CO Study Guide 2026
Everything you need to pass the CO exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 CO Exam Format at a Glance
📚 CO Topics to Study (27)
✍️ Sample CO Questions & Answers
1. When using a prism bar to measure a horizontal deviation, the prism base direction should be oriented in which direction to neutralize an esotropia?
Base-out prisms neutralize esotropia by shifting the image toward the deviated eye, allowing the cover-uncover test to show neutralization.
2. The optic nerve exits the eye through which structure and is surrounded by an extension of the meninges?
The optic nerve exits through the lamina cribrosa, a sieve-like region of the sclera, and is surrounded by extensions of the dura, arachnoid, and pia mater.
3. When performing a cover-uncover test on a child, a refixation movement of the uncovered eye indicates which condition?
If the uncovered eye moves to take up fixation when the other eye is covered, a manifest tropia (heterotropia) is present in that eye.
4. The AAPOS guidelines recommend that vision screening in children should begin at which age?
AAPOS and AAP guidelines recommend that all children have a vision screening at age 3 years, when cooperation allows photo-screening or acuity testing.
5. Accommodation is primarily achieved by which change in the crystalline lens?
During accommodation, ciliary muscle contraction causes the zonular fibers to relax, allowing the inherently elastic lens to become more convex (increased curvature) and thus more powerful.
6. The Bagolini striated lens test is used to evaluate which aspect of binocular vision?
Bagolini striated lenses test retinal correspondence and suppression under near-natural viewing conditions by creating streak images from a point source.