Optics and Refraction — Flashcards

Flashcard 101: A patient with 1 D myopia would exhibit _____ movement of red reflex when retinoscopy is done from a distance of 1m without cycloplegia.

Answer: no

Flashcard 102: High myopia is defined as a refractive error of _____ D or more.

Answer: -6

Flashcard 103: The Placido disk test assesses the curvature of the cornea, which is normally not a perfect sphere but is _____

Answer: Aspherical (Prolate)

Extra: Placido's disk (keratoscopy) projects concentric rings onto the anterior surface of the cornea. It is used to evaluate corneal curvature and regularity, helping to detect conditions like keratoconus and astigmatism. A normal cornea is not a perfect sphere but is aspherical (prolate), meaning it is steeper in the center and flattens toward the periphery.

Flashcard 104: Low hypermetropia: error of _____D or less

Answer: + 2

Flashcard 105: A total of _____ Purkinje images are formed in normal eyes.

Answer: 4

Flashcard 106: Myopia must never be _____-corrected with spectacles.

Answer: over (under/over)

Flashcard 107: Jack-in the box is seen in the correction of aphakia with _____

Answer: spectacles

Flashcard 108: Refractive index of the cornea: _____.

Answer: 1.376

Flashcard 109: In high myopia, it is better to slightly _____-correct for distance

Answer: under (over/under)

Flashcard 110: The refractive index of lens cortex is _____ than lens nucleus

Answer: less