Ophthalmology Question Bank

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1. A patient undergoing fogged refraction with an astigmatic dial sees the 9 to 3 o'clock line clearer than all the others. At what axis should this patient's minus cylinder correcting lens be placed?

On the astigmatic (clock) dial, the clearest line indicates the meridian needing minus correction; a clear 9-to-3 (horizontal, 180) line means the minus cylinder axis is placed at 90 degrees (perpendicular, by the rule of 30/the clearest meridian).

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2. Myopia is associated with all of the following conditions except

Myopia is associated with pigment dispersion syndrome, spherophakia and nuclear sclerotic cataract (which causes myopic shift); NANOPHTHALMOS causes HYPEROPIA, so it is the exception.

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3. What is the ratio of the magnification from a direct ophthalmoscope to the magnification from an indirect ophthalmoscope with a 20 D lens at a distance of 25╯cm if the patient and examiner are both emmetropic?

Direct ophthalmoscope magnification is about 15x and indirect with a 20 D lens about 3x, giving a ratio of about 5:1.

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4. A patient with anisometropia wears glasses with a prescription of +5.00 OD and +1.25 OS. Which of the following actions will not reduce the amount of aniseikonia?

Aniseikonia is reduced by changing base curve, vertex distance or using contact lenses; DECREASING the CENTER THICKNESS of the left (lower-power) lens does NOT meaningfully reduce the image-size disparity, so it is the exception.

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5. The principal measurement determined by a Prince's rule and +3 D lens in front of the patient's eye is the

Prince's rule with a +3 D lens measures the AMPLITUDE OF ACCOMMODATION by determining the near point with the added plus lens.

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6. The 10× eyepiece of the slit-lamp biomicroscope is essentially a simple magnifier. Using the standard reference distance of 25╯cm, what is the dioptric power of the 10× eyepiece?

A simple magnifier's power = magnification x 4 (using the 25 cm reference, M = D/4); a 10x eyepiece corresponds to +40 D.

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7. When refracting an astigmatic patient with a Lancaster dial, the examiner should place the

With a Lancaster/astigmatic dial during fogging, the entire conoid of Sturm is placed IN FRONT OF the retina (fogged with plus) so the patient identifies the clearest meridian; thus the conoid is anterior to the retina.

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8. To increase the magnification of the image during indirect ophthalmoscopy, the examiner should

To increase magnification during indirect ophthalmoscopy, MOVE CLOSER to (or use a higher dioptric) condensing lens... moving closer to the condensing lens increases the image size; the keyed answer is moving closer to the condensing lens.

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9. Which antibiotic results in the highest intravitreal concentration when administered orally?

CIPROFLOXACIN, an oral fluoroquinolone, achieves the highest intravitreal concentration of the listed agents due to good ocular penetration.

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10. Which anesthetic agent would most interfere with an intraocular gas bubble?

NITROUS OXIDE diffuses into and expands an intraocular gas bubble, dangerously raising IOP, so it must be avoided when a gas bubble is present.