Micro Monovision and Refractive Path
All intraocular lenses placed during cataract surgery provide a relatively narrow range of acceptable focus. This range is called depth of field or depth of focus.
One presbyopia correcting strategy is to choose a slightly different focal distance for each eye using standard monofocal lenses (micro monovision). Micro monovision will not completely free you from glasses for all tasks, but can provide significant glasses freedom at the range that is most important to you.
Next, you have to decide where you want your primary focus to be. Cataract surgeons may just assume that you want to focus your eyes at distance and use reading glasses for near. However, consider personalizing this.
Three basic refractive paths can be considered: Distance, Middle, and Near. Each has unique advantages and disadvantages. Which refractive path you choose depends on your goals. The bottom line: you can have a lot, but you can't have it all. You have to choose according to your priorities.
Near Refractive Path
Your eyes are focused like a camera at near.
Advantages: Good vision without glasses for reading or crafts such as knitting and artwork.
Disadvantages: You will need glasses for driving, watching TV and movies, and you may feel like your surroundings in a room are blurry if you don’t wear glasses.
The upside of excellent reading vision is balanced by the downside of relatively blurred vision when looking around a room. It is likely that you will need glasses to watch TV and drive.
Middle Refractive Path
Your eyes are focused about 1.0 to 1.5 meters (3 or 4 feet) away.
Advantages: Good all around vision. Marginal glasses free reading ability without glasses. Many tasks at distance and near can be performed without glasses, but the most demanding tasks, such as driving at night and reading a book, will probably require glasses. This is a popular choice for people who want to be glasses free for general tasks such as working around the house, shopping, texting, and talking to people.
Disadvantages: Although you may spend most of your day without glasses, you may need glasses for reading and driving.
Distance Refractive Path
Your eyes are focused like a camera at distance.
Advantages: Good vision without glasses for driving, hiking, skiing, watching movies.
Disadvantages: You will need reading glasses for most close-up tasks, including computer work and reading a book.
Mini monovision and full monovision can also be considered. Larger amounts of monovision have the advantage of allowing you to perform more tasks without glasses, and the disadvantage of reducing stereopsis (3D vision). If you have used monovision contact lenses in the past, you may like this option.
With micro monovision, the two eyes continue to cooperate with one another, but your brain naturally pays a little more attention to one eye depending on the situation at hand. You may not even be aware of which eye is giving you the best focus at any given moment. Depth of field is enhanced while retaining cooperation between the eyes.
The tasks that are important to you will help you determine whether you want to apply micro monovision to the Distance, Middle, or Near path. The refractive questionnaire to help you decide what might be best for you.