What is divergence insufficiency (DI)?
An eso deviation that is:
* Greater at distance than near
* Associated with low AC/A ratio
* Inadequate divergence for distance viewing
DI is characterized by a specific type of esotropia that primarily affects distance vision.
What are the key clinical features of divergence insufficiency?
- Esophoria greater at distance
- Low AC/A ratio
- Reduced negative fusional vergence (NFV) at distance
- Normal near findings
These features help in diagnosing DI during clinical assessments.
What symptoms do patients with DI experience?
- Intermittent diplopia at distance (worse when tired)
- Headaches
- Asthenopia
- Photophobia
- Motion sickness
These symptoms can significantly affect the quality of life for individuals with DI.
What are the key signs of divergence insufficiency?
- Poor NFV at distance
- Distance eso deviation > near
- Low AC/A (calculated AC/A used)
- Normal accommodation and stereopsis at near
Identifying these signs is crucial for accurate diagnosis.
Why is NPC normal in divergence insufficiency?
Because the deviation occurs at distance, not near → convergence system is intact.
This indicates that the near vision system functions properly despite distance issues.
What is the distance point of divergence (DPD)?
The distance at which fusion breaks and esotropia appears.
* Beyond this point → fusion lost and stereopsis absent.
Understanding DPD is important for assessing the severity of DI.
What are normal near findings in divergence insufficiency?
- Normal amplitude of accommodation (AoA)
- Normal binocular and monocular facility
- Normal PRA and NRA
- Normal MEM
These findings help differentiate DI from other conditions affecting near vision.
Why is accommodation normal in DI?
Because DI is a vergence (divergence) problem, not an accommodative problem.
This distinction is vital for understanding the nature of DI.
What conditions must DI be differentiated from?
- Convergence excess
- Basic esophoria
- VI nerve palsy
- Divergence paralysis
- Heavy/sagging eye syndrome
Accurate differentiation is essential for effective treatment planning.
Why is VI nerve palsy an important differential?
It also causes distance esotropia, but due to lateral rectus weakness, not a vergence issue.
Recognizing this difference is crucial for appropriate management.
What is heavy/sagging eye syndrome?
A myopia/age-related strabismus with:
* Progressive esotropia ± hypotropia
* Due to degeneration of LR-SR band
* Causes displacement of lateral rectus pulley
This syndrome can mimic DI but has distinct underlying causes.
Who is at risk of heavy eye syndrome?
- High myopes (≈ > −12D)
- Axial length > 25 mm
- Older patients
Identifying at-risk populations can aid in early diagnosis and intervention.
What is the treatment goal in divergence insufficiency?
Restore comfortable distance binocular single vision by reducing eso deviation and improving divergence.
This goal guides the therapeutic approach for managing DI.
What are the treatment options for DI?
- Correct ametropia
- Prescribe maximum plus (reduces accommodative convergence slightly)
- Prism correction (main treatment)
- Surgery (in severe cases)
Each treatment option addresses different aspects of DI.
Why is prism the most effective treatment in DI?
It directly reduces divergence demand at distance, relieving diplopia immediately.
Prism therapy is often the first line of treatment for DI.
How should prism be prescribed?
Split equally between both eyes
* Consider prism effect at near
Proper prescription is crucial for maximizing the effectiveness of prism therapy.
