Convergence Excess ET Characteristics

Summary

This video explains the characteristics of convergence excess, focusing on intermittent exotropia (XT) with a convergent success pattern. It discusses the two main causes: high AC/A ratio and hypoaccommodation. A high AC/A ratio results in excessive accommodative convergence, leading to intermittent deviations at near distances. In contrast, hypoaccommodation causes excessive accommodation during close work, which also leads to deviation. The video highlights how these conditions affect binocular function and can lead to amblyopia in children due to constant suppression before refractive error correction.

Takeaways

• 😀 Convergence excess (CE) refers to a condition where the eye deviation is greater at near distances than at far distances, leading to intermittent exotropia (XT).
• 😀 Two primary causes of convergence excess include a high AC/A ratio and hypo-accommodation.
• 😀 A high AC/A ratio results in excessive convergence when the eyes accommodate for near tasks, causing intermittent exotropia at near.
• 😀 Patients with a high AC/A ratio typically show normal refractive error, but experience excessive accommodative convergence, leading to intermittent exotropia at near distances.
• 😀 Hypo-accommodation is when the patient struggles to focus on near objects, leading to excessive accommodation, which in turn causes excessive convergence and intermittent exotropia.
• 😀 The deviation caused by hypo-accommodation is also intermittent and typically only present at near distances, not at far distances.
• 😀 With both high AC/A ratio and hypo-accommodation, there is no manifest eye deviation at far distances, but the eyes may deviate at near due to increased accommodation.
• 😀 Suppression often occurs in patients with convergence excess to avoid double vision, particularly in children, raising the risk of developing amblyopia.
• 😀 Refractive correction can help identify and manage intermittent exotropia caused by high AC/A ratio or hypo-accommodation.
• 😀 While both conditions cause similar symptoms, patients with high AC/A ratios generally have normal accommodation, while those with hypo-accommodation show a remote near point of accommodation.
• 😀 Identifying whether the cause is high AC/A ratio or hypo-accommodation is key to selecting the appropriate treatment to manage convergence excess effectively.

Q & A

What is convergence excess in the context of eye conditions?

Convergence excess refers to a condition where there is an excessive amount of accommodative convergence, leading to intermittent strabismus (eye deviation) that is more pronounced when focusing on near objects compared to distant ones.

What causes a convergence excess pattern?

A convergence excess pattern can be caused by either a high AC/A (Accommodative Convergence to Accommodation) ratio or hypoaccommodation. The high AC/A ratio is the more common cause.

How does a high AC/A ratio affect eye convergence?

A high AC/A ratio causes excessive accommodative convergence, meaning that as the fixation point moves closer, the convergence effort increases disproportionately, leading to a deviation of the eyes at near distances.

What is hypoaccommodation, and how does it relate to convergence excess?

Hypoaccommodation refers to the inability to fully accommodate or focus on near objects. This leads to excessive convergence when the patient attempts to focus on close-up work, causing an intermittent deviation (tropia) of the eyes at near distances.

Why is the deviation intermittent in convergence excess?

The deviation is intermittent because there is no manifest eye deviation at distance vision, and the excessive convergence only becomes noticeable when the person focuses on near objects.

What role does the near point of accommodation play in hypoaccommodation?

In hypoaccommodation, the near point of accommodation is further away than normal, meaning that when the patient tries to focus on near objects, the eye exerts excessive accommodation, which increases convergence and causes an intermittent tropia.

How does a high AC/A ratio contribute to strabismus at near distances?

A high AC/A ratio causes excessive accommodative convergence. As the person focuses on near objects, the excessive convergence leads to strabismus (eye deviation), making the condition more noticeable at near distances.

What is the typical refractive condition seen in patients with a high AC/A ratio?

Patients with a high AC/A ratio typically have normal refractive conditions, meaning their strabismus is not due to a refractive error but rather due to the abnormal convergence response.

How does correction of refractive error impact convergence excess in patients?

Correcting the refractive error in patients with convergence excess often leads to intermittent eye deviation. Without correction, some patients may experience constant strabismus, especially at near distances.

How does a patient with hypoaccommodation differ from one with a high AC/A ratio in terms of eye alignment?

Patients with hypoaccommodation tend to have a remote near point of accommodation and excessive accommodation efforts, leading to convergence excess at near distances. In contrast, patients with a high AC/A ratio experience an excessive convergence response, even without hypoaccommodation, leading to intermittent strabismus at near distances.