34 Questions
What does a larger base curve result in?
More flat lens
What does a smaller base curve result in?
More steep lens
By how much does the flat diameter increase as the flat K goes up by 0.2?
0.5
What is the base curve (BC) value mentioned in the text?
7.23 mm
What does no movement in blink or up gaze indicate about the base curve of the lens?
The base curve is too tight for the cornea
What is the purpose of the push-up test mentioned in the text?
To check for lens tightness
What should be quantified when observing movement of the lens during blinking?
$1mm dot on nasal edge
What does it indicate if there is no movement when focusing a 1mm circle on the inferior nasal aspect of the soft lens and half on bulbar conj during blinking?
Lens is too tight
What is half a movement of the dotted line during blinking equivalent to?
$1mm dot on nasal edge
"+ push-up test" is used to determine what about the lens?
There is lens tightness
What does a negative push-up test indicate?
The lens is tight on the eye and has to come off or with wearing time, it will become tighter
What does the push up test help determine?
The interaction between the lid and the lens
Why might the lens feel sore and cause red eyes?
Insufficient tear exchange resulting in dryness
What is the primary purpose of performing a piggy back lens system?
To address limbal region issues
How is the base curve related to the fit of the lens?
A steeper base curve tightens the fit
What is indicated by excessive lens movement during primary and up gaze?
Inadequate tear exchange and discomfort
What does the presence of central air bubbles in the lens indicate?
Tight fit with no tear exchange
What is a common method to resolve a loose lens fit?
Steepening the base curve while keeping diameter constant
Why might there be hyperemia in the nasal quadrant when using a piggy back lens system?
Improper fitting of the GP lens
What does it mean if the lens edge does not move and stays stationary?
The base curve is too tight or there is little friction
What is indicated by more than 0.5mm of lag down as the patient looks up or laterally?
The lens will come more down to bulbar conj affecting correction
How is the sag depth related to changing the lens fit?
Enlarging diameter increases sag depth for a tighter fit.
What is the main difference between Hydrogel and Silicon Hydrogel lenses?
Silicon Hydrogel lenses have lower water content than Hydrogel lenses.
What happens if a person with dry eyes is fitted with a contact lens with high water content?
The lens becomes tighter, causing more water loss.
What is the purpose of the ultrasoft hydrophilic polymer network on the surface of DAILIES TOTAL1® lenses?
To reduce friction and minimize interaction with the eye tissues.
What is the potential consequence of using reusable Silicon Hydrogel lenses?
Increased risk of corneal ulcers due to trapped debris.
What should be considered when selecting a replacement lens care appropriate for a patient?
The power range that suits the patient.
What should be avoided when fitting soft lenses using keratometry?
Risking exposure of the limbal region.
How does oxygen transmission relate to the water content in contact lenses?
Lower water content results in higher oxygen permeability.
Why do Silicon Hydrogel lenses have more stiffness compared to Hydrogel lenses?
Because of the addition of silicone in the lens material.
What is the potential consequence of insufficient tear exchange under a soft lens?
Increased risk of red eye and trapped debris.
Why is fitting a person with dry eyes with a contact lens with high water content not recommended?
The lens becomes tighter, leading to increased water loss.
Why is corneal topography not used to fit soft lenses?
Keratometry is used instead for measuring 3mm of the cornea.
What is the role of keratometry in fitting soft lenses?
It measures 3mm of the cornea for better fit and comfort.
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