PrepTest 108, Section 3, Question 17
Radial keratotomy (RK), a surgery that is designed(47 more words not shown)
Each of the following, if(13 more words not shown)
- AAs the eye(18 more words not shown)
- BThe more severe(17 more words not shown)
- COccasionally an RK(22 more words not shown)
- DRK patients who(21 more words not shown)
- EThose who choose(19 more words not shown)
Reading the argument
What if they're farsighted? Fixing nearsightedness wouldn't necessarily fix every reason someone might need glasses.
That's my first response to the supposed discrepancy. RK is designed to correct nearsightedness, but the study says some patients still need corrective lenses afterward. Maybe they have another vision problem. Having had the surgery doesn't automatically mean having no remaining need for lenses.
What we’re looking for
The question asks for the exception. Four choices will help explain why those patients still need glasses or contacts; we want the one that doesn't help. Keep asking what each choice tells us about the need for lenses after surgery. A fact about the patients is useful only if it helps connect the operation to that remaining need.
Working the answers
- A
This helps, so eliminate it. It fits the prediction: a patient can end up farsighted even though the surgery was intended to correct nearsightedness. A explains how the healing process can create that new problem. The patient still needs corrective lenses, but for a reason the operation wasn't supposed to leave behind.
- B
The surgery is less effective for more severe cases. That gives us a reason some patients might still have enough nearsightedness to need glasses or contacts afterward. RK can help without completely fixing their vision. We don't need to explain every patient; the study only says some still need lenses.
- C
Different healing in the two eyes can leave a difference in visual acuity, and the choice explicitly says corrective lenses are needed to overcome it. That directly explains why someone who underwent RK could still need lenses. Correcting the original problem doesn't prevent this uneven-healing problem.
- D
This gives another specific route to a remaining need for lenses: uneven healing can produce astigmatism. Even someone whose original nearsightedness was mild could now need lenses for that condition. We don't need outside knowledge of astigmatism; D tells us it requires corrective lenses.
- ECorrect
This compares how nearsighted two groups were before surgery: people who chose RK and people who didn't. It says nothing about why anyone still needs glasses after the operation.
Suppose the two groups started with exactly the same degree of nearsightedness. We would still have the whole original question: why did some of the people who had RK need corrective lenses afterward? E gives us no remaining condition, incomplete correction, or other reason for that outcome.
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