Monovision Lasik
Technique to reduce the need for reading glasses or bifocals with contacts, Lasik, and Lasik alternatives.
| Reading glasses become necessary in middle age. Although there is no "cure" for the underlying cause, monovision may be an appropriate workaround. |
Monovision is a technique to reduce the need for reading glasses or bifocals by working around presbyopia. Monovision can be accomplished with Lasik or contact lenses.
The need for near vision lenses is almost universal for people as they enter their middle years. As we mature, the natural crystalline lenses in our eyes become firm, enlarged, and will lose flexibility. This naturally occurring event will decrease the ability of the crystalline lens to vary its shape for different ranges of focus. This condition is known as presbyopia and is most often first detected in people between 40 and 50 years of age. A sure sign of presbyopia is when you cannot read without holding the item far away from you. For many, distance vision remains relatively unaffected by presbyopia.
Near Sight
When presbyopia occurs, most people do well with reading glasses, bifocals, or trifocal lenses. Reading glasses, bifocals, and trifocals are plus-powered lenses that would normally be used for someone who has hyperopia (farsighted, longsighted), however a plus-powered lens helps someone who is presbyopic because these lenses provide a small amount of myopic (nearsighted, shortsighted) vision.
There are two ways to describe myopia. One is that you cannot see things far away very well. The other is that you can see things close very well. People with a small amount of myopia can simply remove their glasses to read. However, people with previously normal vision, those already hyperopic, or those who wear contact lenses with full distance correction may need to use reading glasses for close work.
Even if not currently having problems with presbyopia, if contemplating refractive surgery and near age 40, after correction with refractive surgery a person may be hit with the immediate need for reading glasses due to a phenomenon we call "Sudden Presbyopia".
Bifocals and trifocals are used to provide both near and far vision without having to constantly put on and take off a pair of glasses or switch between two pairs of glasses.
Cannot Be Nearsighted and Farsighted
Because reading glasses provide a plus power that would normally be used to correct hyperopia, many people incorrectly believe they are becoming hyperopic. Those previously myopic may believe they are both hyperopic and myopic, which are mutually exclusive. Whenever changes in vision occur, it is always best to be evaluated by a competent eye care physician to determine the problem exactly.
Anyone who has needed to use readers, as they are often called, knows just how frustrating and irritating presbyopia can be. Many people have had excellent near and distant vision without glasses all their lives, until those dreaded readers become necessary because of presbyopia.
No Cure But A Reliable Workaround
There are currently no reliable and predictable surgery techniques or medications that will outright cure presbyopia, however there are a number of permanent and semi-permanent techniques to deal with the focusing changes and challenges caused by presbyopia. One of the more popular ways to work around presbyopia is with monovision correction. For many, monovision will reduce or eliminate the need for readers, bifocals, or trifocals. The concept of monovision is very simple. One eye is corrected for near vision and the other eye is corrected for distance vision. The brain figures out which eye to use and when. How to achieve monovision varies, depending upon the patient's current eyesight.
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If a person has never needed corrective lenses like glasses or contacts before, then a small amount of myopia can be induced in that person's non-dominant eye. The dominant eye remains uncorrected, as it already provides full distance vision. Download the USAEyes Dominant Eye Test and check which eye is dominant now.
If a person already has less than two diopters of myopia, that person's dominant eye can be fully corrected for distance vision, and the non-dominant eye not changed, which already provides good near vision.
People with greater amounts of myopia may have the dominant eye fully corrected to provide good distance vision, and the non-dominant eye undercorrected to less than two diopters myopic for good near vision. A patient who is already hyperopic may have the non-dominant eye overcorrected into myopia, plus the dominant eye either corrected for distance vision or untouched.
Contacts or Surgery
Monovision can be achieved through contact lenses or through refractive surgery. NearVision CK has been specifically approved by the FDA for monovision correction and is most ideal for patients who are mildly hyperopic or are plano and have never needed glasses. NearVision CK uses radio waves to change the shape of the cornea and create a small amount of myopia in the non-dominant eye. This myopia provides near vision, while the other uncorrected eye provides distance vision. NearVision CK is considered temporary because the effect does diminish with time, however the regression of the NearVision CK effect is very slow and can last for years.
Although not specifically approved by the FDA for monovision, the use of Lasik, LASEK, PRK, and Epi-Lasik are also appropriate techniques to create monovision as an off label use of the excimer laser.
The chief advantage of monovision is the freedom it can provide from reading glasses. After six to eight weeks the brain makes the vision changes automatically, without any conscious effort or awareness. Monovision makes it possible to repeatedly change the range of focus, without having to constantly remove or add corrective lenses.
Monovision Drawbacks
As with many good things, monovision comes with some disadvantages. People with monovision may have some degree of decreased depth perception unless corrective lenses are used to fully correct the slightly myopic eye. They may also notice blurred vision in the "near" eye when glancing in the side mirror of their cars or when the vision in the "distance" eye is blocked by an object.
We highly recommend someone with monovision have a pair of glasses made that provide full distance vision correction for those situations where excellent distance vision and/or depth perception are desirable. For detail activities such as prolonged reading, have a pair of reading glasses made that provide balanced near vision. It may be possible to purchase an identical pair of readers with two different powers of correction, and switch lenses to provide the balance to full near correction with both monovision eyes.
Try In Contacts First
If monovision seems desirable, you should try to achieve the effect with contact lenses prior to surgery to determine if monovision is suitable for your individual needs and your ability to adapt. Should you initially choose surgical monovision and subsequently become unhappy with it, enhancement surgery to fully correct the undercorrected eye and reverse the monovision effect is often an option.
People who are entering mid-life and are interested in monovision should discuss the matter with their doctor prior to undergoing surgery. It is surprising how many patients adapt readily and happily to this vision option, however monovision is not for everybody and some people dislike its effect.
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