This document discusses common vision defects and how they can be corrected using lenses. Myopia, or near-sightedness, is corrected using concave lenses, while hypermetropia, or far-sightedness, is corrected using convex lenses. The document also notes differences in eye anatomy between various animals, such as crabs having small eyes that allow wide vision, and owls having large corneas and pupils to let in more light as well as more rod cells in their retinas compared to day birds.

8. Defects of
Vision
Myopia (short-
sightedness) can
be corrected
using concave
lens
Hypermetropia
(long-sightedness)
can be corrected
using convex lens

10. • Eyes of crab are small but it can
look all around with those eyes.
• The owl has a large cornea and a
large pupil to allow more light in
its eye. It’s retiŶa has ŵore rods
thaŶ cones. The day birds have
more cones and less rods.