L3 Power and Lenses Flashcards Preview

Opthalmic Lenses and Dispensing > L3 Power and Lenses > Flashcards

Flashcards in L3 Power and Lenses Deck (4):

Lensmakers Equation

F = (n-1)(1/r1 - 1/r2)
for overall power of the lens


Fundamental Paraxial Equation



Effective Power of the Lens

In distance vision:
The back vertex distance in mm is the distance bet the back vertex of the lens and the cornea and it affects the power of the lens (BVD)
If you increase the distance from the lens to the eye then the lens becomes more positive - so you have to make the prescribed lens more negative


Does thickness matter?

When light travels through a medium other than air, so real thickness of the material (t) can be replaced by an equivalent thickness of air (d)