4. Assessment of eye movements

What reading-related symptoms are commonly seen in oculomotor dysfunction?

Ineffective saccadic eye movements during reading lead to:

• Frequent loss of place while reading

• Skipping words or lines

• Slow reading

• Reduced reading comprehension and attention

• Increased regressions (re-reading text)

• Excessive head movement while reading

Besides reading difficulties, what other academic and functional complaints may suggest oculomotor dysfunction?

Patients may report:

• Difficulty copying from the board

• Difficulty performing math in columns of numbers

• Difficulty completing computerized scan-sheet tests

• Poor sports performance

What clinical signs are associated with oculomotor dysfunction?

Common signs include:

• Inaccurate fixation

• Inaccurate saccades

• Inaccurate pursuits

• Performance below age-expected norms on oculomotor testing

What should be considered in the differential diagnosis of oculomotor dysfunction?

Rule out:

• Neurologic and pathologic causes of eye movement abnormalities (e.g., cranial nerve palsies, INO, myasthenia gravis, cerebellar disease, Parkinson disease, Alzheimer's disease)

• Ocular motor disorders such as nystagmus or ocular motor apraxia

• Medication effects that can impair eye movements

What are the major components of an oculomotor assessment?

Assessment typically includes:

• Fixation stability

• Saccadic eye movements

• Pursuit eye movements

Saccades may be evaluated with:

• NSUCO

• DEM (Developmental Eye Movement test)

• King-Devick (KD)

• Electro-oculographic/eye-tracking instruments

What does the NSUCO saccadic test evaluate?

The NSUCO saccadic test evaluates:

1. Ability to complete saccadic movements

2. Accuracy (need for corrective refixations)

3. Head movement

4. Body movement

Poor performance suggests deficient oculomotor control.

How is the NSUCO saccadic test performed?

The patient:

• Views binocularly

• Stands facing the examiner

• Looks back and forth between two targets

• Targets are ~20 cm apart on the horizontal meridian

• Performs 10 shifts (5 round trips)

The examiner grades:

• Ability

• Accuracy

• Head movement

• Body movement

What are the advantages and limitations of subjective observation tests (e.g., NSUCO) for evaluating saccades?

Advantages:

• Easy to learn and administer

• Provides clinical information about eye movement behavior

Limitations:

• Observations can be difficult to master

• Interobserver and intraobserver variability

• Difficult to quantify results

• Less useful for objectively monitoring progress during therapy

How does the DEM (Developmental Eye Movement) test assess saccadic function?

The DEM is a timed, standardized visual-verbal test that simulates eye movements used during reading.

The patient:

• Names numbers as quickly as possible

• Is scored on time and accuracy

• Is compared with age-based norms

The DEM provides a more objective measure than simple observation alone.

Compare NSUCO and DEM for assessing oculomotor dysfunction.

NSUCO	DEM
Subjective observation	Timed standardized test
Evaluates ability, accuracy, head and body movement	Evaluates reading-related eye movement performance
Easier to perform clinically	More objective and quantifiable
Observer-dependent	Compared against age norms
Limited for tracking progress	Useful for diagnosis and monitoring therapy outcomes

What is the King-Devick (KD) test and what is it used for?

The King-Devick is a timed reading/saccadic eye movement test in which the patient rapidly reads numbers. Performance is compared with expected values and can be used to assess oculomotor function.

A major application is concussion screening.

How is the King-Devick test used for concussion screening?

The patient's post-injury performance is compared with a baseline score.

Key points:

• Baseline testing should be established before injury.

• Best error-free performance is used as the baseline.

• Slower times and/or increased errors after injury may indicate concussion.

What is the advantage of objective eye-tracking systems (e.g., Visagraph, ReadAlyzer) over observational tests?

Objective eye trackers provide quantitative measurements of eye movements rather than subjective observations.

They can measure:

• Number of fixations

• Number of regressions

• Fixation duration

• Reading rate

This improves objectivity and allows comparison with normative data.

What does ReadAlyzer/Visagraph evaluate in patients with suspected oculomotor dysfunction?

These systems objectively assess reading eye movements, including:

• Fixation patterns

• Regressions

• Reading speed

• Overall reading efficiency

They are useful for diagnosing and monitoring reading-related oculomotor deficits.

How are pursuit eye movements clinically assessed?

The patient follows a moving target:

• In a broad H pattern and circular motion

• Tested binocularly and/or monocularly

• Examiner evaluates smoothness and accuracy of tracking

Performance is graded based on fixation losses during pursuit.

How is pursuit performance graded?

• 4+ = smooth and accurate pursuit

• 3+ = one fixation loss

• 2+ = two fixation losses

• 1+ = more than two fixation losses

Expected performance: 3+ or better

What information can objective eye-tracking systems (e.g., Visagraph/ReadAlyzer) provide?

They provide quantitative measures of reading eye movements, including:

• Number of fixations

• Number of regressions

• Fixation duration

• Reading rate

These measurements can be compared with normative data and used to monitor treatment outcomes.

What is the natural history and treatment goal of oculomotor dysfunction?

Oculomotor dysfunction often does not resolve spontaneously.

Evidence cited in the lecture:

• 72% (26/36) of untreated patients still failed the DEM when retested 1 year or more later.

Treatment goal:

• Normalize ocular motor function

• Eliminate symptoms

Improved reading and sports performance may occur indirectly as ocular motor function improves.

What should be addressed before treating oculomotor dysfunction?

Correct any uncorrected refractive error first.

Reason:

• Adequate visual acuity is necessary for accurate eye movements and assessment of oculomotor function.

How is isolated oculomotor dysfunction managed, and what improvements can be expected with therapy?

Vision therapy can improve:

• Saccades

• Overall visual skills

• Fusion ranges

• Accommodation

Studies cited in the lecture reported improved reading performance after approximately 20-30 sessions of computer-based therapy.

Treatment goal: Normalize ocular motor function and eliminate symptoms.