W11: Non-Strabismic Binocular Vision Disorders

Non-Strabismic Binocular Vision (NSBV) Disorders

  • Definition: Accommodative or oculomotor alignment anomalies characterized by symptoms such as blur or asthenopia.

  • Key Features:

    • Fusion is consistently present.

    • No constant manifest strabismus.

    • Anomalies may occur in accommodation, ocular alignment, vergence capacity, or interactions between accommodation and vergence.

  • Clinical Measures:

    • Compare clinical findings with age-specific expected measures.

    • Findings that are outside the normal range support the diagnosis of NSBV disorder.

Classifying NSBV Disorders

  1. Symptom Assessment:

    • Symptoms must correlate with the function of the eyes.

    • Severity of symptoms tends to increase later in the day when the patient is fatigued or has used their eyes for extended periods

    • If no symptom escalation is noted, consider alternative etiologies (non-functional or malingering).

    • Non-functional causes to consider:

      • Convergence paralysis from ischemic infarction, demyelination, viral infections, Parkinson's disease.

    • Case History Questions:

      • Recent illnesses or medications taken? Changes in medication dosage?

      • Experiencing dizziness or balance issues?

      • Recent trauma?

      • Had any fainting spells or numbness/tingling sensations?

  2. Clinical Testing:

    • To rule out non-functional aetiologies, perform evaluations such as:

      • External evaluation of eyes.

      • Pupil evaluation.

      • Colour vision test (monocularly)

      • Ophthalmoscopy.

      • Versions assessment.

      • Cover test (distance and near, including 9 positions of gaze).

      • Confrontation fields examination.

  3. Evaluation of Vision and Health:

    • Confirm that vision, eye health, and refractive error are normal or corrected.

  4. Progress to Classification:

    • Utilize multiple approaches: flow charts that differentiate between vergence and accommodative dysfunction.

Esophoria: investigate PFV data = anything related to BO or anything related to NRA

Exophoria: investigate NFV data = anything related to BI or PRA / accommodation

Distance problem = divergence

Basic exophoria / esophoria: distance and near phoria within 10.

Near problem = convergence

excess conditions = high AC/A

  • responds well to added lenses (e.g., minus to exo will help change vergence posture).

    • over minus for divergence excess

    • over plus for convergence excess

insufficiency conditions = low AC/A

  • do not benefit from added plus or minus

  • need vision therapy or prisms.

  • convergence = vision therapy

  • divergence = prisms.

No significant phoria → look into accommodative findings.

  • MEM / Fused crossed cyl

  • Facility

  • Amps

  • PRA / NRA

when unable to clear minus lenses - reduced AA, PRA, facility → not able to accommodate = accommodative insufficiency.

when unable to clear positive lenses - reduced NRA, facility → can’t relax accommodation = accommodative excess.

Inconsistent - accommodative infacility.

Accommodation not influenced by AC/A

^^ don’t spend to much time ^^

Symptoms associated with NSBV Disorders

  • Vision acuity is typically normal.

  • Eye health is normal.

  • Refractive error is correctable.

  • Assess phoria:

    • Distance phoria: Greater than near phoria indicates possible issues.

    • No significant phoria at distance or near implies further investigation needed.

Investigation Procedures for NSBV Disorders

  • Group Data Analysis:

    • Evaluate Positive Fusional Vergence (PFV) and Negative Fusional Vergence (NFV) group data.

    • Analyze associated conditions and responses to clinical measures (e.g., AC/A ratio comparison).

Exodeviation: Convergence Insufficiency

  • symptoms related to near work:

    • Asthenopia/headaches (HAs)

    • Intermittent blur/diplopia

    • Worse at end of day

    • Burning/tearing

    • Inability to sustain and concentrate

    • Words move on the page

    • Sleepiness when reading

    • Decreased reading comprehension over time

    • Slow reading

  • higher score = worse.

  • Signs:

    • Greater exophoria at N (than D)

      • May be orthophoria at D

      • May be intermittent exotropia at N

    • Reduced PFV

    • Reduced vergence facility with BO

    • Intermittent suppression (if significant, stereopsis may also be reduced)

    • Receded NPC

    • Low AC/A ratio

    • Fails binocular accommodative facility with + lenses

    • Low MEM/FCC

    • Low negative relative accommodation (NRA)

    • Exofixation disparity

  • Management:

    • primary approach = vision therapy for sensory motor function (Children and adults)

      • build BO fusion range (to twice of phoria)

      • build awareness of NPC

    • secondary option = prism (BI at N)

      • especially in adults who don’t want to do vision therapy.

      • use fixation disparity as a guide.

Exodeviations: basic exophoria

  • symptoms:

    • asthenopia (D and N)

    • Intermittent blur / diplopia (D and N)

    • worse at end of day

  • Signs:

    • Similar exophoria at D and N

    • Reduced PFV

    • Reduced vergence facility with BO

    • Low NRA

    • Fails binocular accommodative facility with + lenses

    • Low MEM/FCC

    • Exofixation disparity

  • Management:

    • Primary approach = vision therapy for sensory motor function

      • Build BO fusion range

    • Secondary option = added lenses

      • over minus if IXT

      • prism (BI if >20pd)

Exodeviation: divergence excess

  • symptoms:

    • intermittent eye turn (turning out)

    • occasional near point asthenopia

    • child closes one eye in bright light

  • Newcastle control score:

    • useful for determining when ophthal referral is needed.

  • score 9 - full IXT.

  • problem - on review score may go up due to patients’ parents being more attentive in future.

  • alternate: IXT control scale

  • Signs:

    • Greater exophoria or IXT at D (compared with N)

    • High AC/A ratio

    • Suppression at D

    • Normal NPC

    • Fusional vergences may or may not be reduced

    • Normal stereopsis at N

  • Management:

    • Primary approach = vision therapy for sensory motor function

      • Create awareness of diplopia and then build BO fusion range

    • Secondary option = added lenses (over-minus if child <6 years)

      • Determine lowest ‘minus’ that will eliminate symptoms/normalise data

      • Promotes accommodative vergence to achieve alignment

      • two options:

        • -2.50D on top of cyclo refraction (not good for myopia management!!)

        • formula used to calculate the over minus. Considers accommodation and reserves.

Esodeviations: convergence excess

  • Symptoms: near work issues.

    • Asthenopia/HAs

    • Intermittent blur/diplopia

    • Worse at end of day

    • Burning/tearing

    • Inability to sustain and concentrate

    • Words move on the page

    • Sleepiness when reading

    • Decreased reading comprehension over time

    • Slow reading

    • May have symptoms of intermittent diplopia/blur/asthenopia at distance as well

  • Signs:

    • Significant esophoria at N

    • Reduced NFV

    • Reduced vergence facility with BI prism

    • Low PRA

    • Fails binocular accommodative facility with minus

    • High MEM/FCC

    • Esofixation disparity

  • Management:

    • Primary approach = added lenses (plus)

      • Lowest plus to eliminate symptoms/normalise data

      • Consider FCC/MEM or midpoint between NRA/PRA

      • Use AC/A as a guide

      • three ways

        • look at accommodative posture and aim to add plus to get to normal range (+0.50)

        • balance NRA and PRA

          • underaccommodating - PRA will be reduced compared to NRA

          • add shifts range

          • e.g., -1/+3 - balanced is -2/+2 → needs + 1 Add.

        • ESO and AC/A

          • aim for range to be half of their negative fusional vergence

          • use AC/A as a guide.

    • Secondary option = vision therapy

      • Aim to build negative fusional vergence (BI) range

        • quite difficult to teach divergence at distance.

Esodeviations: basic esophoria

  • Symptoms:

    • Asthenopia (D and N tasks)

    • Intermittent blur/diplopia (D and N)

    • Worse at end of day

  • Signs:

    • Esophoria of similar magnitude at D and N

    • Reduced NFV

    • Reduced vergence facility with BI

    • Low PRA

    • Fails binocular accommodative facility with minus

    • High MEM/FCC

    • Esofixation disparity

  • Management:

    • Primary approach = vision therapy and added lenses (plus)

      • Aim to normalise negative fusional vergence (BI) range (especially if no refractive error)

      • Added lens power may be moderately effect; lowest amount plus to eliminate symptoms/normalise optometric data

      • Consider NRA/PRA, MEM, AC/A

    • Secondary option = prism (BO)

      • May be considered if no plus refractive error correction indicated

      • Use fixation disparity measure to guide amount of BO prism to prescribe

Esodeviations: Divergence insufficiency

MUST EXLUDE OTHER PATHOLIGES - RED FLAG!

  • Symptoms:

    • Asthenopia (D tasks)

    • Intermittent blur/diplopia (D)

    • Worse at end of day

    • Generally long-standing (not acute symptoms)

  • Signs:

    • Esophoria greater at D (compared with N)

    • Reduced NFV

    • Reduced vergence facility with BI

    • Esofixation disparity

  • Management:

    • Primary approach = prism (BO)

      • Majority require relieving horizontal prism

      • Fixation disparity/associated phoria measure OR

      • Dissociated phoria and vergence range (1:1 rule – see later slides)

    • Secondary option = vision therapy

      • Aim to normalise negative fusional vergence (BI) range

      • May need to consider surgery if distance esotropia

Accommodative dysfunction: Accommodative insufficiency

  • Symptoms

    • Blurred near vision

    • Discomfort/strain associated with N tasks

    • Fatigue associated with N tasks

    • Difficulty with attention and concentration when reading

  • Signs

    • Low accommodative amplitude

    • Low PRA

    • Fails monocular and binocular accommodative facility with minus lenses

    • Esophoria at N

    • High MEM/FCC

  • Management

    • Primary approach = added lenses (plus)

      • Consider additional + at near based on MEM, PRA/NRA midpoint, FCC

    • Secondary option = vision therapy

      • Improve ability to stimulate accommodation and normalise amplitude of accommodation

Accommodative dysfunction: Accommodative excess

  • Symptoms:

    • asthenopia / HAs with near tasks

    • intermittent blurred distance vision

  • Signs:

    • Variable VA findings

    • Variable refraction (dry)

    • Low level of ATR astigmatism

    • Low MEM/FCC

    • Low NRA

    • Esophoria at N

    • Fails monocular and binocular accommodative facility with plus

  • Management:

  • Primary approach = vision therapy

    • Improve ability to relax accommodation

Accommodative dysfunction: Accommodative infacility

  • Symptoms

    • Difficulty focussing from D to N and N to D

    • Asthenopia with N tasks

    • Difficulty with attention and concentration when reading

    • Intermittent blur at N

  • Signs:

    • Fails binocular and monocular accommodative facility with plus and minus

    • Low PRA

    • Low NRA

  • Management

  • Primary approach = vision therapy

    • Improve ability to stimulate and relax accommodation

DONT OVERLY STUDY PARTS BELOW HERE!! (2 minutes)

Fusional vergence dysfunction

  • Symptoms

    • Asthenopia/HAs at N

    • Intermittent blur at N

    • Worse at end of day

    • Burning/tearing with N tasks

    • Inability to sustain and concentrate

    • Sleepiness when reading

    • Decreased reading comprehension over time

    • Slow reading

  • Signs: poor in both directions

    • Orthophoria or low eso/exophoria

    • Reduced NFV and PFV (D and N)

    • Reduced vergence facility (BI and BO)

    • Low PRA and NRA

    • Fails binocular accommodative facility with both plus and minus

    • Normal monocular accommodative facility

  • Management:

    • Primary approach = vision therapy

    • Establish normal PFV and NFV ranges and facility

Vertical Phoria

  • Symptoms

    • Blurred vision

    • Asthenopia/HAs

    • Diplopia

    • Car/motion sickness

    • Inability to attend and concentrate during sustained visual tasks

    • Sleepiness

    • Loses place when reading (returns to wrong line)

  • Signs:

    • Anomalous head position

    • Hyperphoria

    • Reduced PFV and NFV (horizontal)

    • Reduced vergence facility (BO and BI)

    • Vertical fusional vergence may be reduced or unusually large

  • Management:

    • Primary approach = vertical prism

      • Prescribe associated phoria (reduce fixation disparity to zero)

    • Secondary option = vision therapy

      • Extend vertical vergence ranges

      • not a good option / very hard

Ocular Motor Dysfunction

  • Symptoms:

    • Excessive head movement

    • Frequent loss of place

    • Omission of words

    • Skipping lines

    • Slow reading speed

    • Poor comprehension

    • Short attention span

    • Difficulty copying from board

    • Difficulty with tasks requiring columns of numbers (e.g. test sheets, maths)

    • Poor performance in sports

  • Signs:

    • Below 15th percentile on DEM test

    • Below 15th percentile on NSUCO tests

  • Management:

    • Primary approach = vision therapy

      • Improve large saccadic ability and small excursion/pursuit ability

Management options - NSBV

Added Lens Power:

  • Accommodative insufficiency - add plus

  • Convergence excess - add plus

  • Basic esophoria - add plus

  • Divergence excess or intermittent exotropia - add minus

Plus power:

  • AC/A is primary test to determine effectiveness of added lenses

    • If high AC/A, generally effective approach

    • E.g. 12 esophoria at N and AC/A ratio of 10:1; an addition of +1.00 expect 2 esophoria

  • Bifocal lens design is preferred (higher seg height in children)

Minus power:

  • Determine least amount of minus that allows fusion

    • 1.00D – 2.50D

    • AC/A ratio is not critical factor

  • Single vision lens as fulltime wear

  • suited for really young children, and people without history of family myopia.

Prism Use:

  • Horizontal relieving prism

  • vertical relieving prism

Horizontal relieving prism:

  • Exophoria:

    • Sheard’s criterion: fusional reserve must be at least twice demand

      • Prism needed = 2/3(demand) – 1/3(reserve)

      • E.g. 10 exophoria at N, BO = 12/20/10

        • Prism required = 2/3(10) – 1/3(12) = 6.67 – 4 = 2.67Δ BI

        • one dioptre increments for left / right → prescribe 1pd right & 1 pd left.

  • Esophoria:

    • 1:1 rule

      • BI recovery should be at least as great as amount of esophoria

      • BO required = (esophoria – BI recovery)/2

      • E.g. 12 esophoria at N, BI = 12/18/8

        • Prism required = (12 – 8)/2 = 2Δ BO

    • Percival’s criterion

      • Prism needed = 1/3 (greater lateral range blur limit) – 2/3 (lesser of lateral range blur limit)

      • E.g. BI = 26/30/20; BO = 6/14/8

        • Prism required = 1/3 (26) – 2/3 (6) = 4.66 BOΔ

Vertical relieving phoria:

  • Prescribe associated phoria measurement

    • I.e. amount of prism that reduces fixation disparity to zero

  • electronic charts with polarised lenses.

Conditions best managed with prism:

  • Divergence insufficiency - prism

  • Vertical heterophoria - prism

Vision therapy

  • Effective for:

    • Reducing symptoms

    • Increasing amplitude of accommodation

    • Increasing accommodative facility

    • Improving near point of convergence

    • Increasing fusional vergence amplitudes

    • Increasing fusional vergence facility

    • Eliminating suppression

    • Improving stereopsis

    • Improving accuracy of saccades and pursuits

Conditions best managed with vision therapy:

  • Convergence insufficiency

  • Divergence excess

  • Fusional vergence dysfunction

  • Basic exophoria

  • Accommodative excess

  • Accommodative infacility