Astigmatism Flashcards
All the patients are uncorrected and viewing a distant point source of light. Which patient will report that the distant target looks like an oval with the long axis in the horizontal meridian?
a. –3.00 –3.00 x 180
b. +3.00 –6.00 x 180
c. +3.00 –4.00 x 180
d. +3.00 –9.00 x 180
e. +3.00 –1.50 x 90
WTR Mixed Astigmatism:
ex. +3.00 -4.00 x 180
Assume all the individuals are viewing a distant circular target, and all the ametropias are refractive in nature. Which of the following individuals would have the largest retinal image in the horizontal meridian?
a. an emmetrope
b. +5.00 –2.50 x 90
c. +5.00 –2.50 x 180
d. +0.50 –2.50 x 90
e. –2.50 –2.50 x 180
A pt who has more plus in the magnified in the horizontal meridian
ex. +5.00 -2.50 x 180
A patient is corrected for infinity with a +6.00 –8.00 x 180 spectacle lens positioned 20 mm in front of the eye’s principal plane. What is the patient’s principal plane refractive error?
a. +6.82 –4.90 x 180
b. +6.82 –8.74 x 180
c. +6.82 –8.82 x 180
d. +6.82 –8.26 x 180
e. +5.36 –7.27 x 180
b. +6.82 –8.74 x 180
A distant circular object subtends a visual angle of 0.3 radians. What would be the angle of incidence of the chief ray for the vertical meridian of an astigmat corrected with a –4.00 –4.00 x 90 spectacle lens positioned 20 mm in front of the eyes principal plane? Assume effectivity is significant for errors beyond 4.00D just for this example.
a. 0.26 radians
b. 0.24 radians
c. 0.28 radians
d. 0.29 radians
e. 0.22 radians
0.28 radians
Which of the following refractive corrections would be classified as a compound hyperopic, with-the-rule astigmatism?
a. +5.00 –3.00 x 90
b. +5.00 –6.00 x 180
c. +3.00 –0.50 x 180
d. +3.00 –3.00 x 180
e. +5.00 –6.00 x 90
c. +3.00 –0.50 x 180
A refractive ametrope has a +7.00 –3.50 x 180 ocular Rx. To correct the patient for distance, what would be the desired power of a spectacle lens that was positioned 20 mm in front of the eye’s principal plane?
a. +6.14 –3.07 x 180
b. +6.14 –3.27 x180
c. +6.14 –2.87 x 180
d. +6.36 –3.27 x 180
e. +6.14 –3.50 x 180
c. +6.14 –2.87 x 180
The following individuals are viewing a distant point source. Assuming that the patients are uncorrected and unaccommodated, which one will have a retinal image that is oval in shape with the long axis of the ellipse oriented vertically?
a. a compound hyperopic, A-t-R astigmat
b. a compound hyperopic, W-t-R astigmat
c. a compound myopic, A-t-R astigmat
d. a simple hyperopic, A-t-R astigmat
e. a simple myopic, A-t-R astigmat
a. a compound hyperopic, A-t-R astigmat
The far point for the vertical meridian of the eye is 10cm in front of the eye’s principal plane. The far point for the horizontal meridian is 20cm behind the eye’s principal plane (i.e., behind the retina). What is the eye’s ocular refractive correction?
a. +5.00 –10.00 x 180
b. +5.00 –10.00 x 90
c. +5.00 – 15.00 x 90
d. +5.00 –15.00 x 180
e. +10.00 –15.00 x 90
d. +5.00 –15.00 x 180
Assume that all of the ametropias are refractive in nature, the spectacle lenses correct the eyes for infinity, the vertex distance is 15mm, and all the individuals are viewing the same circular distant object. Which of the following spectacle plane refractive corrections would produce the largest “in focus” retinal image in the horizontal meridian?
a. an emmetrope
b. –2.00 –2.00 x 90
c. –2.00 –2.00 x 180
d. +4.00 –2.00 x 90
e. +4.00 –2.00 x 180
e. +4.00 –2.00 x 180
. For the elderly, astigmatism is
a. with the rule.
b. against the rule.
c. oblique.
d. equally divided between WTR and ATR.
e. very rare.
b. against the rule
Which of the following is not true concerning the magnification differences between two meridians in spectacle corrected high astigmatism?
a. It can cause meridional aniseikonia
b. It can cause spatial distortions
c. It makes a leaf room not look like a normal square shape
d. Selective magnification of the horizontal meridian in the right eye extends the right side of the leaf room back further than the left side
e. Selective magnification of the horizontal meridian in the right eye extends the left side of the leaf room back further than the right side
e. Selective magnification of the horizontal meridian in the right eye extends the left side of the leaf room back further than the right side
Irregular astigmatism means that
a. the principal meridians are not perpendicular.
b. the residual astigmatism is not ATR.
c. there is an optical distortion due to irregular eye movements.
d. the astigmatism changes in an irregular way with age.
e. the astigmatism causes the 1st PS image to appear irregular.
a. the principal meridians are not perpendicular.
