Question and Answers | Latest
version 2024/2025
Steep Fluorescein Pattern - ANSWER -Bright green pooling center, very faint green pooling on
diameter of lens
Flat Fluorescein Pattern - ANSWER -Bright green pooling on diameter of lens, very faint green
in center
Against-the-rule Astigmatism Pattern - ANSWER -Bright green pooling horizontally, faint green
pooling vertically
With-the-rule Astigmatism Pattern - ANSWER -Bright green pooling vertically, faint green
pooling horizontally
Prism Ballast - ANSWER -Common technique to stabilize lens from rotating. Added thickness
will position lens inferiorly (bottom of cornea)
Truncation - ANSWER -Cutting off .50mm to 1.50mm of bottom edge of lens to provide
stability. Reduces diameter, making a looser fit.
Double Slab-off - ANSWER -Lens is thicker centrally and thinner at top and bottom of lens.
Provides comfort to wearer, but may cause some stability issues.
Aspheric Lens Design - ANSWER -
Hyperflange - ANSWER -Used to correct high riding minus lenses.
Myoflange - ANSWER -Used to correct low riding plus lenses.
Monovision - ANSWER -Corrects presbyopia in contact wearers. One eye uses distance
(dominant) and the other eye uses reading (resessive)
, Segment Bifocal - ANSWER -Same concept as spectacle bifocal. Must be prism ballast. Often
crescent shaped.
Toric Lenses - ANSWER -Anterior (front surface), back spherical surface or posterior (back
surface), toric back curve
Front Toric Lens - ANSWER -Corrects a low to moderate amount of corneal astigmatism
Back Toric Lens - ANSWER -Corrects a mid to high amount of corneal astigmatism
Bitoric Lens - ANSWER -Corrects 1.50D of corneal astigmatism and high residual astigmatism
Aphakic - ANSWER -Condition of no crystalline lens
Psuedophakic - ANSWER -Implant, intraocular lens
Corneal Edema - ANSWER -Always causes a poor fitting lens
Spectacle Blur - ANSWER -Temporary blurred vision upon switching from contact lenses to
eyeglasses
Crystalline Lens - ANSWER -The main focusing mechanism of the eye
The Main Supply of Oxygen to the cornea is provided by - ANSWER -Tear Film
Keratometry mires which are only clear when the wearer blinks are indicative of a - ANSWER -
Steep Fit
Keratometry mires which blur immediately following blink are indicative of a - ANSWER -Flat
Fit
A rigid contact lens shows a flourescein pattern inferiorly and superiorly beneath the lens. This is
indicative of which type of astigmatism - ANSWER -With-the-rule
A bi-toric rigid lens will show - ANSWER -Two base curves on the radiuscope, sphero-
cylindrical rx on the lensometer
The ANSI tolerance for a soft lens diameter is - ANSWER -±0.25