Bausch & Lomb’s 3-Zone Progressive Design

Over the age of forty, people continue to lose their eye’s natural ability to focus (accommodate) from far to nearer objects. This can create difficulty with a contact lens that is designed for only far away optics. To create consistent quality vision for distance, intermediate and near ranges for someone who’s losing their ability to focus, Bausch & Lomb has engineered a design referred to as “3-Zone Progressive”. This contact lens design is utilized in the following lenses:

• Ultra for Presbyopia
• BioTrue for Presbyopia
• Infuse Multifocal

The following is a graph from Bausch & Lomb demonstrating the power change from the center of the lens, indicating that there are THREE main ZONEs (near, intermediate, distance) with a gradual change in between each zone. This gradual change is from its aspheric design, and is where the word, PROGRESSIVE, comes in.

The center of the lens is in the near zone because the pupil tends to get smaller when a person looks at something up close. The further away a person looks, the pupil gets wider to include more of the intermediate zone and then more of the distance zone. The design makes sense and has worked well for Bausch & Lomb and their customers for many years.

What makes a Soft Contact Lens Multifocal (for Presbyopia) different from other lenses?

To see clearly when looking far away, light must focus at a point in the back of the eye called the fovea. If optically corrected for far away, this point of focus will shift behind the fovea causing the eye to be blurry. In response to this blur, muscles behind the iris (ciliary muscles) flex and cause the crystalline lens behind the pupil to change from a flatter shape to a rounder shape, therefore altering the focus point back onto the fovea. This flexing of the lens for focus to see up close is called accommodation. Around the age of 40 years of age, all humans start to lose the elastic nature of the crystalline lens. This hardening of the lens is called presbyopia, and makes accommodation more difficult. Around the age of 53, this lens will be completely hardened, and all accommodation will be lost. This slow loss of focus up close between 40-53 requires a separate prescription for nearer points of focus.

Spectacle glasses provide additional focus in the form of multifocals. Multifocals can be utilized as bifocals (two focal distance zones), trifocals (three focal distance zones), or progressives (a gradual change of focus from far to near without lines). Both eyes can look through the top, middle, or bottom zones for far, computer, or phone distance viewing. In glasses, these different zones are entirely devoted to a specific focal distance, so the eyes have the opportunity for complete binocular focus.
This zone of focus is different for multifocal soft contact lenses when compared to multifocal spectacles. With soft contact lens designs, instead of the eye being able to translate through the different zones of the glasses, the entire multifocal is jammed into the area over the pupil, the optic zone of the contact lens. Therefore, when looking far away, the distant and near focal zone may conflict with each other, and disrupt clarity when compared to spectacle lenses.

To account for the variant focus zones each being incorporated into the optical zone, manufacturers each optically design their multifocals so that the different ranges of vision will all be as clear as possible. Bausch and Lomb has the 3-Zone Progressive Design in the Ultra for Presbyopia, BioTrue for Presbyopia, and the Infuse Multifocal.