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Introduction to Eye Disease - Year 2 > Optic Nerve Anomalies - Congenital > Flashcards

Optic Nerve Anomalies - Congenital Flashcards

1
Q

What does a normal optic nerve look like?

A

Normally, the optic nerve is around 1.5mm in diameter horizontally, it is either oval or round in shape and has defined margins with a pink neural retinal rim. It is very slightly raised with the middle area known as the cup dipping in slightly. Depending on the cup size and depth, the amount of centralized depression varies.

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2
Q

Describe the anatomy of the optic nerve extra-cranially (outside of the cranium)

A

•It Consists of axons of the retinal ganglion cells (RGCs) which in turn receive impulses from the photoreceptors (rods and cones)

-It passes through the optic canal

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3
Q

Describe the anatomy of the optic nerve intra-cranially (inside the cranium)

A
  • Optic nerve from each eye unite to form optic chiasm
  • At the chiasm – fibres from the nasal half of each retina cross over to the contralateral optic tract, while fibres from the temporal halves remain ipsilateral
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4
Q

Describe the optic pathway

A
  • Each optic tract travels to its corresponding cerebral hemisphere to reach the lateral geniculate nucleus (LBN)
  • Axons then travel from the LGN to a pathway known as the optic radiation
  • Upper optic radiation – carries fibres from the superior retinal quadrants (corresponding to the inferior visual fields quadrants). It travels through the parietal lobe to the visual cortex
  • Lower optic radiation – carries fibres for the inferior retinal quadrants (corresponding to the superior visual field quadrates). It travels through the temporal lobe, via a pathway known as Meyer’s loop to reach the visual cortex
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5
Q

Where does the optic chiasm sit?

A

It sits above the pituitary gland

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6
Q

What is the blood supply for the optic radiation?

A

Blood supply is from the internal carotid, middle and posterior cerebral arteries.

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7
Q

What are symptoms associated with optic nerve abnormalities?

A
  • Loss of vision (if papillomacular fibres are affected)
  • Positive scotoma (loss of visual field)
  • Desaturation of colours - +/- reduced colour vision
  • Decreased brightness perception – things may appear dimmer
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8
Q

What are possible clinical signs associated with optic nerve abnormalities?

A
  • RAPD – impaired retarded conduction of the ON
  • Reduced contrast sensitivity
  • Visual field defects e.g. central, centralcoecal, arcuate or altitudinal
  • Impaired colour vision
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9
Q

What clinical features may be present with an abnormal optic nerve?

A
  • Swelling – total or sectoral
  • Diffuse dropout of RNFL (retinal nerve fibre layer)
  • Optic atrophy
  • Disc drusen
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10
Q

How can we classify optic nerve anomalies?

A

By whether they are acquired or congenital

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11
Q

What is hypoplasia?

A

Underdevelopment of a tissue or organ

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12
Q

What is optic nerve hypoplasia and what does this mean for transmisson of signals?

A
  • Means underdevelopment of a tissue or organ – There are fewer nerve fibres than a normal eye due to underdevelopment of the optic nerve.
  • In this instance, the optic nerve does not transmit impulses from the nerve-rich membranes lining the retina to the brain
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13
Q

True or false- px with optic nerve hypoplasia can present with VA unaffected

A

True - •Can present as a normal (VA unaffected) or a very abnormal eye (NPL - no perception of light)

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14
Q

What can be seen in the fundus image below?

A

Severe optic Nerve hypoplasia

No foveal reflex

Very small optic disc

Thinned retinal fibre layer

The distance between macula and temporal edge of the disc is 0.4.

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15
Q

How does a px with moderate optic nerve hypoplasia present?

A

Vessels also tend to be very tortuous

Distance from fovea to optic nerve tends to be equal to or greater than 3DD - this is a sign of hypoplasia

As well as points mentioned in the picture

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16
Q

How does hypoplasia of the optic nerve head present?

A
  • As Non-progressive
  • Non-inherited – may be associated with parental alcohol or drug abuse
  • May be associated with other systemic manifestations e.g. pituitary and endocrine disorders
  • VF defects
  • RAPD
  • Colour vision defect
  • Foveal hyperplasia
  • Microophthalmus and aniridia
  • IF bilateral, strabismus and nystagmus
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17
Q

What is the managment of hypoplasia of the optic nerve head?

A
  • Refer if not already been investigated – may have systemic associations
  • Correct refractive errors to avoid amblyopia

[Including associated astigmatism]

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18
Q

What is a coloboma?

A

•Incomplete closure of the embryonic tissue

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19
Q

How does a colobomatous disc appear?

A
  • Disc is enlarged – see a white bowl-shaped excavation inferiorly – vessels appear normal.
  • May extend inferiorly to involve retina and choroid
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20
Q

What is the aetiology of a coloboma?

A

•Sporadic and autosomal dominant inheritance

21
Q

What is being shown in the fundus image below?

A

Retinochoroidal coloboma involving the optic disc

22
Q

What is the black arrow in this fundus photo showing?

A

ON coloboma

[Colour fundus photograph of the left eye showing the colobomatous disc (black arrow), retino-choroidal coloboma (red arrow), foveal retinal pigment epithelial atrophy and macular elevation (blue arrow).]

23
Q

What are the symptoms of Optic nerve coloboma?

A
  • VA may be affected depending on severity
  • Can be unilateral or bilateral
  • May be associated with neurological defects
24
Q

What is optic nerve coloboma often mistaken for?

A

Glaucoma

25
Q

What is the managment of optic nerve coloboma?

A
  • Congenital abnormality – monitor its visual field defect – there always a superior VF defect which can be confused with normal tension glaucoma
  • Ensure no associated glaucomatous changes
  • Inform GP and patient – refer routinely if diagnosis is uncertain
26
Q

What are possible complications of optic nerve coloboma?

A
  • Px at Risk of serous retinal macula detachment – urgent referral
  • Progressive visual field loss associated with neural retinal thinning – routine referral
  • Rhegmatogenous retinal detachment – urgent referral
  • Systemic associations – heart defects, choanal atresia, retarded growth
27
Q

What is an optic disc pit?

A
  • A Crater in the optic disc which can appear:
  • Round/oval
  • Grey white/yellow
  • It represents herniation (abnormal protrusion of tissue through opening) of rudimentary neuroectoderm tissue
28
Q

Where is the optic disc pit typically located?

A

•Commonly temporal (but could be anywhere)

29
Q

How does an eye with an optic disc pit appear?

A

•ON nerve looks larger than normal with a temporal (sometimes central) or oval pit.

Pit can be yellow or grey/white, crcular or oval

30
Q

What symptoms is an optic disc pit associated with?

A

•VA not usually affected but patients will usually have a VF defect which might be confused with glaucoma

31
Q

How does an optic disc pit caused visual field defect present?

A

•Variable VF defects – usually paracentral arcuate connected to the blind spot

32
Q

What are possible complications/risks of an optic disc pit?

A
  • Temporally located pits are associated with serous macular detachment – subretinal fluid is thought to be from the vitreous
  • Around 45% of eyes with optic pits develop serous retinal detachments (fluid collects under the retina – no tear)
33
Q

What is the managment for an optic disc pit?

A
  • If previously investigated do not refer – simply educate patient on risks/complications
  • If not previously investigated – refer routinely and educate patients as to the risk of serous or rhegmatogenous retinal detachments e.g. flashes/floaters/blurred vision/curtain-like shadow
  • Refer urgently if presenting with recently reduced visual acuity
34
Q

What is congenital tilted disc syndrome and what is it typically associated with?

A
  • A Non-hereditary condition where the
  • Supertemporal disc is elevated and the inferonasal disc is displaced posteriorly.
  • ON enters globe at an oblique angle
  • It is Associated with thinning of inferior RPE and choroid and myopic astigmatism.
35
Q

Is congenital tilted disc syndrome bilateral or unilateral?

A

•Usually bilateral but can be unilateral

36
Q

Does congential tilted disc syndrome affect vision?

A

•Doesn’t typically affect vision

37
Q

Are there any visual field defects associated with congenital tilted disc syndrome?

A

•May have a superotemporal visual field defect that doesn’t obey the mid-line

38
Q

True or False- Drusen around the optic nerve head tend to be asymptomatic

A

True

39
Q

What are drusen?

A

Hyaline like calcific material deposits

40
Q

What is the prevalence of drusen?

A

•Present in 0.3-1 % of the population – 70% cases are bilateral

41
Q

What is drusen around the optic nerve head often mistaken for?

A

•Can be mistaken for papilloedema as disc margins are ill-defined – this is called ‘pseudo-papilloedema’

42
Q

How may we diffrentiate between drusen around the optic nerve head border and papilloedema?

A
  • Check for swelling and elevation – vessel engorgement is usually first sign of papilloedema
  • Refer urgently if unsure – difficult to tell without imaging/OCT

[In cases of drusen the eye is usually hypermetropic, there is an absence of exudates and haemorrhages and a normal VF with a small sized physiological blind spot]

43
Q

What is a glial remnant and how may it appear?

A
  • It is the Posterior portion of the hyaloid artery. Which may still be present, extending into the vitreous from the disc surrounded by glial tissue.
  • It can cover the disc giving rise to a grey filmy appearance
44
Q

What can be seen in the following fundus photo?

A

Myelinated nerve fibres

45
Q

Are myelinated nerve fibres progressive?

A

No - they are non-progressive

46
Q

Are myelinated nerve fibres symptomatic?

A

No they are asymptomatic

47
Q

In which Pxs are myelinated nerve fibres more common?

A

Px with down syndrome

Px with neurofibromatosis

48
Q

What are myelinated nerve fibres often mistaken for and how can you tell the difference?

A
  • They are often mistaken for cotton wool spots
  • Myelinated fibres are whiter. Larger and denser and almost always adjacent to the disc
  • Their Course follows an arcuate pattern – pattern of the RNFL (retinal nerve fibre layer) axonal distribution

Introduction to Eye Disease - Year 2 (40 decks)

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