Lens designs

Question 1

Prism ballast

Answer 1

Most common stabilization technique
- Base down prism in the peripheral carrier
- Gravity dependant
- Increased prism means thicker and heavier lens
Ex. Biofinity, Ultras, AirOptix

Question 2

Perriballast

Answer 2

Has a minus power lenticular carrier to produce prism like rotational effect
- Lens not as thick and heavy
Ex. Biotrue

Question 3

Dynamic Stabilization

Answer 3

Overall thinner profile than ballast design
- Prism free optic zone
- Has biodirectional stabilization design allowing lens to settle/realign faster
Ex. Acuvue

Question 4

Truncation

Answer 4

Rarely used with soft lenses
Bottom of lens is cut off

Question 5

Rotation of Toric Lens

Answer 5

LARS
Left add right subtract

Question 6

Multifocals considerations

Answer 6

• Pupil size
• Eye dominance
• Refractive status of patient
• VA should be at least 20/30
  Goal is to decrease dependency on glasses not eliminate

Question 7

Monovision

Answer 7

Dominant eye is corrected for distance, opposite for near
- Oldest option for presbyopes
- Loss of stereopsis