Single vision lenses correct for only one distance. Single vision lenses can be made for far or near distance. If they correct for far distance, the person must accommodate to see clearly up close. If the person cannot accommodate, they may need a separate pair of single vision glasses for near distances, or else use a multifocal lens (see below).
A bifocal is built for two distances, usually far and near. With a bifocal, the upper part of the lens is generally used for far distance vision, while the lower part is used for near vision, such as reading. A visible segment line separates the two zones.
Trifocal lenses are similar to bifocals, except that it is built to correct for three distances. This lens type has two visible segment lines, dividing the three different correcting segments. The upper area is typically used for far distance vision, the middle area is used for the intermediate distance and the lower part is for near vision. Intermediate distance is about an arm's length away, ie. a computer.
Progressive lenses correct for three distances but without any visible lines. Progressive lenses provide a smooth transition from far distance to intermediate to near.
If you use one or more digital devices on a daily basis or work in an environment where you primarily use near and intermediate distances, then this task-specific lens provides maximum comfort and natural posture for these situations. Primary candidates include people who work in an office environment, who use computers for many hours per day, and people who spend most of their day doing household activities.
Single Vision Lens
Anti-reflective coatings help the wearer see more clearly by limiting distracting reflections from bright objects (e.g. lamps, windows) and allowing light to easily reach the eye. This is especially useful at night to help reduce headlight glare from oncoming cars, street lamps and heavily lit signs. Anti-reflective coatings also help with the aesthetics of eyewear by reducing the glare seen on the lens.
A UV coating is used to reduce the transmission of light in the ultraviolet spectrum. UV-B radiation increases the likelihood of cataracts, while long term exposure to UV-Aradiation can damage the retina. DNA damage from UV light is cumulative and irreversible.
An anti-scratch or scratch-resistant coating is a film or coating that can be applied to optical surfaces, such as the faces of a lens or photographic film. The coating does not interfere with how the lens functions and does not affect vision, but creates a permanent bond with the lens that reduces the appearance of hairline scratches which is common to eyeglass lenses. Though an anti-scratch coating is not 100% scratch-proof, it helps to prevent minor scratches that can easily happen to a regular lens. These minor scratches can damage the surface of the lens and impair vision. An anti-scratch coating acts as a protective layer thus making the lenses more durable and safe.
Blue Light Blocker
These days, it’s impossible to escape blue light. TVs, computers, smartphones, tablets and e-readers bombard our eyes with blue light emissions day and night.
Electronic devices aren’t the only culprits. Energy-saving light bulbs (notably LEDs) may be “green” but they also emit a significant proportion of blue light (also known as High-Energy Visible [HEV] light). While present in natural light, blue light occurs in abnormal proportions in artificial light sources.
Blue/HEV light covers wavelengths from 380 to 500 nanometers (nm). Our eyes do not block blue/HEV light, meaning it is able to pass through the cornea, the crystalline lens and the vitreous, resulting in potential damage to the retina. HEV light is toxic for the crystalline lens and retina which can lead to retinal cell death and early cataract and macular degeneration formation.
Now, multiple lens manufacturers have developed new products designed to address the dangers posed by blue light.