Assessment Flashcards
How are most rigid gas permeable contact lenses manufactured?
Lathe cutting
A diameter gauge is most commonly used to measure the diameter of a gas permeable contact lens. What is the other instrument that can be used to measure diameter?
A hand magnifier
When viewing the star pattern in a radiuscope what would be indicated if some of the lines were darker and others blurred?
A toric lens
A warped lens
What is the most accurate instrument for assessing a gas permeable contact lens edge profile?
A stereomicroscope
Which gas permeable edge problems can cause 3 and 9 staining?
The square edge
The rolled in edge
The rolled out edge
What technique is used to modify a gas permeable lens sharp edge?
Place the contact lens concave side down into the hollow sponge tool for 15 to 20 seconds.
Which gas permeable modification is possible?
RARLID Limited power change Diameter reduction Increasing or flattening peripheral curves Reducing optic zone Altering edge design Reducing sagittal depth
Identify reason(s) for an adhesion phenomenon caused by gas permeable contact lenses. There may be more than one answer.
LD SOS Overnight wear of RGP lenses Steep peripheral curve Steep base curve Large diameter Displacement during sleep
Identify plan(s) for correcting an adhesion phenomenon.
RID FD Flatten lens cornea relationship Increase center thickness Decrease O.Z. and/or diameter Discontinue extended wear Re-roll edges
What are the subjective symptoms of gas permeable lens induced corneal edema? There may be more than one answer.
Halos or streamers around lights.
Photophobia.
Spectacle Blur
Identify plan(s) for correcting a decentered gas permeable lens. There may be more than one answer.
Increase the total diameter of the lens.
Use a toric lens design.
Use a spherical lens fit steeper than K.
Identify plan(s) for correcting residual astigmatism of 1.00 D for a gas permeable lens wearer with a spherical cornea. There may be more than one answer.
Fit a prism ballasted front toric gas permeable lens.
Wear astigmatic eyeglasses over the gas permeable lenses.
Use the spherical equivalent of the gas permeable lens.
When a spherical lens is fit on a cornea with three diopters of against the rule astigmatism, what will be the shape of the darker band (less fluorescein) in the fluorescein pattern observed under the lens?
An hour glass.
Prolonged hypoxia causes cells to die, leading to polymegatism. Which part of the cornea will be affected?
Endothelium
When refitting a PMMA contact lens wearer with gas permeable lenses what is the best method to determine the lens power?
By over refraction.
