| Single Vision |
Single vision lenses are uncoated, plastic lenses with a single prescription that corrects
myopia, hyperopia, or astigmatism. |
| Bifocal |
Bifocal lenses are uncoated, plastic lenses that correct
both for distance and near vision in individuals with presbyopia. The top of the lens corrects for
distance vision. In the lower part of the lens, there is a visible semicircle ground into the lens that
corrects for near vision. |
| Trifocal |
Trifocal lenses are uncoated, plastic lenses that correct for vision at three distances.
The top of the lens corrects for distance vision. In the lower part of the lens, there is a visible semicircle
ground into the lens that corrects for near vision. Just above this semicircle is an additional lens segment
that corrects for distances of about an arm's length away. |
| Lenticular |
Lenticular lenses are designed to treat eye conditions that
are more serious than simply myopia, hyperopia, presbyopia, or astigmatism. They are often prescribed after
cataract surgery for patients without intraocular implants. |
| Progressive |
Commonly called "no-line bifocals", progressive lenses are bifocal or trifocal lenses that
have an invisible corridor of increasing power that leads from the distance portion of the lens down to the
reading portion. |
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| Plastic |
Common uncoated lens material.
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| Polycarbonate |
Polycarbonate lenses are made of a material similar to standard
plastic, but are lighter in weight and thinner than uncoated plastic lenses. They offer protection from surface
abrasions like scratch resistant coated plastic lenses, and they do not shatter like glass or standard plastic lenses.
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| Photochromic |
Photochromic lenses are light sensitive glass lenses. The glass
contains silver halide crystals that darken when exposed to ultraviolet (UV) light and become clear when removed
from the light. In their darkened state, photochromic lenses offer protection from potentially damaging UV rays.
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| Transition |
Transition lenses are light sensitive plastic lenses, which makes them lighter in weight than
photochromic glass lenses. They become darker when exposed to ultraviolet light and lighten when removed from
the light. Transition lenses resist UV radiation both when light and dark, and the lenses are scratch-resistant.
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| Glass |
Glass lenses are generally heavier than plastic lenses and resist
scratching better than uncoated plastic lenses.
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| Scratch Resistant Coating |
Scratch-resistant coated lenses offer protection from most surface abrasions. The coating is
included as a part of polycarbonate lenses, but is also available as an option that is applied to the surface
of standard plastic lenses after the lenses are ground.
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| Ultra-Violet Filter |
Reduces transmission of harmful ultra-violet rays from the sun.
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| Anti-Reflective Coating |
Increases light transmission through the lens by reducing reflections that cause unwanted glare.
Anti-reflective coating can improve vision while driving at night.
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| Polarized |
Polarized lenses reduce light transmission and reflection from
horizontal surfaces, such as snow or water and may improve vision during outdoor activities.
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| Tint |
Tinted lenses reduce light transmission.
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| Daily Wear Contact Lenses |
Daily wear contact lenses can be soft or rigid contact lenses made of different types of
plastic, depending on the specific type of lens. Daily wear lenses are to be worn for periods of less than
24 hours at a time, and should be removed each night before the wearer goes to sleep. Lenses generally need
to be replaced annually or biannually.
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| Extended Wear Contact Lenses |
Extended wear contact lenses are usually soft contact lenses,
but are designed to be worn for 24 hours or more at a time. Some lenses are FDA approved for up to 30 days of
continuous wear, but most doctors recommend removing and cleaning the lenses at least weekly. Extended wear
lenses have replacement schedules that vary significantly by the specific type of lens and length of continuous
wear.
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| Disposable Contact Lenses |
Disposable contact lenses are soft contact lenses, either daily wear or extended wear, that
are replaced on a 7 to 30 day cycle. Wearers generally purchase a supply of disposable lenses that will last six
months to one year.
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| Hard Contact Lenses |
Hard contact lenses are made from a rigid plastic resin,
polymethylemethacrylate (PMMA). The lenses are more durable and easier to handle than soft contact lenses,
but many people may find them uncomfortable. PMMA does not absorb water, and does not allow for the
transmission of oxygen through the lens to the eye. Hard contact lenses should be removed daily.
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| Rigid Gas Permeable Contact Lenses |
Rigid gas permeable (RGP) contact lenses are made of a non-absorbent material that is
oxygen permeable. RGP lenses are durable and easy to handle like hard contact lenses, but more comfortable
to wear, though usually not as comfortable as soft contact lenses. Most RGP lenses are used for daily wear,
but some lenses can be worn for extended periods of time.
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| Toric Contact Lenses |
Toric lenses are either hard or soft contact lenses used
to treat astigmatism, which cannot be corrected with traditional spherical contact lenses.
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