Around the age of 40, people begin to find it hard to focus on near objects. Blurring occurs during near point activities, such as reading. This unavoidable condition is known as presbyopia and affects everyone at some point. As difficult as it may be to face the fact that your eyes are aging, even more difficult may be choosing the best lens for correction.
Reading glasses and mutifocal lenses are used for correcting presbyopia. Multifocal lenses include bifocals, trifocals and progressive eyeglass lenses. Various configurations of multifocal lenses are available, depending on your prescription.
Reading glasses are single-vision lenses that are worn for near tasks only.
- Availability: Reading glasses may be prescribed by your eye doctor or bought over-the-counter.
- Simplicity: Reading glasses may be put on or off depending on your task.
- Distance viewing: Because reading glasses bring only near items into focus, looking through them at a distance will usually cause blurred vision. Many people who have blurred vision at near but see well at a distance simply look over the top of the glasses when viewing something at a distance.
Bifocal lenses provide two ranges of vision correction: distance and near. Benjamin Franklin deserves credit for inventing bifocals when he decided to glue two lenses together so that he would not have to change from one pair of glasses to another while working.
- Simplicity: Bifocals allow the wearer to look near and far without removing their glasses.
- Dividing line: Bifocal lenses usually have a noticeable line or segment dividing the upper distance zone from the lower near zone.
- Candidates: Bifocal lenses can be worn by people with myopia, hyperopia or presbyopia.
As the name implies, trifocal lenses have three distinct ranges of corection: distance, intermediate and near.
- Dividing line: Trifocal lenses have a noticeable line or segment diving each zone.
- Candidates: Trifocals are usually prescribed for people in their 50's.
- Computer users: Trifocal lenses are being prescribed more recently because of widespread computer use.
- Occupational trifocals: Trifocal lenses also come in the form of occupational lenses. These are customized according specific tasks or jobs.
Progressive lenses are often referred to as "invisible" bifocals or trifocals because there is no visible dividing line. Progressives give a smooth range of vision from distance to near.
- Invisible dividing line: Progressive lenses hide the fact that you need reading glasses.
- Adaptability: It takes about a week to adapt to wearing progressive lenses.
- Constant graduation: The constant graduation of the prescription allows you to look up to see in the distance, look ahead to view things in the intermediate zone, and look down to do close up activities, such as reading.