Lens Options Flashcards
If cra greater than 1.00 d
Front surface toric
If flattest and steepest differ by more than 3.00 d
Back surface of bi toric
If cra greater than 1.00d and k’s less than 3.00d
Front surface toric solves optical problem
Spherical rigid
If cra less than 1.00d
K’s less than 3.00d
Blend curve needed if
Secondary curve is 8.9mm
Perif curve is 12mm
Blend curve is 10.5mm
Rigid lens diameter
7.00mm to 10.5mm
Soft lens diameter
12.5mm to 16mm
Lenticular flange. 2 types
Myoflange
Hyperflange or CN bevel
Myoflange
Adds thickness
Remember: edge like lens for myopia (flared)
Hyperflange
Thinned edges
Like lens for hyperope flat on edge
Prism ballast
Weights bottom edge (inferiorly). For proper orientation of astigmatic or bifocal CL
Squeezing action watermelon seed effect
Truncation
Removal of inferior or superior portion
For front toric or bifocal
Back surface toric
Two curves align with two principal meridians
Which lens design:
If astig less that 1.00d
Rx sphere to cyl ratio 3:1
Spherical soft
Patients can tolerate up to 1.00d uncorrected astig as long as sphere power is 3x stronger than cyl
Which lens design:
Rx astig greater than 1.00d
Sphere to cyl ratio less than 3:1
Toric soft lens
Need axis stabilization
If sphere is not 3x stronger than cyl needs toric
