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

Different causes 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

Visual development

Answer 3

 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

• Current wait time in G&GC = 1 year)

Question 4

Amblyopia therapy

Answer 4

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 5

Follow up

Answer 5

 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 6

Types of BV conditions

Answer 6

• 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 7

Chalazion

Answer 7

• Descript - Sterile inflammation of meibomian gland (cyst) causing stagnation of secretion from the gland, leading to a more chronic lesion. Can follow an internal hordeolum
• Cause - May occur spontaneously or follow an acute hordeolum (internal), chronic bleph
• Sxs - painless lid lump, rarely induced astigmatism
• Management - warm compress & massage. Steroid or excision

Question 8

Accommodative Insuffiency

Answer 8

• 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 9

What is the critical period?

Answer 9

Up to age 8

Question 10

What is emmetropisation?

Answer 10

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 11

What cortical mechanism triggers amblyopia to occur?

Answer 11

• 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

Question 12

Types of Amblyopia

Answer 12

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 13

Management of amblyopia

Answer 13

• 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 14

Indications of type & duration of therapy

Answer 14

• 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 15

When is occlusion stopped?

Answer 15

• WHEN EQUAL VA!! - CONSIDER CROWDING
• When alternation occurs (implies equal VA)
• When no further improvement
• When risk of decompensation or diplopia

Question 16

Management depending on Presenting H&S

Answer 16

• 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 17

Principles of Different Types of Management

Answer 17

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 18

Convergence Insufficiency:

Answer 18

• Pen to Nose (Push-up Test)
  • Main issue: Patients with convergence insufficiency may not easily perceive physiological diplopia when convergence breaks.
  • Use two pens:
    • One held stationary in the background.
    • One moved slowly toward the nose.
  • If the background pen appears single → convergence has broken.
  • Pull the closer pen back until background pen appears double again → helps train anti-suppression.
  • Positive fusional convergence reserves are being trained.
  • Exercises should be performed while wearing spectacles.
• Dot Card Exercise
  • A card with a line of dots is placed along the nose.
  • Patient focuses on the furthest dot first — should see a V pattern due to physiological diplopia.
  • Gradually shift focus to closer dots — aim to see the chosen dot singly while others appear double.
  • If unable to make the dot single, stop at that point.
  • Repeat in similar fashion to pen push-up exercise.
• Stereograms Exercise
  • Two images (e.g., cats) shown side by side on a stereogram.
  • Hold a pen between the images and bring it slowly toward you.
  • Goal: fuse the images into a central third image while maintaining three visible images (2 originals + 1 fused).
  • If fusion is lost (only 2 cats seen), restart the test.
• Exercise Frequency
  • Perform 3–4 times per day, 5 minutes each session for about 2 months.
  • Reduce frequency if symptoms improve or no further progress is noted.
  • Recommended to rest eyes by staring into the distance for a few minutes after each session.

Question 19

Esophorias:

Answer 19

• Esophoria Management
  • Treat by stimulating negative fusional vergence (i.e., divergence).
  • Eso-deviations are generally more difficult to treat with exercises compared to exo-deviations.
• Stereograms for Esophoria
  • Hold stereogram at 30 cm with a pen placed behind it.
  • Focus on the pen (causing accommodation to remain in front while vergence shifts back).
  • Maintain 3 cats image on the stereogram while moving the pen further back.
  • May require using a more distant object to continue practicing successfully.
• Other Techniques
  • Bar reading and base-in (BI) prism exercises are useful to train divergence.
• General Advice
  • Always rest the eyes after completing any vergence exercises to avoid fatigue.

Question 20

Extra Topic: Microtropia

Answer 20

• Microtropia Overview
  • Small angle strabismus (<10 prism dioptres)
  • Often associated with anisometropia (≥1.5D)
  • Amblyopia in the strabismic eye (typically 1–2 lines worse)
  • Typically no treatment needed unless the deviation worsens
• Fixation and Binocular Vision
  • Eccentric fixation: Patient uses a non-foveal area to fixate
  • Results in a suppression scotoma around the fovea
  • Eye turn aligns with the eccentric fixation point → no movement on cover test
• Retinal Correspondence
  • Can have Normal Retinal Correspondence (NRC) or
  • Abnormal Retinal Correspondence (ARC): Fovea of fixating eye shares visual direction with a non-foveal point of deviating eye
• 4 Base Out Prism Test
  • Used to detect suppression
  • If RE is suppressing:
    • Placing prism in front of RE → no movement in either eye
    • Placing prism in front of LE → LE moves in, RE moves out but does not re-fixate
• Stereopsis
  • Reduced: 100 arc seconds or worse
• Types of Microtropia
  • With identity: No cover test movement + eccentric fixation
  • Without identity: Cover test movement + no eccentric fixation
• Management
  • Usually fully adapted, no active treatment
  • Prescribe refraction and monitor
  • Treat only if deviation breaks down into a larger squint