Binocular vision workshop Prof Bruce Evans BSc (Hons) PhD FCOptom DipCLP DipOrth FAAO FBCLA Director of Research Institute of Optometry Visiting Professor City University Visiting Professor London South Bank University Private practice Cole Martin Tregaskis, Brentwood, Essex © 1990-2015 Bruce Evans Reference: Pickwell’s Binocular Vision Anomalies, 5th Edition, Elsevier, 2007 Handout from www.bruce-evans.co.uk

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DISSOCIATED HETEROPHORIA

fusional reserves

motor fusion

sensory fusion

fusion lock

COMPENSATED or NOT

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Q: Which of the following is not a definition of decompensated phoria? 1. A heterophoria that produces symptoms 2. A heterophoria that is worse at near than distance 3. A heterophoria that produces signs 4. A heterophoria that requires treatment

DEFINITION OF DECOMP. PHORIA A heterophoria that produces symptoms “symptomatic heterophoria” A heterophoria that produces signs Depends on tests used A heterophoria that requires treatment

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FACTORS AFFECTING COMPENSATION (a) Stress on the visual system (1) Excessive use of vision circumstances (a) (b) (c) (d)

under

adverse

Work held too close to the eyes for long periods. A sudden increase in the amount of close work. Poor illumination or contrast Increased use of the pursuit reflexes

(e) Tasks which dissociate accommodation and convergence.

(2) Accommodative anomalies. (3) Refractive error. (4) Imbalanced and/or low fusional reserves.

FACTORS AFFECTING COMPENSATION (b) Stress on the well-being of the patient (1) Poor general health. (2) Worry and anxiety. (3) Old age. (4) Emotional and temperamental problems. (5) Adverse effect of medicines.

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KEY SIGNS OF DECOMP. PHORIA Symptoms Poor cover test recovery Aligning prism Low fusional reserve opposing phoria Sheard’s criterion Particularly useful for exophorias For esophorias, size and imbalanced fusional reserves are relevant For hyperphorias, size matters

Q: Which of the following is not a symptom of decompensated phoria? 1. Dyslexia 2. Blurred vision 3. Double vision 4. Headaches 5. Aching eyes

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SYMPTOMS OF DECOMP. PHORIA 1. Blurred vision 2. Diplopia 3. Distorted vision 4. Difficulty with stereopsis 5. Monocular comfort 6. Difficulty changing focus 7. Headache 8. Aching eyes 9. Sore eyes 10.General irritation

KEY SIGNS OF DECOMP. PHORIA Symptoms Convergence insufficiency symptom survey (CISS) Validated & reliable for CI in children aged 9-18y (Borsting et al., 2003) Used in 14 other studies

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KEY SIGNS OF DECOMP. PHORIA Symptoms Poor cover test recovery

Grade 1 2 3 4 5

Description rapid and smooth slightly slow/jerky definitely slow/jerky but not breaking down slow/jerky and breaks down with repeat covering, or only recovers after a blink breaks down readily after 1-3 covers Scale

3.00

2.0 1.8 1.6 1.4

1st appt. difference (TP-BE)

2.00

1.2 1.0

orthophoria

hyperphoria

esophoria

exophoria

1.00

0.00

-1.00

-2.00

-3.00

0.00

Panesar & Evans, in preparation

1.00

2.00

3.00

4.00

5.00

1st appt. mean (TP & BE)

Q: What does the Mallett fixation disparity test measure (more than 1 may be correct)? 1. Fixation disparity 2. Aligning prism 3. Associated heterophoria 4. Decompensated heterophoria 5. Suppression

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KEY SIGNS OF DECOMP. PHORIA Symptoms Poor cover test recovery Aligning prism (FD test) Low fusional reserve opposing phoria Sheard’s criterion Particularly useful for exophorias For esophorias, size and imbalanced fusional reserves are relevant For hyperphorias, size matters

ALIGNING PRISM: Mallett Unit •

aligning prisms/spheres to eliminate FD

•

good foveal and peripheral fusion lock

•

question set is important • ask if a line ever moves • Karania & Evans (2006)

•

for symptomatic phoria:

1.0

1 ∆+

• sensitivity 75%

.8

• specificity 78%

.6

• Jenkins, Pickwell, & Yekta (1989)

1∆+ 2 ∆+

.4

2∆+

3∆+ aged 40 years and over

.2

3∆+

0.0 0.0

under the age of 40 years .2

.4

.6

.8

1.0

1-SPECIFICITY

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ALIGNING PRISM: Mallett Unit • Maintain normal binocular vision •

Increase lighting, full field of view

•

Use hand held loose prisms

•

Minimum prism for alignment

•

Re-normalise BV between prisms

•

Prism dioptre steps: 0.5, 1.0, 2.0, 4.0 1.0

1 ∆+ ∆

1+

.8

2 ∆+

.6

.4

2∆+

3∆+ aged 40 years and over

.2

3∆+

0.0 0.0

under the age of 40 years .2

.4

.6

.8

1.0

1-SPECIFICITY

KEY SIGNS OF DECOMP. PHORIA Poor cover test recovery Aligning prism Low fusional reserve opposing phoria Sheard’s criterion Particularly useful for exophorias For esophorias, size and imbalanced fusional reserves are relevant For hyperphorias, size matters

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FUSIONAL RESERVES Can be measured with:

loose prisms

prism bar

rotary prisms

Q: Which fusional reserve should you measure first? 1. Divergent at distance, convergent at near 2. The fusional reserve that opposes the phoria 3. Divergent 4. Convergent 5. Base up 6. Base down

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FUSIONAL RESERVES Measure the reserve that opposes the phoria first Rosenfield Often the blur point cannot be measured (Horwood & Toor, 2014)

KEY SIGNS OF DECOMP. PHORIA Poor cover test recovery Aligning prism Low fusional reserve opposing phoria Sheard’s criterion Particularly useful for exophorias For esophorias, size and imbalanced fusional reserves are relevant For hyperphorias, size matters

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MALLETT FOVEAL SUPPRESSION TEST Tang & Evans (2007)

R

L

1. Only show patient test with visor on 2. Have patient read down test binocularly 3. You are assessing monocular acuities under binocular conditions

MALLETT FOVEAL SUPPRESSION TEST R

L

Binocular R L

x x 1. 2. 3.

RE reads to 5 mins of arc, LE only to 10 mins of arc Is the reason for the poor acuity in the LE foveal suppression or poor VA? To find out, keep visor in place and occlude RE, re-measuring LE

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MALLETT FOVEAL SUPPRESSION TEST R

L

Binocular Occluded R R L L

x x 1. 2. 3.

x

RE near VA 5 mins arc LE near VA 7 mins arc Under binocular viewing conditions, LE has 3 min arc foveal suppression

FOVEAL SUPPRESSION TEST: norms R

L

For 95% of the population, the VAs under binocular viewing conditions should be within one line of the VAs obtained under monocular viewing conditions Tang & Evans (2007)

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STEREOTESTS www.bernell.com

BINOCULAR INSTABILITY: DIFFERENTIAL DIAGNOSIS SIGN

B.I.

DECOMP. PHORIA

phoria variability of phoria cover test recovery fusional reserves

may/may not be present > ±1.75 ∆ may/may not be abnormal convergent & divergent usually low, worse as tires unstable FD, may be aligned "on average" significant correlate

must be present < ±1.75 ∆ usually slow & hesitant low reserve opposing phoria

aligning prism dyslexia

misaligned, may/may not be unstable non-significant correlate

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BINOCULAR INSTABILITY: MANAGEMENT treat any sensory factors interfering with fusion. train the fusional reserves. if temporary poor health, can use prisms or spheres to correct any aligning prism.

Optometric correlates of dyslexia: Meares-Irlen Syndrome/Visual Stress (MISViS) PREVALENCE:

30% of people with dyslexia

AETIOLOGY:

cortical hyperexcitability causing pattern glare from text

SYMPTOMS:

asthenopia, headaches, perceptual distortions

SIGNS:

coloured overlays alleviate symptoms and improve rate of reading

TREATMENT:

Precision Tinted lenses

Allen, Evans, Wilkins (2010) Vision & Reading Difficulties

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Differential diagnosis: Binocular vision anomaly or MISViS Sign

Binocular vision anomaly

Meares-Irlen Syndrome

Significant phoria

May be present (not if binocular instability)

Unlikely

Low fusional reserves

Present

May be present

Symptoms alleviated by occlusion Pattern glare

Yes

Unlikely

Unlikely

Present

Photophobia

Yes, but not colour specific

Yes, colour specific

Symptoms alleviated by coloured filters

Unlikely

Yes

In the CITT RCT of VT for CI (2008) ONLY 56% of those receiving optimal VT were asymptomatic at the end of 12 weeks of treatment (CITT, 2008). Allen, Evans, Wilkins (2010) Vision & Reading Difficulties

SUMMARY:

DIAGNOSIS

Sign or symptom one or more of the symptoms of decompensated heterophoria cover test: heterophoria detected cover test: absence of rapid and smooth recovery (+1 if quality of recovery 'border-line') aligning prism (Mallett): 1∆+ for under 40 years or 2∆+ for over 40 years aligning prism (Mallett): 3', or diplopia during foveal suppression test if score: 5 treat, 4-5 continue down table adding to score so far Sheard's criterion: failed Percival's criterion: failed dissociated heterophoria unstable so that result is over a range 3∆ (i.e., phoria ±2∆) fusional amplitude (divergent break point + convergent break point) < 20∆ if total score: 8 cm jump convergence (see next slide)

amplitude of accommodation heterophoria tests for near vision fixation disparity tests at reduced distance

PRACTICAL SESSION GOALS Test 3 people with Mallett-type unit Evans units are a copy of Mallett made by a different person called Evans, not the presenter! Genuine Mallett units from www.ioosales.co.uk Be careful to detect any movement Use loose prisms to find minimum prism to align strips

Other tests: fusional reserves Randot stereotest

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Q: With the Mallett fixation disparity test, which of the following is recommended? 1. Use a prism bar leaving in place all the time 2. Carry out in the dark 3. Use 5 prism dioptre steps 4. Allow binocular vision to re-normalise between prisms

ALIGNING PRISM: Mallett Unit • Maintain normal binocular vision •

Increase lighting, full field of view

•

Use hand held loose prisms

•

Minimum prism for alignment

•

Re-normalise BV between prisms

•

Prism dioptre steps: 0.5, 1.0, 2.0, 4.0 1.0

1 ∆+ 1∆+

.8

2∆+

.6

.4

2∆+

3∆+ aged 40 years and over

.2

3∆+

0.0 0.0

under the age of 40 years .2

.4

.6

.8

1.0

1-SPECIFICITY

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