Lecture Series: Cover Test

A complete set of 50 question-and-answer flashcards based on the Cover Test lecture notes, covering definitions, setup, step-by-step procedures, directional neutralization, and standardized shorthand recording rules.

What is fusion in binocular vision?

Fusion is the process by which two eye images are combined into a single perception, with neurons and extraocular muscles (EOMs) working together to maintain a clear, single image.

What is motor fusion?

Motor fusion is the use of vergence eye movements to position the eyes to corresponding points.

What is sensory fusion?

Sensory fusion is the neurophysiological and psychological process of combining two images in the visual cortex.

What is the definition of version?

Version is a binocular movement or rotation of the eyes in the SAME direction.

What is the definition of vergence?

Vergence is a binocular movement of the eyes in the OPPOSITE direction.

How is a visual deviation defined?

A deviation is defined as a difference in eye position BETWEEN the two eyes.

What is a phoria (or heterophoria)?

A phoria is a deviation that can be compensated for with vergence movements and is not present in full binocular viewing.

What is a tropia (or strabismus)?

A tropia is a deviation that can NOT be compensated for with vergence movements and is present in both binocular and monocular viewing.

What is the primary purpose of performing a Cover Test?

Cover Test is the primary method to measure fixation deviations between the right and left eye and to assess the presence or absence of motor fusion.

When motor fusion is present, what does the Cover Test determine?

When motor fusion is present (no strabismus), Cover Test determines the magnitude of the demand on the patient's fusional vergence system.

What five materials are needed to perform a Cover Test?

• Visual Acuity (VA) Chart

• Near target

• Occluder

• Overhead Lamp

• Horizontal and Vertical prism bars or loose prisms

What target setup is required for distance Cover Test?

An isolated letter one line larger than the best corrected visual acuity (VA) in the poorer seeing eye.

What target setup is required for near Cover Test?

An accommodative target at $40\,cm$ using a Snellen letter one line larger than the best corrected VA in the poorer seeing eye.

Why are uncorrected myopes more likely to show a false exophoria during Cover Test?

Uncorrected myopes do not need to accommodate at near, resulting in less accommodative convergence because accommodation is linked to convergence.

Why are uncorrected hyperopes more likely to show a false esophoria during Cover Test?

Uncorrected hyperopes must accommodate excessively to see clearly, driving extra accommodative convergence because accommodation is linked to convergence.

What are the two main parts of the Cover Test procedure?

The Cover-Uncover Test (Unilateral) and the Alternating Cover Test.

Which phase of the Cover Test is performed first?

The Cover-Uncover (Unilateral) phase is performed first.

What is the specific goal of the Cover step in Cover-Uncover testing?

The Cover step differentiates between a phoria and a tropia.

Which eye does the examiner observe during the Cover step of Cover-Uncover testing?

The examiner watches the unoccluded eye.

What is the specific goal of the Uncover step in Cover-Uncover testing?

The Uncover step determines if a tropia is alternating or unilateral.

How is an alternating tropia defined during Cover-Uncover testing?

An alternating tropia is able to keep its visual axis aligned with the target when both eyes are open.

How is a unilateral tropia defined during Cover-Uncover testing?

A unilateral tropia habitually fixates with one eye when both eyes are open and only fixates with the troping eye when the fixating eye is occluded.

How long should the occluder be held over an eye during Cover-Uncover testing?

The occluder should be placed in front of the eye for $3-5\text{ seconds}$ before removing it.

What finding on steps 2 and 3 of Cover-Uncover testing confirms a phoria?

No movement observed in either eye when covering the opposite eye.

What movement observation during Cover-Uncover testing distinguishes an alternating tropia from a constant unilateral tropia?

In alternating tropia, both eyes move to fixate depending on which eye is covered, whereas in constant unilateral tropia, only one eye moves.

What is the purpose of the Alternating Cover Test?

To determine the direction and magnitude (size) of a phoria or tropia.

Does the Alternating Cover Test differentiate a phoria from a tropia?

No, the Alternating Cover Test does NOT differentiate a phoria from a tropia.

How is the occluder moved during the Alternating Cover Test?

It is moved quickly from one eye to the other and held for $3-5\text{ seconds}$ over each eye, ensuring full dissociation without allowing the patient to re-fuse.

What does a reversal of eye movement indicate during prism neutralization?

A reversal of movement indicates that too much prism has been added and you have gone past neutralization.

How is bracketing performed to verify orthophoria?

Start with Base In (BI) prism until reversal (eye swinging outward), then repeat with Base Out (BO) prism until reversal (eye swinging inward).

True orthophoria shows reversal at equal amounts of BI and BO.

If an eye moves IN when uncovered, what is the direction of deviation and what prism neutralizes it?

Direction: Exo; Prism: Base In (BI).

If an eye moves OUT when uncovered, what is the direction of deviation and what prism neutralizes it?

Direction: Eso; Prism: Base Out (BO).

If an eye moves UP when uncovered, what is the direction of deviation and what prism neutralizes it?

Direction: Hypo; Prism: Base Up (BU).

If an eye moves DOWN when uncovered, what is the direction of deviation and what prism neutralizes it?

Direction: Hyper; Prism: Base Down (BD).

In this Cover Test flowchart, if covering OS causes OD to move, what diagnosis is established?

Tropia.

In this ocular alignment diagram, which diagram shows an upward deviation of the eye?

The HYPER quadrant (top right).

What six parameters should be included when recording Cover Test findings?

1. Magnitude

2. Frequency

3. Eye involved

4. Direction

5. Distance (distance vs. near)

6. Comitancy

What criterion defines a noncomitant deviation?

A deviation where the magnitude varies by $5\,\Delta$ ($5\text{ PD}$) or greater depending on gaze direction.

What underlying medical conditions are suggested by a noncomitant deviation?

• Stroke

• Tumor

• Trauma (indicating unequal innervation or muscle function).

What is an intermittent tropia?

A tropia that is sometimes present and sometimes not, depending on viewing conditions or time of day (patient fatigue).

What symbol represents Eso in shorthand recording?

The letter E (or EP for esophoria, ET for esotropia).

What symbol represents Exo in shorthand recording?

The letter X (or XP for exophoria, XT for exotropia).

Why is there no standard shorthand symbol for a Hypo deviation?

Examiners must either write out Hypo longhand or record the finding relative to the Hyper eye.

Do lateral phorias include an eye designation in shorthand recording?

No, lateral phorias DO NOT have a designated eye (e.g., $6\,\text{EP}$).

Do vertical phorias include an eye designation in shorthand recording?

Yes, vertical phorias DO have a designated eye specified with R or L (e.g., $1\,\text{RH}$).

What notation designates that a Cover Test finding was recorded at near?

An apostrophe ($'$) placed after the direction symbol (e.g., $6\,\text{XP}'$).

What symbol is used for prism diopters and where is it placed in shorthand recording?

The delta symbol ($\Delta$) is placed after the magnitude number and before the direction symbol.

Translate the recorded finding "25 Δ LET" into plain English.

25 prism diopter left esotropia.

Translate the recorded finding "10 Δ IRXT" into plain English.

10 prism diopter intermittent right exotropia.

Where should neutralizing prism be placed when evaluating a patient with strabismus?

Place the prism over the deviating eye.