Binocular Vision & Accommodative Dysfunction

Advantages of BV

1. single and clear vision

2. stereopsis

3. VF enlargement

4. compensation of the Blind spot

what is stereopsis

the most precise kind of depth perception

anomalies of BV categories

1. BV is maintained (fusion)

2. BV is absent

examples of fusion anomalies

1. heterophorias

2. fixation disparity

3. accommodation anomalies

examples of BV absent anomalies

1. strabismus (heterotropia)

2. suppression = amblyopia

3. eccentric fixation

4. anomalous retinal correspondence (ARC)

what is heterophoria

position the visual axes take with respect to one another in the absence of all a stimulus to fusion

“Physiological position at rest”

how do you test for heterophorias

1. alternating cover test

2. von graefe phorias

what is a corresponding retinal point (CPR)

two retinal points, one in each eye, facing in the same direction, that when stimulated simultaneously, send impulses to the same point in the visual cortex = fusion (one single image)

in what direction do the points correspond to

the point nasal to the fovea of one eye corresponds to the point temporal to the fovea of the opposite eye and vice versa

what is a cyclopean eye

an imaginary eye situated midway between the two eyes

what do you use to see crossed and uncrossed diplopia?

a maddox rod in OD

what is a crossed diplopia?

In OD object image is to the right of the fovea but its perceived to the left VF

What is uncrossed diplopia?

In OD object image is to the left of the fovea but its perceived to the right VF

uncrossed diplopia is what

esotropia

crossed diplopia is what

exotropia

what is anomalous retinal correspondence (ARC)

corresponding retinal points DO NOT have the same visual direction

ARC is frequently seen in what condition

strabismus

T/F: ARC is an attempt to regain the binocular advantage

True

what are retinal disparities

the small difference between the image projected on each retina while looking at an object

what is necessary for depth perception and stereoacuity

retinal disparities

what occurs when retinal disparities are too big

causes diplopia

what is necessary for binocularity

vergences

what are vergences

binocular eye movements in opposite directions (disjunctive eye movements)

• convergence

• divergence

when the vergence demand increases what is necessary to maintain SCBV?

motor fusion

what is fusional demand

the maximum vergence movement enabling SCBV

what are fusional reserves

amount of vergence remaining after compensating for the phoria

How are positive relative vergence (PPV) and Negative relative vergence (VRV) measured?

from the demand point (zero point)

• what we record as blur

How are positive fusional vergence (PPV) and Negative fusional vergence (VRV) measured?

from the phoria position

• what we record as double

what can lead to the inability to converge or diverge?

1. loss of control of ocular alignment

2. decompensation of a latent phoria

what is the difference between a phoria and a tropia

fusional vergence

how do we prevent latent deviation from becoming manifested

we make fusional movements according to the disparity information given

what condition has a higher risk of developing functional strabismus in children?

hyperopia due to the constant accommodation (positive fusional vergence)

what visual skills are needed for day to day tasks

1. eye tracking

2. eye teaming

3. eye focusing

what percentage of what is learned is received via the visual system?

80%

What is the COV-QOL used for

• 19 item survey to assess quality of life and vision comfort of individuals

what are common complains children have about their vision?

1. they get too close to read

2. report headaches after school

3. need to trace with fingers while reading

what is accommodative dysfunction?

interferes with the ability of the eyes to focus clearly on objects at various distances = blurry vision

what is vergence dysfunction?

involves disjunctive eye movements of convergence or divergence resulting in the inability of the eyes to accurately fixates and stabilize a retinal image

what are more common organic or functional accommodative anomalies?

organic accommodative problems

symptoms of organic accommodative problems?

1. sudden onset loss of accommodative in one eye

2. severely diminished amplitude of accommodation

3. neurological findings

4. diplopia

5. dizziness

6. visual disturbances

risk factors for accommodative dysfunctions

1. need to sustain increased accommodation for near targets

2. accommodative fatigue

3. accommodative adaptation

4. slow accommodation

5. various drugs and systemic diseases

symptoms of accommodative dysfunctions

1. decreased VA at distance and near

2. falls asleep or loses concentration easily while performing near work

3. eyestrain or fatigue

4. headaches during school days

5. light sensitivity

6. letters in and out of focus

7. bringing reading material very close

8. visual guessing

general signs of accommodative dysfunction?

1. fluctuating VA findings during the exam

2. fluctuating pupil response

3. fluctuating retinoscopy

4. significant phorias

Test for accommodative amplitudes

1. donders

2. sheards

3. BCC

4. MEM

Test for accommodative facility

1. NRA

2. PRA

3. Flippers

what is the most common accommodative problem?

accommodative insufficiency

symptoms of accommodative insufficiency

1. blurred vision

2. asthenopia at near

3. sometimes burning, irritation, photophobia, or nausea

signs for accommodative insufficiency

1. low amplitude of accommodation

2. higher lag of accommodation

3. low PRA

4. fails monocular and binocular flippers with minus lens difficulty

5. tends towards convergence insuffiency

6. school age to late 20’s

associated conditions to accommodative insuffiency

1. convergence insufficiency

2. emotional distress or fatigue

3. endocrine conditions

4. decompression sickness

5. down syndrome

6. cerebral palsy

7. ADHD

Management for accommodative insufficiency

1. treat underlying conditions

2. correct refractive error

3. plus, lenses at near

4. vision therapy

what is accommodative infacility

inadequate speed and accuracy

what are symptoms of accommodative infacility

1. intermittent blur when changing point of focus

2. headaches

3. asthenopia at near

4. poor attention/concentration while reading

5. diplopia

what are signs of accommodative infacility

1. poor facility of accommodation

2. fails flippers difficulty with plus and minus lenses

3. low NRA and PRA

4. fluctuations during MEM and BCC test

conditions associated with accommodative infacility

1. learning disabilities

2. measles

3. graves disease

4. DM

5. alcoholism

6. migraines

7. cerebral palsy

8. adie’s tonic pupil

what is ill sustained accommodation

is a condition where the eye's ability to focus diminishes over time during near tasks, leading to blurred vision and discomfort.

symptoms of ill sustained accommodation

1. blurred vision after prolonged near

2. asthenopia

signs of ill sustained accommodation

1. normal AoA but fatigue after a while

2. slow accommodation

3. normal to hight lag MEM and BCC

4. low PRA

5. fail flippers when repeated

when does accommodative excess occur

occurs after prolonged near work and diminishes after 10 minutes after stopping the task

causes of accommodative excess

1. young hyperopes accommodating

2. young myopes with excessive near work

3. young patients with accommodations

4. improper spectacle fit

symptoms of accommodative excess

1. intermittent blurred vision (especially at distance)

2. asthenopia

3. ocular pain

4. headaches

5. ineffective prescriptions or frequent changes

6. sluggishness when changing from D to N (more than 1 sec)

7. micropsia/macropsia

signs of accommodative excess

1. normal Aoa

2. lead of accommodation (lead BCC)

3. low NRA

4. fails flippers monocular or binocular (trouble with plus lenses)

5. low ATR cylinder

6. variable VA’s

7. variable retinoscopy

management of accommodative excess

1. decrease near work for several weeks

2. correct ametropia (with cyclorefraction)

3. VT emphasis on accepting plus

DX for accommodative dysfunctions

1. emerging myope

2. spasm of accommodative/near reflex

3. accommodative paralysis

4. binocular dysfunction

5. uncorrected refractive error

6. streff syndrome

what is harmon’s distance

at elbow distance for reading