What type of lenses have a consistent prescription to correct various vision problems for individuals under 40?

Single vision lenses are designed to provide a uniform prescription that corrects a specific vision problem, whether it be for nearsightedness, farsightedness, or astigmatism. For individuals under 40, these lenses are highly effective because they address one type of visual correction without incorporating the more complex dual or multifocal capabilities found in bifocal, trifocal, or progressive lenses. As a result, single vision lenses offer clarity and ease of use for activities such as reading or driving, making them a suitable choice for patients who do not yet require correction for presbyopia, which typically starts to develop after 40.

In contrast, bifocal and trifocal lenses incorporate multiple prescriptions for different viewing distances, which may not be necessary for individuals without presbyopia. Similarly, progressive lenses offer a gradient of vision correction from distance to near, but they are often not suitable for younger individuals whose vision needs are simpler and can be met with a single lens prescription.