Soft Lens Fitting & Care
What does TBUT measure?
Tear film stability / break-up time
Which instrument verifies base curve?
Radiuscope
What does the acronym LARS stand for?
Left Add, Right Subtract
What does ANSI stand for?
American National Standards Institute
A soft toric lens rotates 10° to the right. How do you adjust the axis?
Subtract 10° (Right Subtract)
What is residual astigmatism?
Cylinder not explained by cornea
Which in-office tool smooths rough lens edges?
Polishing / blending tool
Which stabilization method uses the watermelon seed principle?
Prism ballast
What color marks the right GP lens?
Green
A patient’s Rx cyl = -1.00, corneal cyl = -0.50. What type of astigmatism remains?
Residual
A patient’s HVID is 13.0 mm. Why might a 13.2 mm lens be inadequate?
Too small for proper coverage
Pooling in the center fluorescein pattern means the lens is too _____.
Steep
Each “clock minute” of lens rotation = how many degrees?
6°
Name two parameters ANSI requires for GP verification.
Any two: Diameter, optic zone, base curve, power, thickness, optical quality, color
Which instrument verifies truncation on a GP lens?
Diameter gauge
Which solution step removes protein deposits over time?
Enzymatic cleaner
Which polishing compound degrades GP lenses and should never be used?
Silvo (ammonia-based)
In toric calculations, how much of the spectacle cylinder power is used?
75%
What’s the purpose of fenestration in a GP lens?
Loosen the fit (not for tear exchange)
Name two common in-office modifications for GP lenses.
Any two: Polishing, power changes, edge modification, blending, diameter reduction
What lens modality is the Kontur 55 Sphere?
Conventional daily wear
A GP lens shows two different curves in the radiuscope and one power reading in the lensometer. What’s the likely problem?
Warped lens
Which stabilization method is most comfortable but least stable?
Dynamic stabilization / double slab-off
A warped GP lens is suspected. Which two instruments together confirm this?
Lensometer + Radiuscope
Compare front vs. back toric design stability: which provides better axis orientation, and why?
Back surface toric; stabilizes against cornea, especially ATR