Optics and Refraction Principles Flashcards
7 cards from real Board Certified Ophthalmologist practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Optics and Refraction Principles flashcards as text
An uncorrected -2.00 D myope has a near point of 10 cm. What is the amplitude of accommodation?
Answer: 8.00 D
Near point vergence is 10 D and far point vergence is 2 D, so accommodation amplitude is 10 - 2 = 8 D.
A +10.00 D spectacle lens worn at a 10 mm vertex distance is converted to a contact lens. What contact lens power is approximately needed?
Answer: +11.00 D
Effective power is 10 / (1 - 0.01 x 10) ≈ +11.1 D, since plus lenses moved closer to the eye need more power.
Which is the correct minus-cylinder transposition of +2.00 +1.00 x 090?
Answer: +3.00 -1.00 x 180
Add the cylinder to the sphere, change the cylinder sign, and rotate the axis 90 degrees.
Using a 67 cm working distance, retinoscopy neutralizes with a +4.00 D lens. What is the patient's refractive error?
Answer: +2.50 D
A 67 cm working distance corresponds to 1.50 D, which is subtracted from the gross retinoscopy finding.
In with-the-rule astigmatism, at what axis is the minus cylinder correction typically placed?
Answer: 180 degrees
With-the-rule astigmatism has the steeper vertical meridian, corrected by minus cylinder with axis near 180.
Which optical aberration contributes most to night myopia when the pupil dilates?
Answer: Positive spherical aberration
With a larger pupil, peripheral rays are refracted more strongly and focus anterior to the retina, producing a myopic shift.
Using the standard 25 cm reference distance, what is the nominal magnification of a +20.00 D simple magnifier?
Answer: 5x
Simple magnifier magnification is the lens power divided by 4, so 20 / 4 = 5x.