Amblyopia Flashcards
(23 cards)
What is amblyopia?
Amblyopia refers to a unilateral or bilateral reduction in visual acuity, caused by abnormal vision development in childhood or infancy.
- Common vision problem in children and is the leading cause of decreased vision among children
- Most vision loss is preventable or reversible with the right kind of intervention.
Clinical definition of amblyopia?
- Unilateral amblyopia: difference of
2 or more lines on the Snellen chart
6/60——
6/36*
6/24*
6/18——- - Bilateral amblyopia: visual acuity of 6/12 or worse
What is epidemiology of amblyopia?
- Amblyopia is the most common cause of reduced vision in a single eye among children and young adults.
- It affects approximately 2% to 4% of the pediatric population.
- No significant differences in prevalence based on race or gender
Pathophysiology of amblyopia?
- Most crucial stage for visual development is from birth to 3 months, some development until 7-8 years
- Visual pathways are actively developing during this period
- One or both eyes may send poor or conflicting visual signals to the brain
- Brain suppresses input from one or both eyes to avoid confusion
- Suppression leads to underuse of the affected eye
- Insufficient visual stimulation results in incomplete development of visual cortex
Causes of amblyopia?
- Visual deprivation
e.g ptosis, cataracts, corneal opacities - Strabismus
- Significant refractive errors
Risk factors for amblyopia?
- Premature birth (before 30 weeks gestation)
- First-degree relatives with amblyopia
- Developmental delays
- Childhood glaucoma
- Early-onset cataracts
Classification of amblyopia?
- Strabismic amblyopia
- Refractive amblyopia
- Anisometropic amblyopia
- Isoametropic amblyopia
- Meridional amblyopia - Visual deprivation amblyopia
- Reverse(occlusion) amblyopia
- Organic amblyopia
- Idiopathic amblyopia
Strabismic amblyopia?
- Condition develops when eyes fail to align correctly
- In children the brain avoids diplopia by suppressing input from one eye
- Suppression leads to poor visual development in affected eye
- Retinas receive stimulation in non-matching areas, disrupting binocular vision
- Misalignment prevents proper image fusion from eyes
- Suppressed eye becomes amblyopic due to lack of consistent visual input
Refractive anisometropic amblyopia?
- One eye is affected due to unequal refractive errors
- Brain favors clearer image
- Weaker eyes becomes amblyopic
Refractive isoametropic amblyopia?
- Decreased visual acuity in both eyes caused by equal and significant refractive errors.
- Isoametropic amblyopia occurs when both eyes are amblyopic from a significant yet similar refractive error.
Refractive meridonal amblyopia?
A type of vision loss caused by uncorrected astigmatism, leading to poor visual development
Visual deprivation amblyopia?
- Occurs when a visual pathway is blocked by a pathology, resulting in blurred or degraded images reaching the retina
- Pathologies causing blockage of visual pathway: early-onset or congenital cataracts, corneal opacity, intraocular inflammation of either noninfectious or infectious origin, vitreous hemorrhage, retina damage, optic nerve pathologies, or ptosis
Reverse amblyopia?
Results from prolonged visual deprivation of healthy eye, often caused by therapeutic patching
Organic amblyopia?
Absence of obvious easily visible abnormalities in an eye that shows subtle retinal damage not visible through standard ophthalmoscopy.
Signs of amblopia?
- tilting head
- squinting
- closing one eye
- strabismus - misalignment of the eyes that may be associated with amblyopia
History in amblyopia?
- Ask parents about head tilting, squinting, drifting/wandering eye
- Birth history (prematurity)
- Family history of amblyopia and other ocular conditions
Physical exam for amblyopia?
- External examination: ptosis, strabismus, hemangioma
- Visual acuity
- Fundoscopy
- Relative afferent pupillary defect (Marcus Gunn pupil)
Investigations for amblyopia?
Diagnosis of amblyopia is clinical, however investigations can help in excluding other pathologies
1. Optical Coherence Tomography (OCT)
2. Magnetic Resonance Imaging (MRI)
Treatment goals for amblyopia?
- Improve Visual Acuity: Enhance the vision in the weaker eye to match the stronger eye.
- Correct Underlying Causes: Address any refractive errors, strabismus, or other contributing conditions.
- Eliminate Obstructions to Visual Input: Address conditions such as cataracts or ptosis that block light from entering the eye, enabling proper visual development.
- Promote binocular vision: encourage binocular vision to enhance depth perception and visual function.
Management of amblyopia?
- Patching therapy: covering stronger eye with a patch to force the weaker eye to develop its visual pathway
- Corrective glasses or contact lenses: Prescribing glasses or contact lenses to correct refractive errors
- Atropine therapy: Using atropine eye drops to blur vision in the stronger eye, encouraging the weaker eye to work harder
- Surgery: strabismus and cataracts
Patching time?
Moderate: 2 hours per day of patching
Severe: 6 hours per day of patching
Prognosis of amblyopia?
- Best outcome when treatment is started before age 7 or 8
- If treatment is delayed, particularly after the critical period, full recovery of vision may not be possible, and some degree of visual impairment may remain.
Complications of amblyopia?
- Irreversible Vision Loss: If left untreated, the affected eye may have lifelong poor vision
- Social Stigma: Wearing a patch, especially to school, may lead to social stigma in some cases.
- Reverse amblyopia from patching therapy on healthy eye
