Optometry Guidelines and Eye Movements

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Questions and Answers

What does a decompensated phoria cause in terms of visual symptoms?

It causes blur, diplopia, and fatigue.

How does poor accommodation or convergence relate to phoria decompensation?

They can create stress on binocularity, resulting in phoria decompensation, especially at near distances.

Differentiate between 'palsy' and 'paresis' concerning extraocular muscle function.

Palsy indicates total loss of EOM function, whereas paresis indicates weakness in EOM function.

Which cranial nerve innervates the Superior Oblique muscle?

Cranial nerve IV (Trochlear). Signup and view all the answers

What is indicated when the Cover Test shows no tropia or phoria?

It indicates that the eyes are properly aligned and functioning well together. Signup and view all the answers

What role do agonist muscles play in eye movements?

Agonist muscles contract to pull the eye in the desired direction. Signup and view all the answers

Define ipsilateral muscles and provide an example related to eye movement.

Ipsilateral muscles are on the same side as the movement; for instance, the right lateral rectus muscle controls the right eye's outward movement. Signup and view all the answers

Explain the relationship between contralateral muscles and horizontal eye movement.

Contralateral muscles are on the opposite side; for horizontal movement to the right, the left medial rectus is the contralateral muscle that moves the left eye inward. Signup and view all the answers

Why is it important for both ipsilateral and contralateral muscles to work together during eye movements?

Both types of muscles must coordinate to allow both eyes to focus on the same target smoothly. Signup and view all the answers

What happens to the antagonist muscle during eye movements?

The antagonist muscle relaxes to allow for smooth movement of the eye. Signup and view all the answers

What test is used to measure A tropia and phoria?

The Cover Test is used to measure A tropia and phoria. Signup and view all the answers

How does one indicate a left or right exotropia using the Cover Test?

Exotropia is indicated by the movements of the eyes when base IN is applied for EXO or base OUT for ESO. Signup and view all the answers

What is the difference between a tropia and a phoria?

A tropia is a constant misalignment of the eyes, whereas phorias are latent misalignments that occur only when binocular vision is disrupted. Signup and view all the answers

What is the purpose of the Maddox rod in testing for phorias?

The Maddox rod is used to determine the direction and degree of a phoria by creating a specific fixation disparity. Signup and view all the answers

Describe what is meant by fixation disparity.

Fixation disparity refers to the misalignment of the visual axes at a specific distance, leading to visual discomfort or diplopia. Signup and view all the answers

What tests can be performed to assess ocular motility?

Ocular motility tests include assessing smooth pursuit movements, any reported diplopia, and evaluating the size of palpebral apertures. Signup and view all the answers

In the case of reported diplopia, what initial step should be taken?

The direction where the images of diplopia are furthest apart should be determined. Signup and view all the answers

What does strabismus refer to in clinical terms?

Strabismus refers to the misalignment of the eyes, where they do not properly coordinate to focus on the same point. Signup and view all the answers

What does the 'A' and 'V' notation indicate in relation to eye movement deviations?

'A' indicates greater inward drift in superior gaze, while 'V' indicates greater inward drift in primary or inferior gaze. Signup and view all the answers

What is the role of agonist muscles in eye movement?

Agonist muscles are responsible for contracting to pull the eye in a specific direction during movement. Signup and view all the answers

How do antagonist muscles function in relation to agonist muscles during eye movements?

Antagonist muscles relax to allow the movement initiated by the contracting agonist muscles. Signup and view all the answers

What are the two main types of extraocular muscles, and what movements do they control?

Rectus muscles control basic up, down, left, and right movements, while oblique muscles manage more complex movements like rotation. Signup and view all the answers

What is the importance of synergist muscles in upward gaze?

Synergist muscles assist the primary agonist muscle in performing movements more effectively. Signup and view all the answers

Why is understanding eye movement deviations like ESO or EXO important?

Understanding these deviations helps in diagnosing and managing conditions related to strabismus. Signup and view all the answers

What determines whether the inward drift in eye movements increases or decreases?

The specific gaze direction, whether downgaze or upgaze, determines the variation in primary deviation (PD). Signup and view all the answers

How does the interaction between agonist and antagonist muscles facilitate smooth eye movements?

The contraction of agonist muscles and the simultaneous relaxation of antagonist muscles create a coordinated movement. Signup and view all the answers

What characterizes a V-pattern strabismus during upgaze?

A V-pattern strabismus during upgaze shows an exotropia of 15 PD, with the deviation decreasing or reversing in downgaze. Signup and view all the answers

In X-pattern strabismus, how does the deviation behave in primary gaze compared to upgaze and downgaze?

In X-pattern strabismus, there is 10 PD exotropia in primary gaze, but 20 PD exotropia in both upgaze and downgaze. Signup and view all the answers

Describe the features of Y-pattern strabismus.

Y-pattern strabismus shows 20 PD exotropia in upgaze and 0 PD exotropia in downgaze, indicating significant deviation upward. Signup and view all the answers

What does λ-pattern strabismus indicate in terms of horizontal and vertical deviations?

λ-pattern strabismus presents both horizontal (exotropia) and vertical (hypertropia) deviations that vary with gaze. Signup and view all the answers

What is the significance of a 15 PD difference from downgaze to upgaze in diagnosing strabismus patterns?

A significant 15 PD difference indicates the presence of specific strabismus patterns, particularly a V-pattern. Signup and view all the answers

How does downgaze differ in strabismus types like the V-pattern compared to the X-pattern?

In V-pattern, downgaze may show 0 PD or slight esotropia, while in X-pattern, it maintains 20 PD exotropia. Signup and view all the answers

What are the main considerations when evaluating strabismus patterns like A and V?

The main considerations are the pattern formation and the degree of deviation in various gazes. Signup and view all the answers

What would you expect to see in terms of horizontal and vertical alignment in λ-pattern strabismus during upgaze?

During upgaze in λ-pattern strabismus, one would expect significant exotropia alongside upward hypertropia. Signup and view all the answers

What characterizes A-pattern strabismus in terms of eye alignment during upward and downward gaze?

In A-pattern strabismus, the eyes are more esotropic when looking upward and more exotropic when looking downward. Signup and view all the answers

What is the cause of A-pattern strabismus?

A-pattern strabismus can occur due to overaction of the superior oblique muscles or underaction of the inferior oblique muscles. Signup and view all the answers

How does V-pattern strabismus affect ocular alignment in various gazes?

In V-pattern strabismus, the eyes are more exotropic when looking upward and more esotropic when looking downward. Signup and view all the answers

What muscular actions are generally involved in causing V-pattern strabismus?

V-pattern strabismus typically results from overaction of the inferior oblique muscles or underaction of the superior oblique muscles. Signup and view all the answers

Describe the eye alignment in X-pattern strabismus during upward and downward gaze compared to primary gaze.

In X-pattern strabismus, there is more exotropia in both upward and downward gaze than in primary gaze. Signup and view all the answers

What is a notable characteristic of Y-pattern strabismus regarding eye alignment?

Y-pattern strabismus displays more exotropia when looking upward but less or no exotropia in downward gaze. Signup and view all the answers

What specific gaze pattern do the eyes exhibit in Y-pattern strabismus?

In Y-pattern strabismus, the eyes are more exotropic in upward gaze and less or not exotropic in downward gaze. Signup and view all the answers

How do the degrees of misalignment change during downward gaze in A-pattern strabismus?

In A-pattern strabismus, the degree of misalignment decreases when looking downward. Signup and view all the answers

Study Notes

Optometrist Guidelines

Eye examinations must assess and record habitual ocular muscle balance, using at least a cover test for both distance and near.
This should be performed with typical vision and/or without prescription if appropriate.
Clinically appropriate additional tests may be performed, including convergence and ocular motility assessment.

Comitant and Incomitant Deviations

Comitant: The angle of deviation stays constant in all gaze directions.
Incomitant: The angle of deviation changes with gaze direction.
Congenital or acquired deviation may indicate systemic disease.
Possible causes for incomitant deviation include paralysis, paresis (nerve damage), or restrictions of extraocular muscles.

Associations

Potential associated conditions include amblyopia, sensory adaptation, hyperopia, poor stereopsis, and diplopia.

Eye Movements: Versions

Versions: both eyes move in the same direction.
Examples
- Dextroversion (RE abducts, LE adducts)
- Levoversion (RE adducts, LE abducts)

Eye Movements: Vergences

Vergences: both eyes move in the opposite direction.
Examples
- Convergence (RE and LE adduct)
- Divergence (RE and LE abduct)

Key Words

Heterophoria: a latent deviation.
Heterotropia: a manifest deviation.

Heterophoria and Decompensation

Compensation: Controlled phoria, no manifest deviation present with binocular stimulus; only present in dissociation.
Decompensation: Present binocular deviation in the presence of binocular stimulus, leading to blur, diplopia, and fatigue.
Poor eye accommodation or convergence can stress binocularity, leading to decompensation, particularly focusing on near objects.

EOM Palsies and Pareses

Palsy: Total loss of EOM function.
Paresis: Weakness in EOM function.

Extraocular Muscle Innervation

Superior Oblique (SO): Cranial nerve IV (Trochlear).
Inferior Oblique (IO): Cranial nerve III (Oculomotor).
Superior Rectus (SR): Cranial nerve III (Oculomotor).
Inferior Rectus (IR): Cranial nerve III (Oculomotor).
Medial Rectus (MR): Cranial nerve III (Oculomotor).
Lateral Rectus (LR): Cranial nerve VI (Abducens).

The Cover Test

Step 1: Checks for tropia.
Step 2: If no tropia, checks for phoria.
Subjective cover test: performed for phoria or tropia
Measurements of Exo and Eso to establish the base position of IN and OUT.

Fixation Disparity

Distance: aligned disparity (LE only).
Distance: vertically aligned disparity.
Data in terms of the difference in alignment between right and left eyes are collected for each test. (examples provided as OXO)

Suppression

Bagolini Lenses
Worth 4 dot test

Ocular Motility Test

Symptom checks (any discomfort, diplopia, smooth pursuit movements affected etc.)
STAR MOTION – checking for any irregularities

What is Diplopia Reported?

Locate: Direction where diplopia images are furthest apart.
Establish: Which eye sees each image.

A/V/X/Y Patterns and Lambda

Strabismus: Misalignment of eyes.
Patterns: A, V, X, Y, and λ (lambda) patterns observed in misalignment changes during different gazes.

Breakdown of Each Pattern

A-pattern: more esotropia (inward turning) when looking upward and more exotropia (outward turning) when looking downward.
V-pattern: more exotropia when looking upward, more esotropia when looking downward.
X-pattern: More exotropia in both upward and downward gaze as compared to primary gaze.
Y-pattern: More exotropia in upgaze and less or no exotropia in downward gaze.
Lambda (λ): Combination of horizontal and vertical deviations varying with gaze.

Clinical Relevance

A and V-patterns: Most frequent and significant functional and cosmetic issues, causing head or chin tilts.
Treatment: Usually eye muscle surgery to balance tension in oblique or rectus muscles, depending on the cause.
Diagnosis: Recognizing the specific pattern allows for appropriate diagnosis and surgical planning Different patterns of strabismus are described in terms of prism diopters.

More tests for phoria

Maddox Rod: Used to test for phoria (base in or base out, up or down).
Near Maddox Wing: Used for near testing of phoria.

Summary of Key Optometrist Concepts

Ipsilateral muscles: Muscles on the same side of the body/eye as the movement.
Contralateral muscles: Muscles on the opposite side of the body/eye.
Eye movements, especially horizontal ones, require coordinated pairs of ipsilateral and contralateral muscles to focus on the same target.

Agonist Muscles

Definition: The primary muscle responsible for a specific eye movement.
Function: Pulls the eye into the desired direction.

Antagonist Muscles

Definition: The muscle that works in opposition to the agonist, relaxing when the agonist contracts.
Function: Relaxes to allow smooth movement in the opposite direction.

Synergists

Definition: Muscles that assist the primary agonist to produce a smooth movement in a given direction.
Function: Assists primary agonist in a coordinated manner for smooth and efficient eye movement.
Relationships: Agonist and Antagonist muscles work together in coordinated pairs and their relationship. Ipsilateral and contralateral muscles work together in coordinated pairs to allow the eyes to move as a complete unit.

Ipsilateral Muscles

Definition: On the same side of the body or head.
Application to eye movement: Muscles on the same side as the movement.

Contralateral Muscles

Definition: On the opposite side of the body or head.
Application to eye movement: Muscles on the opposite side of the movement.

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Description

This quiz covers essential guidelines for optometrists regarding eye examinations and the assessment of ocular muscle balance. It differentiates between comitant and incomitant deviations, discusses associated conditions, and explains eye movement versions. Test your knowledge on these critical aspects of optometry.