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57 Cards in this Set

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Contact rests on the

Tearfilm layer of the cornea

What produces the power of a contact len?

The difference between the front surface curvature and the back surface curvature.

Two ways to list k readings?

1.list the flat k first followed by the steep k and its axis


2. List horizontal meridians first regardless if its the steep k or not.

If the back surface of a lens is to be the same radius as the k's then that is called?

Fitting on the k

Rgp lens can be fitted?

Flatter, steeper , or on the k

Soft contacts are fitted how?

3-5 diopters flatter than k

How is the total lens diameter measured?

One edge of the lens to the opposite side.

The higher the the minus the ___ the center of the lens. The higher the plus the _____the center of the lens.

Thin, thick

Why are lenses truncated?

It adds stabilty, and prevents rotation.

When a base curve lens says it needs to be steeper what happens to posterior radius of the curvature?

Its decreased it is opposite if the curvature lens needs to be flatter.

How is the wetabililty of a surface measured?

Its measured in terms of contact or wetting angle.

The lower the wetting angle the greater the?

Spreading of tears

The oxygen abbreviation in contacts is?

Dk

What is the minimal safe level of equivalent oxygen percentage (EOP) in dailies, extended wear? Whats ideal for extended wear?

9%


12%


18%

When the corneas astigmatism is different than the cylinder in the prescription this is known as?

Residual astigmatism

How is the optic zone determined?

The difference bt the diameter and width of the peripheral curves.

What are the causes of a 3:00-9:00 staining from contacts?

Lid gap, poor blinking , poor tear film.

What instrument measures the base curve of a lens?

Contacto gauge (radiusscope)

How can the power of a lens me measured?

Lensometer

Describe giant papillary conjunctivitis.

Its more common with gas perm, has a cobblestone appearance under the lid.

What is a 'tight ' lens

A lens that causes hypoxia aka low oxygen causing corneal edema.

What causes one to change their blink rate?

Awareness of the lens.

What are multiple causes of a contact lens causing corneal edema?

Flat lens compressing cornea


Steep lens lacking tear flow


Poorly centered lens


Incorrect blinking


Incorrect cleaning of lens

Edema can do what to previous k readings

Increase

How are soft lenses classified ?

How their made, water content. Dk permeability, and by their function

Advantage a of hydrophilic soft contacts?

Comfort, rapid adaptation, lack of spectacle blur, dispisability, minimal lens loss, minimal overwear reaction, protects entire cornea, no corneal abraisions on insert, lack of glare.

Advantages of silicone hydrogel?

Rapid adaptation, low rate of deposits, easy to handle, high DK value, suitable for extended wear.

What are disadvantages of a soft contact?

Doesn't corrext high astigmatism, variable vision, lack of durability, faulty duplication, deposit forms, modifications are impossible, disinfect problems

How can one disinfect soft lenses?

Boiling , chemical, and uv methods.

Thing to consider in a patient interested in contacts?

Age


Hygiene


Reoccurent infections, susyemic disease, dryness of eyes


Patients motivation


Corneal sensitivity test


Occupation


Lid tension

How are soft lenses manufactured and which is the most common?

Spin casting, lathecut, and molding methods. Lathe cut and molded are most common.

A soft lens should rest on how many points?

Three, apex and at the periphery of the cornea

When fitting a soft contact lens the goal is to have

The flattest lens possible with clear vision and comfort.

Symptoms of a tight lens

Fluctuating vision


Comfort at first that gets worse throughout the day


Coneal injection around the cornea


Corneal indentation


No movement after blinking


K's that are clear than are distorted after a blink


Retinoscopic reflex is fuzzy than clear .

Signs of a loose lens

Fluctuating vision


Awareness of lens


Poor centering


Lens falls out


Bubble under lens


Ks that blur after blinking


Retinoscopic reflex that is clear than is fuzzy.

The lens is cleaned by rubbing both sides of a lens with a finger for 20 seconds, this is known as?

Digital cleaning.

What is the minimal time needed to disinfect lenses with peroxide?

20 minutes

What is bullous keratopathy

Described as a corneal blister.

Symptoms like flare or streaming lights with contacts could mean?

Optic zone is too small

Blurring vision in daytime could be a result of

The contact lens riding too high or too low

Signs that indicate a contact lens needs to be changed or wear time needs to be reduced?

Change in k's over 1 diopter and distortion in the mires.

What does a contact wetting solution do?

Turns surface into a water loving surface making the tear film spread easier.

What do soaking solutions do?

Cleans lens of oil and sebaceous secretions.

What does a cleaning solution do?

Cleans lens of oil, mucus, crystalline deposits.

What kind of diameter does a tricurve lens have?

Large diameter

Tinted lenses use what type of scale to note tint intensity?

1-3 1 being the lightest.

What does it mean when the base curve of the lens is made steeper?

Posterior radius curvature is decreased

What is a frequent cause of patients rejection of contacts?

Edge design

What are the peripheral curves designed for?

Allows tear flow under the lens

Lid gap is more prone in what script and why?

High myopes from thickness of periphery of lens

Is it helpful to wet the finger befor putting a gp lens in?

Yes but don't have to wet a finger for soft lenses

How often and how is a contact lens case cleaned?

Scrub with a toothbrush and soap atleast once a week

How often should a soft contact be cleaned with an enzyme and what needs to be done after its cleaned?

Twice per month, rinse with saline and disinfectant before insertion

Should contacts be removed for air tonometer?

Yes

Should contacts be removed during a vf?

No

True or false? The zone of flare is always opposite of the displacement of lens?

True

If a keratometer can't read a steep cornea what can be attached?

INNS extension disc