Optics and Refraction Flashcards
6 cards from real AOA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Optics and Refraction flashcards as text
In an eye with simple myopia, the far point is located:
Answer: At a finite distance in front of the eye
In myopia the parallel rays from infinity focus in front of the retina; the far point (where diverging rays appear to come from) is at a finite real distance anterior to the eye.
When performing retinoscopy, a 'with' reflex indicates that the eye's far point is:
Answer: Behind the examiner (hyperopia or low myopia)
A 'with' motion reflex during retinoscopy means the far point is beyond the examiner's working distance, indicating hyperopia or myopia less than the working lens.
The principal effect of a minus cylinder lens is to:
Answer: Reduce power in one meridian while leaving the other unchanged
A minus cylinder lens has zero power along its axis meridian and maximum minus power 90° away, selectively reducing power in one meridian.
Chromatic aberration in the eye is primarily responsible for which clinical phenomenon?
Answer: Blue light focusing slightly anterior to red light (longitudinal chromatic aberration)
The ocular media have higher refractive index for shorter wavelengths; blue light focuses about 2D anterior to red, a phenomenon used in the duochrome (red-green) test.
The power of a thin lens required to correct a 4D myope is:
Answer: -4.00 D
To move the far point from 25 cm in front of the eye to optical infinity, a diverging lens of -4.00 D (focal length -25 cm) is required.
Astigmatism is defined as a refractive condition in which:
Answer: The eye has different powers in different meridians
Astigmatism occurs when the refracting surfaces of the eye have different curvatures in different meridians, preventing parallel rays from converging to a single point focus.