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These 10 free CO questions are organized by exam domain, so you can see how each part of the Certified Orthoptist blueprint is tested. Reveal the answer and explanation under each question.
During rightward saccades, an adult's left eye adducts slowly and incompletely while the right eye develops abducting nystagmus. Left-eye abduction, vertical movements, and adduction during convergence are preserved. There is no ptosis or pupillary abnormality. Where does this pattern most strongly localize the lesion?
Correct answer: D - Left medial longitudinal fasciculus
A 7-year-old with longstanding infantile esotropia has fine horizontal nystagmus with both eyes open. With gaze held straight ahead, covering the left eye increases the nystagmus and makes it right-beating; covering the right eye makes it left-beating. The reversal follows the change in viewing eye rather than a spontaneous time cycle. Which nystagmus pattern does this demonstrate?
Correct answer: D - Fusion maldevelopment nystagmus syndrome
Phenylephrine 2.5% is the only drop used before a 4-year-old's dilated examination. The pupils enlarge well, and an autorefractor records mild hyperopia. A note describes this as a cycloplegic refraction. Which statement about this result is accurate?
Correct answer: A - Latent hyperopia may remain masked because accommodation has not been adequately suspended.
No exotropia appears while a 9-year-old watches a target at 3 meters for 30 seconds. At the same distance, three successive 10-second monocular occlusion trials produce outward deviations that recover in 2, 8, and 3 seconds after uncovering. On the Mohney-Holmes 0-5 office control scale, what distance control grade should be recorded?
Correct answer: C - Grade 2
At 6 meters in the same spectacles, simultaneous prism-and-cover testing repeatedly measures 6Δ of esotropia, whereas prism alternate-cover testing measures 18Δ of esodeviation. Fixation is clear and reliable, and the viewing distance and head position are unchanged. How should the difference be represented in the sensorimotor assessment?
Correct answer: D - A 6Δ manifest esotropia with an additional latent component revealed by alternate occlusion.
A patient has no vertical deviation when viewing through the optical centers of single-vision spectacles. The prescription is right +5.00 −2.00 × 180 and left +2.00 −1.00 × 180, with no prescribed prism. For reading, both lines of sight pass 10 mm below their respective optical centers. Using Prentice's rule, what additional prism placed over the right lens would neutralize the lens-induced vertical imbalance at those reading points?
Correct answer: B - 2 prism diopters base-down
An 8-month-old has had a large, constant esotropia since 3 months of age. With both eyes open, the infant uses the left eye for targets on the right and the right eye for targets on the left, so neither eye appears to abduct. Development, pupils, and fundus examination are otherwise normal. Which examination step should precede a diagnosis of bilateral abduction paresis?
Correct answer: B - Occlude each eye in turn and assess the uncovered eye's abduction.
A 5-year-old with right anisometropic amblyopia has worn the appropriate cycloplegic spectacle correction consistently. Acuity remains 20/60 right and 20/20 left at two successive follow-ups. The ophthalmologist prescribes patching of the left eye for 2 hours daily. The parent asks, ‘Shouldn't we start with six hours to avoid wasting time?’ Which explanation is best supported?
Correct answer: A - Two hours is an evidence-supported starting regimen; subsequent dosing depends on the measured response.
An 8-year-old's esotropia measures 36Δ without glasses and a reproducible 20Δ at distance and near while wearing the full +4.50 D hyperopic correction. Acuity is 20/20 in each eye. The ophthalmologist proposes surgery for the persistent deviation. The parent asks whether the operation will remove the need for glasses. The most accurate response is:
Correct answer: C - Surgery treats the residual crossing, not the hyperopia; glasses are expected to remain necessary.
Genetic testing identifies an autosomal recessive form of oculocutaneous albinism in a child with nystagmus. Each parent carries one pathogenic allele in the same gene. Their older child is clinically unaffected and has not had genetic testing. Assume that inheriting two pathogenic alleles invariably causes the phenotype in childhood. What is the probability that this unaffected older child is a carrier?
Correct answer: C - 2 in 3
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