COT Pupil Assessment 2 — Questions and Answers
Question 1: When performing a confrontation visual field test, a patient fails to see the examiner's finger in the inferior nasal quadrant of the right eye. Which cranial nerve or structure is most likely affected?
- Optic chiasm
- Right optic nerve (Correct answer)
- Right optic tract
- Left optic radiation
Correct answer: Right optic nerve
A monocular field defect affecting only one eye points to pathology anterior to the optic chiasm — specifically the right optic nerve. Chiasmal or post-chiasmal lesions produce binocular (bilateral) field defects.
Question 2: A 7-year-old child exhibits a constant left esotropia of 30 prism diopters with no fixation preference. Best corrected visual acuity is 20/20 OD and 20/80 OS. Which test is most appropriate to quantify the depth of suppression in the amblyopic eye?
- Worth 4-dot test
- Bagolini striated lenses
- Neutral density filter bar (Correct answer)
- Hirschberg corneal reflex test
Correct answer: Neutral density filter bar
The neutral density filter bar progressively reduces luminance over the fixating eye to measure how deep suppression is in the amblyopic eye. Worth 4-dot and Bagolini lenses detect the presence of suppression but do not quantify depth. Hirschberg estimates the angle of deviation, not suppression depth.
Question 3: During cover-uncover testing of a patient, you observe that the uncovered left eye moves outward when the cover is placed over the right eye. What does this finding indicate?
- Left exophoria
- Left esotropia (Correct answer)
- Right exotropia
- Left exotropia
Correct answer: Left esotropia
In the cover-uncover test, movement of the uncovered eye reveals a manifest tropia. The left eye moving outward (temporally) to pick up fixation means it was previously deviated inward (esotropia). This is a left esotropia — a constant, manifest inward deviation of the left eye.
Question 4: A patient has a best corrected visual acuity of 20/400 in one eye. According to standard clinical definitions, this level of vision corresponds to which category?
- Normal vision
- Low vision
- Legal blindness (Correct answer)
- Total blindness
Correct answer: Legal blindness
Legal blindness is defined as best corrected visual acuity of 20/200 or worse in the better eye, or a visual field of 20 degrees or less. At 20/400, this patient meets the threshold for legal blindness. Low vision typically refers to 20/70 to 20/200. Total blindness implies no light perception.
Question 5: When using the Hirschberg corneal light reflex test, the examiner notes the reflex is displaced 2 mm temporally in the left eye relative to the right. Approximately how many prism diopters of deviation does this represent, and in which direction?
- 7 prism diopters of esotropia
- 15 prism diopters of esotropia (Correct answer)
- 15 prism diopters of exotropia
- 7 prism diopters of exotropia
Correct answer: 15 prism diopters of esotropia
Each 1 mm of corneal light reflex displacement corresponds to approximately 7–7.5 prism diopters of deviation. A temporal displacement of the reflex in the left eye means the eye is deviated nasally — an esotropia. At 2 mm, this equals roughly 14–15 prism diopters of esotropia.
Question 6: A COT is performing a cycloplegic refraction on a 6-year-old. The cycloplegic agent has been instilled and 45 minutes have passed. The pupil is dilated but the patient can still accommodate 2 diopters. What is the most appropriate next step?
- Proceed with refraction, as residual accommodation is clinically insignificant
- Instill an additional drop of the cycloplegic agent and wait another 20–30 minutes (Correct answer)
- Switch to a miotic agent to reverse the effect and restart
- Document the finding and refer to the ophthalmologist for adult refraction technique
Correct answer: Instill an additional drop of the cycloplegic agent and wait another 20–30 minutes
Adequate cycloplegia requires the elimination of accommodation (typically less than 0.50 D residual). If 2 diopters of accommodation remain after the standard waiting period, cycloplegia is incomplete. The correct response is to instill an additional drop and wait longer before refracting, ensuring accurate measurement of the true refractive error.
COT Pupil Assessment 2
When performing a confrontation visual field test, a patient fails to see the examiner's finger in the inferior nasal quadrant of the right eye.
Which cranial nerve or structure is most likely affected?