monovision for farsighted

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monovision for farsighted

Postby ngdiva » Tue May 06, 2008 6:38 am

I have been told by a lasik eye surgeon that monvision surgery does not work well for farsightedness. does anyone know the complication or the success rate
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Re: monovision for farsighted

Postby beingbobbyorr » Wed May 07, 2008 9:19 am

ngdiva wrote:I have been told by a lasik eye surgeon that monvision surgery does not work well for farsightedness. does anyone know the complication or the success rate

a) I've also heard that monovision is not indicated for high myopes .... but I don't know where the lines are drawn (-__ diopters to distinguish high vs. medium myopia and -__ diopters to distinguish medium vs. low myopia). I'm -7.5 & -9.0 contact lens scripts and I tried monovision with contact lenses. I could see how it 'worked', but it isn't something I'd want to do permanently, and I would assume I'm a high myope.

b) I'd be hard pressed to know how "success rate" would be measured for grossly subjective things like this ..... I guess polling patients for their binary decision: satisfied? vs. dissatisfied? .... but who has conducted such surveys across the industry? Do individual doctors even conduct such surveys among their own monovision patients? Doubt it.

The best thing to do is try it with contact lenses for at least a week.
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Postby LasikExpert » Wed May 07, 2008 6:19 pm

Monovision most certainly is successful for people who are hyperopic (farsighted, longsighted), but not everyone who is hyperopic.

Whether or not you would tolorate the monovision effects is rather easy to establish. Just try monovision correction in contact lenses for a few weeks and see how you like it. It may be, however, that to correct your hyperopia and induce enough myopia to create monovision would be too great a challenge.

Monovision requires that the nondominant eye first have all hyperopia resolved and then to be "overcorrected" into myopia (nearsighted, shortsighted) vision by about 1.50 to 2.00 diopters. If a person is 3.00 diopters hyperopic, a total of 5.00 diopters (3.00 of hyperopia plus 2.00 induced myopia) would be necessary.

Hyperopic Lasik is much more challenging than myopic Lasik with a somewhat less predictable outcome. 3.00 diopters of hyperopia is considered rather severe. Making 5.00 diopters of correction is considered by many to be pushing hyperopic Lasik to its limits.
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Postby excimer_guy » Sun Jun 22, 2008 12:08 am

The limit with hyperopia is just how steep you should make the cornea. A normal cornea has a power of 43D. When you correct hyperopia you increase the cornea's curvature. About 1D steeper for a correction of 1D, e.g. if you start out with 43 and +3D of hyperopia you would end up with a corneal steepnees of 46D. To get monovision you need an additional +2D to make that eye myopic. In total, you'd end up with a corneal steepness of 48D. That'd still be acceptable.
However, if you start out from a cornea that's a little steeper to begin with -but still within normal limits- like 45D you'd run into trouble since you'd want to keep corneal steepness below 50D.
Going above 50D, you might encounter problems with the increased chance for dry eye. Furthermore, optical quality will decline because you'll create what is called a hyperprolate cornea.
Therefore, monovision for hyperopia is a bit trickier. But depending on your prescription, it can work.
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