Reading vision gradually gets less with age due to presbyopia. The opportunity to treat presbyopia with intraocular lenses (IOLs) occurs when you need cataract surgery, or even if you have had cataract surgery and want better near vision.
Presbyopia is when your eyes gradually lose the ability to see things clearly up close. It is a normal part of aging. In fact, the term “presbyopia” comes from a Greek word which means “old eye.” You usually start to notice presbyopia shortly after age 40. For example, you may find that you hold reading materials farther away in order to see them clearly. This makes reading a newspaper, a restaurant menu, or trying to see your smartphone screen difficult(Figure 1).
Figure 1. Lady trying to read with presbyopia
Reading vision after cataract surgery
You get the same effect if you have had cataract surgery and your vision is set to distance using standard monofocal lenses IOLs, the most common type of lens used with cataract surgery. It has one focusing distance. It is set to focus for up close, medium range or distance vision. Most people have them set for clear distance vision. Then they must wear eyeglasses for reading or close work(Figure 2).
Figure 2. Diagram showing how the lens fails to accommodate with age to give presbyopia and requires correction for near vision.
With cataract surgery, or even after monofocal IOLs have been implanted, there are more sophisticated IOLs that have different focusing powers within the same lens that can be used. These are called multifocal and accommodative lenses. These IOLs reduce your dependence on glasses by giving you clear vision for more than one set distance(Figure 3).
Figure 3. Intraocular lens to treat presbyopia
There are ways of using monofocal IOLs to treat some of sometimes all of a patient’s presbyopia. This is with the monovision principal that uses the fact that people have a dominant (preferred) eye. With monovision, the vision in your dominant eye is corrected for distance vision, while your other eye is intentionally left a bit near-sighted to allow you to see close objects. The difference between eyes is not large enough to stop them working together, allowing you to increase your depth of vision. While this way of seeing may sound complicated, many people find they adapt well to this technique. In fact, with both eyes open, they often can’t tell which eye is set for distance and which is set for near.
However, monovision is not for everyone. Some people find they simply cannot adapt to it. This is why eye doctors usually recommend trying monovision with contact lenses first before committing to surgery for presbyopia correction or monovision IOLs as part of cataract surgery. An ophthalmologist can thoroughly evaluate your eyes and discuss your vision needs to help you find the best vision correction option for you.
Other treatments for presbyopia
Spectacles: The other solutions to visual problems caused by presbyopia include using reading, bifocal or varifocal glasses. These have stronger lenses that allow you to see more clearly at near, but you will not be able to see at distance through the near vision lens. Using magnifying glasses or readers can become annoying, as people become very dependent on their glasses and often lose them at the wrong moment.
Contact lenses: Contact lens wearers with presbyopia will often use multifocal lenses or the monovision concept to improve reading without glasses. multifocal lenses have different focusing powers within the same lens allowing you to see at distance using the distance power in the lens and at near using the near correction. If these people need cataract surgery, they tend to be particularly happy with multifocal IOLs.