8. Summary Case analysis and diangosis of management of nonstrab BV disorders Summary

What is the diagnostic pattern for convergence insufficiency (CI)?

The patient must have:

Greater exophoria at near than distance, plus at least one of:

• Receded NPC: break ≥6 cm

• Reduced near PFV: BO break ≤15Δ or failure of Sheard’s criterion

• Reduced vergence facility: ≤10 cpm, with difficulty clearing BO

How does convergence deficit differ from convergence insufficiency?

Both demonstrate deficient convergence findings:

• Receded NPC: ≥6 cm break

• Reduced PFV: ≤15Δ BO break or Sheard’s criterion not met

• Vergence facility ≤10 cpm, with difficulty clearing BO

• Difficulty with binocular plus lenses may be present

However, convergence deficit does not require greater exophoria at near than distance, whereas CI does.

What findings define divergence insufficiency (DI)?

The patient must have:

1. Esophoria greater at distance than near

2. At least one sign of inadequate divergence compensation:

   • Reduced distance NFV

   • Failure of Sheard’s criterion at distance

What is the diagnostic pattern for basic exophoria?

The patient must have exophoria at distance and near that is approximately equal:

• At least 4Δ exophoria at distance and near

• Distance-near difference no greater than 3Δ

Plus two supporting findings:

• Receded NPC: ≥6 cm

• Reduced PFV: ≤15Δ BO break or Sheard’s criterion not met at near and distance

Difficulty with binocular plus lenses may also occur.

What is the diagnostic pattern for basic esophoria?

The patient must have:

1. At least 3Δ esophoria at distance and near, with a difference no greater than 2Δ

2. At least one supporting NFV finding:

   • Near BI break <8Δ

   • Failure of Sheard’s criterion at near and distance

Difficulty with binocular minus lenses may be present.

What findings define fusional vergence dysfunction?

There is poor function in both vergence directions, despite no defining phoria pattern. Either may establish the diagnosis:

• Reduced vergence amplitudes:

  • BO break ≤15Δ or Sheard’s criterion not met

  • BI break <8Δ or Sheard’s criterion not met

• Vergence facility ≤10 cpm, with difficulty clearing both BO and BI

Difficulty with binocular plus lenses may also occur.

What is the diagnostic pattern for convergence excess (CE)?

The patient must have:

1. Near esophoria >3Δ, typically greater at near than distance

2. At least one sign of reduced divergence at near:

   • BI break <8Δ or failure of Sheard’s criterion

   • Vergence facility ≤10 cpm, with difficulty clearing BI

Difficulty with binocular minus lenses commonly supports the diagnosis.

What is the diagnostic pattern for divergence excess (DE)?

The characteristic findings are:

• Exophoria greater at distance than near

• Inadequate distance PFV relative to the deviation

• Failure of Sheard’s criterion at distance

An intermittent exotropia may occur at distance.

What symptoms are characteristic of convergence excess?

Symptoms occur primarily with sustained near work:

• Asthenopia or headaches

• Ocular burning or tearing

• Intermittent blur or diplopia

• Words appearing to move

• Loss of concentration

• Sleepiness while reading

• Reduced comprehension over time

• Slow reading

• Symptoms worsening later in the day

Symptoms are often chronic and longstanding. A CISS score around 16 may help differentiate symptomatic CE in young adults.

What clinical findings support convergence excess?

Common findings include:

• Greater esophoria at near than distance

• Reduced near NFV for the magnitude of the phoria

• Failure of Sheard’s criterion

• High accommodative lag

• Low PRA

• Reduced binocular accommodative facility, especially difficulty with minus

• Eso fixation disparity at near

• Generally good stereopsis

• Possible intermittent suppression

• Possible vertical deviation

A high lag can conceal part of the esodeviation because the patient is accommodating less and therefore producing less accommodative convergence.

Why must accommodation be carefully controlled when measuring the near phoria of a patient with suspected CE?

Underaccommodation produces less accommodative convergence and can make the measured esophoria appear smaller than it truly is.

To reveal the deviation:

• Use a small, detailed target

• Encourage the patient to maintain clarity

• Compare the phoria with accommodative testing and MEM findings

How can untreated convergence excess affect binocularity over time?

Persistent CE may produce:

• Eso fixation disparity

• Intermittent suppression

• Reduced stereopsis

• Increasing inability to compensate for the eso deviation

• Possible decompensation into strabismus

This is why treatment is appropriate even when the patient maintains relatively good stereopsis initially.

What functional disorders should be differentiated from convergence excess?

Differentiate CE from:

• Basic esophoria

• Divergence insufficiency

• Accommodative disorders

• Uncorrected or latent hyperopia

A cycloplegic refraction is important when hyperopia may be contributing.

What findings suggest that a new esodeviation is pathological rather than ordinary convergence excess?

Red flags include:

• Acute onset

• Unilateral findings

• Neurological symptoms

• Significant medical problems

• Recent medication or drug exposure

• Signs of ocular inflammation

Potential causes include:

• Spasm of accommodation or convergence

• Iritis or other local inflammation

• Sympathetic pathway dysfunction

• CNS disease

• Medication effects, including miotics such as pilocarpine

What is the first management step for convergence excess?

Begin with accurate refractive management:

1. Obtain a cycloplegic refraction when appropriate.

2. Correct clinically significant refractive error.

3. Reevaluate the distance and near phorias after correction.

4. Determine whether additional near plus, vision therapy, or prism is needed.

CE generally has an excellent prognosis when properly treated.

How are near plus lenses selected for convergence excess?

Near plus reduces the accommodative demand and therefore reduces accommodative convergence.

Selection should consider:

• Magnitude of the near esophoria

• Change in phoria through plus

• Gradient AC/A ratio

• Working distance

• Symptoms and functional demands

The prescription may be provided as a:

• Bifocal

• Progressive or near addition

• Separate reading prescription

What is the role of vision therapy in convergence excess?

Vision therapy primarily develops:

• Negative fusional vergence or divergence

• Vergence facility

• Flexibility between convergence and divergence

• Accommodation-vergence integration

A typical program may require approximately:

• 12 to 16 sessions per 10Δ to 15Δ change in divergence ability

• Approximately 12 to 24 sessions, depending on severity and response

When might prism be added for convergence excess?

A patient with clinically significant esophoria at both distance and near, with greater eso at near, may also require base-out prism if the deviation cannot be adequately managed with lenses and therapy alone.

Prism direction follows the deviation:

• Eso → BO relieving prism

• Exo → BI relieving prism

An 8.5-year-old has 10Δ near esophoria, orthophoria at distance, BI vergence of X/4/2, BO vergence of X/40/35, and a high MEM of +1.50 D. What is the primary binocular diagnosis?

Convergence excess.

Evidence:

• Esophoria is greater at near than distance

• Near BI break is only 4Δ, showing deficient NFV

• BO is very large, consistent with excessive convergence ability

• High MEM lag may be masking an even larger near esophoria

• Reading avoidance and eye rubbing are consistent with a symptomatic near disorder

In the CE case, why is the measured 10Δ near esophoria probably an underestimate?

MEM is +1.50 D, approximately 1.00 D more lag than expected. This means the child is underaccommodating and generating less accommodative convergence.

The cover test changed from:

• 10Δ EP normally

• 5Δ EP through +1.00 D

This suggests a gradient AC/A of approximately 5:1. If the child accommodated about 1.00 D more appropriately, the near phoria would be expected to increase to approximately 15Δ EP.

What management should be considered for the child with CE, a high accommodative lag, and uncorrected hyperopia?

Management should include:

• Confirm the refractive finding with cycloplegia

• Address the clinically significant hyperopia

• Reassess accommodation and near alignment after correction

• Consider an appropriate near addition based on the gradient AC/A and response

• Consider vision therapy to improve NFV and accommodation-vergence integration

• Monitor for suppression or progression toward strabismus

What is the typical presentation of divergence excess?

DE usually develops in childhood and is characterized by:

• Exodeviation greater at distance than near

• Frequent intermittent exotropia at distance

• Average deviation larger at distance than near

• Worsening control with:

  • Inattention

  • Fatigue

  • Illness

  • Daydreaming

Parents may be more aware of the deviation than the child.

What symptoms are typical of divergence excess?

Common reports include:

• One eye turning outward intermittently

• Asthenopia

• Photophobia

• Possible diplopia

• Closing one eye in bright light

• Occasional near discomfort, although near symptoms may be absent

Patients with suppression at distance often do not report diplopia.

What examination findings support divergence excess?

Findings include:

• Greater exodeviation at distance than near

• Exotropia occurring more frequently at distance

• Comitant deviation

• Normal NPC

• Inadequate PFV relative to the exodeviation

• Possible suppression or anomalous correspondence at distance

• Typically normal stereopsis at near

• Often an eso fixation disparity at near

• Possible inferior oblique overaction

• Usually no primary vertical deviation

Why can a patient with divergence excess have numerically normal or large PFV and still be unable to compensate?

Fusional vergence must be interpreted relative to the size of the phoria, not solely by comparison with population norms.

A patient with a large distance exophoria may have an apparently normal BO range but still fail:

• Sheard’s criterion

• Sustained control

• Real-world binocular demands

Clinical rule: Compare compensating vergence with the deviation.

What AC/A findings may occur in divergence excess?

DE commonly demonstrates:

• High stimulus AC/A

• Normal to slightly high response AC/A, approximately 3:1 to 9:1

This distinction matters because the near deviation may appear smaller due to accommodative convergence or other fusion-related mechanisms.

How are true and simulated divergence excess differentiated?

Dissociate the patient to uncover a hidden near deviation using:

• 30 minutes to 3 hours of monocular occlusion, with no fusion before the post-occlusion cover test

• A +3.00 D lens test OU at near

If the near exodeviation increases and becomes similar to the distance deviation, the patient has simulated DE, not true DE.

Concept: Simulated DE is often caused by tenacious proximal fusion or an altered near accommodative-convergence response.

What disorders are included in the differential diagnosis of divergence excess?

Differentiate DE from:

• Basic exophoria

• Simulated divergence excess

• Convergence insufficiency

The most important distinctions are:

• Distance-near relationship

• Response to occlusion or +3.00 D testing

• NPC

• Near PFV and near symptoms

What is the primary goal of vision therapy for divergence excess?

Therapy aims to improve:

• Awareness and control of the distance exodeviation

• Positive fusional vergence

• Vergence facility

• Accommodation-vergence integration

• Ability to distinguish physiological from pathological diplopia, when normal retinal correspondence is present

A typical course may be approximately 24 to 36 sessions, or 6 to 8 sessions per 10Δ to 15Δ change.

What factors predict a poorer vision-therapy prognosis in divergence excess?

Negative prognostic factors include:

• Large horizontal deviation

• Large vertical deviation

• Noncomitancy

• Abnormal sensory correspondence

• Poor ability to recognize diplopia or misalignment

What options besides vision therapy may be used for divergence excess?

Additional options include:

• Added minus lenses

• Therapeutic lenses

• Full-time spectacle wear when indicated

• Surgical referral for large, poorly controlled, or refractory deviations

Mechanism of added minus: Minus stimulates accommodation, increasing accommodative convergence and helping reduce the exodeviation.

An 8-year-old has 16Δ distance exophoria with occasional intermittent exotropia, 5Δ near exophoria, normal NPC, and distance BO of X/20/10. What is the primary diagnosis?

Divergence excess with intermittent exotropia at distance.

Evidence:

• Distance exo exceeds near exo by 11Δ

• Intermittent exotropia is observed at distance

• NPC is normal, arguing against CI

• Distance BO break of 20Δ is inadequate for 16Δ exophoria because Sheard’s criterion would require approximately 32Δ of compensating PFV

Why is this DE patient symptomatic even though the distance BO break is 20Δ?

A 20Δ BO break may look numerically reasonable, but it is inadequate relative to the patient’s 16Δ distance exophoria.

Using Sheard’s criterion:

• Compensating reserve should be at least twice the phoria

• Required PFV ≈ 2 × 16Δ = 32Δ

• Measured PFV break = 20Δ

Therefore, the patient lacks enough PFV to compensate comfortably.

What secondary finding should be considered in the DE case if binocular accommodative facility is only 5 cpm?

The low binocular accommodative facility suggests a possible accompanying accommodative dysfunction.

However, a specific accommodative diagnosis requires knowing:

• Whether difficulty occurred with plus, minus, or both

• Monocular facility

• Accommodative amplitude

• MEM

• NRA and PRA

Do not diagnose accommodative infacility from the cpm value alone without identifying the lens side causing difficulty.

What symptoms suggest a clinically significant vertical phoria?

Common symptoms include:

• Headache and asthenopia

• Blur

• Diplopia

• Frequent loss of place while reading

• Skipping or repeating lines

• Motion sickness

• Difficulty concentrating during sustained tasks

• Fatigue or sleepiness during prolonged visual work

Even a small vertical deviation may be symptomatic because vertical fusional reserves are limited.

What signs may accompany a vertical phoria?

Common signs include:

• Compensatory head tilt

• Reduced horizontal positive and negative fusional ranges

• Abnormally low or exceptionally large vertical fusion ranges, depending on chronicity

• Possible association with reading or learning difficulties

A longstanding deviation may develop unusually large vertical fusion ranges as compensation.

What ocular or mechanical factors can cause a vertical phoria?

Possible causes include:

• Hyperorbital asymmetry

• Abnormal extraocular muscle insertion

• Vertical rectus anomalies

• Oblique muscle dysfunction

• Ocular surgery, including lens extraction

• Unilateral or bilateral pseudophakia

Acquired deviations require comparison with prior alignment and surgical history.

Which causes of vertical diplopia require investigation for neurological or neuromuscular disease?

Important etiologies include:

• Skew deviation

• CN III palsy

• CN IV palsy

• Ocular myasthenia

• Inferior oblique overaction

• Superior oblique overaction or dysfunction

• Vertical rectus abnormalities

Acute vertical diplopia, incomitancy, ptosis, pupil abnormalities, or neurological symptoms should not be assumed to be a benign vertical phoria.

How is a symptomatic vertical phoria managed?

Treatment options include:

• Vertical prism, especially when the symptomatic deviation is approximately 0.75Δ or greater

• Some clinicians consider treatment beginning around 0.50Δ

• Prism based on the associated phoria or X-intercept of the vertical fixation-disparity curve

• Vertical fusional vergence therapy in selected patients

• Treatment or referral for the underlying cause when the deviation is acquired or pathological

What symptom pattern supports a functional accommodative or binocular vision disorder?

Functional disorders typically produce symptoms that are:

• Chronic or longstanding

• Associated with specific visual tasks

• Worse with prolonged visual activity

• Worse later in the day

• Relieved by stopping the provoking task

Symptoms that do not follow this pattern should raise concern for an organic cause, unreliable reporting, or another diagnosis.

What history questions help rule out an organic cause of new binocular or accommodative symptoms?

Ask about:

• Exact onset and progression

• Recent illness

• New medications

• Appetite, sleep, or weight changes

• Dizziness or balance problems

• Fainting

• New or worsening headaches

• Headaches that awaken the patient

• Recent trauma

• Muscle weakness

• Numbness or tingling

What minimum examination should be performed when an organic cause of binocular symptoms is possible?

• External examination

• Pupils, including APD testing

• Versions

• Distance and near cover testing

• Cover testing in at least two positions of gaze

• Evaluation for a vertical deviation

• Color vision

• Ophthalmoscopy

• Confrontation visual fields or formal field testing when indicated

The goal is to identify incomitancy, neurological asymmetry, optic nerve dysfunction, or ocular disease.

What is the basic sequence for analyzing accommodative and binocular findings?

• Determine whether an accommodative abnormality is present.

• Determine whether a significant lateral phoria exists at distance or near.

• If a phoria is present, ask whether fusional reserves adequately compensate.

• Evaluate the distance-near pattern.

• Evaluate the AC/A relationship.

• Integrate vergence, accommodation, fixation disparity, stereopsis, and symptoms.

• Rule out organic disease before labeling the condition functional.

If no significant lateral phoria is present, what disorders should still be considered?

• Accommodative dysfunction

• Fusional vergence dysfunction

• Oculomotor dysfunction

• Hyperphoria

• Fixation disparity

• Aniseikonia

• Latent hyperopia

• Cyclophoria

What should be reconsidered when the initial findings do not produce a clear diagnosis?

Reassess:

• Accuracy and repeatability of test results

• Objective observations versus subjective responses

• Whether difficulty occurs with one specific task or with all tasks

• Effect of fatigue and time of day

• Possibility of organic disease

• Comprehension of test instructions

• Possibility of noncredible or exaggerated responses

How should the clinician interpret apparently conflicting BV test results?

Findings should be understood as an interacting system rather than isolated pass/fail values.

Consider how:

• Accommodation changes accommodative convergence

• Phoria magnitude determines the fusional reserve required

• Suppression may eliminate diplopia

• Chronic deviations may produce unusually large compensating ranges

• A high accommodative lag may conceal esophoria

• A numerically normal vergence range may still fail Sheard’s criterion

How should a binocular vision diagnosis be explained to the patient or parent?

The explanation should:

• Use nontechnical language

• Connect examination findings to the patient’s symptoms

• Describe common symptoms of the condition

• Explain why measurable signs may exist without current symptoms

• Demonstrate the problem or treatment effect when possible

The patient should understand not only the diagnostic label, but how the disorder affects visual function.

What must be established before beginning treatment for a BV disorder?

Establish a complete diagnosis, including:

• Refractive status

• Accommodative function

• Phoria pattern

• Compensating vergence ability

• AC/A relationship when relevant

• Sensory status

• Presence or absence of pathology

Treatment should target the mechanism causing the symptoms, not a single abnormal test value.

What should be included when presenting management options for a binocular vision disorder?

Discuss:

• Available treatment options

• Advantages and disadvantages of each option

• What the treatment involves

• Expected duration

• Expected success rate

• Patient responsibilities and keys to success

• Alternatives if the initial plan is unsuccessful

The goal is to help the patient or parent make an informed treatment decision.

What should be included in reports to parents or other professionals?

Reports should:

• Use language appropriate for the recipient

• Avoid unexplained abbreviations

• Summarize relevant findings

• State the diagnosis and functional implications

• Describe the treatment plan

• Provide useful recommendations

• Be sent promptly

• Include acknowledgment or thanks when appropriate

How can the major horizontal binocular vision disorders be rapidly differentiated by their phoria pattern?

• Near exo > distance exo: Convergence insufficiency

• Distance eso > near eso: Divergence insufficiency

• Similar exo at distance and near: Basic exophoria

• Similar eso at distance and near: Basic esophoria

• Near eso > distance eso: Convergence excess

• Distance exo > near exo: Divergence excess

• No defining phoria pattern + poor BI and BO: Fusional vergence dysfunction

Then confirm the diagnosis by determining whether the patient’s compensating fusional vergence is inadequate.