Bifocals prescription specs, or lenses that combine two different powers, are prescribed to aid both near and far vision in one pair of lenses. Usually the lower part of the lens is to help see clearly at close distances and the upper part is to aid focusing at far distances. Bifocal glasses have been the correct answer to presbyopia.
The segment that is devoted to near-vision correction can be in one of several shapes. We have two types of bifocals lens available with us:
The lens is divided into two parts: an upper part for distant viewing and a lower part for near point viewing. The straight line dividing the two parts may be above, or below the normal line of sight for distant objects, and both parts provide a wide field of view.
It comes in a shape of half-moon, which is also called a flat-top or D rim. This type of lens is satisfactory for occasional near-point work or near-point work that is usually in, or may be easily moved to, the lower part of the field of view. In this case, however, lateral viewing of near point objects is restricted.
Progressive lenses are a part of bifocal lenses however they have no line. They offer near, intermediate and distant vision correction with no rapid changes or hideous lines. The change in vision correction is much less noticeable and more gradual than with old style bifocals, hence progressive lens also improve vision in the middle distances.
Ultraviolet (UV) protection is invisible to the naked eye. UV treatment in eyeglass lenses blocks the rays that burns the skin and can damage the eyes. An ultraviolet treatment is simple and quick to apply to most plastic eyeglass lenses, and it does not change the appearance of the lenses at all.
Anti reflective coating also known as computer lenses. A common problem with prescription glasses and sunglasses is called "back-glare” which is light that hits the back of the lenses and bounces into the eyes. The purpose of an anti-reflective coating is to reduce these reflections off the lenses. They are perfect for night driving and computer use because they absorb reflections and increase the light that passes through the lenses, providing sharp, fatigue-free vision. Anti-reflective coated lenses improve your eyeglasses appearance by making your lenses look invisible.
Ant scratch coating is a special coatings have been developed to help protect lenses from normal scratching as lightweight plastic lenses can be more easily be scratched than glass lenses. Anti-scratch coating does not affect the optical description of the lens. Coated lenses can be easily cleaned and sanitized.
Photo chromic lens change from light to dark in response to changing levels of UV light. They do not replace sunglasses in all situations, because the windshield filters UV light, which keeps these lenses from darkening. In addition to their convenience and fashion appeal, they are perfect for people who are sensitive to light.
Tint lenses or fix colour lenses, as opposed to the changeable photochromics, remains constant at all times. Tints are available in 40 colours. They are applied to plastic lens materials through a process of absorption. The lenses are immersed into a warm colour bath, and depending on the length of time they sit in the tank, emerge in varying shades of darkness.
