Also HOW "farsighted" is he. +1/2? +1.0? +5?

It makes a difference.

Best

Otis
Engineer

 

That tiny screen is too close for most people to accommodate for it, so it

These guys wear glasses. I think it are plus lenses

 

His precription for left eye is +1.75, but his doctor said his true
precription is about +3.50. he wants to correct halfway due to the
spasm and then correct more at the next visit after my cousin got used
to the current prescription. he sees about 20/40 in the left eye, but
if he strains really hard he can see few letters in the 20/20 line.

sam

 

It's easy for me to understand. However, being that I was very
near-sighted most of my life, my understanding my not be correct.


It isn't perfectly clear from what was posted originally (see above), but
if the cousin can accommodate to see clearly at distance, that implies
that he *can't* accommodate to see clearly up close. The contact will
allow him to focus both far and near with both eyes, thus helping his
depth perception.

 

Dear Jan,

In fact I do suspect the real reason.

There a pilots with focal status of +0.5 diopters each
eye. Because of age (50 years), they can not
read "up close.

What is done in that case is to put a mild plus 1 or 2 diopter
contact on one eye. Because the mind can
"merge" the two images, this step allows
clear distant and near vision.

I was curious if THAT were the reason for
the use of a plus (or minus) contact lens.

Best,

Otis

 

I only suggest what some ODs and MDs do for pilots
who have focal states of zero (emmetropic by your description),
and have a range of accommodation from zero to -1.0 diopters.

For that reason, images closer than 1 meter will be blurred,
depending on depth-of-field, and therefore illumination level.

Provide the pilot understands the goal, it is possible
to put a +1.0 diopter lens on one eye, and allow him
to see at -2.0 diopters (or 20 inches).

This works, and depends on the pilots choice.

Since the word "emmetropia" has rubber-bands on it, I simply
do not use the word. Just say 20/20 and a focal state
from zero to some positive value.

I hope the above description is clear about how
a "plano" pilot with presbyopia, and use the
"fusion" capability of the eye to restore
some of his near vision.

Focal status is a simpler and clearer term.

You check this by reading the eye-chart at 20/20 (3/8) inch
letters. This will confirm 20/20 for you.

The next step is to apply +1/4 diopter lenses in increments
until you find a lens that "just blurrs" the 20/20 line.

Depends on what your mean by "too much". For natural I would
refere to the required visual standards at the U. S. Naval
academy. They required.

1. 20/20 vision -- both eyes

2. Focal status of no greater than +1.5 dipoters.

The standard term you use would describe these
eyes as having "refractive errors". I believe
this is not correct in misleads anyone.

Would you describe them as "normal" or emmetropic
or hyperopic. Where do YOU draw the line?

Sinc we do not have any details it is not possible to
make a real judgment. If he had said the focas
status is +0.5 diopters then we would have known
with precision.

I have heard that term also. But since the person sees with
both eyes, and the brain selects the sharper image, then
the question is -- does it really matter?

We still do not know what the "real reason" was, since
we do not know the man's focal status. If he
were "hyperopic" at +1/4 diopters, (or do you
call that "emmetropic") then the amount of
"refractive error" would make a difference.

Best,

Otis