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| Types
of Contacts |
Confused about contacts? Advances in
contact lens technologies have created many options in addition to hard and soft
lenses. Today, contact lenses are likely to be described in one or several of
the following ways.
By their prescribed wearing period:
The time that the lenses are left in the eyes.
- Daily Wear (Up to 18 hours)
- Extended Wear (For overnight
use, up to seven days)
By their replacement schedule:
The time interval for replacing lenses.
- Planned - (Frequent replacement:
1 month, 1-2 weeks; daily disposable)
- Unplanned, or Conventional
Replacement - (No specific time schedule before lenses
are replaced)
By the type of vision correction
for which they are designed:
- Spherical (For near- or farsightedness
-- myopia or hypermetropia) Toric
(For astigmatism)
- Bifocals (For presbyopia)
By the type of tint they have:
- Tinted to improve handling
only Tinted to enhance
your eye color (For light-color eyes) Tinted
to change your eye color (Opaque tints for light or dark
eyes)
- Clear - without tints
Of course, contact lenses are
also still described by the basic type of material of which
they are made.
- Soft (hydrophilic)
- Rigid Gas Permeable
By Wearing Period
Daily Wear: Lenses prescribed for daily
wear are to be worn only during waking hours, usually
up to a maximum of 18 hours. Daily wear lenses
are removed at night and cleaned and disinfected
after each removal.
Extended
Wear: Extended wear lenses may be worn on an
overnight basis for up to seven consecutive days
(six nights). You should wear your lenses on an
extended wear basis only on the advice of your
optometrist. Extended
wear lenses generally have a higher water content
or thinner center thickness than other lenses and
permit more oxygen to reach the eye. However, their
use has been linked to a higher incidence of eye
problems. Extended wear lenses need to be cleaned
and disinfected at recommended intervals or discarded
after use.
By
Replacement Period
Contact lens are often prescribed with a specific replacement
schedule suitable to your specific needs. Planned (or
Frequent) Replacement contacts are disposed of and replaced
with a new pair according to a planned schedule. Unplanned
replacement lenses (often called conventional lenses)
are not replaced according to a pre-determined schedule.
They are typically used for as long as they remain undamaged,
usually around 12 months for soft lenses.
Why
replace lenses frequently?
Almost immediately after they are inserted, contact
lenses begin attracting deposits of proteins and lipids.
Accumulated deposits, even with routine lens care,
begin to erode the performance of your contacts and
create a situation that presents a greater risk to
your eye health. A
specific replacement schedule helps to prevent problems
before they might occur. Contact lens wearers, in turn,
enjoy the added comfort, convenience and health benefits
of a planned replacement program. Planned replacement
lenses are generally a thinner design or are made of
different, more fragile materials with a higher water
content than unplanned replacement or conventional
contact lenses. Based
on a complete assessment of your needs, a prescription
for planned replacement lenses may call for replacement:
- Quarterly, Monthly Every
1-2 weeks
- Daily
Except for daily disposables,
planned replacement lenses require cleaning and disinfection
after each period of wear unless they are discarded immediately
upon removal. Planned replacement lenses can be worn as daily
wear -- removed before sleep -- or as extended wear, if recommended
by your practitioner.
By
Type of Vision Correction Required
Contact lenses may be identified by the type of refractive
error they are designed to correct.
- Spherical contact lenses for
nearsightedness (myopia) and farsightedness (hypermetropia); Toric
contact lenses for astigmatism;
- Bifocal lenses for presbyopia,
the loss of ability to focus on reading or close-up activities.
As an alternative to special bifocal
contact lenses, many practitioners use a system called monovision
where one eye is fitted with a distance lens and the other
with a reading lens. Approximately two-thirds of patients
adapt to this type of contact lens wear.
By
Type of Tint
Contact lenses may be described as clear or tinted. Tints
are used to make lenses more visible during handling, or
for therapeutic or cosmetic reasons. Tints can enhance eye
color, or change it altogether. Three
categories of tinted contact lenses are available.
- Cosmetic enhancement tints
are translucent and are designed to enhance your natural
eye color. They are best for light-colored eyes (blues,
greens, light hazel or grays). When wearing these tints,
the color of your eye is a blend of the lens tint and your
natural eye color and iris pattern. Opaque
or "cosmetic" tints change the color of your
eyes whether they are dark or light. The pattern on the
lens, which is colored, overlies the colored part of your
eye, resulting in a color with a natural look.
- Visibility tints are very pale,
colored just enough to make the contact lens visible while
you are handling it. They usually have no effect on eye
color.
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