Explanation:
The correct answer is A: myopia.

Explanation:
Biconcave lenses are used to correct myopia, also known as nearsightedness. In myopia, the eye focuses images in front of the retina, making distant objects appear blurry. The biconcave (concave) lens diverges light rays before they enter the eye, helping the light to focus on the retina, which improves the vision for distant objects.

Here's why the other options are not correct:
- B. Colour blindness: This condition is related to the inability to perceive certain colors, and it's not corrected with lenses.
- C. Old age: Refers to presbyopia, which is corrected using bifocal or reading glasses, not biconcave lenses.
- D. Hypermetropia: Also known as farsightedness, is corrected using biconvex (convex) lenses, not biconcave lenses.
- E. Weakening of ciliary muscles: This can contribute to presbyopia, but it's not specifically corrected with biconcave lenses.

So, myopia is the correct condition corrected with biconcave lenses.