Bi-Focal Lenses: Flat-top 28mm

Bi-Focal Lenses

This particular lens can be called a multi purpose lens. It has 2 different fields of vision in one visible lens. The larger of the lens usually has the prescription necessary for you to see for distance. However, this can also be your prescription for computer use or intermediate range, as you would normally be looking straight when you view through this particular part of the lens. The lower part, also called the window, typically has your reading prescription. Since you generally look down to read, this is the logical place to put this range of vision assistance. The different types of bi-focal lenses usually mean the size of the window. Flat top 28 means the small window is 28mm the 35 version simply means the window is 35mm wide.

Example of Bifocal Lenses:

ST- Straight Top
FT- Flat Top
FT 28 – Flat Top 28mm
FT 35 – Flat Top 35mm
D28 – 28mm
D35 – 35mm
Round 24 - 24mm
Round 38 – 38mm
Executive – Executive Bifocal

Safety Concerns

Although there are many positives to bifocal and trifocal lenses, there is also a negative. Sometimes you may feel like objects that you are looking at appear blurry unless you tilt your head down. This can be dangerous if you are walking down stairways or crossing the street.

A recent study was published in the UK which states that single vision lenses are a better choice for people with presbyopes because they help to judge the height of lower steps.

The authors of the article stated that having a second pair of single vision lenses can prove useful and help eliminate falls. It is also suggested to have a pair of walking glasses with single vision distance lenses while walking in places that have poor lighting.

These are important to take into consideration for safety benefits.