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Is there a term for extra-far farsightedness?
Hyperopia is usually described (broadly or vaguely, I'm not sure) as inability to focus up close combined with "usually" being able to focus well at infinity except in extreme cases. To me this seems synonymous with (usually) good eye chart performance and poor accommodation. Or does "usually" focusing well at infinity actually mean focusing barely acceptably, erring on the far side? Is there an unambiguous term for inability to focus well at any distance with no exceptions, always requiring a +diopter correction at infinity?
Al: Thanks for a fine answer with excellent references.
If the opticians, optometrists and oculists are partying, they're not talking with each other much. Among your references, the 3rd one says hyperopia "in extreme cases" prevents focusing at distance, and the 2nd one says (unconditionally), "The hyperopic person cannot see clearly up close or at distance."
Actually both are sort of right, but only the 1st ref. makes it clear why. Hyperopia is a condition of the focusing power of the cornea plus lens and/or the eyeball size/shape (and the dependent parameter, the distance from the front of the eye to the retina). The <relaxed> eye focuses the image behind the retina, always. Whether or not the hyperopic person ("hyperope") sees clearly at distance thus depends on that person's accommodation and the severity of the hyperopia. (more)
With or without good distance vision, accommodating, or trying to accommodate, for most of one's waking hours tends to accumulate effects of strain including head and/or eye ache and vision quirks. So doubtless some hyperopes will relax the eye and accept poorer vision to avoid these effects. Since accommodation power tends to decrease with age, it's generally more difficult for older people to deal with hyperopia without correction.
Problems with accommodation only (not eye geometry-related) are called presbyopia.
I'm going to extend the question a few more days just in case someone comes up with the word for hyperopia that can't be corrected by one's accommodation. But now that you've helped me clear up the concepts I'm not expecting it.
2 Answers
- Al PLv 71 decade agoFavorite Answer
You're probably well up to speed on this
so I'll drop the boilerplate, By the way,
converting light into well focused energy via
the brain is a very complicated physical process
as you know involving accommodation, spherical and
chromatic aberration, genetic, and a host of other
factors.
I can't find the unambiguous term you seek.
According to one reference below and I quote:
"The hyperopic person cannot see clearly up
close or at distance."
If the eye brain system cannot accommodate infinity the
object will still focus in back of the retina thus
requiring possibility different +dioper convex lenses for
each eye. Barring "automatic" eyeglasses separate +dioper
glasses are needed for corrected near vision and compromised
far vision. For example, wearing an inexpensive pair of +1.25 reading
glasses may represent a good compromise for medium vision. I'm
okay so far, but according to reference, most of us are likely to
develop varying degrees of hyperopia in time.
Is everyone in medicine having a tea and crumpet convention?
Edit:
kirch, I think the expression you looking for is:
absolute hyperopia: accommodation cannot correct
the problem. Further reading suggests that the
probability of the curvature of the cornea and lens
matching the length of the eyeball to acceptable degree
is low. Hence, the eye/brain system is in a constant battle
to keep objects in focus. Since hyperopia is usually present
at birth and exists in varying degrees throughout life it's now
easy to intuitively understand the tremendous amount of work the
eye-brain system must do. Headaches, eyestrain, depression, and
a host of unknown maladies may result if one doesn't understand
their specific ability to focus, accommodation. Very interesting
question.
Source(s): http://www.mcnelisfamilyeyecare.net/specialty1.htm http://www.corneatexas.com/html/eye_info_refractiv... http://en.wikipedia.org/wiki/Hyperopia http://www.ebiomedia.com/Eyes/The-Living-Camera-Ho... http://sifter.org/~simon/journal/20030521.h.html - Anonymous6 years ago
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