Bi-Focal Lenses: Flat-Top 28mm
The most popular bifocal design with distance and reading correction in one lens
How Bi-Focal Lenses Work
This particular lens can be called a multi-purpose lens. It has 2 different fields of vision in one visible lens.
Upper Portion (Distance)
The larger part of the lens usually has the prescription necessary for you to see for distance. This can also be your prescription for computer use or intermediate range.
Lower Window (Reading)
The lower part, also called the "window," typically has your reading prescription. Since you generally look down to read, this is the logical place for this vision correction.
Size Difference: Flat top 28 means the small window is 28mm wide; the 35 version means the window is 35mm wide.
Examples of Bifocal Lenses
Straight Top
Flat Top
Flat Top 28mm ★
Flat Top 35mm
28mm / 35mm
Round Segment
Executive Bifocal (Full-width segment)
Safety Concerns
Although there are many positives to bifocal and trifocal lenses, there is also a negative. Sometimes you may feel like objects appear blurry unless you tilt your head down. This can be dangerous when walking down stairways or crossing the street.
A recent study published in the UK states that single vision lenses are a better choice for people with presbyopia because they help to judge the height of lower steps.
Recommendations:
- Consider having a second pair of single vision lenses to help eliminate falls
- Have walking glasses with single vision distance lenses for poorly lit places
Benefits of Flat-Top Bifocals
Two Prescriptions in One
Distance and reading correction without switching glasses
Clear Visible Segment
Easy to locate reading area of the lens
Cost Effective
More affordable than progressive lenses
Easy Adaptation
Quick adjustment period for most wearers