Question 1
A patient's spectacle prescription is -12.00 DS worn at a vertex distance of 14 mm. What is the approximate equivalent power at the corneal plane?
Show answer & explanation
Correct answer: D - -10.25 D
10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
The ABS exam has 370 questions and runs 8 hours.
These 10 free ABS questions are organized by exam domain, so you can see how each part of the NBEO Part I Applied Basic Science blueprint is tested. Reveal the answer and explanation under each question.
A patient's spectacle prescription is -12.00 DS worn at a vertex distance of 14 mm. What is the approximate equivalent power at the corneal plane?
Correct answer: D - -10.25 D
A patient wears OD -5.50 DS and OS -1.50 DS. The reading position is 8 mm below the optical centers of both lenses. What is the vertical prismatic imbalance at that point?
Correct answer: A - 3.2 prism diopters
A rigid gas permeable lens is fitted with a base curve 0.15 mm steeper than flat K. The patient's refraction at the corneal plane is -3.00 DS. What lens power should be ordered?
Correct answer: C - -3.75 D
A neonate is brought in on the third day of life with copious, rapidly reaccumulating purulent discharge, marked lid edema, and severe chemosis in both eyes. Which cause is MOST likely?
Correct answer: B - Neisseria gonorrhoeae
All of the following ocular structures are derived from neural crest EXCEPT:
Correct answer: C - Iris dilator muscle
Eight months after penetrating keratoplasty, a patient develops an advancing line of keratic precipitates across the graft endothelium with adjacent stromal edema. This rejection episode is mediated PRIMARILY by which hypersensitivity mechanism?
Correct answer: D - Type IV, T cell-mediated
A 68-year-old has sudden, painless, profound loss of vision in one eye. The fundus shows diffuse retinal whitening with a cherry-red spot at the fovea. The red appearance of the fovea is BEST explained by which of the following?
Correct answer: A - The intact choroid shows through the thin fovea
A patient has a right superior homonymous quadrantanopia that respects the vertical midline. The lesion is MOST likely located in the:
Correct answer: B - Left temporal lobe
In a patient with poorly controlled diabetes, lens fibers accumulate an osmotically active alcohol that draws in water and produces opacification. Which enzyme catalyzes the formation of this compound?
Correct answer: A - Aldose reductase
A photon is absorbed by rhodopsin in a rod outer segment. Which combination of changes occurs in that photoreceptor?
Correct answer: D - Hyperpolarization with decreased glutamate release
The ABS exam also covers these domains. Drill them in the full free practice test:
The full bank has 1,020 more ABS questions with explanations.
Continue in the free practice test →
View plans