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
What refractive index does a standard keratometer assume to convert corneal radius of curvature into dioptric power?
Answer: 1.3375
The keratometric index of 1.3375 is a fictitious value chosen to account for the negative power of the posterior cornea.
What wavelength does the argon fluoride excimer laser used in refractive surgery emit?
Answer: 193 nm
The ArF excimer laser emits ultraviolet light at 193 nm, which ablates corneal tissue by photodecomposition.
What optical thickness does a single-layer anti-reflective coating need for destructive interference of reflected light?
Answer: One-quarter wavelength
A quarter-wave coating makes the two reflected waves differ by half a wavelength in path, so they cancel.
What is the approximate optimal pinhole diameter for clinical testing of potential visual acuity?
Answer: 1.2 mm
A pinhole of about 1.2 mm balances reduced blur circle size against increasing diffraction at smaller apertures.
Without correction, at what distance can an otherwise normal -3.00 D myope read clearly with accommodation fully relaxed?
Answer: 33 cm
The far point of a myope is 1 divided by the refractive error, so 1 / 3 = 0.33 m.
A presbyopic hyperope slides plus-power reading glasses farther down the nose. What happens to the effective lens power?
Answer: Effective plus power increases
Moving a plus lens away from the eye increases its effective plus power at the eye.
A patient wears OD -1.00 D and OS -4.00 D spheres and reads 10 mm below the optical centers. What vertical prismatic imbalance is induced?
Answer: 3 prism diopters
By Prentice's rule, each eye gets 1 cm x its power, and the difference is (4 - 1) x 1 = 3 prism diopters.