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

Question 1

amblyopia

Answer 1

 A developmental condition that is characterised by reduced vision in 1 eye
 Cortical changes result in defective VA (6/9 or worse) in one, or both eyes, which persists after refractive error correction & removal of pathology (2-line difference for unilateral amblyopia i.e., majority)
 Light deprivation, form deprivation, abnormal binocular interactions

Question 2

Cause of amblyopia

Answer 2

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 3

Other risk factors for amblyopia

Answer 3

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

Question 4

Visual development

Answer 4

 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 5

Amblyopia therapy

Answer 5

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 6

Follow up

Answer 6

 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

Question 7

Management of amblyopia

Answer 7

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?

Question 8

Indications of type & duration of therapy

Answer 8

• 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 9

When is occlusion stopped?

Answer 9

WHEN EQUAL VA!! - CONSIDER CROWDING

When alternation occurs (implies equal VA)

When no further improvement

When risk of decompensation or diplopia

Question 10

Types of BV conditions:

Answer 10

• 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 11

Different Types of Management

Answer 11

• 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 12

Orthoptic excersises Convergence Insufficiency:

Answer 12

• Pen to Nose - With convergence insufficiency, the main problem with the pen to nose push up exercise arises when the patient does not easily notice physiological diplopia once their convergence breaks. Advise patient to have two pens, one held stationary further from the pen being moved closer, this way, they can be trained to appreciate physiological diplopia of the more distant object as an anti-supression check. Try this yourself & you will see that the pen in the background should stay double. If it goes single, then convergence has broken & you need to bring the closer pen further back until physiological diplopia noticed again.
  
  • Remember that positive convergent fusional reserves are being trained
  • Advice doing excersises with spex on
• Dot card —> Px has a line of dots put against their nose & they look at the dot furthest away from them. It should look like a V pattern due to physiological diplopia. They then converge on dot closer than the previous until single. The other lines should appear double. If you cannot make it single then that is where you stop. This test is repeated like with prev excersises
• Stereograms —> 2 cats on the gram. Put pen in between the cats. Bring pen towards you until the cats fuse to become a middle image. The aim is to bring pen as close as possible, keeping 3 cats. If unable to do so, then restart the test
• Excersises done 3-4x/day for 5 mins each for next 2 months or so. Can reduce if sxs improve or until no further improvements can be made.
  
  • Adv taking breaking afterwards by staring into the distance for a few minutes

Question 13

Esophorias

Answer 13

• 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 14

Amblyopia

Answer 14

• 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 15

Extra Topic: Microtropia

Answer 15

• 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