contact lenses sss 2013
TRANSCRIPT
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N U R C H A L I Z A H A Z A R I A S I R E G A R
D E P A R T E M E N I L M U K E S E H A T A N M A T A
F K U S U
CONTACT LENSES
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Contact lenses were thought of as early as1508 when Leonardo da Vinci sketched and
described several forms of them.
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Contact lenses are a changing area ofoptometry with new lenses being constantly
developed
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Refractive errors are corrected by contactlenses, which are placed directly on the cornea
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Lid
margin
iriscornea
conjunctiva
sclera
pupil
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Long-sightedness
(Hyperopia)
Difficulty seeing clearly and comfortablyup close.
Long-sighted
focus
Long-sightedcorrection
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Astigmatism
Irregular curvature of the eye (shapedmore like a football than a basketball)
Light in different planes focuses atdifferent points
A
B90
180
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There are many types of contact lenses
Hard lenses
RGP lenses
Soft lenses Disposable or non-disposable
Coloured or clear
Spherical or toric
Extended wear
Multifocal
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Hard lenses
Plastic polymer.
Most durable.
Rigid, therefore may scratch the cornea.
Not gas permeable
corneal hypoxia
corneal ulcers. Cannot be worn continuously.
Difficult to get used to (because they are very rigid).
Less susceptible to infection + allergy.
Best for treating astigmatism (smoothes out the unevencurvature).
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Hard lenses
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Hard lenses
Hard contact lenses are used in
orthokeratology: the fitting of a
series of rigid contact lenses to
reshape the cornea. It is an
alternative to glasses and surgery
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Hard lenses
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RGP lenses (rigid gas permeable)
They are permeable only to gases.
They are more comfortable than hard lenses, butless than soft ones.
They are more durable than soft lenses, but lessthan hard lenses.
Allow oxygen to pass, but also allow proteins todeposit.
More durable than soft lenses, but less durablethan hard ones
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Soft lenses
Most commonly used (90%)
Made from hydrogel plasticmaterial containing water
Are 1-2mm larger than
cornea
Easy to adapt to
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Soft lenses
Permeable forbothgases + liquids Could be worn for long periods. Tolerated much better.
They do not correct astigmatism. Are the most comfortable lenses. Are the least durable lenses (must be replaced
more often).
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Soft Lenses
Susceptible to accumulation of deposits (becausethey absorb more water, which binds proteins).This accumulation of protein deposits leads to
allergic conjunctivitis and other allergies.
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Spherical lenses
Correct short or long-sightedness
Cheapest, most comfortable lenses
Easy to get in disposable form
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Toric lenses
Are similar to soft contact lenses, but have acouple of extra characteristics:
They have 2 powers in them: 1 for spherical
correction + 1 for astigmatism. They are designed to keep the lens in a stable
position even on movement.
Lens is specially weighted to conform to irregularcornea
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Toric lenses
They offer the comfort of soft lenses ,and at thesame time they correct astigmatism, but theirdisadvantage is that the lens will sometimes rotate,
and this creates a very irritating change in vision asthe lens rotates
More expensive than spherical
Some are available in disposable
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Disposable lenses
Daily, two-weekly or monthlyreplacement
Very simple cleaning (no cleaning fordaily)
Latest designs and materials
Very popular
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Coloured lenses
Handling tint Lens more visible when inserting or removing
Enhancing tint
Makes light coloured eyes more vivid
Opaque tint
Can change brown eyes to blue
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Multifocal contact lenses
Can wear one reading lens, one distance
Can have dual focus lenses
New technology slightly more expensive
Available as a disposable lens
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Advantages of contact lenses over glasses
Better field of view
No fogging up
No one has to know you have refractive error
No frames eg, useful for sport
Sometimes the vision is better
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Consultations for contact lenses
Contact lenses need to be fitted to eachindividual eye
Several tests are required for:
measuring and trying the lenses teaching insertion and removal
after care
Ophthalmologist can advise you about thetests are required
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Contraindications to using contact lenses
History of atopy.
Dry eyes.
Previous glaucoma filtration surgery. Inability to handle and cope with the lenses.
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