8.1.2 Understands management of px with anomay of BV Flashcards
What is amblyopia?
a lack of visual stimuli to one or both eyes during the critical period resulting
in structural and functional damage in the LGN and V1 in the form of atrophy of
connections, lack of cross-linking between connections and a loss of laterality of
connections. This leaves the child with permanently reduced VA (6/12 or less).
Describe strabismic amblyopia?
- Constant or near constant childhood squint
- FT glasses wear
- Occlusion or atropine
- Ask parent to watch for swapping fixation
- Risk of intractable diplopia in older children
- Prognosis: depends on age of onset (constant/intermittent), initial VA, age tx started, associated pathology, eccentric fixation
Describe anisometropic amblyopia?
- at least 1D difference - hyperope, myope or meridional
- FT glasses wear, no need for occlusion if VA consistently improving
- Less risk of occlusion to older children than strabismic amblyope
- supplemented wiht enar worrk
- marked anisometropia may want to consider CL
- Prognosis: - high myopia not good, once optimum VA obtained continue with FT wear, amblyopia less likely to occur in presence of BSV, high anisekonia may occur
Describe meridional amblyopia?
- mod/high degree of uncorrected astigmatism
- unilateral or bilateral
- more risk if oblique astig
Describe ametropic amblyopia?
- usually bilateral
- high degree of bilateral refractive error (likely hyperopia) oges uncorrected during critical period
- blurred vision in BEs at all distances
- > 6D hypermetropia (can’t accom through)
Describe organic amblyopia?
- Reversible:
Toxic Optic Neuropathy: painless, progressive, bilateral vision loss, dychromatopsia (CVD)
Nutritional amblyopia: Vit B12 deficiency - children with ASD, may see recovery with improved diet/vitamin intake - other causes: alcohol, tobacco, antimalrials e.g. chloroquine, anticancers e,g Vincristine
- irrevesible: not able to be treated
- Nystagmus: never clear image so annot develop good vision
- Albinism (usually assoc with nystagmus)
Describe stimulus deprivation amblyopia?
- difficult to treat, little or no light entere eye
- haemangiioma, corneal scar, vitreous bleed
- treat primary pathology - cataract, ptosis
- full rx, and constant wear
- total occlusion preferrable - risk of occlsion amblyopia
- if pathology from birth, progression/prognosis is poor - pathology from early infancy much better
- Likelihood of BSV poor with unilateral cataract
Describe surgical management for squints? Post-op diplopia test?
o Medial Recti mainly work at near
o Lateral Recti mainly work at distance
o Recessions weaken muscles
o Resections strengthen muscles
o Botulinum Toxin is a neurotoxin protein
o Paralyzes the muscle within 5 -7 days, Recovery of muscle function up to 3 months
o Functional Cure – Aiming to restore BSV
o Cosmetic Cure – aiming to improve cosmetic appearance
o Post-operative diplopia test – used in patients diagnosed with suppression. Px fixates on target and
correcting prism is added until px reports diplopia. This is done to determine suitability for surgery and risk
of intractable diplopia post-surgery. If px reports diplopia after 1 prism placed in front of eye then they’re
poor candidate. If px complains only after neutralisation or over correction px is a good candidate.
Essentially trying to avoid removing px from suppression area to avoid intractable diplopia.
What is the management of infantile eso, constant eso, near eso, distance eso and convergence excess eso?
infantile eso: bimedial rectus recession
constant eso: patching to get eyes straight as poss then surg. Non-accom so no Rx helps. Surgery after amblyopic tx - purely cosmetic
near eso: bilateral MR recession
distance eso: exclude VI nerve palsy (if eso gets bigger on one side then CN palsy). LR resection
convergence excess eso: correct Rx: fully if +, under if -. Bifocals stop px accom at near (prevents eso), improve -ve fusional vergence using exercises. Surgery: bimedial recessions
Describe the management of constant exo, distance exo, near exo?
constant exo: treat amblyopia. BoTox injections into LR muscle. Surgery: MR resection and LR recession in affected eye
distance exo (intermittent): orthoptic exercises (<15^), prism BI, minus lenses when accom is good, tinted gls - in high light intensity due to dissociation effect. True type: bilateral rectus recession. Simulated type: MR resection and LR recession in one eye.
TRUE vs SIMULATED: carry out CT after 45 mins of occlusion. If deviation controlled at near then TRUE. IF near approximates distance then SIMULATED.
near exo: under correct + Rx, orthoptic exercises: for deviation <20^, emphasise +ve (BO) amplitude, convergence, +ve relative convergence, prism BI, surgery: bilateral MR resection
Describe spec correction as tx for amblyopia?
- Correct any significant refractive errors
- Allow a period of 16 weeks for adaptation and then review VA.
- If VA has not improved, commence occlusion therapy
- Allow VA to plateau
Describe occlusion therapy as tx for amblyopia?
The fixating eye is occluded to encourage the patient to use the amblyopic eye.
o VA 6/9-6/24 à 2 hrs of patching per day
o VA >6/24 à 6 hrs of patching per day
Advantages
* Cheap
* Can be used in severe amblyopes
Disadvantages
* Poor Cosmesis
* Poor compliance from children
Contraindications
* Poorly controlled Phoria
* Older strabismatic amblyope
* Failure to regularly attend
Describe optical penalisation as tx for amblyopia?
Vision is blurred in the better eye to encourage the patient to use the amblyopic eye.
Used in px who can’t tolerate occlusion therapy
Atropine or Spectacle lenses are used
Can be total penalisation or specifically at dist or near
Advantages
* Cosmesis
* Good for children who aren’t compliant with patching
* Good for manifest or latent nystagmus
Disadvantages
* Px may be allergic
* Drops sting
* Constant blurred vision
* Can’t be used in severe amblyopia
* Can’t be used with px with heart defects
When should you review pxs who are being tx for amblyopia?
Review: At least every 3 months, younger px are reviewed more regularly. Once VA has
stablised over 2 consecutive visits, consider stopping
