|Prescription glasses generally come with corrective lenses, which are mainly used to treat myopia, hyperopia, astigmatism and presbyopia. Typically prescribed by an optometrist, corrective lenses are an integral part of prescription glasses.
Just like prescription glasses, there are various kinds of corrective lenses. When the optical point over the entire area of the lens remains same, they are called prescription glasses with ‘Single Vision Corrective Lens’. In case of ‘Bifocal Corrective Lens’, the upper part is used for distance vision, while the lower part of the prescription glasses are used for near vision. When a middle layer is also present in the prescription glasses for viewing objects at an intermediate distance, ex: computer distance, they are called ‘Trifocal Corrective Lens’. This kind of lenses has two segment lines dividing the three regions.
Progressive or varifocal prescription glasses come with an advantage of eliminating segment lines and offering an effortless transition from distance correction to near correction. Prescription glasses with adjustable or variable lens are mostly used to treat the loss of accommodation which is common to presbyopia.
When it comes to shape, corrective lenses can be produced in any kind of shape but prescription glasses with convex-concave lenses are the most common ones. The difference in curvature which exists between the front and back surfaces leads to the corrective power of the lens.
Though there are many advantages of prescription glasses with corrective lenses, one of its drawback is the facial distortion it causes.