Ocular Motility/ Binocular Vision Flashcards
(46 cards)
What is forced duction testing used for?
Differentiating between muscle weakness and restrictive causes of limitations in extraocular muscle movements
This test helps identify whether the issue is due to muscle paresis or restriction/entrapment.
(+) = muscle problem
(-) = cranial nerve palsy
What type of anesthesia is typically used during forced duction testing?
Topical eye drops
This method is used to minimize discomfort for the patient during the procedure.
What is the initial instruction given to the patient during forced duction testing?
Look as far as possible in the direction of the suspected underacting muscle
This action recruits maximum innervation to the muscle being tested.
What tool does the examiner use to perform forced duction testing?
Forceps
The forceps are used to grasp the conjunctiva near the limbus.
What indicates muscle paresis during forced duction testing?
If the forceps can rotate the globe further than the patient can move it on his own
This suggests some degree of muscle weakness.
What indicates restriction or entrapment of the muscle during forced duction testing?
If the globe cannot be rotated farther than the patient’s movement
This implies that the muscle is likely restricted or entrapped.
In a scenario where the patient has a deficit in superior gaze, which muscle should be anesthetized?
Inferior rectus muscle
This muscle is involved when testing for deficits in upward gaze.
What is considered a positive forced duction test?
Resistance during further superior rotation of the eye
This indicates potential muscle paresis.
What is considered a negative forced duction test?
Effortless rotation of the eye
This suggests that there is no muscle paresis present.
What is the Worth-4-dot test?
A visual test used to assess binocular vision and perception of color.
It involves projecting four dots onto a screen to evaluate how each eye perceives them.
What colors are typically used in the Worth-4-dot test?
Red, green, and white
The top circle is usually white, the bottom circle is red, and the two horizontal circles are green.
What does the presence of three green circles viewed to the right of two red circles indicate?
Crossed diplopia (exo deviation)
This suggests a misalignment in the eyes where the images appear crossed.
What does the perception of three green circles viewed to the left of two red circles indicate?
Uncrossed diplopia (eso deviation)
This indicates a different type of misalignment where images appear uncrossed.
What does viewing three green circles alone signify?
Right eye suppression
This suggests that the right eye is not contributing to the visual perception.
What does a patient reporting two red circles indicate?
Suppression of the left eye
This indicates that the left eye is not being utilized in visual perception.
In the Worth-4-dot test, what color does the right eye perceive for the top circle if the patient has simultaneous perception?
Pink/red
The right eye views the top circle as a mix of red and the white light.
What should both eyes combined view in the Worth-4-dot test under normal conditions?
Four circles: two green, one red, and one red/green
This is the expected outcome if both eyes are functioning properly.
What is the purpose of dissociating methods in ophthalmology?
To cause diplopia with prism, enabling the clinician to quantify a phoria.
Phoria refers to a latent deviation of the eyes that is not present when both eyes are open.
What is the Von Graefe method?
A dissociating technique involving placing a 4 base-up dissociating prism before the left eye and a biasing prism before the right eye.
This method helps to quantify phoria by aligning two perceived targets.
What should the patient initially perceive when using the Von Graefe method?
Two targets, one up and to the right, and the other down and to the left.
This initial perception is crucial for assessing the alignment of the eyes.
What is recorded when the targets are aligned horizontally in the Von Graefe method?
The amount of prism before the left eye.
This amount indicates the degree of phoria present.
How is a deviation described when there is base-up prism in front of the left eye?
As either right hyperphoria or left hypophoria in the amount equal to the neutralizing prism before the left eye.
Hyperphoria indicates an upward deviation, while hypophoria indicates a downward deviation.
What do distortion methods do in the context of ophthalmology?
Blur one or both retinal images to eliminate the reflex for binocular fusion.
This helps in assessing the alignment of the eyes by disrupting normal visual perception.
What is the Modified Thorington method?
A technique that utilizes a Maddox rod to create distortion.
This method aids in determining the presence and degree of strabismus.
