Chapter 7 Refractive Management and Optics
7.1 Questions
Easy | Medium | Hard |
1. (Medium) Which of the following is correct regarding light waves?
Light rays from a point source are parallel in uniform media.
A light ray is a vector parallel to a wavefront surface.
Uniform heating of air causes a desert mirage.
Light waves maintain an identifiable direction during specular reflection.
2. (Medium) Which of the following is correct regarding magnification?
Transverse magnification can be calculated by dividing object distance by image distance.
Linear magnification is synonymous with transverse magnification.
Axial magnification refers to the area of the image perpendicular to the optical axis.
Longitudinal magnification is equal to the square of the transverse magnification.
3. (Hard) Which of the following is true regarding the concept of refractive index?
The refractive index (n) of a medium is the ratio of the speed of light in air to the speed of light in that medium.
Silicone has a different index of refraction at room temperature than at body temperature.
Dispersion of light occurs in a vacuum.
Cornea has a lower index of refraction than water.
4. (Easy) Which of the following is correct regarding Snell’s law?
The refractive index of both incident and transmitted medium must be known to calculate a transmission angle.
The Fermat principle was derived from Snell’s law.
Snell’s law relates the cosine of the incidence angle to the transmission angle.
Snell’s law is insufficient to calculate the critical angle of an interface.
5. (Medium) An object is 10 cm to the left of a +6 D lens. A +4 D lens is 25 cm to the right of the +6 D lens. Which of the following is true regarding the image of the object?
The image is 50 cm to the right of the +4 D lens, upright, and smaller.
There is no image formed by this system.
The image is 50 cm to the right of the +4 D lens, inverted, and larger.
The image is 50 cm to the left of the +4 D lens, inverted, and smaller.
6. (Hard) Which of the following is true about the central or chief ray in an optical system?
In ray tracing optics, the central ray is required to locate the image of an object.
In thin lens systems in uniform media, the central ray passes undeviated through the lens.
In lens systems with different media on alternate sides, the nodal point(s) are shifted toward the less dense medium.
The central ray may pass through one of the focal points in thick lens optics.
7. (Medium) Which of the following is true regarding Knapp’s law?
Knapp’s law is applicable at standard spectacle vertex distances of 10 to 15 mm.
The Badal principle is Knapp’s law applied to lensometers.
The optometer principle does not relate to Knapp’s law.
Knapp’s law is clinically very useful when prescribing spectacles.
8. (Medium) Which of the following correctly describes the parameters in a focal system?
+2 D objective, −5 D eyepiece, 30 cm apart, Keplerian, transverse magnification −0.4 ×
+2 D objective, +5 D eyepiece, 70 cm apart, Keplerian, transverse magnification +2.5 ×
+2 D objective, −5 D eyepiece, 30 cm apart, Galilean, transverse magnification +2.5 ×
+2 D objective, + 5 D eyepiece, 70 cm apart, Galilean, transverse magnification +0.4 ×
9. (Hard) Which of the following is correct regarding the power for a cornea with a radius of curvature of 10 mm? Use the standardized cornea index of refraction of n = 1.3375.
Refracting power +43.75 D
Reflecting power +200 D
Refracting power +33.75 D
Reflecting power −250 D
10. (Hard) If a 20 D posterior-chamber intraocular lens (IOL) is tilted 20 degrees around its horizontal axis, what is the functional power when viewing obliquely through the IOL?
+19.50 +1.50 × 090
+19.50 +2.00 × 180
+20.75 +2.75 × 180
+21.25 +3.50 × 090
11. (Medium) Regarding aberrations of ophthalmic lenses, which of the following is a correct pairing?
High minus lenses–pincushion distortion
Object off-axis–coma
Aspheric lenses–field curvature
High plus lenses–barrel distortion
12. (Hard) You stand 1 m from a concave “shaving” mirror with a 1-m radius of curvature. Which of the following is correct?
Your image is real and not magnified.
The reflecting power of the mirror is −2 D.
Your image is 100 cm behind the mirror.
Your image is erect.
13. (Easy) What is the result of combining the following spherocylindrical lenses?
+2.00 −3.00 × 180 and +3.00 +5.00 × 090
+5.00 +2.00 × 180
+1.00 +2.00 × 090
Plano −8.00 × 180
+2.00 +8.00 × 090
14. (Medium) Which of the following is true regarding Jack-son’s cross cylinders?
A cross cylinder of ± 0.50 D is appropriate for a patient with 20/70 best visual acuity (VA).
The spherical equivalent of a ±1.00 D Jackson cross cylinder is +0.50 D.
It is usually ground as a combination of two cylinders.
The spherocylinder +0.25 −0.50 × 180 is equivalent to a ±0.50-D Jackson cross cylinder.
15. (Medium) When the approximation of sin θ = θ is used in optical calculations, which of the following is not a correct notation of this?
Small-angle approximation
Paraxial approximation
First-order approximation
Radian approximation
16. (Hard) A patient is phakic and emmetropic in the right eye and aphakic in the left. With an aphakic contact lens with power +15.00, they report symptomatic aniseikonia. The patient refuses surgery. What should be done to improve the aniseikonia?
Reduce contact lens power to +12.00, wear +3.00 in spectacles over contact lens.
Increase contact lens power to +18.00, wear −3.00 in spectacles over contact lens.
Discontinue use of contact lenses and use full correction in spectacles.
Investigate other causes as contact lenses do not induce symptomatic aniseikonia.
17. (Easy) An eye focuses light on the fovea only when the inbound rays of light have positive vergence (see diagram). Where is the far point of the eye?
At infinity
In front of the eye
Behind the eye
There is insufficient information to determine the far point
18. (Medium) You are looking at the letter “E” on a street sign 20 m away. The letter is 1 m in height. The nodal point of your eye is 20 mm anterior to your retina. How large is the image on your retina?
2.0 mm
1.8 mm
1.0 mm
0.8 mm
19. (Hard) A person with myopia of 10 D has +48 D corneal power at the anterior surface and −5 D power at the posterior surface. If the refractive index of cornea = 1.37 and that of water = 1.33, which of the following ametropic results would you expect this person to have underwater?
+58 D hyperopia
58 D myopia
+43 D hyperopia
+33 D hyperopia
20. (Easy) Which of the following applies to the two diagrams of the same eye shown below looking at a point of light far away without accommodating? Assume the light rays are colored as shown.
The eye is myopic.
The eye is emmetropic.
The eye is hyperopic.
The eye is astigmatic.
21. (Medium) A patient’s retinas are conjugate with a plane 1/3 m in front of the eyes. Which of the following diagnoses is correct? Assume the patient is not wearing any refractive correction.
The patient is emmetropic and is accommodating 2 D.
The patient is myopic and is accommodating 2 D.
The patient is hyperopic and is accommodating 2 D.
The patient emmetropic and is not accommodating.
22. (Hard) You are performing retinoscopy on a pseudophakic patient. Without any lens in place, you notice a wide bright reflex with fast “with” movement in all directions. What is the patient’s approximate refraction?
−3.00
–2.00
−1.00
Plano
23. (Easy) You are measuring the manifest refraction of a pseudophakic patient using a Jackson cross cylinder. You start by correcting their sphere. Next, you determine the axis and then the magnitude of their astigmatism using the Jackson cross. What is the next step you should perform?
Refine the axis of cylinder with the Jackson cross.
Refine the spherical correction.
Use a duochrome red-green chart to ensure you haven’t overminused the patient.
Record their visual acuity.
24. (Medium) You want to measure the accommodative convergence to accommodation (AC/A) ratio in a child. You decide to use the gradient method. Which of the following is true of the gradient method?
You need to measure interpupillary distance.
You need to measure phorias at 6 m and again at 0.33 m.
You need to measure phorias at 6 m with and without −1.00 correction in front of both eyes.
None of the above.
25. (Medium) You perform manifest refraction on yourself in clinic. After you correct sphere, cylinder axis, cylinder power, and refine sphere, you see the following image on duochrome test. What is the correct next step, and why?
Add plus; the red light is focused in front of the retina.
Add plus; the red light is focused behind the retina.
Add minus; the red light is focused in front of the retina.
Add minus; the red light is focused behind the retina.
26. (Medium) A patient reads a letter E that is 4 mm in size and subtends an angle of 30 minutes of arc. What is the Snellen acuity?
20/120
20/600
3/4
0.5 M
27. (Easy) A hyperopic patient has right hypertropia. One may correct the deviation by decentering the lens correction by which of the following?
Right optical center downward
Left optical center downward
Right and left optical centers temporally
Right and left optical centers downward
28. (Medium) A young myopic patient complains of uncomfortable, new −1.50 OU glasses. The refraction has been verified. Optical centers are centrally placed. The lenses are ground correctly. Which of the following one may consider?
Aniseikonia
Meridional magnification
Pincushion distortion
Facial asymmetry
29. (Hard) Where should a +3 D lens be placed to correct a patient who can be corrected with a +10 D lens at vertex distance of 20 mm?
10 cm in front of the cornea
25 cm in front of the cornea
33 cm in front of the cornea
35 cm in front of the cornea
30. (Medium) The light filament in the retinoscope must be conjugate with which of the following?
The subject’s retina
The far point of the patient
The far point of the observer
None of these
31. (Medium) When neutrality is achieved in retinoscopy, which of the following is true?
The far point of the subject’s eye is at the observer’s pupil.
The far point of the subject’s eye is at infinity.
The far point of the subject’s eye is at the retinoscopy filament.
The far point of the subject’s eye is anywhere behind the observer.
32. (Medium) When does the “with-motion” in cycloplegic retinoscopy occur?
The observer’s far point is beyond the subject.
The subject’s far point is beyond the observer.
The observer’s far point is in front of the subject.
The subject’s far point is in front of the observer.
33. (Medium) You refract a patient in your phoropter and find a correction of −10.0 D. Assuming a vertex of 11 mm, what would you expect his or her contact lens prescription to be?
−10.0 D
−9.5 D
−9.0 D
−8.5 D
34. (Easy) You need to increase the sagittal depth of a contact lens. Which of the following would achieve this?
Increasing the lens diameter
Increasing the base curve
Increasing the minus power of the lens
Increasing the plus power of the lens
35. (Medium) You see a 44-year-old patient in consultation for refractive surgery. You would like her to try contact lenses first. Which of the following is true regarding accommodation?
Hyperopic patients will lose some accommodative range going from glasses to contact lenses.
Myopic patients will lose some accommodative range going from glasses to contact lenses.
Toric contact lenses do not affect accommodative range as much as spherical ones.
None of the above.
36. (Easy) A patient with a manifest refraction of −4.00 +2.00 × 180 has keratometry measuring 45.00 D @ 180 and 47.00 D @ 90. Which of the following lenses would be easiest to fit?
Spherical rigid gas permeable (RGP)
Toric RGP
Soft toric contact lens
Scleral lens
37. (Easy) Which statement about scleral lenses is true?
Scleral lenses may be therapeutic in severe ocular surface disease.
Keratoconus patients who fail rigid gas permeable (RGP) lenses are not good candidates for scleral lenses.
Air bubbles between the lens and the cornea are usually well-tolerated.
Soft contact lenses can be placed over scleral lenses as a “piggyback.”
38. (Medium) You are fitting a rigid gas permeable (RGP) lens. The patient reports good vision with the lens. At the slit lamp, you see the following fluorescein pattern. What is the best next step?
Order this lens, the fit is correct.
Place a large-diameter soft lens as a piggyback to improve fit.
Increase the diameter of the lens.
Increase the base curve of the lens.
39. (Medium) You place fluorescein in the eye of a patient wearing rigid gas permeable (RGP) lenses and see the pattern below. Which of the following is most likely to be true?
The contact lens rocks vertically during blink.
Keratometry may indicate 44.00 D @ 90, 46.00 D @ 180.
Vision would be poor with glasses.
The patient would be more comfortable in the RGP lens than a soft contact lens.
40. (Medium) You are examining a patient with cataract in the right eye. The appearance of the cataract is shown. What is true regarding lens calculations for this patient?
Optical axial length measurement is likely to be the most accurate for this eye.
Applanation A-scan measurement may result in a hyperopic visual outcome.
Manual keratometry measures the anterior and posterior corneal curvatures.
None of the above.
41. (Hard) Your attending breaks capsule during cataract surgery. The surgical plan was for a one-piece lens with an A constant of 119. The attending asks you to pick out a three-piece lens for placement in the sulcus. The three-piece lens has an A constant of 118. How do you need to adjust lens power?
Difference in A constant: lower power lens. Sulcus lens placement: lower power lens.
Difference in A constant: lower power lens. Sulcus lens placement: higher power lens.
Difference in A constant: higher power lens. Sulcus lens placement: lower power lens.
Difference in A constant: higher power lens. Sulcus lens placement: higher power lens.
42. (Easy) You are seeing a 68-year-old patient for cataract evaluation. She has keratoconus and wears gas permeable lenses. Which of the following is true for this patient?
Multifocal lens can be offered because the gas permeable lenses correct any astigmatism.
Toric lens can be offered because the gas permeable lens will help to correct the astigmatism.
Simultaneous penetrating keratoplasty can be considered to improve the refractive outcome.
None of the above.
43. (Hard) You perform cataract surgery and place a toric intraocular lens. You measure 4.00 D of corneal astigmatism. Calculations indicate a desired lens axis of 100 degrees, with an expected refractive outcome of −0.50 +0.25 × 100. Postoperatively, you note the lens to be positioned at 115 degrees. Which of the following refractive outcomes would you expect?
−0.50 +0.25 × 100
−1.00 +2.00 × 125
−1.00 +2.00 × 85
−2.00 +4.00 × 125
44. (Medium) Following refractive surgery, what is the name of the intraocular lens calculation error in which the effective lens position is incorrectly assumed?
Instrument error
Index of refraction error
Capsular error
Formula error
45. (Easy) Which factor is thought to reduce the incidence of posterior capsular opacification?
Single-piece lens design
Three-piece lens design
Round edges on the lens optic
Square edges on the lens optic
46. (Medium) You are performing cataract surgery on a high myope. Your lens calculations indicate you should place a 0.0 D lens. Is there an advantage to implanting this lens over leaving the patient aphakic?
Yes, it may reduce the rate of retinal tear or detachment.
Yes, it may reduce the rate of endothelial failure.
Yes, it may reduce the rate of postoperative cystoid macular edema.
No, there is no advantage.
47. (Medium) You are planning cataract surgery for a patient with a history of retinal detachment and silicone oil placement. The silicone oil cannot be removed. How should you adjust lens power?
Decrease power by 6 to 8 D.
Decrease power by 3 to 5 D.
Increase power by 3 to 5 D.
Increase power by 6 to 8 D.
48. (Medium) After myopic laser vision correction, keratometry power (K) readings result in which of the following errors when calculating intraocular lens (IOL) power for cataract surgery?
The posterior cornea is flatter than estimated.
The total corneal power is less than estimated.
The emmetropic IOL power is less than calculated.
The effective lens position is less than estimated.
49. (Easy) Diffractive multifocal intraocular lenses (MFIOLs) have which of the following properties?
Contrast sensitivity is increased compared to monofocal lenses.
Blur circles with a uniform intensity are formed by different diffractive rings.
Apodization of diffractive MFIOL rings may allow for a smoother transition between distance and near images.
Regular corneal astigmatism may improve near image clarity with MFIOLs.
50. (Easy) Negative dysphotopsias from intraocular lenses (IOLs) are created by which of the following mechanisms?
Light reaches the retina directly, without passing through the IOL
Reflection of light from the retina
Reflection of light from the anterior surface of the IOL
Reflection of light from the posterior surface of the IOL
51. (Hard) You are screening a 25-year-old patient for refractive surgery. Her manifest refraction is −10.00 and cycloplegic refraction −9.50. The corneas are sufficiently thick. Your laser is approved for treatments up to −10.00. Keratometry by multiple methods measures 39.0 centrally without any irregularity. What is the recommended treatment for this patient?
Perform LASIK correcting for −10.00.
Perform LASIK correcting for −9.75.
Perform LASIK correcting for −9.50.
This patient is not a candidate for LASIK.
52. (Medium) You are examining a 55-year-old patient who had LASIK in both eyes at age 35. He reports difficulty reading street signs at night. His right eye has uncorrected vision of 20/25, which corrects to 20/20 with −0.50. His left eye has uncorrected vision of 20/60, which corrects to 20/20 with −1.50 correction. He does not use any glasses currently. A sagittal curvature map for his left eye is displayed below. Which of the following is the most appropriate management for this patient?
Dispense spectacles.
Retreat the left eye with PRK to correct −1.50.
Fit a rigid gas permeable lens in the left eye to correct his decentered ablation.
Perform cataract surgery in the left eye to correct his myopic shift.
53. (Medium) You are reviewing the topography of a patient who had previous laser keratorefractive surgery. He is currently 20/25 uncorrected and happy with his vision. Which of the following is true?
PRK will reduce higher-order aberrations in this eye.
This cornea probably has less spherical aberration than a typical cornea.
Keratorefractive surgery should never have been performed in this patient.
It is unlikely that a rigid gas permeable lens would fit on a cornea as irregular as this.
54. (Medium) A patient with −7.00 D of myopia has a relatively thin cornea but normal topography. You are concerned about leaving enough residual tissue. Your laser defaults to a 7.0-mm optical zone. Which of the following is true?
LASIK will leave a thicker stromal bed than PRK.
Reducing the optical zone to 6.0 mm will leave more residual tissue than reducing treatment power to −6.00.
Wavefront-guided treatment will leave a thicker stromal bed than wavefront optimized.
None of the above.
55. (Medium) Which of the following is true regarding the asphericity factor (Q) and spherical aberration?
As corneal Q becomes more negative, the corneal spherical aberration increases.
The Q factor for the average human cornea is −0.50.
Aspheric intraocular lenses should not be used in post-myopic LASIK patients.
A hyperopic LASIK treatment results in a more negative Q factor.
56. (Medium) A hyperopic patient being evaluated for LASIK is noted to have an increased angle kappa. Which of the following is most correct?
The treatment should be centered on the geometric center of the cornea.
Centering the treatment on the midpoint of the entrance pupil is ideal.
Monocular diplopia is likely if the treatment is centered on the visual axis.
When the corneal apex is decentered from the pupillary axis, significant angle kappa occurs.
57. (Easy) A patient interested in LASIK is noted to have “large” pupils in dim light. Which of the following is correct regarding such patient?
Large pupils are defined as 7.0 mm.
The transition zone between ablated and unablated cornea should be 1.5 mm larger than the pupil.
Older generation lasers used larger optical zones without transition zones.
Brimonidine 0.2% may help with postoperative night vision issues.
58. (Medium) Following refractive surgery, a patient has uncorrected visual acuity of 20/25 but complains of poor quality of vision. Which of the following is most likely correct regarding this patient?
Autorefraction may show a high degree of cylinder.
Retreating residual cylinder will likely resolve the symptoms.
Corneal topography may show a symmetrical bow tie pattern.
The Jackson cross cylinder will be very helpful in refraction.
59. (Hard) Which of the following is a third-order wavefront aberration?
Horizontal coma
Secondary astigmatism
Spherical aberration
Defocus
60. (Medium) Which of the following would be least likely to cause irregular astigmatism?
PRK treatment centered on the pupillary axis
Epithelial basement membrane dystrophy
LASIK flap microstriae
LASIK with nonuniform stromal bed hydration after flap lift
61. (Hard) Which of the following is correct when viewing an emmetropic patient’s retina using an indirect ophthalmoscope and a 20 D lens? Assume the clinician has an interpupillary distance of 60 mm, which is effectively reduced to 15 mm by the ophthalmoscope.
The image of the retina is virtual and inverted.
The perceived axial magnification is 2.25 ×.
The retinal image is 5 cm further from the observer than the 20 D lens.
The transverse magnification is 15 ×.
62. (Hard) A rectangular postage stamp which is 1 cm in height and 2 cm wide is 50 cm from a +3 D convex lens. Which of the following is true about the image of the stamp?
The image of the stamp is real and upright.
The transverse magnification is 0.4 ×.
The image size is 2 × 4 cm.
The image of the stamp is virtual and minified.
63. (Hard) How much accommodation is required for an emmetropic eye to view an object at 33 cm through a 2 X telescope?
3 D
6 D
9 D
12 D
64. (Medium) Which of the following pairings is correct when referring to an optical system?
Aperture stop–minimum size opening for system to function.
Entrance pupil–the eye’s aperture stops.
Field of view–the range of object space visible in the image plane.
Depth of focus–distance the object can be moved without noticeable image blurring.
65. (Medium) When performing direct ophthalmoscopy on an aphakic eye with refractive error of +12 D, what would be the approximate simple angular magnification?
3 ×
12 ×
15 ×
18 ×
66. (Medium) When viewing the patient’s eye at the slit lamp, which type of illumination best allows the observer to see the corneal endothelial cell pattern?
Direct illumination
Retroillumination
Specular reflection
Sclerotic scatter
67. (Hard) You have a patient look at a distant light source. They look through an occluder with two pinholes, one above the other. The patient reports seeing two spots of light. When you cover the upper light, the patient reports that the bottom spot disappears. From this test, what can you infer about the patient’s refractive error?
The patient is emmetropic.
The patient is hyperopic.
The patient is myopic.
To make a determination, you need to repeat the test covering the other pinhole.
68. (Easy) Which of the following is true regarding manual keratometry?
The instrument directly reads the refractive power of the cornea.
It measures the central corneal power at a 2-mm diameter.
It relies on the cornea’s reflective power.
It provides reliable measurements of irregular astigmatism.
69. (Medium) Which of the following is true regarding simple magnifiers when used as low-vision aids?
A +4 D hand magnifier can have 2 × magnification.
A +28 D hand magnifier is a good choice for those with hand tremors.
The common range for hand magnifiers is +20 to +30 D.
Continuous text reading is difficult with lower power hand magnifiers.
70. (Easy) Which of the following is true regarding telescopic visual aids?
Near vision loupes provide a narrow field of view but good depth of field.
Distance telescopic aids enhance contrast.
Bioptic spectacle-mounted telescopes are allowed for driving in certain regions.
Telescopic spectacles require a casing.
71. (Medium) Which is the most suitable option for a +2.00 hyperopic patient with symmetric binocular visual loss to the 20/120 level?
+2.00 bifocals with a +6.00 add
+8.00 single vision reading glasses without prism
+12.00 monocular reading glass without prism for the dominant eye
+6.00 laptop computer reading glasses with 8 prism diopter (PD) base-in OU
72. (Easy) Which of the following is the least appropriate low-vision aid when visual loss becomes more profound?
Video magnifiers
Tactile aids/Braille
Optical character recognition with audio output
Mobility training
73. (Medium) The indirect ophthalmoscope must meet which of the following requirements for even illumination?
Observer and patient pupils are conjugate.
Observer pupil and patient retina are conjugate.
The far point of the patient is in front of the observer.
All of these.
74. (Medium) The direct ophthalmoscope gives a more magnified view of a myopic fundus than an emmetropic one because of which of the following?
The effect of a simple magnifier
The effect of a telescope
The effect of pincushion distortion
The effect of all of these
75. (Easy) There is an optimal pupil size to maximize the resolution of the eye and make the smallest possible point-spread function (PSF). Which of the following is true of the optimal pupil size, which has the smallest possible PSF?
Diffraction plays a larger role than aberration.
Aberration plays a larger role than aberration.
There is no diffraction or aberration.
Diffraction and aberration play an equal role.
76. (Easy) The green-colored appearance of the reflections in this lens is caused by which of the following mechanisms?
Diffraction
Dispersion
Interference
Refraction
77. (Easy) Polarizing lenses are used in sunglasses because of which of the following properties?
They diminish the brightness of images.
They reduce reflected light.
They reduce refracted light.
They reduce reflected and refracted light.
78. (Medium) Rainbows are caused by which physical process?
Dispersion
Diffraction
Scatter
Absorption
79. (Medium) The scratches on a pair of glasses degrade vision because of which optical phenomenon?
Refraction
Diffraction
Reflection
Prismatic deviation
80. (Medium) Orange-tinted sunglasses may sharpen distance vision because of which of the following?
Short-wavelength light scatter between subject and object is screened out.
Long-wavelength light scatter between subject and object is screened out.
Short-wavelength light scatter at the subject is screened out.
Long-wavelength light scatter at the subject is screened out.
81. (Hard) You see a patient who reports seeing rainbow halos around lights. On examination you note corneal edema. Which process is most likely causing the colored halos?
Total internal reflection
Absorption
Diffraction
Refraction
82. (Medium) The red appearance of the retina is caused by what?
Dispersion
Reflection
Refraction
Absorption
83. (Medium) What is the optimal pupil size with respect to chromatic aberration?
4.4 mm
2.4 mm
3.4 mm
1.4 mm
84. (Easy) What is the pupil size which will optimize the point-spread function (PSF) in an emmetropic eye?
1.4 m
2.4 mm
3.4 mm
4.4 mm
85. (Hard) This is a picture of a dust storm. Why is the sky red and not blue?
Short-wavelength light penetrates lower in the atmosphere than longer wavelengths.
Short-wavelength light is scattered by dust particles more than longer wavelengths.
Long-wavelength light is scattered more in the atmosphere than short-wavelength light.
Long-wavelength light penetrates lower in the atmosphere and is scattered by dust particles.
86. (Easy) Your technician refracts a patient without realizing that he or she is wearing toric soft contact lenses. The over-refraction was −1.00 +1.00 × 90. The contact lens they are wearing is −3.00 −1.00 × 180. What would the true refraction be in this instance, assuming the contact lens was oriented properly?
−4.00 +2.00 × 180
−4.00 −2.00 × 180
−5.00 +2.00 × 90
−5.00 −2.00 × 90
87. (Medium) Which of the following is an example of the particle nature of light?
Interference patterns produced by a double slit
Blue light creating images in fluorescein angiography
Glare being reduced by polarized sunglasses
Antireflective coating applied to camera lenses to improve low-light image quality
88. (Medium) What is the correct description of accommodation in the human lens?
The ciliary muscle contracts, which loosens the zonular fibers.
The ciliary muscle relaxes, which loosens the zonular fibers.
The ciliary muscle contracts, which tightens the zonular fibers.
The ciliary muscle relaxes, which tightens the zonular fibers.
89. (Easy) Which of the following is true about the attached diagram of a wavefront?
“w” represents an image point.
“x” represents the direction of travel of the wavefront.
“y” represents the frequency of the wavefront.
“z” represents a ray of light.
90. (Medium) Which of the following is true about the diagram below? The diagram demonstrates both two-and three-dimensional representations of the same optical system.
The planar wavefronts must have originated from a distance approximating infinity.
The lens material must have higher refractive index than the surrounding medium.
The light leaving the lens will have zero vergence at the focal point of the lens.
The vergence of light is uniform on both sides of the lens.
91. (Medium) Which of the following accurately describes the power and/or direction of induced prism in the lens shown?
The lens induces 5 prism diopters base down at point x.
The lens induces ✓2 prism diopters with base toward the center of the lens at point z.
The lens induces 5 prism diopters base down at point y.
The lens induces base-down prism in the upper half of the lens.
92. (Hard) A wavefront has vergence of −4 when it strikes a 5 D lens. What is the transverse magnification created by the 5-D lens?
0.8
0.8
2
4
93. (Medium) You have a patient who complains that the world appears tilted when he or she wears his or her glasses. You look at your computer screen and see the first image. You then put on the glasses and the screen appears tilted, as in the second image. What is most likely to be the patient’s wearing prescription?
−1.00 +2.00 × 090 OD -1.00 +2.00 × 180 OS
−1.00 +2.00 × 075 OD -1.00 +2.00 × 165 OS
−1.00 +2.00 × 135 OD -1.00 +2.00 × 045 OS
−1.00 +2.00 × 180 OD -1.00 +2.00 × 180 OS
94. (Hard) Which of the following is true regarding real versus virtual images?
Real images are always formed by converging rays.
Virtual images are always formed by converging rays.
Virtual images are always upright.
Real images are always upright.
95. (Medium) You have a lens of unknown power. You hold it in sunlight and find that the lens creates the finest point of sunlight when you hold it 20 cm from the ground. What is the magnification of this lens when used as a simple magnifier?
0.2 ×
1 ×
1.25 ×
10 ×
96. (Medium) Which of the following is true regarding conjugacy in optics?
The conjugate plane to the fovea in a cyclopleged eye is at the far point of the eye.
Every lens has two planes which are conjugate.
The focal points of a lens are conjugate.
The nodal point is unrelated to the concept of conjugacy.
97. (Hard) You learned about the Airy disk and that the pupil size which allows best resolution is 2.4 mm. You take the pinhole occlude in your office and bore out each hole to 2.4 mm. What would you expect the result to be?
The larger pinhole is more effective at improving uncorrected vision, because it reduces the amount of diffraction.
The larger pinhole is more effective at improving uncorrected vision, because it reduces the amount of aberration.
The larger pinhole is less effective, because it increases the amount of diffraction.
None of the above.
98. (Medium) An object is 5 m to the left of a +5.2 D lens. There is a +10 D lens 30 cm to the right of the first lens. Where is the image formed by the system?
Minus infinity
Infinity
10 cm to the right of the minus lens
At the +5.2 D lens
99. (Medium) You have a patient who is an engineer and spends a lot of time on the computer. She reports that at the end of the day, her eyes become misaligned and she sees double. Using a ruler, she measured the image displacement, and knows the right eye image is shifted 10 cm to the left. She measured the distance from her eye to the computer screen as 50 cm. What prism correction would resolve the diplopia?
5 PD base out both eyes
10 PD base out both eyes
5 PD base in both eyes
10 PD base in both eyes
100. (Medium) You are trying to perform laser retinopexy in a patient with a dispersed vitreous hemorrhage. Which laser would be most effective and why?
Blue: highest energy per photon
Red: less absorption by hemoglobin
Green: less scatter from hemoglobin
Yellow: more absorption by retinal pigment
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