BVP

What is a cover test?

Objective assessment of the patient's eye alignment

What is the cover test used for?

Distinguish between heterophoria and strabismus

What additional information should be recorded about a deviation found?

Degree & Magnitude

How can you estimate the compensation of a phoria?

Estimating the recovery of the movement (fast, slow recovery)

What distance should the cover test be performed?

DV & NV

What should the target for DV cover test be?

a letter on the chart from the line above the VA threshold for the lowest acuity

What should the target for DV cover test be if VA < 6/36?

spot light

What is the first step of the cover test?

As one eye is covered (1-2 seconds), observe the other eye: any movement indicates that it was deviated and had to move to take up fixation - Repeat for other eye

What is the second step of the cover test?

One eye is covered (1-2 seconds), observe the eye under the cover as the cover is removed: any movement indicates that the eye was deviated under the cover and recovers when the cover is removed to take up fixation- Repeat for other eye

What is the third step of the cover test?

Alternating cover test When the cover/uncover has been conducted, it is sometimes useful to transfer the cover from one eye to the other and back several times

What is the purpose of first stage of the cover test ?

Find Strabismus/ Heterotropia

What is the purpose of the second stage of the cover test?

In the ABSENCE OF STRABISMUS this shows a HETEROPHORIA

What happens to the degree of deviation during the alternating cover test?

usually increases

What additional info should be recorded when strabismus is found?

Constancy, Direction of deviation, Eye preference, Degree of deviation

What additional info should be recorded when heterophoria is found?

Direction of deviation, Degree of deviation, Compensation

Give an example when NV CT is useful?

an SOP may only break into a tropia when the patient accommodates

What do observations of the deviating eye indicate about VA?

Better fixation indicates better VA, If it does not take fixation it indicates poor VA

What does alternating deviation indicate?

similar VA in each eye

Which eye is the prism bar held in front of during prism cover test?

In front of manifest deviation (tropia), can be either eye for phoria

What should the base direction be during prism cover test?

opposite to deviation

What do you record during the prism cover test?

Record prism magnitude when no movement is observed

What is the ocular motility test for?

Objective test explores the ability of the patient to move the eyes into all parts of the motor field

What is the only objective routine clinical test for incomitant eye movements?

ocular motility

What info does the ocular motility test provide?

Fixation, Pursuit eye movements, Vertical movement of the eyes and lids, Comitancy, Cover test in peripheral gaze, Reports of diplopia

How far is the pen light held for ocular motility test?

~50cm

IS ocular motility performed monocular?

Usually done binocularly, if abnormality suspected then repeat monocularly

How would you perform an ocular motility test?

Move penlight slowly into the 8 directions of gaze from centre to periphery

What instructions would you give when performing ocular motility test?

Ask patient to report pain discomfort or double vision

What does it mean if a deviation is comitant?

If a deviation (strabismus) remains the same in all positions of gaze

What does it mean if a deviation is incomitant?

the deviation changes in any position of gaze the deviation

What could cause an incomitant deviation?

potential nerve weakness, muscle weakness or mechanical restriction)

What should you observe when performing the ocular motility test?

any under action or overaction of one eye compared to the other

Why would you perform a cover test in peripheral gaze?

to identify any underaction or overaction

With diplopia which position will identify the primary muscle problem?

the position of gaze with maximum diplopia

Conducting an ocular motility assessment - what should be observed and recorded?

Ptosis, Lid function, Pain, Changes in palpebral fissure, Pupil abnormalities, Up-shoots, down shoots, Up-drifts, down-drifts, Nystagmus, Underactions / over-actions (version), Limitation (ductions)

What is ptosis?

droopy eyelid

What is nystagmus?

involuntary eye movement (wobbly eye)

How to detect under and over actions using corneal reflections?

If the corneal reaction is not centred

How can you tell which eye is over or under action using corneal reflections?

the eye without a centred reaction

Why should an alternating cover test still be performed if a px doesn't complain of double vision?

might have suppression

What is a "v" pattern ?

Exo (phoria or tropia) that increases on up-gaze and decreases on down-gaze or Eso (phoria or tropia) that increases on down-gaze and decreases on up-gaze

What is "a" pattern?

Exo (phora or tropia) that increases on down-gaze and decreases on up-gaze or Eso (phoria or tropia) that increases on up-gaze and decreases on down-gaze

What does the assessment of versions (binocular) and ductions (monocular) discriminate?

Difference between paretic and mechanical abnormalities

What does Equal movement on ductions and versions suggest?

Mechanical problem

What does More movement on ductions than versions suggest

neurogenic problem

What are the two aspects of convergence movements?

Pursuit & Step convergence

What is an appropriate target for NPC?

Accommodative target, Size resolvable by each eye

What correction if any should px wear during NPC test?

near vision where approprite

What should NPC value be?

≤8cm, ideally should be ≤5cm

What should you ask the px to do when testing jump convergence?

to alternate fixation between a near target and distance target

What is observed in normal eyes when testing jump convergence?

The patient's eyes should be seen to converge promptly and smoothly from the more distant object to the nearer one

What do difficulties in jump convergence test indicate?

a failure of normal convergence and that the patient is unable to maintain convergence for near vision

What might poor jump convergence look like?

unstable convergence movement and/or a slow or hesitant convergence movements

What are fusional reserves?

Represent the amount of vergence that can be induced before fusion is compromised and blurred or double vision occurs

What 2 values should be recorded when measuring fusional reserves?

break & recovery

What are the different aspects of accommodation that can be assessed?

Amplitude of accommodation, Accommodative facility, Accommodative accuracy

What is amplitude of accommodation?

Measure of the closest point at which the eyes can focus

if any what specs should be worn when testing amplitude of accommodation?

distance Rx

How can you calculate the Expected minimum accommodative amplitude for various ages (push up)?

15D - (age/4)

What is accommodative facility?

Measure of the rate of change of accommodation

What equipment is used to test accommodative facility?

+-2D flippers

What is typical response for accommodative facility?

8 cpm with a standard deviation of 5cpm

What is accommodation accuracy?

Measure how accurate the accommodation is when performing a near target

How is accommodation accuracy measured?

Dynamic Retinoscopy

What are the 2 methods of dynamic Retinoscopy?

Monocular Estimate Method (MEM) & Nott/Modified Nott Retinoscopy

What is typical accommodative lag?

+0.75

What does it mean if more plus is required during MEM?

excessive accommodative lag; accommodation deficit

What does it mean if negative required during MEM?

excessive lag; accommodative excess or spasm

When is NOTT extremely useful?

very young children, infants, patients with limited cooperation and patients with special needs

How can you tell the px is accommodating accurately during NOTT?

reflex will be neutral

How can you tell the px is under-accommodating accurately during NOTT?

a lag ("with reflex") will be observed

How can you tell the px is over-accommodating accurately during NOTT?

a lead ("against reflex) will be observed

What is the normal range of accommodative lag?

0 to 0.75D using a viewing distance of 25cm

What is steropsis?

the perception of depth arising from binocular horizontal retinal disparity

At what age do infants begins to reach for objects?

3.5 months

At what age to infants have good visual tracking and convergence?

6 months

What can effect eye development in the 1st trimester?

Drug abuse, infection, medications

What is contrast sensitivity?

amount of contrast required to detect grating of different spatial frequencies

How does CSF change with age?

at eye Peak CSF shifts towards higher SF with age

What factors limit acuity and contrast sensitivity during development?

Changes in optical properties and focusing of eyes. Differentiation of the fovea. Myelination of the visual pathway. Increase in number of synaptic connections

What do normal eye movements indicate?

normal visual development

If interested what eye movements should infants be able to do?

Fixate on stationary objects, Follow a moving target, Move their eyes towards a stimulus in the peripheral field.

At what distance do new-borns have accuracy of focus?

<75cm

When are adult levels of accuracy of accommodation present?

2-3 months

Why is depth of focus greater for infants?

smaller eye size and pupil

What are the types of convergence?

Accommodative (driven by blur) Fusional ( driven by diplopia)

What is accommodative convergence driven by?

blur

What is Fusional convergence driven by?

Diplopia

When is accommodative convergence developed?

1 month

When is fusional convergence developed?

intermittent at 2 months and improves in accuracy with age

What are the 3 levels of binocular function?

Bifoveal fixation, Fusion, Stereopsis

When does stereopsis develop?

between 2 and 6 months

What is fusuion?

Relates to the visual system's ability to combine similar and perhaps non-identical information from two eyes into one image

How does fusion develop?

No fusion before 3.5 months of age. Consistent fusion by 6 months of age

When does colour vision develop?

between the ages of 1 and 3 months has been demonstrated

What conditions are infants sensitive to that can interfere with normal development of vision?

Amblyopia, Suppression, Anomalous Correspondence

What arre the types of visual acuity?

Detection, Resolution, Recognition/identification, Hyperacuity

What is detection VA?

Smallest test object that can just be detected

What can be used to test detection VA?

Stycar balls or 'Hundreds and thousands'

What is the drawback of detection VA?

May grossly over-estimate VA in visually impaired children