Presbyopia
Presbyopia is an eye condition occurring in people after the age of 40, which results in difficulty focussing on near tasks. Presbyopia will effect both previous eyeglass wearers as well as people who have never worn eye correction. Many people will elect to wear reading glasses to correct presbyopia, while others will prefer the use of contact lenses.
One way to correct presbyopia with contact lenses is through the use of a process called monovision. In monovision, one eye is used for distance vision, while the other is used for near vision. Patients with monovision learn to use only one eye at a time, depending upon the visual task. Most patients prefer to use their dominant eye for distance, and their nondominant eye for reading. Monovision is a practical solution for many presbyopic patients who want to reduce or eliminate the need for eyeglasses. This method does, however, cause a reduction of depth perception and a slight loss of clarity of vision. Monovision is not recommended for driving at night due to significant increase in glare and reduction of depth perception. Patients may elect to wear a special pair of driving eyeglasses over their monovision contact lenses to allow for safe night driving.
Another option for presbyopic patients is bifocal contact lenses. Most of these lenses use the concept of simultaneous vision . Simultaneous vision means that the patient looks through the distance prescription and the near prescription at the same time. Frequently, this results in a slight reduction of clarity of vision both at distance and at near. Other bifocal contact lenses are designed like bifocal eyeglasses, in that the patient looks through the upper portion for distance and the lower portion for near. Since the contact lenses must move with blinking, there are resultant fluctuations in vision associated with this type of contact lens. While most visual tasks can easily be performed with the use of bifocal contact lenses, some tasks which require higher amounts of visual precision may necessitate the use of reading glasses over the contact lenses, or may be more easily performed with conventional eyeglass correction. Bifocal contact lenses, therefore, reduce dependency on eyeglasses, but may not totally eliminate the need for eyeglasses for certain visual tasks.
Remember that presbyopic patients who already wear distance correction can continue to wear their distance contact lenses, and wear reading glasses over them. This option provides the best clarity of vision at all distances.
In summary, patients over 40 may choose monovision, bifocal contact lenses, or distance correction combined with reading glasses to provide adequate distance and near correction. Depending upon each patient's individual preferences and visual needs, any of these options may be selected as a solution to focussing problems associated with presbyopia.