Pediatric Opthalmology Flashcards
Functional reduction in the visual acuity of an eye, either unilaterally or bilaterally, caused by disuse or misuse during the critical period of visual development
Functional reduction in visual acuity of eye
Amblyopia
What is the most common cause of pediatric visual impairment
Amblyopia
What causes amblyopia?
- Abnormal vision development in infancy/childhood
- Unilateral or bilateral
- Brain receives poor image from eye and thus does not “learn to see well”
- Vision loss because nerve pathways between brain and eye are not properly stimulated
Risk factors for amblyopia
- Prematurity
- First degree relative with amblyopia
- Small size for gestational age
- Neurodevelopmental delay
Classifications of amblyopia
- Strabismus
- Refractive
- Deprivational
Misalignment of visual axes of the two eyes
Strabismus
One or both eyes having refractive error causing imbalance between eyes
Refractive
Obstruction by a cataract or complete ptosis prevents formation of a formed retina
Deprivational
What is strabismic amblyopia?
- One eye may turn in, out, up, or down
- Described by direction of deviation
- Brain ignores or turns off eye that is not straight and vision drops in that eye
- Foveas of the two eyes are presented with two different and unfusable images
- Visual cortex suppresses image from one eye in order to avoid having diplopia; long term suppression of one eye results in strabismic amblyopia
What is refractive amblyopia?
- Most commonly due to asymmetric refractive error
- Foveas of two eyes presented with different image clarity d/t unequal uncorrected refractive errors; image in one eye not focused on the fovea at same time as the other
- Brain does not learn how to see wellfrom the eye that has a great need for glasses
- Most commonly in hyperopic (farsighted)
When is refractive amblyopia most often detected?
- Older age than strabismic amblyopia because children with refractive amblyopia lack obvious external abnormalities and visual functioning appears normal because see well with fellow eye
- Often diagnosed at first vision screening when old enough to identify letters or figures (ages 4 or 5)
What is deprivational amblyopia?
- Least common form but most severe
- Results from vision deprivation, typically as result of interruption of visual axis or severe distortion of foveal image
- Congenital cataracts, ptosis, congenital corneal opacities, vitreous hemorrhage, and severe refractive errors may cause
- Results in permanent visual impairment if not treated urgently
Amblyopia evaluation in pre-verbal child
- Fixation reflex
- Differential occlusion objection test
What is fixation reflex? How will it present in amblyopic eye?
- Testing involving moving visual target to and from child’s visual space, each eye tested by occluding fellow eye
- Amblyopia will rarely maintain fixation with amblyopic eye when both eyes uncovered
Differential occlusion objection test
- Monitor child’s response to alternate occlusion of eyes
- Children with equal vision respond equally, or not at all
- Children with moderate-to-severe visual impairment in one eye become more irritable when other eye with better vision occluded