W6_02 Optics Flashcards
1
Q
the snellen fraction refers to what?
A
e.g. 20/20 vision is a snellen fraction.
2
Q
how far away do you test vision with the snellen fraction?
A
6 metres
3
Q
vision to be able to drive?
A
20/50
4
Q
legally blind vision?
A
20/200
5
Q
OD refers to what?
OS refers to what?
OU refers to what?
A
OD = right eye OS = left eye OU = both eyes
6
Q
what is emmetropia?
A
normal refractive error
7
Q
what is presbyopia?
A
near objects out of focus;
insufficient accommodation;
focus is behind retina
8
Q
what is myopia?
A
far objects out of focus;
power too high;
focus in front of retina
9
Q
what is hyperopia?
A
near objects out of focus;
eye is too short;
focus is behind retina
10
Q
what is astigmatism?
A
focusing is ellipsoidal (so never sharp)
