Subjective Measurement of Heterophoria Flashcards
(20 cards)
What is the definition of heterophoria?
heterophoria is a latent misalignment of the eyes, which occurs when fusion is disrupted, such as when one eye is covered.
What is the difference between heterophoria and heterotropia?
Heterophoria: A latent deviation of the eyes that only becomes apparent when fusion is disrupted.
Heterotropia (also known as strabismus): A manifest deviation where one eye is consistently misaligned even with both eyes open.
Why is heterophoria important to measure?
Measuring heterophoria helps to identify latent deviations that may cause eye strain, headaches, blurred vision, and double vision, even when the eyes appear to be aligned.
What is the purpose of the Maddox Rod test?
The Maddox Rod test is used to measure the horizontal, vertical, and cyclophoria at distance by dissociating the eyes and observing the deviation in a fixed light target.
How does the Maddox Rod test work?
The Maddox Rod is placed in front of one eye, typically the right eye, and the patient is asked to focus on a spotlight. The red streak produced by the rod is misaligned with the target, revealing any horizontal, vertical, or cyclophoric deviations.
What is the expected result when performing the Maddox Rod test for horizontal phoria?
SOP (Simulated Overaction of the Eye): The red line appears to the right of the target (indicating esophoria).
XOP (Crossed Overaction of the Eye): The red line appears to the left of the target (indicating exophoria).
What is the expected result when performing the Maddox Rod test for vertical phoria?
Hyperphoria: The red line appears above the target.
Hypophoria: The red line appears below the target.
What is the difference between horizontal phorias and vertical phorias?
Horizontal phorias are related to esophoria (inward deviation) or exophoria (outward deviation).
Vertical phorias are related to hyperphoria (upward deviation) or hypophoria (downward deviation).
How can cyclophoria be measured using the Maddox Rod?
Cyclophoria can be measured by observing the tilt of the red line as it deviates from the target.
Incyclophoria: The line tilts inward.
Excyclophoria: The line tilts outward.
What is the Maddox Wing test used for?
The Maddox Wing test is used to measure near phorias at a distance of approximately 30 cm by assessing the alignment of a red line and a white scale in the patient’s field of view.
How does the Maddox Wing test work?
The patient looks through the horizontal slits at a red arrow and a white scale.
Horizontal phorias are measured by seeing where the white arrow points.
Vertical phorias are measured by the position of the red arrow.
Cyclophoria is assessed by the alignment of the red bar.
How is horizontal phoria recorded using the Maddox Wing?
SOP: The white arrow points to an odd number.
XOP: The white arrow points to an even number.
Ortho: The white arrow points to zero.
How is vertical phoria recorded using the Maddox Wing?
Hyperphoria: The red arrow points to an odd number.
Hypophoria: The red arrow points to an even number.
Ortho: The red arrow points to zero.
What is the Modified Thorington method used for?
The Modified Thorington method is used for measuring both near and distance phorias by using a tangent scale that indicates prism diopters.
How does the Modified Thorington method work?
The patient looks through a hole in the test card with a penlight shining through.
Horizontal phorias are recorded by observing the number where the white arrow points on the tangent scale.
Vertical phorias are recorded by the red arrow’s position.
Cyclophorias are determined by aligning the red bar to appear horizontal.
What are the potential errors when performing the Maddox Rod and Maddox Wing tests?
Incorrect patient fixation or failure to ensure they are looking at the correct distance.
Misinterpretation of phoria direction (e.g., confusing esophoria with exophoria).
Inadequate control of accommodation, which could influence the results.
How do you determine the magnitude of a phoria?
The magnitude of the phoria is typically measured in prism diopters (∆), where 1 prism diopter corresponds to 1 mm of displacement at 1 meter distance.
What is the importance of measuring heterophoria in optometry?
Measuring heterophoria helps detect latent deviations that may lead to symptoms like eye strain, headaches, and double vision, even when the eyes appear properly aligned during routine examinations.
What is fusional vergence, and how does it relate to heterophoria?
Fusional vergence is the ability of the eyes to align and maintain binocular fusion by adjusting the angle of the eyes when a misalignment occurs. Heterophoria can be compensated by fusional vergence, but if the phoria is uncompensated, symptoms may arise.
How should you record the results of the Maddox Rod and Maddox Wing tests?
Record the type of phoria (e.g., esophoria, exophoria, hyperphoria, hypophoria).
Indicate the magnitude in prism diopters (e.g., 3∆ esophoria at near).
Note if the test was performed at distance or near.
