Retinal Image Quality Flashcards
1. All of the following optical aberrations degrade the clarity of an image from an off axis object emitting monochromatic light, except which one? A. Barrel distortion B. Coma C. Astigmatism of oblique incidence D. Lateral chromatic aberration E. Pincushion distortion
Lateral Chromatic Aberration
Which of the following statements concerning spherical aberrations in the average eye is NOT correct?
A. The amount and nature of spherical aberration varies with the level of accommodation
B. In the unaccommodated state the eye exhibits approximately +1.00D positive spherical aberration
C. An eye accommodating 3.00D will have negative spherical aberration.
D. An eye accommodating 1.00D will have minimal spherical aberration
E. Spherical aberration in a given eye is the same in all meridians without variation.
Spherical aberration in a given eye is the same in all meridians without variation
Which of the following statements concerning the optical aberrations in the average unaccommodated eye is NOT correct?
a. The combination of the cornea and the pupil produce pincushion distortion b. The combination of the crystalline lens and pupil produce barrel distortion c. The curvature of the retina minimizes the effects of astigmatism of oblique incidence and curvature of field d. Having large pupils reduces the blur from spherical aberration. e. The amount of coma increases as the object moves away from the optical axis.
Having large pupils reduces the blur from spherical aberration. (it actually increases the blur)
Which of the following accurately describes the effect of fogging our patients on the duochrome test (Red-Green test)?
a. Fogging makes a patient blurry and so that they can’t see colors, only black and white
b. Fogging brings the chromatic interval to focus behind the retina
c. Fogging removes all colors from our patients’ perception except red and green
d. Fogging guarantees that a patient is not accommodating which places the red end of the chromatic interval closer to the retina
e. Fogging makes a black letter look greener in color
Fogging guarantees that a patient is not accommodating which places the red end of the chromatic interval closer to the retina
Which of the following statements concerning chromatic aberrations in the average adult eye is correct?
a. Assuming the eye is emmetropic for 500nm light, the eye would be myopic for 600nm light. b. The eye has about 0.75D longitudinal chromatic aberration c. Lateral chromatic aberration is due to the different image locations on the optical axis for short verses long wavelengths. d. When viewing a distant target most individuals prefer to have relatively short wavelength light focused on the retina. e. The amount of longitudinal chromatic aberration is variable from one individual to the next.
The eye has about 0.75D longitudinal chromatic aberration
The fact that the retina is concave with respect to object space helps to minimize the effects of ____________
a. oblique astigmatism and coma b. oblique astigmatism and curvature of field c. curvature of field and distortion d. distortion and coma e. curvature of field and coma
Oblique astigmatism and curvature of field
Which is true in reference to the importance of aberrations to human vision?
a. Spherical aberration is more bothersome in larger pupils b. Coma prevents clarity for emmetropes, myopes and hyperopes c. Astigmatism of oblique incidence is not correctable and is very bothersome. d. Distortion disturbs our binocular vision e. Curvature of field is extremely disturbing because the field curves opposite to the shape of our retina.
Spherical aberration is more bothersome in larger pupils
Which of the following statements about chromatic aberrations is NOT true?
a. Chromatic aberrations are due to dispersion.
b. The aberrations are larger at the red end of the spectrum than at the blue end for all types of refractive error.
c. For a myope, the red letter appears to be sharper than the green letter in the red-green test.
d. For a hyperopic patient that is not accommodating the green letter appears to be sharper than the red letter in the red-green test.
e. For an emmetrope, who is accommodating 1.00D for distance, the red letter appears to be sharper than the green letter in the red-green test.
The aberrations are larger at the red end of the spectrum than at the blue end for all types of refractive error.
. In the human eye, spherical aberrations are minimum when we accommodate
a. 0D
b. 0.50D
c. 1.50D
d. 3.00D
e. None of the above since spherical aberrations are never minimized
1.50D
All of the following can degrade the clarity of an image from an on axis object emitting white light through a series of lenses and apertures (like an eye), except which one?
a. Spherical aberration b. Pincushion distortion c. Longitudinal chromatic aberration d. Diffraction
Pincushion
Negative coma and positive coma differ in the sense that
a. Positive coma has its base (tail) closer to the optical axis than its point (or head)
b. Negative coma has its head or point closer to the optical axis than its base (or tail)
c. Positive coma has its head (point) closer to the optical axis than its base (tail)
d. Negative coma images below the optical axis
e. Positive coma images above the optical axis
c. Positive coma has its head (point) closer to the optical axis than its base (tail)
Which is a correct description of the procedure for measuring wavefront aberrations?
A. Light is focused on the retina and when it bounces back out of the eye through all the ocular components the wavefront is captured and analyzed
B. Light is focused on the cornea and when it bounces back off the cornea the wavefront is captured and analyzed
C. Light is focused on the tear film and when it bounces back off of the tear film the wavefront is captured and analyzed
D. Light is focused on the ocular lens and when it bounces back off the ocular lens the wavefront is captured and analyzed
E. Light is focused on the pupil and when it bounces back off the pupil the wavefront is captured and analyzed
A. Light is focused on the retina and when it bounces back out of the eye through all the ocular components the wavefront is captured and analyzed
n reference to higher order aberrations, which of the following is NOT an accurate statement about Coma and Spherical Aberration?
A. They are the HOAs most prevalent in a normal population
B. They are the HOAs most commonly induced by conventional LASIK
C. They have the most impact on visual outcome
D. They are minimized if a patient has smaller pupil size
E. They are not as common as trefoil and quadrafoil.
E. They are not as common as trefoil and quadrafoil.
