contact lenses

Question 1

toric lens nasal swing

Answer 1

naturally soft torics have a nasal swing of 5-10 degrees due to pressure from top lid

every 5 mins on cornea = 30 degrees

CAAS (clockwise add, anti subtract)

Question 2

prism ballast

Answer 2

stabilisation from prism at bottom of lens

1-1.5 base down prism

relied on lid force acting on thickness differences to stabilise lens in eye

Question 3

peri ballast

Answer 3

uses thickness differences to stabilise lens by creating a base down prism effect

lens thinned at superior region

Question 4

truncation vs double slab off

Answer 4

truncation aligned with lower lid margin to stabilise lens

double slab off = thin zone superiorly and inferiorly - lid forces maintain orientation

Question 5

accelerated stabilisation design

Answer 5

thin zone superior + inferiorly

4 active zones of added thickness in mid periphery of lens

designed to be actively rotated into place upon blinking

Question 6

opteyes toric

Answer 6

• Dk/t 116
• XR has good power range -10 to +10
• up to -5.75 cyl
• periballast design

Question 7

linarial toric

Answer 7

• Dk/t 80
• range from -6 to +6
• up to -2.25 cyl
• periballast design

Question 8

soft toric designs

Answer 8

peri ballast
prism ballast
truncation
double slab off
accelerated stabilisation

Question 9

back surface vs front surface toric design

Answer 9

back surface corneal cyl >2D - good for corneal astigmatism

front surface - good for lenticular astigmatism