Presbyopia is the term for the diminishing ability to focus on up-close objects with age. While the ability to focus on near objects grows progressively worse beginning at birth, it is often first noticed at age 40 when the near focus is approximately 40 cm. Since this is a standard reading distance, it is this age that people most often feel that they are losing there near vision. In fact, the ability to focus has grown progressively worse since childhood.
Consider this. A ten year old can focus clearly on a book located 7 cm from his face while a twenty-five year old must now hold the book 10 cm from his face. The loss of 3 cm of focus may be hardly noticeable but is equivalent to a loss of four diopters of focusing ability. As the person ages another fifteen years and loses another four diopters of accommodation, they can now focus at a distance of 16 cm for short periods of time and comfortably for long periods of time at about 33 cm. The forty year old will begin to notice that near vision is not as easy as it once was.
What options are there in correcting near vision? Are there surgeries now that can correct the loss of accommodation (focusing ability)? Are there exercises that can keep the ability to focus up close from deteriorating gradually with age? With more and more Americans in the 40-49 age range, the ability to see up close without glasses is becoming an increasingly important priority and there is significant research going into this market.
Most people believe that once a person reaches 40 years of age or slightly older they are doomed to where glasses for reading. While that was true in the past, there are in fact many people much older than 40 that never where reading glasses and are able to see comfortably up close. How do they do this? There are three main methods of near vision: monovision, multifocal vision, accommodation. Each of the various methods has multiple modalities of achieving near vision.
Monovision refers to using one eye to see near objects and the other eye to see distance. Monovision occurs naturally in some people. Others use vision correction to adjust their eyes to a state of monovision. Studies show that monovision is relatively effective and perhaps 90% of people can adapt to having their eyes focused at different distances. Monovision can be accomplished with contact lenses or through surgical methods such as LASIK, PRK, and cataract surgery.
Multifocal vision refers to mechanisms that allow for each eye to be focused at multiple distances. While vision at each distance decreases slightly, overall the vision tends to be good and many people feel that they have great success through this approach. Contact lenses and multifocal intraocular lenses (IOL) can achieve multifocal vision. Restor and Rezoom are the two FDA approved multifocal lenses that are being used in the United States.
Accommodating Lenses are perhaps the ideal solution. While contact lenses are not currently able to focus on their own, there are translating (or shifting) contact lenses that can provide some pseudo-accommodation. Typically these contact lenses are considered to be multifocal lenses as they have various zones of different focal lengths. Crystalens is the only USFDA approved intraocular lens (IOL) that has shown an ability to provide near vision through a change in focal distance. It is believed that the Crystalens achieves near vision by movement of the lens. This movement is believed to be caused by the shifting vitreous fluid that occurs when the ciliary muscle contracts. There are several other lenses that are being considered that might provide significantly greater focusing ability.
There are some clinicians and eye doctors that recommend eye exercises in order to strengthen accommodation. Thus far, there is mixed opinions on the efficacy of this type of treatment. I would advocate caution before accepting a treatment that promises improved near vision through eye exercises.
While it is unlikely that any new momentous breakthroughs in restoring near vision will occur within the next 5 years, there are currently many effective methods and most people who are motivated to avoid reading glasses can find a method of correction which is suitable to them.