As I understand it an over minused prescription will induce an accommodative reflex. So that having glasses with too much minus is more than having a pair that is less than optimized for best possible acuity, it induces a physiological and unwanted response. Is there a similar or any other reflex induced by an over plused prescription?
Last edited by AngryFish; 09-27-2007 at 11:51 PM. Reason: typo
Don't know about spectacle response but I have found that a high percentage of hyperopes need more plus in rigid contact lenses after a week or so of wear. I have always attributed this to the hyperope relaxing some accomodation that he has been doing for perhaps life prior to CL fitting.
Young Myopes in same situation don't seem to have any ill effects to some over correction (despite theories about same increasing myopia) even if over corrected quite a bit. Presbyoptic Myopes are another story entirely, they will have difficulty reading.
I have also notice of late a lot of myopes over 40 needing a decrease in myopic correction, some of which I would have put in a bifocal CL that didn't seem to need this (yet) if the overcorrection was taken care of.
Chip
If a person has an intermittent exotropia (eye wondering out), giving him his full plus correction will relax his accommodative convergence and will give him a constant eye deviation. Otherwise, over plused Rx will make you blurry.
no, just blurryOriginally Posted by AngryFish
But back to the initial statement. It is not necessarily an "unwanted responsed". It may have been requested by the patient or the Dr. An over minused Rx is better than an overplussed rx for a pre-presbyope. Because they have accomadative reserve, they can accomadate and get the best possible accuity. Some drs I know constantly over-minus to get the patient to see BETTER than 20/20. How so, you ask? Because your accodative ability can make you vision clearer than a lens can.
My own example:
My first distance Rx was +1.00 sph. Result: 20/15 vision.
My actual cyclo-exam showed I needed a +2.00 sph. Result: 20/20 vision and an unhappy pt. So, the Dr over-minused me by 1.00D. Amazing you say? Happens every day.
Over-plussed or overminus is often a matter of patient preference.
On the other side of the spectrum, I have noticed many of our Asian patients can't stand a full correction. They don't like 20/20 vision. They like to be overplussed (or in their case, underminussed).
So you know that it is not from the flattening of the cornea due to the RGP itself?
Yes, you will also see that response in spectacle wearers if they are "latent hyperopes". They are unable to relax their accomadative capacity until after a period of time. Refer to my own experience above. It took me a few months of wear and I was ready for a +0.25D increase. 1 week after that remake, I was ready for another quarter. Next time it took about 2 days. Finally I decided that I didn't like accomadating +2.00D to see down the street. Had a headache all my childhood and didn't know it. Was labeled ADD; wonder why? Would you like to read?
"...My own example:
My first distance Rx was +1.00 sph. Result: 20/15 vision.
My actual cyclo-exam showed I needed a +2.00 sph. Result: 20/20 vision and an unhappy pt. So, the Dr over-minused me by 1.00D. "
This would not be considered an "over-minusing". He just did not correct your full plus. If you can accommodate 1D easily, there's no reason to correct your full hyperopia.
Just a tangential point I'll throw in, inspired by the very good last post:
Hyperopia is not like myopia. They seem like they'd be two variations of the same thing, but they really are distinct.
Thus, it's correct: "Overminusing" is in regards to myopia. "Overminusing" is completely unrelated to hyperopia.
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