Eye University: What’s the difference between progressives, bifocals, and trifocals?

With an aging population multifocal lenses like bifocals are becoming part of the norm in America. U.S. Census Bureau data says over 135 million Americans are age 40 and older were in 2008.  The median age reached 36.8 in 2008, up 1.5 years since 2000. This growing number of older citizens is generating a huge demand for eye wear, contact lenses and surgery due to Presbyopia.

Presbyopia is a condition where the lens of the eye loses its flexibility and elasticity, affecting the eye’s refractive ability.

Presbyopia is usually first noticed in difficulty reading close-up. The condition normally affects a person’s vision when they are in their late 30′s to early 40′s. Presbyopia affects everyone. Currently, there is no known prevention for this condition. The most popular treatments are multifocal lenses.

Leading vision website AllAboutVision.com says multifocal lenses  compensate for presbyopia, in rare cases “bifocals are prescribed for children and young adults who have eye teaming or focusing problems that cause eye strain when reading.” Multifocal lenses are also known as progressives, bifocals, and trifocals.

Multifocal lenses have two or more optical lens powers in one lens. A typical lens has one optical power. The most common multifocal lenses are bifocals.

“Lined bifocals have two viewing areas, one for distance viewing and the other for near,” says Rochester Optical’s Lens Specialist William Fruit. 

Each viewing area is separated by a highly visible line across the lens. Trifocals or lenses with three powers offer patients three different viewing areas for distance, intermediate and near vision. Trifocals are also separated by highly visible lines.

“A bifocal wearer’s reading distance is about 16 inches or across the room and down the hall. There is no in between,” says Fruit.

Bifocals and Trifocals cause what is known as an “image jump” when the eye abruptly crosses the boundary between near and distance viewing areas or between near, intermediate and distance viewing areas.

Progressive lenses are multifocal lenses with a twist. Progressive lenses do not have a line and have many optical lens powers. These lenses progress from a far viewing area into a near viewing area eliminating any image jump.

“No matter how far away, reading distance, computer distance, across the room or down the hallway, there’s an area where you can look through a lens where it can be clear,” says Fruit.

Progressive lenses can be customized for a patient’s vision needs including computer lenses. Computer lenses or occupational lenses fight fatigue and other vision problems such as Computer Vision Syndrome.

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Rochester Optical
Our personalized eye care helps individuals see well, stay healthy and maximize their vision potential. That vision drives everything we do. Thats why we want to equip you with all the information that you need to know, in way that you will understand, so that you and your family can have quality and lasting eyesight for a lifetime.

1 Comment

  1. Sam -at bifocal sunglasses -  May 28, 2013 - 4:41 am

    My wife is a scientist working at Giessen, Germany. Her long work hour in front of her computer made her eyes damaged. The dryness in winter time add the bad effect into cvs. Progressive cvs glasses makes her much better.

    Reply

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