8.1.6 Manages children presenting with an anomaly of binocular vision.

Question 1

Esotropia

Intermittent

Answer 1

• Fully accommodative —> Hyperopic between +3D to +6D; Onset 1.5 - 2.5 years; Child has to overcome higher plus Rx hence converges more & if does it too much & too frequently then fusional reserves overcome & breaks down to esotropia.
  
  • Management is fully correct Rx & squint will go, treat any amblyopia if present, surgery is useless as when the px becomes straight without spex, then puts their plus spex on, it’s likely to induce an exotropia so not worth it
• Convergence Excess —> Onset 2-5 years; High AC/A so loads of convergence for little accommodation, squint at near but straight at distance & goes with +3D Add normally.
  
  • Management requires bifocals so they use the extra plus for reading, this is useful when waiting for their surgery as bifocals suck for children!
• Distance & Near Esotropia —> BSV should develop as binocular in at least one direction for each.
  
  • Correct Rx. Surgery only for cosmesis.
  • DD distance EsoT from 6th palsy (very important)
• Cyclic Esotropia - BSV on straight days & constant esotropia with suppression on alternate days. Unlikely amblyopic as binocular for large parts of the day.
  
  • Correct Rx. Treat with surgery
• Non specific

Question 2

Esotropia

Constant

Answer 2

• With Accommodative Element —> Onset 1.5-3 years; Esotropia increases at near & will still be there with Rx, just reduced, leading to suppression & amblyopia unless alternating.
  
  • Management is correct Rx, treat any amblyopia, surgery only if with spex on, the deviation is still cosmetically poor, surgery for deviation without spex won’t work as already explained above.
• Without Accommodative Element is Infantile & Nystagmus Block Syndrome. Infantile - Large angle & will alternate with cross fixation so little amblyopia present as suppression alternates but poor prognosis for BSV even if early treatment. Abnormal OKN, IO overaction.
  
  • Correct Rx, amblyopia & use bot toxin as some paed doctors prefer not using general anaesthetic but sedating infant in a different way. They then look at surgery later on.
  • Nystagmus block - Large angle (BEs may appear convergent), miosed pupils, face turn toward fixing eye, nystagmus increasing on lateral gaze. Correct Rx & treat amblyopia but harder with nystagmus latent component, surgery very unpredictable!
• Sensory —> Poor VA in one eye leads to esotropia; Onset 6 months to 7 years when accommodative convergence most active. Vision loss so severe that fusion mechanism affected.
  
  • Management is treat cause of poor VA, any amblyopia even if superimposed on cause of poor VA, correct Rx, surgery results unpredictable with poor VA
• Consecutive —> Intentional part of surgery. If px has exotropia initially, overcorrected to small angle esotropia. Eyes generally diverge with time so deviation will straighten

Question 3

Exotropia

Answer 3

• Early Onset —> constant XT, little experience of being binocular, early onset suppression, primary reason for amblyopia is the squint & not something in the fundus for example.
  
  • Low chance of BSV after surgery so cosmetic. Treat amblyopia if in plastic period
• Decompensated Phoria —> diplopia experienced. If alternating tropia, then implies BSV previously (remember that suppression alternates if tropia alternates so equal VA & BSV). If had from young age, most likely amblyopic! Fresnel prism needs to be used to correct diplopia. Surgery is also available. Refer to lecture -
• Distance & Near —> controlled at one distance so BSV can develop as intermittently controlled.
• Sensory —> eye drifts out as poor eye not being utilised very much! Surgery gives poor results/variable results. Try correcting amblyopia superimposed and treat cause of poor VA.
• Consecutive —> most likely a mistake by the surgeon. Requires more surgery to align eyes.

Question 4

Post Operative Diplopia Test:

Answer 4

• Surgery can move px outside their suppression scotoma causing diplopia awareness. Adults cannot reinitiate suppression! It may become intractable!
• This test simulates a range of potential surgical outcomes and seeing if px becomes aware of diplopia. Done using prisms by orthoptics. You now have a range of outcomes you can leave the px with.

Question 5

Botulinum Toxin:

Answer 5

• Botulinum toxin causes a temporary, partial or complete, paralysis (weakness) of the muscle into which it has been injected. To begin with, you may notice a temporary reversal of your squint, followed by gradual straightening of the eyes as the paralysis wears off.
• The treatment takes effect within 2 to 3 days and will be at its greatest 1 to 2 weeks afterwards. The effect lasts for 2 to 3 months and then gradually wears off.
• May experience temporary diplopia which would stop you from driving until corrected. This is the main side effect
• This injection is good if surgeon worried patient may experience diplopia post operatively or if unsure if they are aiming for a functional result. Injection done before surgery to see what will happen
  
  • They will leave px slightly esotropic so long as there is no post operative diplopia. Eyes naturally diverge with time so straightens.
    
    • Surgeon may do post op diplopia test, then injection, then surgery

Question 6

Amblyopia therapy

Answer 6

 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 7

Follow up

Answer 7

 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