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Web site created by Berney Design |
| Refractive imbalance and monovision |
| Refractive imbalance occurs when there is a difference in the quantity and quality of vision between each of the two eyes. Monovision is an intended refractive imbalance, usually when one eye is corrected for distance vision and the other eye is corrected for close vision. This refractive imbalance is usually no more than 1 or 2 D (diopters, or levels of refractive power). Those under 40 don't typically have a problem with close vision, so they usually have both eyes corrected for distance. Those over 40, however, start to lose their ability to focus when looking at things very close to them, such as a book or computer monitor. If someone in this group chooses glasses, they can get one pair of glasses for distance vision and another pair for close vision, or, more commonly, just get a single pair of bifocal glasses. This group can also get contact lenses, correcting one eye for distance vision and the other for close vision (or even some of the newer bifocal contact lenses). Refractive surgery options for monovision almost always correct one eye for distance vision and the other eye for close vision. Some people tolerate the refractive imbalance from monovision quite well. Others find it extremely frustrating because this imbalance can contribute to mobility issues (the brain uses the information from both eyes to judge distances). The fixes for refractive imbalance are dependent upon the cause and amount of the imbalance. Annoying refractive imbalance after monovision refractive surgery can sometimes be corrected with glasses. This imbalance can also usually be corrected with contact lenses (in one or both eyes, as necessary), as well as with additional refractive surgery (usually to correct both eyes for vision). Additional surgery usually comes with a risk level similar to the original surgery. Why don't glasses always correct refractive imbalance? Because when there is a refractive imbalance between the eyes and one wears glasses, one eye has its light refracted on the cornea and other has its light refracted on the lens of the glasses. This means that the size of the image will be slightly different in each eye. Some people can adapt to this, but others cannot and find it extremely frustrating. The problem is generally worse the greater the amount of refractive imbalance. Someone who started off as very nearsighted (for example) who has refractive surgery on one eye but not the other might only be able to obtain comfortable vision while wearing contact lenses. |