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Abnormal visual development Flashcards

1
Q

Mechanism of development, significance 2 and treatment of myelinated nerve fibres

A
  • <1% of ppn has it
  • Ogliodendrocytes produce myelin in the opp direction from optic tract towards globe hence is most often seen at ONH
  • Often benign but can be associated with strabismus, myopia and amblyopia
  • Treatment not required
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2
Q

Mechanism of development 5, significance 2, treatment 4 of congenital cataract

A
  • Occurs after 33 days gestation
  • Idiopathic
  • Metabolic disorders
  • Infection: rubella, toxoplosmosis
  • Gene defect: crystallin encoding genes - altered characteristics make it insoluble, lens specific connexins - important at maintaining gap junctions in avascular lens
  • Leading cause of reversible congenital blindness in children: 1-15/10,000 live births
  • Possibility of FD amblyopia due to the clouding of the lens
  • Treat with cls, surgery, patching (1hr/day for 6 yrs but disapproved as it was too distressing or amblyopia was too dense to be reversed by patching)
  • Majority of children will not achieve greater than a VA of 0.6logMAR in the affected eye
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3
Q

What 2, prevalence 1 and significance 3 of persistent hyaloid artery

A
  • Remnant of hyaloid artery that should degenerate by 7th month
  • Viewed via Ophthalmoscopy
  • 95% of premature infants have it
  • Benign but can cause VF defects or seen as floaters as vitreous liquefies where it then casts a shadow
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4
Q

What 4, genes 3, significance 4, treatment 2 of coloboma

A
  • Due to the incomplete closure of choroidal fissure that corresponds to the ocular structure that did not develop properly eg ON, retina, eyelid
  • Should close by day 37
  • Usually unilateral
  • 1 in 10,000
  • Genes: GDF3, VSX, SHH
  • Associated with microphthalmia
  • Can cause a VF defect if retina/ON coloboma
  • Anterior colobomas - increase glare and light sensitivity
  • Ask px to look up as it is usually inferior (where choroidal fissure used to be)
  • Treat with opaque cls for anterior (risk of hypercapnia) and no cure for VF defect
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5
Q

What 3, signs 2, symptoms 4, treatment 2 of congenital glaucoma

A
  • Abnormality of AH drainage
  • 1 in 10,000 live births
  • Theorised to be due to an atrophy of the visual pathway that has retrograded onto the VF
  • Optic atrophy in severe cases, buphthalmos or macrophthalmos
  • Hazy cornea
  • Tears and closes eyes frequently
  • Photophobia - possibly seen as dysfunction of corneal endo
  • Bilateral surgery to increase AH drainage or remove ciliary processes
  • Eye drops
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6
Q

What, cause, timing and treatment 3 of macrophthalmos

A
  • Abnormally large eyes
  • Most of the eye size grows within the first year, 70% of the globe’s volume by 4yo, 90% by 70yo. Growth of eye ends at 14yo, growth of orbit ends at 11yo for F and 14yo for M
  • Surgery preserves vestigial tissue (development of one leads to development of another)
  • Important to commence early in life
  • Expanding implants that progressively increase in size are given to encourage growth
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7
Q

What, prevalence, cause 3 of microphthalmos

A
  • Abnormally small eye
  • 1 in 10,000
  • Genes or chromosomal defect
  • Environmental factors: rubella infection, teratogen exposure, radiation
  • Can be formed by itself or in part with a syndrome eg coloboma
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8
Q

What, prevalence, timing and treatment of ankyleblepharon

A
  • Eyelids fail to separate
  • Very rare
  • Should separate by week 20
  • Blepharoplasty
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9
Q

What, cause, treatment of blepharonphimosis

A
  • Horizontal aperture is smaller than normal due to incomplete separation
  • FOXL2 gene mutation
  • Blepharoplasty
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10
Q

What, prevalence, cause 2, significance 2 of anophthalmos

A
  • Complete absence of eye
  • Very rare
  • Genetic or chromosome mutation
  • Infection eg rubella or toxoplosmosis
  • Blind
  • May be related to carnio-facial abnormalities
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11
Q

What, prevalence, significance 2 of cilio-retinal artery

A
  • Extra choroidal vessel that has emerged through ON
  • Very rare
  • Benign
  • Beneficial as an extra source of blood supply
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12
Q

What, significance 2 of physiological swelling of ONH

A
  • Common in hyperopia due to small eye
  • VF defect confirms that it is not a normal variation
  • The same number of ganglion cells and axons will be squeezed through ON
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13
Q

What and significance of physiological cupping

A
  • Cup is abnormally large thus C:D ratio is high

- Myopic elongation will stretch it out to make it seem more spread out

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14
Q

Define teratology

A

Study of abnormal development of embryos and the causes of congenital malformations or birth defects

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15
Q

What is a miscarriage?

A

Miscarriage is when the body stops developing the foetus due to too many abnormal chromosomes. If teratogen is active within the first 2 weeks of gestation, then death of embryo will occur

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16
Q

Significance of teratogen activity 3

A
  • If active from day 15 to 8th week gestation –> abnormal structure and function
  • Embryo is the most susceptible to congenital abnormalities as it undergoes rapid differentiation
  • Critical period for brain development is 3-16wks
17
Q

What did Till 2005 do 2 and find 4 about prenatal exposure to toxic substances?

A
  • 21 exposed mum infants (from occupational radiation) and 27 non-exposed infants
  • CS and grating acuity with sweep VEP
  • Chromatic and achromatic (luminance) systems with transient VEP
  • Log CS low in both groups
  • B/Y system no difference
  • R/G system VEP more abnormal in exposed group
  • VA poorer in high exposure group
  • Mothers should work elsewhere or do another job
18
Q

Significance of foetal mercury neurotoxicity and symptoms 4

A
  • Mercury bioaccumulates in the aquatic food chain
  • Highest: Mackerel king, sword fish, shark
  • Lowest: tuna, salmon, scallop, shrimp
  • Symptoms are dose-dependent
  • Ataxia: uncoordinated movement
  • Auditory problems
  • Abnormalities with VF and CV as mercury tends to attack PR outer segments
  • Low IQ and performance in tests - memory, attention
19
Q

Describe congenital rubella syndrome as an infectious disease

A
  • Rubella virus can be transferred to foetus via placenta
  • Mother most susceptible to infections during first 10 weeks and final month of pregnancy
  • Virus can cause still birth, abortion and severe foetal malformations
  • Earlier onset = greater malformations
  • Chorioretinitis (salt and pepper fundus)
  • Cataract
  • Cardiac malformations
20
Q

Describe congenital Zika syndrome as an infectious disease

A
  • If pregnant mother has Zika virus, it may lead to microencephaly in their unborn child
  • 100% will have visual impairment
  • 40% will show ocular abnormalities (nystagmus, strabismus)
  • 60% will show cortical visual impairment
  • Small head and intellectual disability
21
Q

What, prevalence, phenotypic characteristics 5, possible mechanisms 7 for ocular abnormalities of down syndrome

A
  • DS have an extra chromosome, 47 instead of 46
  • 700-900 babies with a chromosomal disorder are born worldwide
  • Heart defects in 50%
  • Retardation of growth and development
  • Flattened face, upward eye slant
  • Premature aging: early onset of Alzheimers disease, life expectancy 60yr
  • Ocular abnormalities: RE (due to incomplete emmetropisation, commonly oblique astigmatism), strabismus (commonly esotropia) –> amblyopia may occur if not corrected early on
  • Visual cortex and cerebellum abnormalities
  • 14-24WG, visual cortex similar
  • 40WG, normal controls have more ordered cells
    1. abnormal layers in visual cortex
    2. decrease dendritic spines and connections
    3. decrease brain SA
    4. increase gyrus thickness
22
Q

Inheritance, prevalence, mechanism, significance of fragile X syndrome

A
  • Recently described X-linked abnormality
  • 1 in 4,000 males
  • Defect of the FMR1 gene –> not making the protein fragile X which is important for NS –> intellectual disability and physical abnormalities
  • Poorly understood visual abnormalities: strabismus and RE
23
Q

Prevalence, disability 2, hypothesis about visual abnormalities 4 and the controversial statement about autism onset
- Different spatial vision processing (weak central coherence hypothesis WCC 4, enhanced perceptual functioning model EPFM, orientation identification task)

A
  • 10-15/10,000 people worldwide
  • Restricted behaviours and interests
  • Deficits in social communication and interaction
  1. Deficits in neural pathway that recognises faces and facial expression –> poor social interaction (superior temporal sulcus STS, amygdala, fusiform gyrus) - evident but poorly understood
  2. Incomplete connections between different brain regions eg between sound and vision –> social and language deficits
  3. Have the same flicker sensitivity when matched with age-norms –> intact motion processing pathway
  4. Different spatial vision processing
    a. Weak central coherence hypothesis WCC: dysfunction of large-scale neuro-integrative mechanisms results in decreased global perception of local and detailed processes
    Evidence:
    - less precise temporal processing observed with increasing stimulus complexity
    - speech-deficit seen in multisensory temporal processing –> low level deficits may cascade to higher order domains such as language and communication
    Anatomical evidence
    - brain pruning scans show enlarged grey matter in frontal and temporal (social, emotional, face and object recognition) lobes compared to age-matched norms
    - normal grey matter in parietal and occipital lobes –> 1 in 10 have extraordinary talents

b. Enhanced perceptual functioning model EPFM: over-functioning of lower-level perceptual mechanisms lead to enhanced extraction of elementary visual and auditory information
c. orientation identification task: poorer performance when more extensive neural processing is required
- MRR vaccine for measles

24
Q

What, prevalence 2 of strabismus

A
  • Misalignment of the eyes when they are both open
  • 2-4% of caucasians (exo 3x> eso)
  • 1% of East-asians (exo>eso)
25
Q

What did Aurell 1990 and Macoconachie 2013 find out about strabismus?

A
  • Longitudinal study and found that 18% of 34 infants who had a parent with estropia strabismus, will have intermittent or constant esotropia strabismus by 6 months –> flawed as the types of ppl varied and there was not consideration for environmental factor
  • Found a higher concordance rate with those who had strabismus in monozygotic over dizygotic twins –> genetic predisposition –> still inconclusive
26
Q

4 possible mechanisms for strabismus

A
  • Disease of EOM
  • Misrouted motor nerves to the EOM
  • Defective fusion area
  • Defective location for EOM pulleys
27
Q

What, mechanism, treatment 3 of retinopathy of prematurity

A
  • Abnormal bv growth as retinal vascularisation ends at 22wks instead of 40wks gestation –> angiogenesis or extension of existing bvs coordinated by proliferation and migration of endo cells along VEGF gradient
  • Reduced GFs from placental circulation –> delayed retinal vascular development –> avascular areas at the retina which can become hypoxic once in room air –> stimulates angiogenic factors –> vasoproliferation –> can attach to lens and zonules –> contraction leads to retinal detachment

Treatment

  • Remove angiogenic factor by burning areas around hypoxic retina (hopefully its far in periphery so it doesn’t impact VA)
  • Anti-VEGF therapy: controversial as still young
  • Supplemental oxygen: controversial as still young and complications - only given if there is >50% chance of it happening

Vision (4 decks)

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