Optics: Monochromatic Aberations 2 Flashcards
What percentage of total aberrations is contributed by defocus and astigmatism?
92%
If astigmatism and refocus make up 92% of aberrations, what makes up the other 8%?
Higher order aberrations
What is the most significant contributor to the higher order aberrations?
Primary spherical aberrations
How are corneal aberrations measured?
From the anterior cornea in a topographer
How are ocular aberrations measured?
For the entire eye using aberrometers
What are internal aberrations?
Posterior corneal aberration plus crystalline lens optics
The aberrations of the internal optics =
Whole eye aberrations - corneal aberrations
The magnitude of aberrations is ________ in the cornea and the internal optics than they are in the whole eye
Larger
What is the active role of the lens involved with aberrations?
Partially reducing the aberrations produced by the cornea
What is partly the reason for the increase of optical aberrations with age?
The disruption of the compensation of corneal and internal optics aberrations
Which direction do the values of spherical aberrations shift to as you age?
More positive direction
Do aberrations change with accommodation?
Yes, since the shape of the lens changes, so do the aberrations
Which aberration has the greatest change with accommodation?
Spherical aberrations (change is always negative)
Which other aberrations changed with accommodation?
Coma and astigmatism (direction of change was variable)
In what type of eye is corneal spherical aberrations typically higher?
Hyperopic eye
Does totoal spherical aberration increase with age? Which eyes experience this more?
Yes, hyperopic eyes
The optical errors of the eye generally increase with _______ ______
Incident angle
What is the peripheral visual field?
The area in the object space that is not imaged to the macula of the eye
Monocular visual filed temporally, nasally, inferiorly, and superiorly
-temp: 90
-nasal: 60
-infer: 70
-super: 50
What is the largest aberration on the optical axis?
Spherical aberrations
Which aberration increases and becomes significant with off-axis angles?
Coma
Which aberration will dominate the further you go out into the periphery?
Oblique astigmatism
Rates entering the pupil further away from the optical axis are refracted _______
More
Marginal rays converge at different ________ and ________ than the paraxial rays through the center of pupil
Distances and height
In the human eye, off-axis coma’s blurred tail points towards the __________ axis which is _________ coma
Optical axis, positive coma
What happens to spherical aberration in the periphery?
Stays relatively unchanged with increasing angle
What is oblique astigmatism?
Astigmatism associated with peripheral vision
What is field of curvature?
The further the object is moved off-axis the further it is from the image plane of the on-axis rays resulting in a curved image plane
The field of curvature aberration makes the eye more ______ in the oblique angles
More myopic
What is distortion?
A point source that is imaged as a point but not at the expected position
(Either further (positive) or closer (negative) to the optical axis)
Is barrel distortion positive or negative?
Negative
Is pincushion distortion positive or negative?
Positive
For off axis aberrations, astigmatism is increases __________ and coma is increased _______ with he horizontal viewing angle
Quadratically, linearly
