Best Form Lenses Flashcards
1
Q
The tschernigs ellipses takes what into account
A
Refractive index and distance of lens from centre of rotation of the eye has been factored in
2
Q
Why use aspheric lenses
A
- Flatter lenses – lower sags means that a lens can be thinner and lighter
- Control of aberrations – particularly oblique astigmatisms, alternative to cosmetically bad best form spherical lens
- Control of distortions
3
Q
What are aspheric lenses
A
A lens with one or more surfaces that is aspherical
4
Q
Aspheric lenses help to reduce…
A
Lens thickness in negative lenses
