Lec 7: Axes and Rx Flashcards
In distance vision, all reference angles are what?
equal
- relationship between ocular parameters and Rx
- paraxial, (Snell’s Law: sinθ ≅ θ, therefore nθ!= n’θ’)
refractive state
n / distance from eye’s anterior principal plane to visual target (in meters). Refractive index n=1 in air.
target vergence
= target vergence required to maximize retinal image quality = vergence of retinal conjugate plane
refractive state
= refractive state of the un-accommodated eye
refractive error
optical conjugate of the fovea in the un-accommodated eye. A target located at the far point maximizes retinal image quality in the relaxed eye.
far point
= a change in target vergence relative to the eye’s far point.
accommodative stimulus
= a change in refractive state that occurs as a result of an accommodative stimulus.
accommodative response
Dioptric focusing errors in object and image space are what?
are identical. All distances are measured relative to the eye’s principal points.
- Interpretation of K as vergence of far point of eye
Definition: the far point of the eye is optically conjugate to the fovea when accommodation is relaxed.
- Interpretation of K as power of the correcting lens
Definition: the refractive correction for a relaxed eye is that lens which allows the eye to produce a clearly focused retinal image for distant objects.
mm of Cornea + lens
5.55 mm
reduced eye axial length
22.22 mm
K of reduced eye
60 D
- Modeling refractive error: altered axial length
clinical rule of thumb
3D refractive error per 1 mm of elongation
