AMD and retinal dystophys

Question 1

Name RFs for Dry AMD

Answer 1

• Age
• HTN
• Smoking
• Female
• High fat and cholesterol intake
• Blue iris and abnormal skin sensitivity

Question 2

Where are drusen located?

Answer 2

Between cell basement membrane and Bruch’s membrane

Question 3

How do Hard drusen appear?

Answer 3

Small and well defined

Question 4

How do soft drusen appear?

Answer 4

Larger than 63um and ill defined borders
- Can increase in size and number with age

Question 5

Are hard drusen or soft drusen a risk factor for Advanced AMD?

Answer 5

Soft drusen

Question 6

What is geographic atrophy?

Answer 6

Atrophy of the RPE

Question 7

What is seen in histology of the macula in dry AMD?

Answer 7

• Atrophy of photoreceptors over well defined eosiniophillic mounds in the RPE (hard drusen) and more linear bands in diffuse drusen
• Bruch’s membrane thickened or calcified
• Choriocapilaries occasionally replaced by degenerative fibrosis

Question 8

What is a basal linear deposit?

Answer 8

Deposits between the RPE cell membrane and its basement membrane

• Linked with Start of neovascularisation or wet AMD

Question 9

What are basal linear deposits associated with?

Answer 9

Start of neovascularisation or wet AMD

Question 10

What is disciform degeneration?

Answer 10

The RPE undergoes fibrous metaplasia with deposition of collagen - causes a disc shaped mass beneath the macula

Question 11

What is the normal age of onset of retinitis pigmentosa?

Answer 11

Early adult life

Question 12

What are the possible modes of inheritance of Retinitis pigmentosa (in order of commonness)

Answer 12

• AD: most common
• AR: less common
• X-linked recessive: least common

Question 13

What mutations are associated with the AD form of Retinitis pigmentosa?

Answer 13

• Gene coding for rhodopsin - on long arm of Chromosome 3q
• Peripherin: On chromosome 6p

Question 14

Which forms of Retinitis pigmentosa has the best and worst prognosis?

Answer 14

AD - best

X-linked - worst, may result in complete blindness by 3rd or 4th decades

Question 15

Name symptoms of Retinitis pigmentosa

Answer 15

• Night blindness
• Progressive visual field loss from periphery towards posterior pole
• At endstage - retinal function is limited to central macula –> ‘tunnel vision’

Question 16

What is seen on fundoscopy in Retinitis pigmentosa?

Answer 16

• Retinal atrophy
• Narrowing and opacification of retinal vessels
• Mixed, coarse strands of pigmentation

Question 17

What is seen histologically in Retinitis pigmentosa?

Answer 17

• Outer nuclear layer at the fovea appears as a single layer of cells with stunted photoreceptors
• Towards the periphery, the outer nuclear layer is replaced by Muller cells, which fuse with RPE
• RPE cells react by proliferation and migration into the retina to become distributed around the hyalinized vessels –> giving bone spicule appearance

Question 18

How is Best’s disease inherited?

Answer 18

AD

Question 19

What is seen on examination in Best’s disease?

Answer 19

Disc of yellow tissue at the macula
Loss of central visual acuity

Question 20

What is seen histologically in Best’s disease?

Answer 20

Lipofuscin accumulation in RPE cells
Atrophy of photoreceptor layer

Question 21

What is the inheritance of Stargardt’s disease?

Answer 21

AR

Question 22

Which gene mutation is associated with Stargardt’s disease?

Answer 22

ABCA4 or ATP binding cassete (also known as STGD1) on chromosome 1p21

Question 23

Describe the pathophysiology of Stargardt’s disease?

Answer 23

ABCA4 gene mutation leads to abnormal transport of metabolites across the photoreceptor disc membrane –>accumulation of lipofuscin in rod and cone disc spaces
–> RPE and photoreceptor destruction

Question 24

What % of ARMD patients also have ABCA4 mutations?

Answer 24

18.7%

Question 25

What is seen on clinical examination in Stargardt’s disease?

Answer 25

Atrophy of the macula
Small yellow flecks