A recap of what we have learned so far:
As we discussed in the last blog post, presbyopia is a universally-occurring, age-related problem that occurs due to changes in the thickness and flexibility of the natural lens inside the eye.The result is a progressive difficulty with near vision – especially seeing details such as small print – that begins to affect individuals 40 to 50 years of age or older.
If presbyopia is so common, what is the solution?
My goal in the next few posts is to describe some of the ways we can treat or cope with presbyopia – what can be done to restore functional near and reading vision?
We’ll start today by discussing glasses and contact lenses that can provide help for presbyopia.
Over the counter (non-prescription) reading glasses are one of the simplest and cheapest ways to overcome presbyopia. Reading glasses are pairs of spherical (no correction of astigmatism) plus (magnifying) lenses in powers from +1.00 up to +3.00 and higher. These glasses can be found at almost any drug store, pharmacy, or convenience store and can be chosen easily without professional assistance. Simply hold a book or magazine with small print at a comfortable reading distance and try on the different numbered pairs – think of this process as similar to fitting yourself for a new pair of shoes. When you find a pair that allows you to see clearly and read at a comfortable distance, the number of the lens is correct. You should continue reading for 5 to 10 minutes to make sure they feel right before you buy them.
Here are a few things to remember about reading glasses:
- Readers are designed to help with near (less than an arm’s length) vision only – for most people, the distance vision will not be clear while wearing them.
- Reading glasses do not correct astigmatism. If you are someone who has a high amount of astigmatism (irregular shape of the eye that requires prescription correction) reading glasses may not provide a clear image for you. To correct this problem, you will need to see your eye doctor for prescription reading glasses or bifocals that can help you see clearly.
- If you have other eye problems – meaning some other condition besides presbyopia – that is affecting your vision, reading glasses may not be able to help you. If you have tried using reading glasses, but are still unable to read or see clearly up close, you should see your eye doctor for a complete eye exam.
Bifocals are simply a pair of prescription glasses with distance correction in the top half and near correction in the bottom half of the lenses. You can think of these as prescription glasses with a pair of reading glasses “built-in” to the bottom. As the wearer looks straight ahead, he or she sees through the distance prescription at the top of the lenses. When the wearer looks down, for example when reading or looking at something held in his or her hands, the line of sight passes through the bottom of the lens which has the near prescription.
In the past, bifocals were made with a line separating the upper (distance) prescription from the lower (near) prescription. Some glasses, called trifocals, were even made with three different levels of prescription – distance, intermediate, and near – separated by lines. Though some people still prefer the older style line bifocals, newer technology has allowed us to now make glasses that have a gradual change from the distance prescription at the top of the lens, to the intermediate and near prescription at the bottom of the lens. These are so-called “no-line” or progressive bifocals.
Although for new wearers, both progressive and line bifocals take some getting used-to, many people appreciate the convenience of having only one pair of glasses for seeing clearly at all distances, rather than separate pairs of glasses for near and distance vision.
Another way of overcoming presbyopia is by a special method of prescribing contact lenses, called monovision. The name “monovision” can be a bit confusing, but basically means one contact lens that helps the wearer see well at distance and a different contact lens in the other eye that helps the wearer see near objects. As you can imagine, it takes some time for monovision lens-wearers to get used to this arrangement. It is important that the lenses are chosen carefully by an experienced prescriber and that the dominant eye (it’s true, everyone actually has a dominant eye, similar to being right-handed or left-handed) is corrected for distance, while the non-dominant eye is corrected for near vision. Not everyone who tries monovision is able to adjust to it, but those who do can enjoy clear vision at both distance and near without the need for reading glasses.
Multifocal Contact Lenses
The last method we will discuss today involves prescribing a special kind of contact lens. Multifocal contacts have concentric rings with different focusing power built into each lens. Analogous to the way that bifocal glasses have different powers built into a single lens, these special contacts allow wearers to see both distance and near with each eye. One of the major difficulties with multifocal contacts is getting just the right fit and centration on the surface of the eye. As any soft contact wearer can tell you, contact lenses do not sit still on the eye but move slightly with every eye movement and blink.
One problem that is frequently encountered with multifocals, therefore, occurs when there is too much movement of the lens (and the concentric rings) relative to the eye, causing the vision to come in and out of focus. For these reasons, properly fitting multifocal contacts can be a challenge even for experienced doctors. As the technology of making and fitting multifocal contacts improves, these lenses may become a better and better option for presbyopic individuals who want to avoid wearing reading glasses.
Today we have covered several methods of coping with presbyopia by wearing corrective lenses – either glasses or contacts. In my next blog post – the third and final edition on presbyopia – I will describe some methods of treating presbyopia directly with surgery and the options for treating presbyopia in patients who are planning to have cataract surgery. While the methods described above are practical ways of coping with presbyopia, surgical management can be a permanent way of eliminating presbyopia or minimizing its effects. There fore, the methods we will discuss in the next post are typically thought of as lifestyle options for those who do not want have to wear reading glasses or contact lenses.
As always, if you have questions or comments, you can post them in response to this blog. If you wish, you may also contact me, Dr. Geoffrey Hill, directly at firstname.lastname@example.org