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Opthalmic Lenses and Dispensing > L1 Introduction > Flashcards

Flashcards in L1 Introduction Deck (8):
1

Spherical Lenses

- Power is the same all around the lens, in all directions
- Used to correct myopic/hypermetropic patients only

2

Toric Lenses

Power of cylindrical lens = no power along the axis, has 2 principal meridians at perpendicular meridians to one another
- axis direction of cylinder is always 90 to meridian where the power is positioned - axis always 90 to cyl power
-still has a max and min power but min power is not zero as it is in a spherical lens
toric is a spherical and cyl lens combined to neutralise both meridians

3

Prisms

-Transparent block of material, has an apex and a base at the bottom which is the thickest part of the lens
-Light deviates towards the base of prism and its because it slows down as it passes through the lens
- Because light is deviated towards the base, vision and so image is deviated towards the apex

4

Why is a prism used?

- Used for patients with muscle imbalance
- there are some pathologies which cause frequent change in vision, so surgery isnt an option
- some people are born with muscle imabalances - EOM can be too long/short so pull eye in a certain direction
- can still get px to see one image, even if both eyes see diff images

5

Surfaces of a lens?

Front surface = away from eye
Back Surface = closest to eye

6

Plano concave/ Plano convex

No power

7

Bi concave/Bi convex

-same curve on front and back surface. but not necessarily of equal power
- when power is same = equi convex/equi concave

8

Meniscus

Most common lens type = gives best optics so ensures image quality
- has one convex and one concave curve