Fundus: Hereditary Posterior Segment Disease

Question 0

Which is the most common inherited retinal condition, and what are the four ophthalmoscopic features on fundoscopy?

Answer 0

Retinitis pigmentosa.

1. Bone-spicule retinal pigmentation (mid-periphery of retina)
2. Waxy disc pallor
3. Attenuated vessels (ie. retinal arterioles become narrowed).
4. Cystoid macular oedema (along with possible cataract development, these may reduce central vision).

Question 1

Name 7 types of hereditary posterior segment disease.

Answer 1

1. Retinitis pigmentosa
2. Congenital stationary night blindness (CSNB)
3. Cone dystrophy
4. Albinism
5. Stargardt’s disease and fundus flavimaculatus
6. Best’s dystrophy
7. Vitreoretinal dystrophies
8. Choroidal dystrophies

Question 2

Name two retinopathies which are caused by treatable systemic disease (and hence should not be missed).

Answer 2

1. Abetalipoproteinaemia

2. Refsum’s disease

Question 3

What five things does high myopia predispose to?

Answer 3

1. Retinal detachment
2. Chorioretinal atrophy
3. Cataract
4. Glaucoma
5. Macular choroidal neovascularisation

There may be night blindness and peripheral visual field loss. Often there is progressive macular atrophy and #5 above, with severe central visual loss.

Question 4

What are six key diagnostic points in identifying hereditary posterior segment disease?

Answer 4

1. Nature of symptoms
2. Family history (determine mode of inheritence, prognostic)
3. Retinal appearance
4. Associated systemic features
5. Electrophysiological tests (ERG, EOG).
6. Fundus fluorescein angiography

Question 5

General management of hereditary posterior segment disease?

Answer 5

Specific measured are rarely possible but counselling, low visual aids and social support are all vital.
Associated treatable pathology like cataract can occur.
Oral acetazolamide has been tried for macular oedema of RP, with limited success.

Question 6

What is retinitis pigmentosa?

Answer 6

RP describes the retinal appearance found in a variety of hereditary PROGRESSIVE degenerations of the retina.
The ocular abnormalities may be an isolated finding or may be part of a systemic condition.
Degeneration of the rod retinal photoreceptors is more marked than that of the cones.

Question 7

How is isolated primary retinitis pigmentosa inherited?

Answer 7

It can be sporadic, or it can be inherited in an autosomal recessive, autosomal dominant, or X-linked pattern.

There are many genetic subtypes of RP, resulting in a wide variation in age of onset and disease severity.

Question 8

Name 5 non-hereditary conditions that may mimic RP (although they may affect only sectors of the retina):

Answer 8

1. Trauma
2. Retinal detachment surgery
3. Infections (eg. syphilis, rubella)
4. Previous occlusion of a retinal artery or vein
5. Drugs (eg. chlorpromazine)

Question 9

What are the four chief symptoms of retinitis pigmentosa?

Answer 9

1. Night blindness (nyctalopia)
2. Decreased peripheral vision
3. Decreased central vision (from macular changes)
4. Glare (from cataract).

Question 10

Name 5 systemic associations with retinitis pigmentosa.

Answer 10

1. Usher’s syndrome (RP with congenital deafness)
2. Bassen-Kornzweig syndrome (aka ‘abetalipoproteinaemia’)
3. Refsum’s disease (polyneuropathy, incl. deafness. Treatable).
4. Kearns-Sayre syndrome (triad of heart, RP and ophthalmoplegia).
5. Leber’s congenital amaurosis (a form of early onset atypical RP).

Question 11

What is congenital stationary night blindness (CSNB)?

Answer 11

A generic term for night blindness which, unlike RP, does not progress.

The retina usually appears normal, but electrophysiological tests show abnormal dark adaptation. A variety of CSNB, fundus albipunctatus, is characterised by multiple white spots in the peripheral fundus.

Question 12

What is cone dystrophy?

Answer 12

A hereditary posterior segment disease whereby there is progressive deterioration in the function of the cone retinal receptors.

Since cones are concentrate at the macula and provide colour vision, central visual loss and loss of colour appreciation are the presenting complaints. Electrophysiological tests are essential in diagnosis.

Question 13

What is albinism, and what is its mode of inheritance?

Answer 13

Failure of normal synthesis of melanin characterises albinism, which may be ocular or oculocutaneous. Inheritance may be autosomal recessive or X-linked. However, genetic mosaicism in X-linked disease causes a spectrum of phenotypes, and affected individuals may go undiagnosed for many years. Mosaicism also accounts for asymptomatic retinal changes in carriers.

Question 14

What are 6 ocular features of albinism?

Answer 14

1. Congenital nystagmus
2. Decreased visual acuity
3. Strabismus
4. Hypopigmented iris
5. Pallor of the fundus
6. Macular hypoplasia

Question 15

What is different about the optic chiasm in albinism?

Answer 15

Majority of fibres from each eye cross into the opposite optic tract.

Question 16

What are Stargardt’s disease and fundus flavimaculatus also known as, and what visual loss do they result in?

Answer 16

Also known as ‘flecked retina’, because of the appearance of creamy-white flecks.
There untreatable conditions cause loss of central vision during adolescence. There is a characteristic appearance on fluorescein angiography: the ‘dark choroid’ effect.