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Introduction to Eye Disease - Year 2 > Retinal Dystrophies Part 1 > Flashcards

Retinal Dystrophies Part 1 Flashcards

1
Q

What is the cause of retinal dystrophies?

A

Mutations on chromosomes - i.e. they are inherited

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2
Q

True or False- Mutations that cause retinal dystrophies can have variable expressivity/penetrance

A

True- the same mutation can cause different signs and symptoms in different people

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3
Q

True or False- Retinal Dystrophies can either affect the full retina or just the macula

A

True

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4
Q

What are some examples of full retinal dystrophies?

A

Retinitis Pigmentosa (RP)

Leber’s Congenital Amaurosis (LCA)

Congenital Stationary Night Blindness (CSNB)

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5
Q

What are some examples of Macula retinal dystrophies?

A

Bests Vitelliform

Juvenile X-linked retinoschisis

Autosomal dominant drusen

Stargardt Fundus Flavaimaculatus

Sorsby Disease

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6
Q

What are the possible causes of Retinitis Pigmentosa (RP)?

A

–Autosomal Dominant RP

–Autosomal Recessive RP

–X-linked RP

-Sporadic mutation

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7
Q

What is Retinitis Pigmentosa (RP)?

A
  • A Heterogeneous group of retinal disorders
  • It is a Rod-cone dystrophy

–Progressive dysfunction of rods, then subsequently the cone photoreceptors and RPE occurs.

It is due to the mutation of the rhodopsin gene.

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8
Q

What are signs of Retinitis Pigmentosa?

A

1.Pigmentation

–Bone-spicule and pigment clumping in mid-perphery of fundus

–This can be Hypo- or hyper- pigmentation of RPE

  1. Thinning/attenuation of blood vessels
  2. Pale waxy disk
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9
Q

Is Retintis Pigmentosa bilateral or unilateral?

A

Biateral although one eye tends to progress faster than the other

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10
Q

What conditions is Retintis Pigmentosa (RP) associated with?

A
  • PSC cataracts
  • CMO
  • Myopia and astigmatism
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11
Q

What are symptoms of Retintis Pigmentosa?

A
  • Nactylopia (night blindness) - this is the first symptom and is due to rod loss (as shortening of rod receptor occurs due to phagocytosis)
  • Progressive loss of peripheral vision – noticed later on

–Tunnel vision

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12
Q

What is sectoral Retintis Pigmentosa (RP)?

A

When signs of Retintis Pigmentosa i.e. that bone spicule pigment clumping exists in one particular quatre of the retina.

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13
Q

What do we have to be careful not to confuse Retintis Pigmentosa with and why?

A

We don’t want to confuse Retintis Pigmentosa with Albipuntcatis (which is a form of congenital stationary night blindness) as the prognosis is different.

Both conditions present with nightblindness as a symptom.

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14
Q

How do we diagnose Retinitis Pigmentosa (RP)?

A

Take a thorough family history to check for inheritance likelyhood.

Full field ERG- rods should behave abnormally ( as seen in the picture highlighted by the yellow circle in comparison to the normal row below)

Test the px’s dark adaptation - RP px cannot dark adapt (as well) - compare the red line to the blue normal line in the graph.

Visual fields - later on RP px develop scotomas which join to form a mid periphery ring scotoma which constricts to form tunnel vision

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15
Q

What is the likelyhood of passing on Autosomal dominant RP to offspring and is it more likely in males or females?

A

50% risk of passing on to offspring

Equally as common in males and females

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16
Q

What is the cause of Autosomal Dominant RP?

A
  • Single gene mutation.
  • However ~30 causative genes have been identified. Rhodopsin gene (RHO) most common one.

[It is responsible for 15-20% of all RP cases in the UK]

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17
Q

How is autosomal recessive RP passed on (i.e. under what conditions does the offspring express RP)?

A

Both parents must have the gene for it in order for it to be expressed in offspring.

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18
Q

What is the cause of Autosomal recessive RP?

A

•Can be mutation in genes including RHO gene, gene encoding alpha or beta subunit of cGMP phosphodiesterase, or the alpha subunit of the cGMP gated channel.

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19
Q

What is the cause of x linked RP?

A

•Most cases (70%) due to a mutation in RGPR gene on the X-chromosome

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20
Q

In what gender is X linked RP more commonly expressed?

A

Males - females tend to just be carriers.

21
Q

Which form of RP is the most severe and why?

A

X linked RP as:

–Childhood onset night blindness occurs from 1st decade

–Px experiences Poor central vision

–Myopia

22
Q

Why are women less affected by X linked RP?

A
  • Women have two X chromosomes and a normal copy on the one X chromosome can partially compensate for a pathological variant on the other X chromosome.
  • Female carriers have variable expression.
23
Q

How can one identify a female carrier of X linke RP from their fundus?

A

They show a tapetal reflex that is specific is RP carriers

24
Q

What are systemic associations of RP like dystrophies?

A

Syndromes such as:

  • Usher’s syndrome (serious hearing loss; 18% of all RP)
  • Kearns-Sayre syndrome (external ophthalmoplegia, lid ptosis, heart block)
  • Bardet-Biedl syndrome (polydactyl - i.e. extra fingers and toes, truncal obesity, short stature)
25
Q

What is Leber’s Congenital Amaurosis (LCA)?

A

•An Autosomal recessive condition in which there is an abnormal development of photoreceptor cells

26
Q

What is the rate of progression and prognosis like in Leber’s Congenital Amaurosis (LCA)?

A

Rate of progression is poor but the prognosis is ultimately poor

27
Q

What is the prevalence of Leber’s Congenital Amaurosis (LCA)?

A

•Prevalence ~3 in 100,000

28
Q

How many different forms of Leber’s Congenital Amaurousis (LCA) is there?

A

At least 20 different forms of LCA, each caused by a defect in a different gene important for normal visual function

29
Q

What is the most common form of inherited sight loss in children?

A

Leber’s Congenital Amaurosis (LCA)

30
Q

What associations does Leber’s Congenital Amaurosis (LCA) have?

A
  • Can be associated with cataract/keratonoconus
  • Can have systemic associations e.g. abnormal kidney function/defects
31
Q

What are symptoms of Leber’s Congenital Amaurosis (LCA) and how may it ultimately be confirmed?

A
  • Parents may notice lack of visual responsiveness, nystagmus, tropia, oculodigital reflex (children press on eyes)
  • Nyctalopia from birth
  • Photophobia
  • Decreased VF from 1 yr
  • VA ~ 6/36
  • May be associated with high hyperopia or myopia
  • Confirmed with genetic test
32
Q

What would be seen on an ERG of a px with Leber’s Congenital Amaurosis (LCA)?

A

Abnormal ERG - signifcantly reduced photopic and scotopic response

33
Q

How may the fundus of a px with Leber’s Congenital Amaurosis (LCA) present?

A

Fundus may appear normal

May have slight Blood vessel attnetuation

May have subtle RPE granularity

34
Q

Is Congenital Stationary Night Blindness (CSNB) a progressive condition?

A

No

35
Q

What are common symptoms of Congenital Stationary Night Blindness (CSNB)?

A

•High myopia at a young age, nystagmus, reduced VA and strabismus are common (especially when X-linked inheritance is the cause).

36
Q

What does the degree of night blindness in Congential Stationary Night Blindness depend on?

A

•Dysfunction depends on mutation. - thus sometimes it can be mild and in other cases it can be severe

37
Q

How do we diagnosis Congenital Stationary Night Blindness?

A

•Diagnosis is by ophthalmological appearance, family history, genetic testing and use of an electroretinogram.

38
Q

True or False- Congenital Stationary Night Blindness is a group of diseases

A

True

39
Q

How can Stationary night blindness be classifed?

A

By cause.

By fundus appearance

By mode of inheritance

By specific of ERG

By gene affected

[Then subclassified By whether it is complete or incomplete]

40
Q

What is the difference between complete and incomplete CSNB?

A

Complete CSNB= complete absence of rod function

Incomplete CSNB = rod ERG reduced

41
Q

How does the ERG of a normal px differ to that of a px with CSNB (both complete and incomplete)?

A
42
Q

What is Fundus Albipunctatus and what does it result in?

A

It is an Autosomal recessive condition that affects rod and cone photopigment kinetics

It leads to Grossly extended dark adaptation times however eventually normal thresholds are reached.

ERGs and EOGs eventually normal, but only after prolonged period of adaptation prior to testing.

43
Q

How does Fundus Albipunctatus present appearance wise?

A

Lots of dull white spots on the retina

44
Q

Oguchi’s Disease

What type of disease is this?

How does the fundus appear?

What kind of abnormality is this?

Can the retina dark adapt?

A

It is a type of congenital stationary night blindness - it is a Rare autosomal recessive disease.

Fundus looks grey/yellow metallic (but appears normal after prolonged dark adaptation).

Post-receptoral abnormality (i.e. its not an abnormality of the photoreceptor but processing further down the line) (Regeneration of the pigment is normal)

Cone adaptation normal, rod adaptation grossly delayed (2-24 hours). Eventually normal thresholds.

45
Q
  • What type of inheritance does retinitis pigmentosa follow?
  • A) Autosomal recessive
  • B) Autosomal dominant
  • C) X-linked recessive
  • D) Any of the above
A

D

46
Q
  • What kind of fundus appearance might you see in someone with LCA?
  • A) Normal
  • B) Bone spicule
  • C) Tapetal reflex
  • D) RPE granularity
A

D) RPE granularity

47
Q
  • Low vision, squint and myopia are most associated with which form of CSNB?
  • A) Autosomal recessive
  • B) Autosomal dominant
  • C) X-linked recessive

D) CSNB with abnormal fundus appearance

A

C) X linked Recessive

48
Q

What is the difference between a dystrophy and a degeneration?

A

A dystrophy is purely inherited, usually as a result of a single gene mutation.

Degenerations are age-related. There may be certain genetic mutations which predispose towards development (e.g. CFH mutations in AMD) but onset is usually multifactorial (not purely inherited).

Introduction to Eye Disease - Year 2 (40 decks)

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