Assessment of Vergence Flashcards
(23 cards)
a) A 20-year-old patient with a distance PD of 64 mm views their phone at 40 cm. What is the total angle of convergence (in prism dioptres) during this task? Show your working.
b) For convergence eye movements, name the agonist and antagonist extraocular muscles.
a)
MA = 1 / 0.4 = 2.5.
Total angle of convergence = 2.5 × 6.4 = 16 prism dioptres.
b)
Agonist muscles: Right medial rectus and left medial rectus.
Antagonist muscles: Right lateral rectus and left lateral rectus.
definition of vergence in optometry?
Vergence refers to the simultaneous movement of both eyes in opposite directions, either towards each other (convergence) or away from each other (divergence), in response to near or distant visual stimuli.
main types of vergence?
Convergence (Positive Vergence): Eyes move inward towards the nose to focus on a near object.
Divergence (Negative Vergence): Eyes move outward to focus on a distant object.
Supravergence: One eye moves upward relative to the other.
Infravergence: One eye moves downward relative to the other.
Incyclovergence: The upper poles of both corneas rotate inward.
Excyclovergence: The upper poles of both corneas rotate outward.
What is the difference between fusional vergence and accommodative vergence?
Fusional vergence is the vergence movement needed to maintain binocular single vision by adjusting the eyes to keep the visual axes aligned.
Accommodative vergence occurs when accommodation (focusing) changes in response to a near object, which also drives convergence of the eyes.
What is Near Point of Convergence (NPC), and how is it measured?
: NPC is the closest point at which an individual can focus on an object while maintaining binocular single vision. It is measured by slowly moving a target towards the nose and recording the break point (when double vision occurs) and recovery point (when the object becomes single again).
What is the normal range for the NPC in a healthy adult?
The normal NPC is usually less than 6 cm for the break point and less than 10 cm for the recovery point. Any deviation beyond this may indicate convergence insufficiency.
: What is jump convergence and how is it tested?
Jump convergence is the ability to alternate convergence between near and distant targets. It is tested by asking the patient to focus on a near object and then quickly shifting focus to a distant target and back again, noting the speed and accuracy of the movement.
What are fusional reserves?
Fusional reserves refer to the maximum amount of vergence that can be exerted to maintain binocular single vision while compensating for misalignments. It is measured by gradually increasing the amount of prism in front of one eye and recording the break point (when double vision occurs) and recovery point (when fusion is restored).
What are prism bars, and how are they used in the assessment of fusional reserves?
rism bars are a tool used to measure fusional reserves by progressively introducing base-in (BI) or base-out (BO) prisms. The patient is asked to report when double vision occurs, and the point at which they can no longer maintain fusion is recorded.
What is the difference between positive fusional reserve (PFR) and negative fusional reserve (NFR)?
Positive Fusional Reserve (PFR): The ability to converge the eyes (moving inward) to maintain single vision with base-out (BO) prisms.
Negative Fusional Reserve (NFR): The ability to diverge the eyes (moving outward) to maintain single vision with base-in (BI) prisms.
What is the typical range for normal fusional reserves in healthy adults?
Positive Fusional Reserve (PFR): 14-20 Δ.
Negative Fusional Reserve (NFR): 10-15 Δ.
Fusional reserves outside these ranges may indicate convergence or divergence insufficiency.
What is the clinical significance of measuring vergence?
Measuring vergence is crucial for assessing a patient’s ability to maintain binocular single vision (BSV) during near and distant tasks. Abnormal vergence responses can indicate issues like convergence insufficiency, divergence excess, and other visual disorders that can affect daily activities like reading.
How is vergence dysfunction related to symptoms such as eye strain and double vision?
Vergence dysfunction, such as convergence insufficiency or divergence excess, can lead to visual fatigue, double vision, and difficulty focusing at near distances. Symptoms include eye strain, headaches, and blurred vision, especially during prolonged near work like reading.
What is vergence adaptation, and how is it measured?
Vergence adaptation refers to the eyes’ ability to adjust and maintain proper alignment with changes in distance and accommodative demands. It can be assessed by observing the patient’s ability to restore fusion during dynamic tasks (e.g., jumping between near and far objects).
How does accommodative convergence (AC) differ from fusional convergence (FC)?
Accommodative Convergence (AC): Convergence induced by the need to focus on a near object.
Fusional Convergence (FC): Convergence required to maintain binocular single vision in response to misalignment of the eyes.
What is the AC/A ratio, and how is it calculated?
The AC/A ratio is the amount of convergence (measured in prism diopters) that occurs per diopter of accommodation. It is calculated by dividing the change in vergence by the change in accommodation. The normal range for the AC/A ratio is typically between 3:1 and 6:1.
What is the clinical significance of an abnormal AC/A ratio?
An abnormal AC/A ratio can indicate a dysfunction in accommodative convergence and lead to conditions like convergence excess or convergence insufficiency. It may also play a role in strabismus and contribute to symptoms of eye strain or double vision.
What is the purpose of the Vergence Facility Test, and how is it performed?
The Vergence Facility Test measures the speed and efficiency of vergence movements using prism flippers. The patient is asked to switch between base-in and base-out prisms while maintaining clear and single vision. A normal result is typically 12-15 cycles per minute (cpm) for near vergence.
What is the significance of measuring vergence near point and vergence reserves during a routine eye exam?
Measuring vergence near point and vergence reserves allows optometrists to evaluate the eyes’ ability to converge and diverge properly during tasks that require binocular vision. This helps identify issues like convergence insufficiency, divergence excess, and other binocular vision disorders that can impact reading and near tasks.
How do abnormal findings in vergence testing relate to ocular motility disorders?
Abnormal vergence findings can be a key indicator of ocular motility disorders such as strabismus, convergence insufficiency, or binocular dysfunction. These conditions can lead to symptoms like double vision, headaches, and eye fatigue, particularly with prolonged reading or screen use.
What are common vergence disorders, and how are they treated?
Convergence Insufficiency: Difficulty converging eyes at near; treated with vergence exercises or prism therapy.
Convergence Excess: Over-convergence when focusing at near; treated with vision therapy to relax convergence.
Divergence Excess: Over-divergence at distance; managed with prism lenses or vision therapy.
What are the differences between comitant and incomitant strabismus in relation to vergence?
Comitant strabismus: The angle of deviation remains the same in all directions of gaze, typically associated with vergence dysfunction.
Incomitant strabismus: The angle of deviation varies with gaze direction, often due to neurological conditions or muscle paresis.
What is the treatment for vergence dysfunction?
Vision therapy to improve convergence or divergence abilities.
Prism lenses to help manage vergence issues.
Oculomotor training exercises to improve vergence adaptation.
