contact lenses sss 2013

8/13/2019 Contact Lenses Sss 2013

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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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contact lenses sss 2013

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