Presbyopia Correcting Lenses and Side Effects
The two major classes of presbyopia correcting lenses that are used in the United States are the Multifocal (MF) and Extended Depth of Focus (EDOF) lenses.
Standard intraocular lenses that do not correct presbyopia have a single focal point. This is the distance at which the best focus occurs, like a camera focusing on a single object. For a little way inside and outside of that point, acceptable but not perfect focus occurs. This is the depth of field of the lens. Even standard lenses have some depth of field. At some point, however, focus becomes unacceptable.
Multifocal presbyopia correcting lenses focus some light at near, and some at distance. Most manufacturers provide three different strengths of near vision add. The higher the power, the closer the near focus, but also the greater the side effects such as glare, halos, and loss of contrast sensitivity.
The lower power multifocals have less noticeable side effects compared with their higher-powered cousins. However the near focus of these lenses is not very close in. This is why they perform better in people with longer arms.
The Symfony extended depth of focus lens lens acts like a low powered multifocal lens. The side effects of this lens are low, and patient satisfaction is high. This lens also comes in several toric powers, allowing patients with moderate amounts of astigmatism to take advantage of presbyopia correction.
Some doctors may recommend mixing the lenses; for example, Symfony EDOF lens in the dominant eye, and Tennis MF lens in the non dominant eye. Feel free to bring this option up to your doctor.
There is an art to choosing the correct lens or lens combination. Your doctor may have found a particular method that works best in their hands.
Side Effects of Presbyopia Correcting Lenses
There is a tradeoff between depth of focus/multifocality on one hand, and glare, halos, and loss of contrast on the other.
The multifocal lenses come in different powers, with low, medum, and high powered reading adds. The higher number options provide a stronger near add, and result in greater side effects. This is a key principle in presbyopia correction- stronger reading corrections cause increased side effects.
The Symfony extended depth of focus lens provides a similar near effect to the low powered multifocal lenses.
The presbyopia correcting lenses are meant to provide near vision for practical and basic tasks including texting and reading menus, but are often not optimal for prolonged reading. Many people who have presbyopia correcting lenses will still choose to use reading glasses occasionally for detail work.
With MF/EDOF lenses, there is almost always some small amount of glare or halos under certain conditions. How happy you are with presbyopia correcting lenses may depend on your personality, health of your eye, and goals. Read more how these issues may influence your choices here.
Consider also the alternative of monovision and custom refractive design.