Objective Assessment of Eye Deviations Flashcards
(22 cards)
What is the primary purpose of the cover test in assessing eye deviations?
The cover test is used to assess ocular alignment and identify whether a person has a heterotropia (manifest deviation) or heterophoria (latent deviation).
How does the cover test help differentiate between tropias and phorias?
Tropia: A manifest deviation, visible when both eyes are open.
Phoria: A latent deviation, visible only when one eye is covered and the fusion reflex is blocked.
What is the procedure for performing a unilateral cover/uncover test for tropia?
Ask the patient to fixate on a target.
Cover one eye and observe if the uncovered eye moves to take up fixation (indicating tropia).
Uncover the eye and observe any movement as it attempts to realign (indicating the type and magnitude of tropia).
What does it mean if an eye moves when uncovered during the unilateral cover/uncover test?
If the eye moves when uncovered, it indicates that there is a tropia (manifest deviation). The direction of the movement reveals whether the tropia is esotropia, exotropia, hypertropia, or hypotropia.
How is phoria detected using the unilateral cover/uncover test?
Phoria is identified when the eye moves to its passive position after the cover is removed. The movement is typically less noticeable than in tropias and indicates latent misalignment.
What is the alternating cover test, and why is it important?
The alternating cover test involves switching the cover between the two eyes while observing for any movement. This test helps detect intermittent tropias and accurately measures the magnitude of a deviation, especially for phorias.
When performing the cover test, what should you do if no movement is observed?
If no movement is observed, it indicates orthophoria, meaning the eyes are aligned and there is no misalignment, either latent or manifest.
How do you measure the magnitude of deviation in the cover test?
The magnitude of deviation is typically measured using prism bars to neutralize the movement observed in the cover test. The prism diopter (∆) is used to quantify the deviation.
How does the fixation distance affect the results of the cover test?
Deviations may change in magnitude depending on the fixation distance. A deviation may be more noticeable at near (due to increased accommodation) or at distance, depending on the individual’s condition.
What is the significance of near and distance testing in assessing phorias and tropias?
Near testing allows for assessment of deviations that occur due to accommodation and convergence (e.g., near exophoria), while distance testing assesses deviations that occur in the absence of accommodation, helping to differentiate between accommodative and non-accommodative deviations.
: What does the term comitancy refer to in the context of eye deviations?
: Comitancy refers to whether the degree of deviation in a tropia remains consistent when the patient looks in different directions of gaze. Comitant tropia means the deviation is the same in all directions, while incomitant tropia means the deviation varies with gaze direction.
What is heterotropia?
Heterotropia (also called strabismus) is a manifest deviation where one eye is misaligned, even when both eyes are open and fixating. It can be constant or intermittent and requires treatment for proper binocular vision.
What is heterophoria?
Heterophoria is a latent deviation, where the eyes are aligned under normal conditions, but one eye may deviate when the binocular system is disrupted (e.g., one eye is covered). Heterophorias can be compensated with fusional vergence.
How do you differentiate between esophoria and exophoria during the cover test?
Esophoria: The eye tends to deviate inward (converge) when the binocular system is disrupted.
Exophoria: The eye tends to deviate outward (diverge) when the binocular system is disrupted.
What are the typical magnitudes of deviation for tropias and phorias?
Phorias: Typically have a smaller magnitude of deviation, often measured in prism diopters (∆).
Tropias: Can have a larger magnitude and are often more noticeable due to the lack of fusion reflex.
What role do prism bars play in the cover test?
Prism bars are used to measure the magnitude of a phoria or tropia by neutralizing the observed deviation. The prism diopter values help to quantify how much deviation is present.
Why is it important to assess binocular fusion during the cover test?
Binocular fusion allows the eyes to work together to align the visual axis. The cover test helps determine whether fusional vergence is compensating for the deviation and whether there is a latent or manifest misalignment.
What is the significance of prism fusion range?
The prism fusion range refers to the range of prism diopters over which the patient can maintain single binocular vision. It is useful in assessing how much deviation can be corrected by the fusional vergence system before the patient experiences double vision.
How does accommodation influence the results of the cover test?
Accommodation can cause a near deviation (such as esophoria), especially when the patient is focused on a near object. The cover test helps to distinguish whether the deviation is due to accommodation or a non-accommodative condition.
How can the cover test be used to diagnose intermittent tropias?
The alternating cover test helps identify intermittent tropias by alternating the cover between eyes, which breaks fusion and reveals deviations that may occur sporadically, providing insight into the magnitude and type of tropia.
What are the potential clinical implications of an uncompensated phoria?
An uncompensated phoria can lead to symptoms like eye strain, headaches, blurred vision, and difficulty with reading. It may also affect binocular vision, leading to challenges in depth perception.
How do you perform a Brückner test to assess eye alignment?
The Brückner test involves shining a direct ophthalmoscope at the eyes from a distance and observing the red reflex in each eye. Any asymmetry in the reflex can indicate a tropia or anisometropia.
