ABO Binocular Vision & Strabismus 1 — Questions and Answers
Question 1: The Hirschberg corneal light reflex test is primarily used to estimate the angle of which condition?
- Amblyopia
- Strabismus (Correct answer)
- Myopia
- Presbyopia
Correct answer: Strabismus
The Hirschberg test uses the position of the corneal light reflex relative to the pupil center to estimate the angle of deviation in strabismus.
Question 2: In esotropia, the deviating eye turns in which direction?
- Outward (temporal)
- Upward (superior)
- Inward (nasal) (Correct answer)
- Downward (inferior)
Correct answer: Inward (nasal)
Esotropia is an inward (nasal/medial) deviation of the eye, commonly called 'crossed eyes.'
Question 3: Which term describes a latent ocular deviation that is controlled by fusion and only becomes manifest when fusion is disrupted?
- Tropia
- Phoria (Correct answer)
- Amblyopia
- Diplopia
Correct answer: Phoria
A phoria (heterophoria) is a latent deviation kept latent by fusional vergence, only revealed by dissociation techniques such as the cover test.
Question 4: The cover-uncover test is the most reliable clinical method to distinguish between a tropia and a phoria because it:
- Measures stereoacuity directly
- Disrupts fusion, revealing any manifest deviation in the covered eye (Correct answer)
- Assesses the AC/A ratio
- Tests for suppression scotoma
Correct answer: Disrupts fusion, revealing any manifest deviation in the covered eye
When one eye is covered, fusional vergence is disrupted; a refixation movement of the uncovered eye upon removal of the cover indicates a tropia, while movement of the covered eye on cover removal indicates a phoria.
Question 5: A positive result on the Randot Stereotest indicates:
- Monocular suppression of one eye
- Bifoveal fixation and intact binocular vision (Correct answer)
- A manifest strabismus
- Reduced contrast sensitivity
Correct answer: Bifoveal fixation and intact binocular vision
Passing the Randot Stereotest demonstrates bifoveal fixation and functional binocular vision with intact stereopsis.
Question 6: The angle kappa is defined as the angle between the:
- Visual axis and the optical axis of the eye
- Pupillary axis and the visual axis (Correct answer)
- Line of sight and the optical axis
- Corneal reflex and the center of the pupil
Correct answer: Pupillary axis and the visual axis
Angle kappa is the angle between the pupillary axis (perpendicular to the cornea through the center of the pupil) and the visual axis (fovea to fixation point).
Question 7: The prism adaptation test (PAT) is used preoperatively in strabismus patients primarily to:
- Measure the amplitude of accommodation
- Reveal the full angle of deviation before surgery (Correct answer)
- Assess contrast sensitivity
- Determine the near point of convergence
Correct answer: Reveal the full angle of deviation before surgery
PAT uses a prism to neutralize the deviation; if the angle increases under the prism (prism adaptation), it reveals the full underlying deviation and improves surgical outcomes.
ABO Binocular Vision & Strabismus 1
The Hirschberg corneal light reflex test is primarily used to estimate the angle of which condition?