Varifocals Flashcards
(19 cards)
What measurements are needed for varifocals?
Mono distance PD
Heights to pupil centre
Panto
BVD if >3D
What are the features of hard varifocal designs?
Large distance area
Narrow inter area
Wide near area
What aberrations might be noticed when wearing a hard varifocal design?
Astigmatism nasally and temporally at inter and near
What types of pxs are hard varifocal designs good for?
Previous bifocal wearers
Give an example of a hard varifocal lens design.
Sola Graduate
What are the features of soft varifocal designs?
Smaller distance area than hard
Large inter area
Narrow near area
What aberrations might be noticed when wearing a soft varifocal design?
Astigmatism at distance
What types of pxs are soft varifocal designs good for?
First time wearers
Lots of VDU use
Give an example of a soft varifocal lens design.
Varilux Liberty
What are the features of supersoft varifocal designs?
Large distance, inter and near areas
Minimal abberations noticed
What types of pxs are supersoft varifocal designs good for?
All presbyopes
Non-tol to other types
Give an example of a supersoft varifocal lens design.
Varilux Physio
What do isocylinder line plots represent in representations of varifocal lenses?
The area of same surface aberrational astigmatism
What do vector plots represent in representations of varifocal lenses?
The area of same surface aberrational astigmatism with the direction of the cyl power
What do mean power plots represent in representations of varifocal lenses?
The distribution of the progressive add
How does the power profile graph represent varifocal lenses?
Shows line where surface aberrational astigmatism ends
How does prism thinning work in a varifocal?
BD prism is added to counteract the BU prism caused by increasing plus towards the bottom of the lens.
Removes 2/3’s of add thickness.
How were traditional varifocal lenses manufactured?
Varifocal design moulded onto front surface
Power worked onto back surface
How are free-form lenses manufactured?
CAD used to customise and carve lens surface.
Can be back surface only (cheaper options) or both surfaces (individual lenses - more expensive, e.g. Essilor X Series needs Eyecode software to measure on px)
