Oc. Manifestations - Week 4 Flashcards
Prevalence of ocular congenital disorders in Aus?
Rare: less than 1.5% of congenital affect the eye
Male: 0.06%, female: 0.04% total: 0.05%
Describe the 5 types of congenital disorders which affect the eye.
- Phakomatoses:
- nuero-cutaneous syndromes of ectodermal origin
- most common manifestation in children = skin lesions - Chromosomal:
- Chrom. or minor gene sequence anomalies - Infections:
- infectious agents affect foetal development - Drug embryopathy:
- maternal drug use affect foetal development
Other:
- cause not determined
List 3 of the most common Phakomatoses/neuro-cutaneous disorders [not from slides, from own study]
- Tuberous Sclerosis (TF)
- Neurofibromatosis (NF): types 1 and 2
- Sturge-Weber syndrome [important one]
Can Phakomatoses cause tumours?
Yes. Can cause benign congenital tumours (I.e birthmarks)
Can Phakomatoses be sporadic or are they only inherited?
They can be both sporadic or inherited
- but they are mostly inherited
Which types of congenital eye disorders are ALWAYS acquired?
Infections and Drug embryopathy
Define Sturge-Weber syndrome:
A sporadic congenital neuro-cutaneous disorder characterised by a port-wine stain affecting the skin in the distribution of the ophthalmic branch of the trigeminal nerve (CNV)
What 3 parts of the body can be affected by Sturge-Weber’s syndrome?
- Skin and/or
- Eye and/or
- CNS
How can Sturge-Weber affect the skin?
Port wine stain (PWS) - capillary hemangioma, cutaneous naevi
How can sturge-Weber affect the eye?
Choroidal hemangioma, glaucoma
Define hemangioma
A benign tumour of blood vessels, often forming a red birth mark
Briefly describe the process of eye embryology (day 19 to day 36)
Day 19: Neural plate forms neural groove
Day 20: Neural folds grow towards each other to form neural tube
3.5wk/~Day 24: Neural tube closes
Day 27: Optic vesicle outgrowth from each side of forebrain
Day 27: Surface ectoderm pushes into optic vesicles and becomes LENS PLACODE, also optic cup forms
Day 36: Lens placode gets suspended from neural ectoderm into eye
How do optic vesicles form, and when do they form? (embryology). What is this stage of embryogenesis known as?
Day 25: Indentations (optic pits) form in neural tube and then expand to form sac-shaped extensions (optic vesicles)
Known as Formative Stage 1
How does embryology form fissures for the hyaloid artery and vein to pass through?
At day 35 (Formative Stage 3): Closure of optic stalks form a cleft called fetal (choroidal) fissure which the hyaloid artery and vein pass through
Are facial port wine stains always indicative of Sturge-Weber’s syndrome?
No. Commonly, facial PWS is not indicative of Sturge-Weber’s.
However, if you have Sturge-Weber’s, you will have a PWS
What is a port wine stain (PWS)?
It’s a discolouration of the skin caused by vascular anomaly, usually on the face
Which location of Port-wine Stain is associated with increased risk of Glaucoma? Where would this Glaucoma most likely develop?
When PWS is distributed along the upper trigeminal nerve on the face (greatest risk if affecting upper eyelid)
- 1/3rd of these patients develop glaucoma
Glaucoma is most likely to be ipsilateral to the PWS
Define Angioma
An abnormal growth/tumour caused by the dilation or formation of new blood vessels
What causes the port wine stain (PWS) in Sturge-Weber?
is caused by excess capillaries just below the skin’s surface, or from capillary hemangioma (benign tumour of blood vessels)
Where can angioma occur in Sturge-Weber?
- lymphatic (lymphangioma)
- vessel walls (hemangioma)
- tissues surrounding the vessels (telangiectasia, ectasia)
Define Ectasia
dilation or distention of a tubular structure
Describe the histopathology of lid angiomatosis
- many capillaries
- thickened vascular endothelial cells
tumour is usually benign
SW syndrome: What happens if there is a anomalous vascularity at the canal of schlemm?
Lead to congenital glaucoma
List eye-related common pathology for Patau’s syndrome
- coloboma: often assoc. with undifferentiated mesenchyme
- microphthalmos
- glaucoma
- retinal dysplasia
- corneal dysgenesis
Describe optic nerve coloboma
optic nerve coloboma shows incomplete retinal/choroidal closure and condensation of the scleral mesenchyme over the gap - forms a staphyloma like structure
in response, parts of the forming optic nerve may prolapse into space
Inheritance pattern for coloboma?
Autosomal dominant/recessive or X-linked
ocular co-morbidities for coloboma?
- gluacoma
- micropthalmia
- retinal dysplasia
- posterior staphyloma
- heterochromia
- nystagmus
Give an example of infectious embryopathy
Congenital Rubella Infection
When does congenital rubella infection occur?
When the virus crosses the placenta into the embryo - most likely in first trimester
How can rubella cause a congenital cataract?
Rubella virus gets into the lens during development before the capsule has formed and destroys the embryonic cells
How does rubella virus enter the lens?
Through the blood supply, because the lens has no barrier to blood circulation during early development
Why is there no barrier b/w the lens and blood circulation during early development?
Because during development, the lens has a vascular supply
True or False: Fibre cells in rubella cataract don’t regenerate
False. New fibre cells are generated to replace space left by destroyed embryonic lens cells
How long can rubella virus remain in the lens?
up to 3 years
What is the risk of surgery for people with Rubella Virus?
Surgery may release live rubella virus and cause endophthalmitis or cataract later on
Describe the histopathology of Rubella Virus
- patchy atrophy and compensatory RPE hypertrophy during retinal development (outer retina becomes necrotic)
- characterisitic “salt and pepper” fundus - due to variable density of melanocytes in RPE and choroid
Name an example of Drug Embryopathy
Foetal Alcohol Syndrome (FAS)
What causes Foetal Alcohol Syndrome (FAS)?
Excessive maternal alcohol consumption during pregnancy
Ocular effects of FAS?
- narrow palpebral fissure
- ptosis
- STRAB
- microcornea
- cloudy cornea
- optic nerve hypoplasia (sectoral, total) etc.
Nice cats meow, purr or scratch
What colour does the cornea appear as in FAS? Why?
Blue. Due to disrupted corneal collagen fibre bundles, which cause light scatter
What proportion of congenital cataracts in victoria are hereditary?
~25%
In what ways/locations can congenital cataracts manifest?
- anterior
- posterior polar
- sutural
- nuclear
Do all cataracts have a profound effect on vision?
no
Polar cataracts can be either ____ or ___
cortical or subcapsular
Which cataract manifestation is more likely to be assoc. with early lens embrologic disorder?
Nuclear cataract
Which cataract can be inheritied by y-crystallin gene mutations
Nuclear cataract
Which cataract is usually caused by an anomaly in the neighboring tissue?
Polar cataract
Which cataract occurs later in development? Why?
Polar cataract - due to incomplete regression of surrounding tissue
(i.e. hyaloid vasculature regresses at beginning of 4th month)
What is a Mittendorf dot? Which cataract manifestation does it appear in?
Is a posterior polar opacity assoc. with a remnant hyaloid artery. Occurs in polar cataracts
How can abnormal proliferation of a vitreal substance cause polar cataract?
is assoc. with incomplete atrophy of the vasculosum lentis, leaving a hyaloid remnant that can cause a polar cataract
What is the effect of the remnant hyaloid (in relation to polar cataract)?
remnant hyaloid affects posterior cortical metabolism –> lens fibre necrosis –> degeneration of posterior subcapsular cortex
How does atrophy of the optic nerve cells affect the appearance of the optic nerve head/disc in ophthalmoscopy?
Has a more white-ish appearance
- this is due to the atrophy allowing for greater light reflection from the collagen of the lamina cribrosa
How does loss of optic nerve fibres affect the size of the optic nerve?
It shrinks the optic nerve from the meninges leaving an abnormally large sub-arachnoid space
Describe the histopathology of optic nerve atrophy
- loss of ganglion cells reduces the bulk of the Optic nerve head: causing increased sub-arachnoid space
- Increased thickness of pial septa
- astrocytic gliosis
- thinned retinal Nerve Fibre Layer (RNFL)
In what 2 ways may acquired optic nerve atrophy travel from it’s lesion (based on lesion position)?
- Ascending (to CNS; e.g. glaucoma)
2. Descending (from CNS; e.g. hydrocephalus)
What sort of genes are often implicated in inherited optic nerve atrophy?
Genes that affect mitochondrial metabolism in retinal ganglion cell axons
What is the cause of Leber’s Hereditary Optic Neuropathy (LHON)?
mutation of mitochondrial DNA
When does myelination of nerve fibres start (embryology)?
Myelination starts once fibres reach LGN (~23 weeks of gestation)
- reaches lamina cribrosa (1-3 months post-natal)
Where does myelin growth usually stop?
At the lamina
What genetic condition is associated with abnormal extra myelination growth beyond it’s normal stopping point?
Trisomy 21
What mediates myelin growth?
Oligodendrocytes
How does myelination affect the thickness of the RNFL
Makes it thicker
