Question

Can't we use concavo-convex or convexo-concave instead of bifocal lens for presbyopia patient?

Answer 1

No

convex lens is used to correct presbiopia. The design of the glasses you make would determine if you use bifocal glasses, Progressive glasses or only near vision glasses.

In only near vision glasses, only convex lens is fitted but if the same glass is used for seeing a distant object, the vision is blurred.

In bifocal glasses, there are two lenses which are fused which help you to see for distance from upper part of the glasses and see near objects clearly with lower part of the glasses so that you do not have to keep removing and putting on the glasses.