Refraction & Visual Acuity Flashcards
6 cards from real ABO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Refraction & Visual Acuity flashcards as text
What does a myopic patient experience without corrective lenses?
Answer: Blurred distance vision
Myopia (nearsightedness) causes light to focus in front of the retina, making distant objects appear blurry while near vision remains clear.
Which instrument is used to objectively measure a patient's refractive error?
Answer: Autorefractor
An autorefractor automatically determines the refractive error of the eye by measuring how light changes as it enters the eye.
A prescription reads -2.50 -1.00 x 180. What type of correction does this represent?
Answer: Compound myopic astigmatism
A negative sphere with a negative cylinder indicates compound myopic astigmatism, where both principal meridians are myopic.
What is the Snellen fraction for a patient who can read the 20/40 line?
Answer: The patient sees at 20 feet what a normal eye sees at 40 feet
In Snellen notation, 20/40 means the patient must be at 20 feet to read what a person with normal vision can read at 40 feet.
Which lens power would be prescribed for a patient with +3.00 D of hyperopia?
Answer: Convex (plus) lens of +3.00 D
Hyperopia requires a convex (plus) lens to add convergence and move the focal point forward onto the retina.
What is the purpose of the Jackson Cross Cylinder during refraction?
Answer: To refine the axis and power of the cylinder correction
The Jackson Cross Cylinder (JCC) is used during subjective refraction to fine-tune both the axis and power of astigmatic correction.