8.1.2. Understands the management of a patient with an anomaly of binocular vision.

Question 1

Accommodative Insuffiency

Answer 1

• Defined as inability to obtain necessary amount of accommodation
  
  • Reduces amplitude of accommodation compared to the normal
• Symptoms
  
  • Blurred near vision, eyestrain, HAs
• Aetiology
  
  • Uncorrected Rx, Sudden increase in close work
  • Poor GH, Viral infection
  • Meds - some hypertensives, high oestrogen contraceptive pills, valium
  • Trauma
• Management
  
  • Correct Rx - plus lenses, Excersises if related to CI, Manage GH
  • Miotics?? - increase depth of focus so less accommodation needed hence why old people have smaller pupils

Question 2

What to do if child is anisometropic?

Answer 2

Give full Rx & monitor to see if vision improves. Refer for patching if not much change after 6 months

Question 3

What is the critical period? What is emmetropisation?

Answer 3

• What is the critical period?Up to age 8
• What is emmetropisation?Process whereby the refractive components and the axial length of the eye come into balance during postnatal development in order to induce emmetropia.Most infants are hyperopic, and in those born myopic, the myopia typically decreases to reach emmetropia by toddler age.~age 2-3

Question 4

How does amblyopia occur? Types of Amblyopia

Answer 4

• How does amblyopia occur?
  
  • Diplopia & Confusion appreciated
  • Suppression occurs
  • Eye becomes less visually developed as not being used as much, therefore visual pathway affected
  • Amblyopia results
• Types of Amblyopia
  
  1. Strabismic - squint used less so supresses due to diplopia experienced
  2. Stimulus Deprivation - e.g. ptosis or over occluding of one eye means it’s used less. Obstructing the pathway of light e.g. with cataract
  3. Anisometropic - uncorrected Rx means one eye is seeing worse than other so less development of it
  4. Meridional - one meridian really uncorrected causing reduced vision overall
  5. Ammetropic - high Rx bilaterally meaning both eyes don’t develop as px doesn’t know what a clear world even looks like!
  6. Idiopathic - no direct cause
  7. Pathological - pathology affects eye meaning less development of it so superimposed amblyopia

Question 5

Management of amblyopia

Answer 5

Should fully correct ansometropia (generally speaking) especially if amblyopia is starting

Many children with anisometropic amblyopia can be managed by optometrists in the community. The improvement of vision in the amblyopic eye with the use of spectacles alone should be monitored regularly over a six-month period (3 months may be more preferred). The child will require referral to an ophthalmologist if:
o there is no improvement on two consecutive visits during this period, and
o the vision is still below normal or
o vision improvement is not sustained

In order of success, what is likely to work in terms of management?

• Refractive error correction using cyclo, Occlusion (total or partial, full or part time), Optical penalisation, Drug penlisation e.g. atropine

Question 6

Indications of type & duration of therapy

Answer 6

• Vision —> worse vision means more occlusion
• Age —> older means more occlusion
• Duration of squint/pathology —> longer means more occlusion
• Intermittent/latent squint —> if you cover an eye, their decompensating phoria may fully decompensate as they are fully dissociate, so use atropine instead to keep both eyes open
• Latent nystagmus —> occlusion makes nystagmus worse so use atropine
• Other contraindications —> allergy or GH issue to drug, social trouble with a patch (teasing!!)

Question 7

When is occlusion stopped?

Answer 7

WHEN EQUAL VA!! - CONSIDER CROWDING

When alternation occurs (implies equal VA)

When no further improvement

When risk of decompensation or diplopia

Question 8

Types of BV conditions

Answer 8

• Patient could present with double vision, headaches, eyestrain, blurred vision, fatigue after near work
• Management will always depend upon cause!
• Types of BV conditions
  
  • Decompensating phoria
  • Decompensated phoria (i.e. recent phoria breaking completely into tropia)
  • Convergence insufficiency or Convergence Excess
  • Vertical phoria (accommodation cannot help to control unlike with horizontal phorias)
  • Incomitant deviation
  • Childhood tropias
  • Microtropia (best left alone as patient is often asymptomatic)
  • Accommodation problems

Question 9

Systemic approach of Different Types of Management

Answer 9

Understand that the order below is the systematic approach to dealing with most binocular vision anomalies.

• Refractive - will be on 8.1.1 notes
  
  • Remember that spherical manipulation does not work on those with no accommodation!
  • With decompensating phorias, refractive correction & corrections in the workplace for example can make a big effect on the phoria itself
  • • Orthoptic - below
• Prismatic
  
  • Fresnel prism e.g. after stroke
  • If prism found that alleviates diplopia, then given so long as other strategies have not worked
• Surgery
  
  • Large angle strabismus may require surgical intervention.
    Prior to surgical intervention a trial botulinum toxin injection can be performed.

Question 10

Orthoptic excersises

Answer 10

• Pen to Nose Exercise
  
  • Main issue: Patients may not easily notice physiological diplopia when convergence breaks.
  • Solution: Use two pens—one stationary further away and one moving closer.
    
    • Observe physiological diplopia of the stationary pen as an anti-suppression check.
    • When the closer pen causes the background pen to appear single, convergence has broken. Move the closer pen back until physiological diplopia is restored.
  • Purpose: Train positive convergent fusional reserves.
  • Tips:
    
    • Perform exercises while wearing spectacles.
    • Try it yourself: The background pen should appear double when convergence is intact.
• Dot Card Exercise
  
  • Use a line of dots held against the nose.
  • Focus on the furthest dot; it should create a “V” pattern due to physiological diplopia.
  • Gradually converge on closer dots until the image is single.
    
    • Other dots should appear double.
    • Stop if unable to make the dot single.
  • Repeat the process.
• Stereograms
  
  • Example: Two cat images on the stereogram.
  • Place a pen between the images and move it closer until the images fuse into a middle image.
  • Goal: Maintain three images (middle cat + double background cats) while bringing the pen closer.
  • If fusion fails, restart the test.
• Exercise Routine
  
  • Frequency: 3–4 times per day for 5 minutes each session.
  • Duration: Continue for ~2 months or until symptoms improve or no further progress is observed.
  • Breaks: Rest by staring into the distance for a few minutes after each session.

Question 11

Esophorias treatment

Answer 11

• Esophoria can be treated by stimulating -ve fusional vergence. This means divergence!
  
  • Eso-deviations are much harder to manage with exercises than exo-deviations.
• Stereograms —> gram is held at 30cm & object like a pen needs to be behind it (vergence behind accommodation). Focus on the pen & notice diplopia of the gram. Ensure 3 cats are formed whilst then moving the pen away & keeping the 3 cats there. You may need to find a further distance object to keep practising
• Bar reading
• BI prism excersises
• REMEMBER: PX NEEDS TO GIVE THEIR EYES A BREAK AFTER PERFORMING ANY EXCERSISES!

Question 12

Amblyopia with children…

Answer 12

• Must be aware of critical period for the development of amblyopia
• You should refer children that you do not feel competent to manage or whose visual acuity does not improve after a suitable period of time
• In all suspect-amblyopes, carry out a full and careful eye examination to ensure you rule out possibility of pathology.

Question 13

Extra Topic: Microtropia

Answer 13

• This is a small angle strabismus, less than 10 dioptres
• Eccentric fixation used to fixate with area that is not the fovea, hence being a suppression scotoma around the fovea. The eye turn is in line with this same point, meaning no movement on cover test
• NRC or ARC - ARC is a binocular condition in which the fovea of the fixating eye has a common visual direction with a non-foveal area of the deviating eye.
• Normally anisometropia (1.5D or above)
• Amblyopia of strabismic eye (1 or 2 lines worse)
• 4 base out prism test shows suppression
  
  • IF RE SUPPRESSING - prism put infront of this eye will not make it move, nor will the LE move. If prism put infront of LE, LE will move in and RE will move out but RE will not move back in as it should
• Reduced stereopsis i.e. 100” or worse
• With identity means no CT movement & eccentric fixation
• Without identity means CT movement & no eccentric fixation
• Treatment not needed as fully adapted normally. Rx given and only if breaks down to larger deviation, is the squint treated

Question 14

Causes of amblyopia

Answer 14

1. Stimulus deprivation
    The result of lack of adequate visual stimulus in early life; little or no light enters the eye & no image is formed e.g., due to ptosis covering pupil or congenital cataract (3%)
2. Strabismic
    Result of manifest strabismus onset in childhood; occurs mainly in SOT as most XOT remain intermittent in childhood (35%)
3. Anisometropic
    Result of significant difference in refractive errors of the 2 eyes; 1 eye receives a clearer image for all distances (22%)
    Developmental issues with weaker eye
4. Ametropic
    Result of high degree of uncorrected bilateral refractive error = blurred image present at all distances (high hypermetropia >6D which cannot be compensated by accommodation)
5. Meridional
    Unilateral or bilateral – meridional amblyopia
    Moderate or high degree of astigmatism in one or both eyes
    Risk increased if oblique astigmatism

Question 15

Other risk factors for amblyopia

Answer 15

 Abnormal OMB
 Positive family history
 Low birth weight (<2.5kg) / forceps delivery
 Poor development – not meeting milestones
 Foetal alcohol syndrome

Question 16

Visual development periods..

Answer 16

 Critical period for binocular vision 0-5 years; most plastic
 Sensitive period 5-8 years; still vulnerable to damage and may respond to treatment
 By age 6; plane of focus should lie on the retina
o 6/6 & 40-60” stereo

Question 17

Amblyopia therapy includes:

Answer 17

1. Refractive adaptation

 Full cycloplegic refractive correction worn – 18 weeks (PEDIG)
 2–3-month review after prescribing
 Expected VA improvement of 2-3 lines
 Allows for improvement of VA before starting occlusion/occlusion may be avoided in some cases

2. Occlusion of better eye
    May take form of adhesive plasters /patches worn on skin/frame
    Opaque CL
    Frosted glass
    Generally recommended 6 hours daily
    Higher-dose rate may be required in older patients/more dense amblyopia
3. Atropine penalisation
    Similar efficacy to 6-8 hours patching in patients with moderate amblyopia
    Not as useful in dense amblyopia
    Better eye is blurred by prevent accommodation
    1 drop 1% instilled on weekends

Question 18

Follow up

Answer 18

 Patient should be reviewed regularly, minimum every 3 months
 Age in years = review in weeks (4 years old = 4-week reviews)
 VA stable 2 consecutive visits = consider tapering off/stopping occlusion
 Amblyopia persist & px compliant = refraction & fundus check, increase occlusion to FT or change therapy
 Amblyopia persist & px non-complaint = instruction leaflet, reward scheme, video game therapy, change regime