Section H: Ophthalmic Lenses

Question 1

Prism Dioptre

Answer 1

1 prism dioptre is the angle whose tangent is 1/100

Question 2

How to convert angle into prism dioptres

Answer 2

P=100xtan(d)

Question 3

How to find angle of deviation

Answer 3

P=100xtan(d) REARRANGE

Tan-1 (p/100)

Question 4

How to find apical angle

Answer 4

1. calc d= Tan-1 (p/100)
2. calc a = (n-1)a REARRANGE
   d/n-1 = a

Question 5

Whta to do when asked to find the true power?

Answer 5

use similar triangles

Question 6

What needs to be remembered about displacement?

Answer 6

1 prism dioptre causes displacement 1cm @ 1m etc.

Question 7

Refracting edge

Answer 7

point on prism where two refractive surface meet

Question 8

Principal section

Answer 8

vertex line from apex to prism base base, is cut perpendicular

Question 9

Prism

Answer 9

Transparent optical medium bounded by two plane polished surfaces

Question 10

prismatic lens

Answer 10

a lens designed to exert a certain prismatic effect at the centration point

Question 11

How to work out the single resultant

Answer 11

do pythag of pv and ph

then tan-1(Pv/Ph)