DIS - Optic Nerve I - Week 10 Flashcards
What is one way of assessing optic nerve head size with a fundus photo?
You can expect the macula to be 2.5 disc diameters away from the optic nerve head for a normal size
How can the optic nerve head size be assessed using central retinal arteries and veins?
Expect 12 to 14 vein widths across the optic disc
Expect 10 to 20 arteriole widths across the optic disc
How can optic nerve head size be assessed using direct ophthalmoscopy?
Expect the disc to be one medium aperture size horizontally
How can a slit lamp be used to assess optic nerve head size? What correction factor is needed for a 90D lens?
Adjust slit width to the optic nerve head width and rotate, read size directly from the graticule
Correction factor - ~1.3 for 90D
What are four developmental issues that can occur affecting the optic nerve head? List the disease associated if applicable.
Embryonic cleft/fissure doesnt close -coloboma Optic nerve is underdeveloped -optic nerve hypoplasia Hyaloid doesnt disappear Normal myelination doesnt stop before the eye -medullated nerve fibres
What tissue does coloboma often involve? what may it be associated with?
Typically involves tissue along inferior orientation
May be associated with chromosomal defects
List three types of coloboma.
Retina/choroid
Optic nerve
Mix of the above
How does the retina appear with retina/choroidal coloboma and what happens to visual fields here? What is vision like? What is there a risk of?
White sclera visible through ectatic/thin tissue Visual field loss over affected region Vision usually ok if fovea spared Risk of retinal detachment -rhegmatogenous due to thin tissue
What is the optic nerve head size like with isolated optic nerve coloboma and how does this affect the blindspot? What is the blood vessel pattern like?
Larger than usual size
Enlarged blindspot on VF testing
Unusual blood vessel patterns
Up to what distance can peripapillary changes be seen in isolated optic nerve coloboma?
2DD
Is vision often affected in isolated optic nerve coloboma?
Yes, but veries from 6/7.5 to hand movements
Is there a risk of retinal detachment with isolated optic nerve coloboma?
Yes
-non-rhegmatogenous due to subretinal fluid
What is the optic disc like in morning glory syndrome and what are the blood vessels like? Is it easy to distinguish arterioles from venules?
Enlarged, funnel-shaped cavity of the optic disc
Anomalous blood vessels radiating circumferentially
Difficult to distinguish arterioles from venules
What is a glial plug and what is it seen in?
Tuft of glial tissue obscuring central cup in morning glory syndrome
What is the peripapillary region like in morning glory syndrome?
Pigment abnormality
-hyper and hypo pigment clumps
What is vision and prognosis like for morning glory syndrome?
Poor vision and prognosis
What pattern do blood vessels have in morning glory syndrome?
They radiate outwards like flower petals
Do congenital and acquired optic disc pits appear similar?
Yes
Define congenital optic disc pit.
Herniation of dysplasic retina extending posteriorly through a defect in the lamina cribrosa
Are congenital optic disc pits round or oval?
Can be either
Where can congenital optic disc pits most often be found (2)?
Commonly temporal, mostly at margin
What disease can congenital optic disc pits occur with?
Optic disc coloboma
Are optic disc pits progressive or non-progressive? What can happen with associated retinal abnormalities?
Optic disc pits are non-progressive
The associated retinal abnormalities may progress
What proportion of patients with optic nerve pits have retinal detachment and which type? Where does it occur?
2/3rds have non-rhegmatogenous detachment
-could be at the macula or close to it
What may contribute to the risk of retinal detachment in optic nerve pits?
Frequent retinoschisis-like separations
What is a retinoschisis-like separation?
Separation of retinal layers near the macula
Define complicated coloboma (3).
Optic nerve head, retina/choroid ± iris involvement
Complicated coloboma has a risk of which type of retinal detacment?
Both
What may management require if complicated coloboma has iris involvement (2)?
Cosmetic contact lens for artificial pupil
Glare protection
What should be considered if one eye has coloboma (2)?
Treatment of anisometropic amblyopia
Ocular realignment surgery if strabismic
When should coloboma be referred and to who?
Refer to vitreoretinal ophthalmologist for:
- retinal detachment
- progression of schisis-like separation
- any presumed subretinal fluid
- vitreoretinal traction, especially macular
- urgency relative to risk of central visiond loss
List two reasons why a referral to a GP should be considered for coloboma.
MRI for brain abnormalities
Association with chromosomal defects
What is the most common congenital optic nerve anomaly and what is it due to?
Optic nerve hypoplasia
Underdevelopment of optic nerve fibres
Is there a genetic component for optic nerve hypoplasia?
Yes
List 6 possible maternal insults that can cause optic nerve hypoplasia.
Diabetes Alcohol abuse Illicit drug use (LSD) Anticonvulsants (phenytoin) Foetal or maternal infection (hepB/CMV) Smoking
Which of the two are a risk factor for optic nerve hypoplasia:
Birth from a young mother
Birth from an old mother
Young mother
List four signs of optic nerve hypoplasia.
Low number of nerve fibres
Pale and small optic nerve head
Small neuroretinal rim
Thin RNFL
What can optic nerve hypoplasia be confused with? Compare them (2).
Optic atrophy
- hypoplasia is non-progressive
- vasculature often appears very large due to hypoplasic disc
Is optic nerve hypoplasia progressive or non-progressive?
Non-progressive
List the two types of optic disc hypoplasia and what you expect it to look like. Which is associated with a tilted disc?
Total disc hypoplasia -pale/pigmented peripapillary halo Sectoral disc hypoplasia -crescent of pallor -associated with tilted disc
What is a halo or crescent on a fundus photo?
The bare, exposed sclera where the normal-sized disc should have extended
Which type of optic disc hypoplasia is the double ring sign seen in and what is it?
Total disc
-pale/pigmented peripapillary halo
What can be seen in ~10% of children to diabetic mothers with poor control? Particularly what type of children (3)?
Superior segmental optic nerve hypoplasia
-particularly in premature females of low birth weight
Can optic nerve hypoplasia be an isolated finding or does it always have an association?
Can be an isolated finding, but is frequently part of a syndrome
Is optic nerve hypoplasia typically uni- or bilateral?
Bilateral
List four times you would refer optic nerve hypoplasia.
Low vision and occupational therapy services
Infants who may require examination with sedation/general anaesthesia
MRI of intracranial visual pathways
GP for neurodevelopmental and endocrinologic deficiency
What is bergmeisters papilla?
Persistent/remnant hyaloid at the ONH
What is a remnant glia?
cellophane sheet or cotton ball of glial tissue overlying blood vessels near the ONH
What is a mittendorf dot and where is it typically located?
Small opacity on the posterior lens capsule
It is the anterior attachment of the hyaloid artery
What is persistent foetal vasculature syndrome, what is globe formation like, what is it also known as, and is it uni- or bilateral?
Aberant globe formation (smaller, white eye)
Retention of primary vitreous and hyaloid
Often unilateral
-also known as persistnet hyperplasic primary vitreous
What is often seen in the affected eye with persistent foetal vasculature syndrome?
Cataract
How should floaters be considered with a suspected case of persistent foetal vasculature syndrome?
Floaters may be common - note baseline
Does persistent foetal vasculature syndromehave any effect on vision?
Typically no
Which population is persistent/remnant hyaloid most common in?
Premature infants
Does persistent foetal vasculature syndrome require referral for management? What about management for unilateral cases?
Referral for surgery
Amblyopia management for unilateral cases
Where does myelination begin in the visual pathway and where is it supposed to stop?
Starts in the LGN, stopping at the lamina
Describe two types of myelination that enters the eye in terms of attachment and their percentages.
80% continuous with the disc
Rest are detached from the disc
How do myelinated/medullated fibres appear?
Feathery white, visible, distinct fibres
Do myelinated/medullated fibres affect the blindspot?
Possible enlarged blindspot visual field defect
What should you do if you suspect myelinated/medullated fibres? Give two differentials.
Differentiate from other white things
- cotton wool spots appear softer, more diffuse
- vasculitis appears dirtier (i.e. with haemorrhages)
Do myelinated/medullated fibres affect vision? What should be done for management?
Typically no effect
- management can be routine eye exam
- record baseline
Can congenital myelinated nerve fibres ever disappear? Explain.
They can, with multiple sclerosis or optic neuropathy
What do congenital optic disc anomalies have in common (2)?
Non-progressive
Potential for associated retinal abnormalities that progress and therefore need monitoring
What two things does management of congenital optic disc anomalies depend on?
Unilateral or bilateral
Systemic associations
