Intro to Refractive Condition Flashcards
What happens when there is a mismatch between the optical power, size, and shape of the eye?
Ametropia.
What happens when there is no mismatch between the optical power, size, and shape of the eye?
Emmetropia.
What are the most common causes of myopia?
A slightly longer-than-average eye, or a cornea that is slightly steeper than normal, and hence more powerful.
What are the most common causes of hyperopia?
A slightly shorter-than-average eye, or a cornea that is slightly flatter than normal, and hence less powerful.
What distance is the minimum to assume optical infinity?
Six meters.
What is refraction condition?
The relationship between the optical power(s) and the size and shape of the eyeball that defines the precision of image clarity of the eye.
What type of lens is used to correct for myopia?
Negative power, concave lens (lens is thicker at the edges).
What type of lens is used to correct for hyperopia?
Positive power, convex lens (lens is thinner at the edges).
What is the power (of the eye) needed to achieve emmetropia, assuming the eye measures 24 mm front to back?
(1/.024m) = 41.67D
What is asthenopia?
Eye-ache.
What is the result of ciliary muscle contraction?
The tension on the zonule fibers lessens, and the lens is allowed to resume its preferred spherical shape. This leads to increased optical power (accommodation).
