Bi-focal lenses are designed with the upper portion as a concave lens for distant vision and the lower part as a convex lens for near vision. This design allows individuals to see clearly at both distances.

Individuals experiencing both myopia and hypermetropia often require bi-focal lenses, which consist of both concave and convex lenses. The upper part facilitates distant vision, while the lower part assists near vision.

Presbyopia arises due to the gradual weakening of the ciliary muscles and diminishing flexibility of the eye lens.

Presbyopia is a defect where the near point gradually recedes as the power of accommodation decreases with age. People find it difficult to see nearby objects comfortably and distinctly without corrective eye-glasses.