Lens Types
The technology behind the manufacturing of lenses today is highly sophisticated. The same Anti-Reflection coatings on your glasses are used on camera, microscopes and aircraft/ helicopter instrument panels. Polycarbonate lenses are made of the same metal used in space helmets, aircraft windshields and compact discs.
Types of lenses
Single Vision:
Single vision lenses provide corrections with only one focal point. They correct hyperopia (farsightedness) myopia (nearsightedness), or presbyopia including the condition of astigmatism.
Multifocal:
These lenses can fit into two categories: Lenses with lines and lenses with no lines. Lenses with lines provide a definitive division of powers. The top portion allows you to see distant objects whilst the segment below allows to view close objects. The disadvantage of these lenses is that they create image jump at the line where the powers change. ·
- Bifocals: Lenses provide two fields of vision, distance and near. There is no correction for the intermediate distance.
- Trifocals: Lenses provide three fields of view. In addition to near and distance, a trifocal provides intermediate, arm’s length vision which is usually out of focus with a bifocal lens.
- Half Eye and reading glasses: Half eye spectacles have plus or magnification lenses for near vision. They are generally worn toward the end of the nose. Looking over the top provides distance vision.
Progressive:
These lenses provide the most natural vision if you are presbyopic. They are cosmetically appealing and attractive in current fashionable frames, because they look like single vision lenses. Vision is clear at all distances. Progressive lenses provide a continuous, gradual change in power from eye-level to the bottom of the lens to achieve the plus or add power the prescription requires. These lenses are generally effective when working on a computer.
Lens Materials
Polycarbonate lenses: This is the strongest, safest and thinnest lens material available. It is more impact resistant than glass, conventional or high index plastic and includes ultraviolet protection and scratch resistant coating.
High Index Plastic: High index plastic is lighter and thinner than conventional plastic and glass. It is more impact resistant than glass, but less impact resistant than polycarbonate. These ultra thin lenses are now available in tints, including photochromatic.
Conventional Plastic: Conventional plastic is more impact resistant than glass and approximately half the weight of glass. It may be tinted for fashion wear and is also available in photochromatic lenses.
Coatings and Tinting
Scratch Resistant Coating: A scratch resistant coating on a lens is a prudent investment. It provides protection against normal scratches on the surface of the lenses.
Ultraviolet protection: The Food and Drug Administration endorses the concept that unseen ultraviolet radiation from sunlight can harm the human eye. It is a health consideration for everyone regardless of age. For that reason, ultraviolet protection should be included in every pair of prescription lenses whether they are for indoor or outdoor use. It has been proven that UV rays can encourage cataract growth and retinal deterioration.
Anti-reflective Lenses: Anti-reflective lenses are much like the lenses used on very fine cameras to reduce or virtually eliminate glare or reflected light. AR lenses allow more light to be transmitted to the eye and the wearer sees things brighter, clearer and with crisper details. They also enhance personal appearance by eliminating distracting reflections for both the wearer and the viewer. Night vision is also enhanced with the use of this product.
Photochromatic (Transitions®) lenses: These lenses darken when exposed to ultraviolet sunlight. Their changeable tint provides comfort from glare in any light, but their use as a sunglass is limited.
Prescription Sunglasses
If you wear spectacles you need a pair of Prescription Sunglasses for the sun. The choice of lenses available are numerous and therefore the most common forms are listed below:
- Plastic with UV treatment and tint
- Lenses that change with the sunlight (Photochromatic)
Contact Lenses
Due to the wide range of contact lenses available, it is essential that you undergo a consultation with a contact lens practitioner. Our practice provides the latest in contact lens care. To be fitted with a contact lens it is necessary to have a one hour appointment for the professional fitting of the contact lenses. The range of contacts available extends from Daily wear to conventional lenses that may last up to one year.