Most people above 40 years of age develop presbyopia, a condition characterized by blurred near vision. It occurs with age, as the crystalline lenses of the eyes gradually lose their elasticity and ability to bring close objects into clear focus. This leads to difficulty in reading and focusing on near objects. The technique of monovision requires a person to wear near vision contact lens on one eye and, if needed, distance vision contact lens on the other eye. Monovision problems occur at the initial stage when one starts wearing the two different lenses; not everyone can adapt well to monovision.
How Does Monovision Work?
All of us have a dominant eye and a non-dominant eye. While looking at distant objects, we actually use the dominant eye more than the non-dominant eye. Our brain processes the visual signals coming from the dominant eye. Therefore, if the non-dominant eye is fitted with a near-vision contact lens, our distance vision will not get affected much. If needed, a contact lens can be worn on the dominant eye to correct distance vision. Through this arrangement, the brain gradually learns to use the distance focused eye for distance vision and near focused eye for near vision. It takes about 1 to 2 weeks to adapt to this different way of wearing contact lenses, but some people may require a month or even more.
Before going in for monovision laser eye surgery, the ophthalmologist would always recommend one to first wear monovision contact lenses, to see whether or not he/she can adjust to the arrangement comfortably. If one is unable to adjust to it, surgery is best avoided. Surgery once done will be permanent and difficult to reverse.
Issues with Monovision
Problems with this technique arises because it basically hampers or compromises binocular vision. Binocular vision is the ability of both eyes to work together to achieve proper focus, depth perception, and range of vision. Through this technique, both the eyes have to perform two different functions independently. It takes time for the eyes to start working as a team again. Till that happens, the person undergoing monovision experiences some loss of depth perception and blurring of vision.
Monovision generally causes blurred near vision because only one eye is fitted with the near-vision lens. If one requires a very sharp vision to perform certain activities like reading fine print, then monovision will create a lot of difficulty in focusing. One would still have to wear reading glasses to help him/her read. Sometimes, one's distance vision would also experience lack of sharpness, because only the dominant eye is fitted with distance vision lens. One would face major discomfort while driving, especially at night, and the glare from headlights would only add to the problem.
One may also have difficulty with his/her intermediate vision. When focusing on distances further than 16 inches but closer than 15 feet, for instance, while viewing a computer screen, he/she would experience blurring. Some people (about 10-15 %) do not adapt well to monovision. They may experience a feeling of being somewhat "off balanced" or will develop eye-strain and frequent headaches.
In spite of all of these problems, lots of people affected by presbyopia are known to give it a try. This is because monovision requires the use of single vision contact lenses, which are less expensive than bifocal and multifocal lenses. A new technique of monovision, known as modified monovision makes use of multifocal rather than single vision near lens and it is believed to be more effective. However, monovision doesn't always produce the desired results and cannot guarantee complete freedom from glasses. It may or may not work for one. Monovision problems are significant and one should discuss them with an eye doctor, before opting for this treatment option.
Disclaimer: This HealthHearty article is for informative purposes only, and should not be used as a replacement for expert medical advice.