Refractometry CH14 Flashcards
Label the following (Figure 14-1):
compound hyperopic astigmatism, compound myopic astigmatism,
emmetropia,
hyperopia,
mixed astigmatism,
myopia,
simple hyperopic astigmatism,
simple myopic astigmatism,
F) compound hyperopic astigmatism
A) emmetropia
H) mixed astigmatism
D) simple hyperopic astigmatism
G) compound myopic astigmatism
B) hyperopia
C) myopia
E) simple myopic astigmatism
Which of the following prescriptions denotes emmetropia?
a) +2.00 sphere
b) –2.00 sphere
c) Plano + 2.00 × 180
d) Plano sphere
d) Emmetropia is the absence of refractive error, hence no correction (plano sphere) is
required.
In hyperopia:
a) the object image focuses on the retina
b) the object image focuses on the cornea
c) the object image focuses in the vitreous
d) the object image focuses beyond the macula
d) The hyperopic eye does not have enough plus power to focus the image on the retina.
Instead, the image falls beyond the retina/macula. (Technically, of course, this is not possible, except in a “virtual” sense.)
Myopia can be caused by:
a) irregular curvature of the cornea
b) removal of the crystalline lens
c) an eyeball that is “too long”
d) a stretched-out retina
c) The myopic eye is usually longer than average, causing the image to fall in front of the retina.
A refractive error of +2.00 + 2.00 × 180 would be classified as:
a) mixed astigmatism
b) compound hyperopic astigmatism
c) compound myopic astigmatism
d) simple hyperopic astigmatism
b) Hyperopia combined with plus cylinder astigmatism is termed compound hyperopic astigmatism.
The condition of having no lens is referred to as:
a) astigmatism
b) ametropia
c) aphakia
d) pseudophakia
c) The prefix a- means without. The term -phakia refers to the lens. So, aphakia means
without a lens.
Farsightedness may be caused by all of the following except:
a) heredity
b) removal of the crystalline lens
c) orbital tumor
d) migraine headaches
d) Migraine headaches do not cause any type of refractive error. An orbital tumor can cause
farsightedness if it has pushed the retina forward.
If your patient complains of blurred vision at near, the most likely cause is:
a) hyperopia
b) presbyopia
c) astigmatism
d) need more information
d) The answer depends on the age of the patient and her previous refractive status. There is not enough information here to make a good choice.
The classic symptom of myopia is:
a) blurred vision at near
b) blurred vision at distance
c) blurred vision at near and distance
d) headaches
b) Myopia is “nearsightedness”; the patient’s vision is at near (ie, blurred at a distance).
All of the following are characteristic of nearsightedness except:
a) it tends to be hereditary
b) it tends to accelerate during adolescence
c) the patient is more prone to retinal detachment
d) presbyopia is delayed
d) Myopia does not delay presbyopia; the myopic eye ages at the normal rate. (It is true,
however, that a mildly myopic patient might not notice the effects of presbyopia until later
than average.) The myopic eye tends to be longer than normal. This may result in the retina’s being stretched, predisposing one to retinal detachment (as in answer c).
Astigmatism occurs when:
a) the cornea is irregularly curved
b) the cornea is curved equally in all directions
c) an individual reaches his or her 40s
d) the retina is irregularly curved
a) Irregular curvature of the cornea is the textbook definition of astigmatism.
A 12-year-old patient complains of problems seeing the board at school. Most likely
the patient is:
a) myopic
b) presbyopic
c) malingering
d) hyperopic
a) A young patient who is having trouble seeing at a distance is most likely myopic. Presbyopia begins around age 40. Hyperopia blurs the near vision. Malingering means to lie, and we have to assume most patients (regardless of age) are telling the truth!
A 45-year-old male who has never worn glasses complains of decreased near vision.
Most likely he is:
a) myopic
b) presbyopic
c) astigmatic
d) aphakic
b) Presbyopia begins around age 40 and onward, whether the patient has worn glasses before or not. Myopia blurs vision at a distance. Astigmatism would likely have been
detected by age 45. Aphakia is the condition of having no crystalline lens in the eye, and
the patient is legally blind without correction (eg, intraocular lens, contact lens).
Presbyopia is caused by:
a) removal of the crystalline lens
b) loss of muscle tone in the ciliary muscle
c) degeneration of the zonules
d) loss of elasticity of the crystalline lens
d) As we age, the lens forms layers that compact, forming a hard nucleus. Thus, the lens loses its elasticity. It is true that the ciliary muscle tone decreases, but this is not the major factor in presbyopia.
A classic complaint of the presbyopic patient is:
a) “I cannot see where I’m going in a dark movie theater.”
b) “My arms are too short.”
c) “My eyes itch and burn.”
d) “My eyes draw and pull.”
b) The loss of near vision is often compensated for by holding reading material at arm’s length. Thus, the patient complains that his or her arms are too short.
Using a plus lens or an add corrects presbyopia because:
a) it restores plus power lost by the crystalline lens
b) it restores minus power lost by the crystalline lens
c) it neutralizes the patient’s hyperopia
d) it neutralizes the patient’s astigmatism
a) It takes more plus to see up close. When the presbyopic eye has lost the ability to add
enough plus, the plus is restored by using glasses with plus lenses.
A presbyopic myope with distance correction may find that his or her near vision
improves if the patient:
a) closes one eye
b) wears contact lenses
c) holds the reading material closer
d) takes off his or her glasses
d) A myope is corrected with minus power. Thus, taking off his glasses adds plus power to the eye, bringing near objects into better focus.
A presbyopic patient who is prescribed his or her first pair of single-vision reading
glasses should be told:
a) that distant objects will appear blurred through the glasses
b) that near objects will appear blurred through the glasses
c) that the glasses can be worn for all activities
d) to wear the glasses at all times to get used to them
a) The focal distance of a pair of reading glasses is usually 14 to 16 inches. Anything further away than that will be blurry. The patient should be warned about this.
Your patient is delighted because suddenly, at age 65, she can now read without her
bifocals. The most likely cause of this symptom is:
a) cataract
b) hyperopia
c) presbyopia
d) ocular hypertension
a) The onset of cataracts causes a myopic shift in the refractive error, often restoring reading vision lost by presbyopia.
A 75-year-old patient states that he wears contact lenses because he had cataract surgery without implants. You need to remove the contacts for part of the exam, but the patient objects. Why?
a) He is virtually blind without them.
b) He can read without the contacts, but cannot drive.
c) He can drive without the contacts, but cannot read.
d) His eyes are more comfortable with the lenses in.
a) A patient with no crystalline lens is legally blind without contacts or glasses. Driving
home without them would be impossible. Even walking around the office would be difficult and possibly embarrassing.
A 2-year-old male wearing -15.00 lenses screams if you take his glasses off. Why?
a) He has gotten used to feeling them on his face.
b) He is totally blind without them.
c) He cannot see more than several inches beyond his face without them.
d) He is probably punished at home if he takes the glasses off.
c) A –15.00 myope is not totally blind without glasses, but is certainly legally blind. A
2-year-old cannot articulate his frustration at not being able to see—he can only cry.
A new patient calls, complaining of poor vision with some glasses made elsewhere. She
wants to start over with your doctor. You should:
a) refuse to see her because she should really go back to her original physician
b) make the appointment, and ask her to bring the problem glasses plus her previous
glasses
c) tell her to return to her optician
d) make the appointment, and ask her to bring only her previous glasses
b) You might suggest that she see the original doctor or optician, but do not refuse to see
her. If she brings both pairs of glasses, you can analyze them and hopefully find the problem.
The automated refractor is an example of:
a) subjective testing
b) objective testing
c) self-testing
d) vision testing
b) The autorefractor takes the reading with no response from the patient, treating the patient as an “object.” This is an easy way to remember the difference between objective and subjective.
An automated refractor reading is especially helpful when the patient:
a) is new and has no glasses
b) has a previous refraction on record
c) has cataracts
d) has a written glasses prescription with him or her
a) In cases b and d, there is information from which a refractometric measurement could
be started. A patient with cataracts may not get an accurate AR measurement because of the opacities, plus the information given in the question does not state whether or not the patient has been seen before. An AR on the new patient (ie, with no refractive record in your practice) who has no glasses (ie, from which to read a prescription) would be the most useful of the bunch.