Single vision lenses are just what its name says, a lens with one prescription throughout the entire lens. Single vision lenses can accommodate a person with myopia, a person with hyperopia , or any other condition that requires only a single Rx to correct, such as astigmatism.
All prescriptions are measured in diopters and run in increments of quarter diopters. A myopic person can have a minor prescription of +0.25 or -0.25, but can also run high, for example +7.50 or a -6.75 and even stronger.
A person’s vision comes into focus at one focal point on the eye’s retina. This is accomplished by the rate at which light rays are bent once they enter the eye; the medical term is index of refraction. Eyeglass lenses work much in the same way with the density of the lens material bending the light rays as they pass through.
Single vision prescriptions work well in different lens materials:
- Glass – works well low prescriptions
- 1.53 Index of Refraction
- Heaviest of all lens materials (higher Rx’s can be quite heavy on the face)
- Hardest of all material
- Safety Issues – most eye doctors will not put into a child’s eyeglass frame
- Most scratch resistant of all lens materials
- Has the sharpest vision acuity
- Slightly more expensive due to not in demand
- CR-39 – works well for low, medium, and slightly high prescriptions
- 1.50 Index of Refraction
- Most commonly used lens material
- Made of a plastic resin material
- Standard thickness
- Thicker than glass lenses of the same strength
- Light weight material
- Soft – scratches easily
- Durable – doesn’t break easily
- Polycarbonate – works well with low, medium, and high prescriptions
- 1.586 Index of Refraction
- Very popular
- Thinner than plastic
- Light weight
- Safer for eyes’ protection
- Used for children’s eyeglasses for safety reasons
- Holds a higher Rx in less lens material as compared to plastic and glass
- Hi-Index – works well with higher prescriptions
- 1.54 – 1.8 and up Index of Refraction
- Most light weight
- Thinnest of all lens materials
- Expensive (the higher the Index of Refraction number, the thinner the lens, the higher the cost)
- Soft – scratches easily
- Recommended and favored for strong prescriptions
There are many other materials and variations of the ones above; all claim to be better than the next. What ever the case may be, there are the listed materials in the most standard in form, sufficiently meet the needs of a consumer who requires a single vision prescription. Some work better than others but all accommodate visual infractions of a person suffering from the vision impairments caused by myopia or hyperopia.
A person wearing a pair of eyeglasses with a minus prescription is myopic and is known as being nearsighted. A person wearing pair of eyeglasses with a plus prescription is hyperopic and is known as farsighted.