Bi-focal lenses

The idea

A person with both myopia and hypermetropia often needs bi-focal lenses: a concave upper portion for distant vision and a convex lower part for near vision.

Two problems at once

A person has myopia and hypermetropia together. Distant things look blurred, and so do nearby things.

What kind of spectacle lens can help with both?

• One with a concave part and a convex part
• One with a flat piece of glass
• One with two concave lenses

One lens, two parts

Open every tab.

Upper and lower

A person who needs both corrections often needs bi-focal lenses. The upper part is concave and helps with seeing far. The lower part is convex and helps with seeing near.

A person with both myopia and hypermetropia often needs bi-focal lenses: a concave upper portion for distant vision and a convex lower part for near vision.

Notes

Bi-focal lenses (for both myopia and hypermetropia): a concave upper portion for distant vision and a convex lower part for near vision.

Check yourself

Who often needs bi-focal lenses?

In a common bi-focal lens, the upper portion is…

In a common bi-focal lens, the lower part is…

• A person with a normal eye. A normal eye does not need corrective lenses. Bi-focal lenses are often needed by a person with both myopia and hypermetropia.
• A person with both myopia and hypermetropia — correct. Yes!
• A person with only myopia. A person with only myopia is corrected by a concave lens. Bi-focal lenses are often needed by a person with both defects.
• a convex lens, which facilitates distant vision. The upper portion is a concave lens.
• a concave lens, which facilitates near vision. The concave upper portion facilitates distant vision.
• a concave lens, which facilitates distant vision — correct. Yes!
• a convex lens, which facilitates near vision — correct. Yes!
• a concave lens, which facilitates near vision. The lower part is a convex lens.
• a convex lens, which facilitates distant vision. The convex lower part facilitates near vision.