Overdominance occurs when a heterozygote has a more phenotype than that of either of its parents.
The lens helps the eye to focus on images.
"The Lens. The lens is composed of transparent, flexible tissue and is located directly behind the iris and the pupil. It is the second part of your eye, after the cornea, that helps to focus light and images on your retina."
True because why would it not be a good way