7: Refractive States of the Eye Flashcards
in an unaccommodated myopic eye, light from a distant object is image:
anterior to the fovea
in an unaccommodated hyperopic eye, light from a distant object is imaged:
posterior to the fovea
in myopia, the eye’s power is too ____ for its axial length
great
in hyperopia, the eye’s power is too ____ for its axial length
low
define the far point of the eye (R)
it is the object point conjugate with the fovea (R’) of the unaccommodated eye
define the far point distance (k)
is that from the first principal point (P) of the eye to the far point (R)
where is the far point of the myopia eye located?
is located in real space somewhere closer than infinity
are the far point distances (k) negative or positive for myopia and hyperopia
myopic eye: k is negative (-)
hyperopia eye: k is positive (+)
where is the far point of the hyperopic eye located?
the far point is a virtual object point located somewhere behind the corneal vertex
what is the ocular refraction (K)?
it is the reciprocal of the far point distance k
ocular refraction depends on a balance between the:
eyeball length and the eye power
total hyperopia is
the amount of hyperopia determined with ‘adequate’ cycloplegia
manifest hyperopia is
the portion of the total that can be obtained without cycloplegia
latent hyperopia is
the portion of the total that remains hidden (or latent) without cycloplegia
(determined by calculation)
facultative component of hyperopia
can be overcome with accommodation
this includes the latent component
