UNIT FIVE - GP Flashcards
What are the three lens design goals necessary for GP lenses?
Optical ( clarity & stability)
Physiological ( maintain ocular integrity)
Comfort
What are some key factors when looking at the optical design goal for GP lenses?
Good centralization Minimum post blink movement Adequate optical zone Minimum lens flexure Deposit resistance
What are some factors when looking at the physiological design goal for GP lenses?
Adequate transmissibility
Sufficient movement ( waste products & oxygen
Minimum corneal bearing
What are some factors when looking at the comfort design goal for GP lenses?
Minimum lid interaction
Tear layer thickness ( Vault)
CPC (B.C. Radius)
POZ diameter
Power of Tear layer ( lacrimal lens)
SAM - steeper add minus
FAP - flatter add plus
What does the acronym SAM stand for?
Steeper add minus
( when referring to the lacrimal lens or power of tear layer) 
What does the acronym FAP stand for?
Flatter add plus
(when referring to the lacrimal lens or power of tear layer)
Why is a peripheral curve necessary?
Allows fresh reservoir of tears to collect around the lens between blinks.
Allows tear exchange between blinks.
Permits lens to glide over flatter peripheral regions of cornea.
What are some of the determining factors for peripheral curves?
Lens diameter, POZ diameter, CPC radius, corneal shape.
What does center thickness effect?
Transmissibility
Centering and movement (gravity)
Lens Flexure
Edge Thickness (hyperflange, myoflange) 
What are some of the determining factors for center thickness?
Prescription
Lens diameter
Lens material
Lens design
What are the General rules for rigid lens design? (3 total)
CPC OR BC
1) as the degree of astigmatism increases, a steeper base curve is needed for centralization.
2) as the size of the OZ increases, The CPC must be made flatter to maintain the correct vault.
3) increasing the vault causes the lens to fit tighter and reduces movement.
What are the General rules for rigid lens design? (3 total)
LENS DIAMETER
1) large (11.5mm), flat (<42.00D) corneas require large lenses.
2) Large palpebral apertures (>10mm) require larger lenses.
3) less than a +2mm upper lid position may require a larger lid attachment design or an inter-palpebral design.
What are the General rules for rigid lens design? (2 total)
OPTICAL ZONE DIAMETER
1) large pupils (>4mm) require larger optical zones.
2) the optical zone usually varies with the lens diameter.