7. Diagnosis of nonstrabismic BV disorders

What are the three classic diagnostic signs of convergence insufficiency (CI)?

• Greater exophoria at near than at distance

• Receded near point of convergence (NPC)

• Insufficient positive fusional vergence (PFV) at near

What pattern of symptoms is typical of convergence insufficiency?

Symptoms occur predominantly during near work and are usually chronic.

They:

• Become worse with prolonged work or fatigue

• Often worsen throughout the day

• May occur at distance if significant distance exophoria is also present

• May be absent if the patient avoids demanding near tasks

Approximately 75% to 85% of patients with CI are symptomatic

What symptoms should raise suspicion for convergence insufficiency in a child with near-work difficulties?

• Eyestrain, sore eyes, or headaches

• Blurred or double vision

• Words appearing to move or jump

• Losing place

• Frequent rereading

• Slow reading

• Reduced concentration

• Difficulty remembering what was read

• Sleepiness during near work

The most frequently reported complaints may be performance-related, such as losing place, rereading, and poor concentration.

What observable behaviors may indicate a binocular vision disorder such as convergence insufficiency?

Watch for:

• Closing or covering one eye while reading

• An unusual head posture

• Avoidance of prolonged near work

• Reduced reading endurance

These behaviors may be attempts to eliminate diplopia or visual discomfort.

How is the Convergence Insufficiency Symptom Survey (CISS) used in CI?

The CISS is a subjective symptom survey that can help distinguish symptomatic CI from normal binocular vision and may increase with the number of CI signs.

However, it is not diagnostic by itself because symptoms may also come from:

• Dry eye

• Allergies

• Other ocular conditions

• The child’s interpretation of “reading” or “close work”

• Increased electronic-device use

What phoria finding supports a diagnosis of convergence insufficiency?

An exo deviation at near that is greater than the exo deviation at distance.

Recent clinical-trial criteria commonly require:

• At least 4Δ more exophoria at near than at distance

Exophoria can still be present at distance, but the near deviation must be meaningfully greater.

What PFV findings support a diagnosis of convergence insufficiency?

Reduced positive fusional vergence at near, meaning that the patient has inadequate base-out vergence to compensate for the near exophoria.

PFV is considered insufficient when:

• It falls below normative base-out values

• It fails Sheard’s criterion

• The base-out blur or break is below a trial-specific minimum

Examples from clinical trials include:

• CITT: BO break ≤15Δ

• PEDIG CITS: BO blur <20Δ

What is Sheard’s criterion, and why is it relevant in convergence insufficiency?

Sheard’s criterion states that the fusional reserve should be at least twice the magnitude of the phoria.

For near exophoria, the compensating reserve is positive fusional vergence, measured with base-out prism.

Failure indicates that the patient may not have enough convergence reserve to compensate comfortably for the near exophoria.

What NPC finding supports a diagnosis of convergence insufficiency?

A receded NPC, commonly defined in clinical trials as a break of ≥ 6 cm

A receded NPC is common but is not present in every patient with CI, so it must be interpreted with near phoria and PFV

How does the NPC target affect the measured result?

An accommodative target generally produces a closer NPC than a penlight viewed with red-green glasses. This is because an accommodative target stimulates accommodative convergence, helping the patient converge farther inward

Why should the NPC be repeated when evaluating convergence insufficiency?

Repeated NPC testing can reveal convergence fatigue that may not appear on the first trial.

After approximately 10 repetitions, the NPC may recede by about 4 cm.

What is the classic clinical-trial definition of symptomatic convergence insufficiency?

The patient typically has:

1. ≥4Δ more exophoria at near than at distance

2. Receded NPC, generally ≥6 cm

3. Insufficient PFV at near, based on:

   • Failure of Sheard’s criterion, or

   • PFV below the required normative or clinical-trial value

4. Symptoms consistent with near visual stress

What additional clinical findings may occur in convergence insufficiency?

• Reduced accommodative ability

• Difficulty with binocular accommodative facility, particularly plus lenses

• Low NRA

• Intermittent or absent suppression at near

• Good stereopsis

• Exo fixation disparity

• Low AC/A ratio

How does convergence deficit differ from classic convergence insufficiency?

• Classic CI: Exophoria is meaningfully greater at near than at distance, with reduced PFV and/or a receded NPC.

• Convergence deficit: The patient has reduced convergence ability, such as decreased PFV or a receded NPC, but may be orthophoric or have only a small near phoria.

What is pseudoconvergence insufficiency?

Pseudoconvergence insufficiency is a CI-like pattern caused primarily by accommodative dysfunction.

Reduced accommodation produces less accommodative convergence, resulting in:

• A secondary increase in near exophoria

• Greater demand on PFV

• Apparently inadequate PFV at near

Treating the accommodative disorder may improve the apparent CI findings.

What findings suggest pseudoconvergence insufficiency due to accommodative dysfunction?

• Reduced amplitude of accommodation

• Difficulty with minus lenses on monocular and binocular accommodative facility

• Reduced PRA

• High accommodative lag

• Secondary near exophoria and reduced PFV

Key clue: The problem is present during monocular accommodative testing, not only during binocular testing

How is pseudoconvergence insufficiency managed?

Treat the underlying accommodative dysfunction with:

• Appropriate lenses

• Accommodative therapy

• Combined accommodative and vergence therapy when indicated

As accommodation improves, accommodative convergence increases and the secondary CI-like findings may resolve

What functional binocular disorders should be differentiated from convergence insufficiency?

• Basic exophoria: Similar exophoria at distance and near

• Divergence excess: Greater exophoria at distance than at near

• Convergence insufficiency: Greater exophoria at near than at distance

• Convergence deficit: Reduced convergence without substantial near exophoria

What underlying pathology should be considered when CI-like findings are sudden or atypical?

• Convergence paralysis from ischemic infarction

• Demyelinating disease

• Viral infection

• Parkinson disease

• Parinaud syndrome

• Medial rectus weakness from multiple sclerosis

• Myasthenia gravis

• Previous strabismus surgery

What is the first step in managing convergence insufficiency?

Correct the patient’s refractive error.

Then consider:

• Base-in prism

• Home-based exercises

• Office-based vergence/accommodative therapy

• Combined office therapy with home reinforcement

What passive and active treatments are available for convergence insufficiency?

Passive treatment

• Base-in prism, which reduces the convergence demand

Active treatment

• Orthoptics

• Vision therapy

• Vergence/accommodative therapy

• Home- or office-based therapy

Is base-in prism an effective treatment for symptomatic convergence insufficiency in children?

Evidence from the BICITT did not show a significant advantage of base-in prism glasses over placebo glasses in children.

Both groups reported decreased symptoms, but there was no significant between-group difference in:

• Symptoms

• Ability to converge

Conclusion: Base-in prism is generally not considered an effective primary treatment for childhood CI

What four treatments were compared in the major Convergence Insufficiency Treatment Trial (CITT)?

• HBPP: Home-based pencil push-ups

• HBCVAT+: Home-based computer vergence/accommodative therapy plus pencil push-ups

• OBVAT: Office-based vergence/accommodative therapy with home reinforcement

• OBPT: Office-based placebo therapy

Which treatment was most effective for symptomatic convergence insufficiency in children in the CITT?

Office-based vergence/accommodative therapy with home reinforcement, or OBVAT.

Compared with pencil push-ups, home computer therapy, and placebo, OBVAT produced greater improvement in:

• NPC

• PFV

• Symptoms in the original CITT

• Composite treatment-success outcomes

How did office-based therapy compare with home-based treatments in the CITT?

• OBVAT produced the greatest improvement in NPC and PFV.

• Home-based treatments produced some improvement in NPC.

• Home computer therapy plus pencil push-ups improved PFV more than pencil push-ups alone.

• Neither home-based approach matched the overall effectiveness of OBVAT.

• Pencil push-ups often performed similarly to placebo on important outcomes.

Approximately how many children improve after 12 weeks of office-based vergence/accommodative therapy?

Approximately 75% achieve normalization or meaningful improvement in symptoms and/or clinical convergence measures after 12 weeks.

Therefore, OBVAT is considered the preferred first-line treatment for symptomatic CI in children when it is accessible

What treatment may be considered when office-based therapy is not available?

Home-based computer vergence/accommodative therapy, often with structured reinforcement, may be considered.

However:

• Expected success is lower than with office-based therapy.

• Pencil push-ups alone have limited evidence of effectiveness.

• The patient and family should be educated about the differences in treatment success and required time

In what order do clinical findings and symptoms improve during CI therapy?

Objective clinical signs generally improve before subjective symptoms.

Expected pattern:

• NPC and PFV may improve by approximately 4 weeks

• Symptoms may take longer to improve

• Treatment should not be judged solely by early symptom reports

How quickly can coexisting accommodative dysfunction improve during CI therapy?

In patients who also have accommodative dysfunction:

• Amplitude of accommodation

• Accommodative facility

may improve by approximately 4 weeks.

The presence of coexisting accommodative dysfunction did not significantly reduce the overall response to therapy

Are the benefits of successful CI therapy maintained after treatment ends?

They are generally stable.

In the CITT:

• Patients who became asymptomatic performed maintenance therapy for approximately 15 minutes per week

• 87.5% of the OBVAT group remained successful or improved at one year

Is vision therapy for convergence insufficiency associated only with clinical test changes?

No. Therapy has been associated with:

• Improved NPC and PFV

• Eye-tracking changes

• Changes in cortical activity measured with functional MRI

These findings support measurable neurophysiologic changes, although clinical management should still be guided by symptoms and binocular vision findings

What did CITT-ART find regarding the effect of OBVAT on objective convergence measures?

OBVAT produced substantially better objective convergence outcomes than placebo.

A normal NPC and PFV composite outcome occurred in approximately:

• 78% with OBVAT

• 29% with placebo

The composite required:

• NPC <6 cm

• PFV meeting Sheard’s criterion and exceeding 15Δ

What unexpected symptom result was found in CITT-ART?

Although OBVAT significantly improved NPC and PFV compared with placebo, the difference in CISS symptom scores was not statistically significant.

Interpretation: Improvement in objective convergence measures does not always correspond directly with changes in self-reported CISS symptoms

Why may the CISS inadequately measure treatment-related symptom changes?

The CISS is subjective and may capture symptoms from:

• Dry eye or allergies

• Normal ocular discomfort

• Homework and reading demands

• Video games and smart devices

• Conditions unrelated to binocular function

The meaning of “reading” and “close work” has also changed since the CISS was originally validated

What reading-related complaints may occur in a patient with convergence insufficiency?

• Loss of place

• Frequent rereading

• Reading slowly

• Reduced concentration

• Difficulty remembering what was read

• Visual discomfort, diplopia, tired eyes, or headaches

These complaints indicate that CI may create a visual obstacle during reading, but they do not prove a primary reading disorder

Does office-based vergence/accommodative therapy improve standardized reading performance in children with CI?

Not more than placebo therapy.

In CITT-ART, 16 weeks of OBVAT did not produce significantly greater improvement in:

• Reading comprehension

• Word reading

• Pseudoword decoding

• Oral reading fluency

• Silent reading fluency

• Listening comprehension

Both groups improved, demonstrating why a control group is essential when evaluating treatment effectiveness

Does successful treatment of the clinical signs of CI necessarily improve reading performance?

No. Even among participants classified as successfully treated:

• OBVAT produced much higher clinical success than placebo

• There were still no significant between-group differences in standardized reading outcomes

Key distinction: Treating CI improves convergence function, but it is not a stand-alone treatment for a reading disorder

Does office-based vergence/accommodative therapy improve attention more than placebo therapy?

No significant advantage was found for:

• Parent- or teacher-rated inattention

• Hyperactivity or impulsivity

• Objective attention-test performance

• Concentration performance

Thus, OBVAT improves convergence function but should not be presented as a primary treatment for attention disorders

What is the most appropriate counseling regarding CI, reading, and school performance?

Treating CI can:

• Reduce a visual obstacle

• Improve convergence function

• Make near work more visually comfortable

However, therapy has not been shown to improve standardized reading or attention outcomes more than placebo.

A child with persistent academic difficulty may still require:

• Educational evaluation

• Evidence-based reading instruction

• Tutoring or other appropriate services

A child has headaches during reading, 10Δ exophoria at near, 2Δ exophoria at distance, an NPC break of 12 cm, and reduced BO vergence at near. What is the most likely diagnosis?

Convergence insufficiency.

Supporting findings:

• Near exophoria is 8Δ greater than distance exophoria

• NPC is receded

• PFV is reduced

• Symptoms are provoked by near work

A patient has a receded NPC and reduced PFV but is nearly orthophoric at near. What diagnosis is more appropriate than classic CI?

Convergence deficit.

The patient has impaired convergence, but classic CI requires meaningful near exophoria, generally greater than the distance phoria

A patient has near exophoria, reduced PFV, reduced accommodative amplitude, high accommodative lag, and difficulty clearing minus monocularly. What should be suspected?

Pseudoconvergence insufficiency secondary to accommodative dysfunction.

Monocular accommodative findings indicate that reduced accommodation may be causing:

• Reduced accommodative convergence

• Secondary near exophoria

• Increased demand on PFV

A child completes several weeks of CI therapy. NPC and PFV improve, but the CISS changes only slightly. Does this mean therapy failed?

Not necessarily.

Objective signs can improve before symptoms, and CISS scores do not always correspond closely with NPC and PFV changes.

A parent asks whether CI vision therapy will improve the child’s reading comprehension and attention. What is the evidence-based response?

Therapy can improve convergence ability and visual comfort, but controlled trials have not shown that it improves standardized reading or attention outcomes more than placebo.

CI therapy should treat the binocular vision disorder, while reading or attention problems should receive their own appropriate evaluation and intervention

What is the high-yield diagnosis and management summary for convergence insufficiency?

Diagnosis

• ≥4Δ more exophoria at near than distance

• Receded NPC, commonly ≥6 cm

• Insufficient PFV at near or failure of Sheard’s criterion

• Near-work symptoms

Differentials

• Basic exophoria

• Divergence excess

• Convergence deficit

• Pseudoconvergence insufficiency from accommodative dysfunction

• Neurologic or extraocular muscle pathology

Management

• Correct refractive error

• OBVAT is the most effective treatment in children

• Pencil push-ups and home computer therapy are less effective

• BI prism is not effective as primary treatment in children

• Objective signs generally improve before symptoms

• Benefits are usually maintained

• Therapy improves convergence but not standardized reading or attention performance beyond placebo

An 8-year-old avoids reading and has 8–10Δ near exophoria, orthophoria at distance, NPC 30/35 cm, and near BO vergence of X/6/4. What binocular vision disorder is present?

Convergence insufficiency.

Supporting findings:

• Exophoria is greater at near than distance

• NPC is markedly receded

• Positive fusional vergence, measured with BO prism, is reduced

• Symptoms occur during near work

What additional disorder is suggested by an 8-year-old with 6 D accommodative amplitude, PRA of −0.25 D, and MEM of +1.50 D?

Accommodative insufficiency.

Supporting findings:

• Expected accommodative amplitude is at least approximately 11 D

• Measured amplitude is only 6 D

• High MEM indicates excessive accommodative lag

• Reduced PRA indicates difficulty stimulating accommodation

Overall diagnosis: Convergence insufficiency with coexisting accommodative insufficiency.

Why might previously prescribed reading glasses have failed to resolve the 8-year-old’s symptoms?

Plus lenses may reduce the accommodative demand, but they can also reduce accommodative convergence, potentially increasing the near exophoria and convergence demand.

Because the patient has both accommodative and convergence dysfunction, treatment must address the complete binocular and accommodative pattern rather than accommodation alone.

A 60-year-old reports losing place and intermittent diplopia while reading. Testing shows 2Δ exophoria at distance, 10Δ intermittent exotropia at near, BI vergence X/4/2, BO vergence X/6/4, and crossed diplopia. What is the likely diagnosis?

Near intermittent exotropia associated with convergence insufficiency.

Supporting findings:

• Exodeviation is substantially greater at near

• The near deviation intermittently becomes a tropia

• Positive fusional vergence is inadequate

• Crossed diplopia is consistent with an exodeviation

What type of diplopia is expected with an exodeviation versus an esodeviation?

• Exodeviation: Crossed diplopia

• Esodeviation: Uncrossed diplopia

This relationship can help confirm the direction of a manifest deviation during sensory testing such as Worth 4 Dot.

What is the defining phoria pattern in divergence insufficiency?

Greater esophoria at distance than at near.

The patient has inadequate divergence ability at distance, resulting in:

• More frequent eso deviation at distance

• Reduced negative fusional vergence at distance

• Possible esophoric fixation disparity at distance

What symptoms are characteristic of divergence insufficiency?

Symptoms occur primarily during distance viewing and may include:

• Intermittent distance diplopia

• Distance blur or asthenopia

• Difficulty driving or watching television

• Headaches, nausea, or dizziness

• Difficulty changing focus from far to near

• Light sensitivity or motion sickness

Symptoms are often longstanding and may worsen with fatigue or later in the day.

What clinical signs support functional divergence insufficiency?

• Greater esophoria at distance than near

• Reduced distance negative fusional vergence, measured with BI prism

• Esophoric fixation disparity at distance

• Comitant deviation

• Usually no significant refractive error

An 11-year-old has 8Δ esophoria at distance, 2Δ exophoria at near, and distance BI vergence of X/6/4. What is the most likely diagnosis?

Divergence insufficiency.

Supporting findings:

• Eso deviation is greater at distance

• Negative fusional vergence at distance is reduced

• The deviation is comitant between primary gaze and downgaze

• Accommodative findings and NPC are relatively normal

What functional disorders and refractive condition must be differentiated from divergence insufficiency?

• Basic esophoria: Approximately equal eso at distance and near

• Convergence excess: Greater eso at near than distance

• Uncorrected hyperopia: Accommodative convergence may create an eso pattern

A cycloplegic refraction may be necessary to exclude latent hyperopia

How can sixth nerve palsy be distinguished from functional divergence insufficiency?

Sixth nerve palsy is more likely to show:

• Acute onset

• Noncomitant deviation

• Abduction weakness

• Possible endpoint nystagmus

• No predictable worsening with ordinary visual fatigue

Functional divergence insufficiency is typically longstanding, comitant, and worsens with fatigue.

What findings suggest divergence paralysis rather than functional divergence insufficiency?

Divergence paralysis may present with:

• Acute-onset distance diplopia and headaches

• Comitant distance esodeviation

• Little change with fatigue

• Possible A-pattern deviation

• Associated neurologic symptoms

Possible causes include multiple sclerosis, encephalitis, head trauma, cerebral hemorrhage, elevated intracranial pressure, brain tumor, and brainstem vascular lesions.

What associated findings make a distance esodeviation concerning for neurologic disease?

• Papilledema

• Vomiting

• Lethargy or irritability

• Dizziness

• Gait disturbance

• Distal paresthesia

• Acute headache

• Sudden-onset diplopia

How is functional divergence insufficiency managed?

1. Correct any hyperopia

2. Prescribe base-out prism when appropriate

3. Consider therapy to improve distance negative fusional vergence

4. Improve near positive fusional vergence if needed to tolerate full-time BO prism

5. Reserve surgery for unusual cases because it is generally not indicated

BO prism is most useful when the required amount is approximately 15Δ or less.

Why is base-out prism prescribed for divergence insufficiency?

BO prism shifts the image in a direction that reduces the divergence demand required to maintain single vision.

High-yield association:

• Eso deviation → BO prism

• Exo deviation → BI prism

What defines a basic exodeviation?

Approximately equal amounts of exophoria or exotropia at distance and near, usually within about 5Δ.

Unlike convergence insufficiency or divergence excess, neither viewing distance produces a substantially larger exodeviation.

What symptoms are typical of basic exodeviation?

Symptoms may occur at both distance and near:

• Intermittent crossed diplopia

• Eyestrain

• Headaches

• Difficulty concentrating

• Intermittent blur

• Reading difficulties

• Fatigue

• Awareness that an eye turns outward

• Photophobia

Symptoms frequently worsen throughout the day, although approximately 10% of patients may be asymptomatic

What clinical findings may accompany basic exodeviation?

• Similar exodeviation at distance and near

• PFV that may be numerically near normal but is inadequate for the phoria

• Receded NPC

• Reduced binocular accommodative facility, especially with plus

• Low NRA

• Plano or lead accommodative response

• Usually normal monocular accommodative function

• Exo fixation disparity at distance and near

• Possible intermittent exotropia

Why can apparently normal PFV still be inadequate in basic exodeviation?

Fusional reserves must be interpreted relative to the magnitude of the phoria.

A patient with a large exophoria may have PFV values within the general normative range but still lack enough convergence reserve to satisfy Sheard’s criterion or maintain comfortable fusion.

What fixation disparity curve is associated with basic exodeviation?

A Type III fixation disparity curve.

Additional findings may include:

• Exo fixation disparity at distance and near

• Intermittent exotropia

• A coexisting vertical deviation, which is relatively common

What disorders should be differentiated from basic exodeviation?

Functional differentials

• Convergence insufficiency: greater exo at near

• Divergence excess: greater exo at distance

Pathologic differentials

• Convergence paralysis

• Medial rectus weakness

• Multiple sclerosis

• Myasthenia gravis

• Effects of previous strabismus surgery

Acute onset, neurologic symptoms, or associated medical problems should raise concern for pathology

How is refractive error managed in basic exodeviation?

Correct clinically significant:

• Myopia

• Astigmatism

• Anisometropia

Hyperopia requires individualized management because correcting plus reduces accommodative demand and accommodative convergence, potentially increasing the exodeviation. The effect is especially important with hyperopia greater than approximately +1.50 D

What is the primary treatment for symptomatic basic exodeviation?

Vergence therapy is the primary treatment.

Goals include:

• Increasing positive fusional vergence

• Improving control of the exodeviation

• Treating associated suppression or amblyopia

• Improving binocular facility and stamina

The slides report a high total or partial treatment success rate for basic exodeviation

What roles do prism and surgery have in basic exodeviation management?

• Horizontal prism is generally unnecessary and is less effective for exo than eso deviations.

• Prism may help if symptoms remain after therapy.

• Vertical prism may be useful for a significant coexisting vertical deviation.

• Surgery is rarely required and is considered mainly for deviations greater than approximately 30Δ after unsuccessful nonsurgical treatment

A 14-year-old has 14Δ exophoria at distance and 16Δ at near, with eyestrain at both distances. What is the most likely diagnosis?

Basic exophoria.

The distance and near deviations differ by only 2Δ, so they are approximately equal.

Additional supportive findings include:

• Symptoms at both distance and near

• PFV that is insufficient relative to the large exophoria

• Reduced binocular accommodative facility with normal monocular facility

What defines a basic esodeviation?

Approximately equal amounts of esophoria or esotropia at distance and near, generally within approximately 5Δ.

It is also called an equal esodeviation

What symptoms occur with basic esodeviation?

Symptoms may occur during both distance and near visual tasks:

• Asthenopia

• Headaches

• Difficulty concentrating at near

• Intermittent blur

• Intermittent uncrossed diplopia

• Worsening symptoms throughout the day

What clinical findings support basic esodeviation?

• Similar eso deviation at distance and near

• Normal-to-low negative fusional vergence at both distances

• Low PRA

• Reduced binocular accommodative facility, especially with minus

• Usually normal accommodative amplitude

• Eso fixation disparity at distance and near

• Possible hyperopia

• Intermittent suppression, good stereopsis, or diplopia

Why can a high accommodative lag conceal part of an esodeviation during cover testing?

A high lag means the patient accommodates less than required. This reduces accommodative convergence and may make the measured esodeviation appear smaller.

Use a detailed target and verify accurate accommodation during the cover test to avoid underestimating the eso deviation.

What fixation disparity curve is associated with basic esodeviation?

A Type II fixation disparity curve.

The patient generally shows eso fixation disparity at both distance and near

What disorders should be differentiated from basic esodeviation?

Functional differentials

• Divergence insufficiency: more eso at distance

• Convergence excess: more eso at near

Pathologic differentials

• Sixth nerve palsy

• Divergence paralysis

Acute onset, noncomitancy, neurologic symptoms, or endpoint nystagmus increases concern for pathology

What is the initial refractive treatment for basic esodeviation associated with hyperopia?

Prescribe the full plus correction.

Plus lenses:

• Correct hyperopia

• Reduce accommodative demand

• Reduce accommodative convergence

• Decrease the eso deviation

The slides indicate that more than 90% of patients can achieve normal binocular function with appropriate management

What additional treatments may be used for basic esodeviation?

• Base-out horizontal prism

• Vertical prism for a coexisting vertical deviation

• Vergence therapy to improve negative fusional vergence

• Occasional added lenses

• Surgery only for a large deviation that fails nonsurgical treatment

Therapy may be used alone or in combination with prism

What is the defining clinical pattern of fusional vergence dysfunction?

The patient has relatively normal ocular alignment but has difficulty rapidly and sustainably changing vergence.

Typical findings:

• Orthophoria or only a small phoria

• Reduced vergence facility

• Reduced positive and/or negative fusional vergence

• Symptoms during near work

What symptoms are typical of fusional vergence dysfunction?

• Eyestrain

• Headaches

• Ocular burning or tearing

• Intermittent blur

• Reduced concentration and endurance

• Sleepiness while reading

• Slow reading

• Decreasing comprehension over time

Symptoms usually worsen later in the day or with sustained near work. Some patients avoid symptoms by avoiding near tasks or covering one eye

What test findings support fusional vergence dysfunction?

• Orthophoria or small phoria at distance and near

• Reduced vergence facility

• Possible reduction of both BI and BO fusional vergence

• Low NRA and PRA

• Reduced binocular accommodative facility with both plus and minus

• Normal monocular accommodative facility

Why is binocular accommodative facility reduced while monocular facility remains normal in fusional vergence dysfunction?

The accommodative system itself is functioning normally, but changing lens power during binocular testing also changes accommodative convergence.

The patient struggles to compensate with fusional vergence:

• Plus lenses: Reduce accommodative convergence, requiring additional convergence

• Minus lenses: Increase accommodative convergence, requiring additional divergence

Therefore, both plus and minus may be difficult binocularly, while monocular facility remains normal

How can fusional vergence dysfunction be differentiated from accommodative infacility?

• Fusional vergence dysfunction: Binocular accommodative facility is reduced, but monocular facility is normal.

• Accommodative infacility: Both monocular and binocular accommodative facility are reduced.

This distinction identifies whether the primary limitation is vergence or accommodation

What conditions should be excluded before diagnosing fusional vergence dysfunction?

• Accommodative infacility

• Latent hyperopia

• Vertical or cyclodeviation

• Fixation disparity

• Aniseikonia

• Systemic disease causing debilitation

• Medication effects

How is fusional vergence dysfunction managed?

Vergence therapy is the primary treatment.

Goals include:

• Improving positive and negative fusional ranges

• Normalizing vergence facility

• Increasing binocular stamina

• Improving the ability to sustain near work

Approximately 12 to 24 sessions may be required. Prism and surgery are generally not the primary treatments

A 16-year-old has near eyestrain, orthophoria at distance, 2Δ exophoria at near, reduced BI and BO vergence, vergence facility of 8 cpm, reduced binocular facility, and normal monocular facility. What is the diagnosis?

Fusional vergence dysfunction.

The key diagnostic pattern is:

• Minimal phoria

• Decreased ability to perform both convergence and divergence

• Reduced vergence facility

• Binocular difficulty with both plus and minus

• Normal monocular accommodative facility

How can the major horizontal vergence disorders be distinguished using distance and near phoria?

• Convergence insufficiency: Exo greater at near

• Divergence excess: Exo greater at distance

• Basic exodeviation: Approximately equal exo at distance and near

• Convergence excess: Eso greater at near

• Divergence insufficiency: Eso greater at distance

• Basic esodeviation: Approximately equal eso at distance and near

• Fusional vergence dysfunction: Orthophoria or small phoria with reduced vergence ability

Mnemonic logic: The name identifies the function that is deficient and the viewing distance where the abnormal deviation becomes most apparent.

Which fusional vergence reserve compensates for an exophoria versus an esophoria?

• Exophoria: Compensated by PFV, tested with BO prism

• Esophoria: Compensated by NFV, tested with BI prism

What lens difficulty is expected with exo and eso deviations during binocular accommodative facility testing?

• Exo pattern: More difficulty with plus, because plus reduces accommodative convergence and increases the convergence demand

• Eso pattern: More difficulty with minus, because minus stimulates accommodation and accommodative convergence

• Fusional vergence dysfunction: Difficulty with both plus and minus

• Accommodative infacility: Difficulty binocularly and monocularly

What is the high-yield diagnostic and management summary for the disorders in this deck?

Divergence insufficiency

• Greater eso at distance

• Reduced distance NFV

• Treat hyperopia and consider BO prism

• Exclude sixth nerve palsy or neurologic divergence paralysis

Basic exodeviation

• Similar exo at distance and near

• PFV inadequate for the phoria

• Vergence therapy is primary

Basic esodeviation

• Similar eso at distance and near

• Low NFV

• Correct full hyperopia; consider BO prism and therapy

Fusional vergence dysfunction

• Small phoria but reduced convergence and divergence facility

• Binocular facility reduced with both plus and minus

• Monocular facility normal

• Vergence therapy is primary