Retinal Dystrophies Part 2 Flashcards
What are some examples of Macular dystrophies?
Best Vitelliform Macular Dystrophy
X-linked retinoschisis
Autosomal Dominant Drusen
Stargardt’s Fundus Flavimaculatus
Sorsby Macular Dystrophy
Describe Best Vitelliform Macular Dystrophy
What type of dystrophy is it?
What gene does it affect and why is this significant?
What clinical appearance does it have?
Is it unilateral or bilateral?
Is the ERG abnormal or normal?
Is the EOG (electro-oculogram) normal or abnormal?
- Autosomal dominant
- Best1 VMD2 gene –which Encodes for protein bestrophin -Bestrophin is linked to abnormal chloride conductance thus a mutation disrupts fluid transport across RPE and leads to accumulation of debris between Bruch’s membrane and the RPE/photoreceptor complex - thus we get that yellow yolk appearnace
- Diagnosis on clinical appearance:
–Egg yolk - which is elevated ( seen via volk)
- Bilateral but usually one eye progresses faster than the other
- Abnormal EOG
- Normal ERG
What is that egg yolk like appearance made up of in Best’s (VIteliform Macular Dystrophy)?
Deposition of lipofuscin around macular area. It’s like a PED, but filled with lipofuscin material
True or False- Best’s Vitelliform Macular dystrophy is shortened to Best’s disease.
True
What is the average age of onset of best disease and why is it not detected at that age?
Average age of onset of Best disease is 6 years. The condition often is not detected until much later in the disease because visual acuity may remain good for many years. Plus fundus appears normal even though the EOG is abnormal.
Describe the stages in the progression of Best’s disease.
Stage 1: pre-vitelliform – normal macula or subtle RPE changes, EOG abnormal.
Stage 2: vitelliform – egg yolk appearance. Can be multifocal.
Stage 3: Pseudohypopeon – yellow lipofuscin breaks through RPE and cumulates in subretinal space in a cyst. (SEE PICTURE ATTACHED)
Stage 4: Vitelliruptive – scrambled egg, pigment clumping, early atrophic changes. Moderate VA reduction
Stage 5: atrophic: yellow material disappears, RPE atrophy remains. VA markedly reduced.
Stage 6: Can develop CNV and fibrous scar.
How does a fundus in the atrophic stage of best’s disease appear?
What is schisis latin for?
Splitting
Juvenile X-linked retinoschisis
What is Juvenile X-linked retinoschisis?
Which gender does it primarily affect?
How does it appear?
It is a mutation of the Retinoschisin gene (XLRS1) and results in splitting of the macula. ( and in 50% of cases splitting of the retina at the periphery too)
It mainly affects males (1 in 15,000-30,000)
It presents as a Spoke-wheel type macular lesion–Atrophy (see picture attached)
What symptoms do px’s with Juvenile X-linked retinoschisis present with and at what age?
Patients typically present at school age complaining of poor vision, although they may present in infancy with nystagmus, strabismus, hyperopia, foveal ectopia, hemorrhage, or retinal detachment.
How is vision affected during the course of a px’s lifw who has Juvenile X-linked retinoschisis?
There is wide variability in disease severity, ranging from normal vision to legal blindness. Vision often deteriorates early in life, but then usually becomes stable until late adulthood. A second decline in vision typically occurs in a man’s fifties or sixties.
How does an ERG look of a px with retinoschisis?
There is no B wave.
[A wave comes from photoreceptors - and outer retinal layers are in tact but everything beyond that is disturbed thus bipolar cells aren’t receiving a proper signal and thus not producing a b wave]
What is autosomal dominant drusen also known as?
‘Doyne Honeycomb Retinal Dystrophy’ and ‘Mallatia Levantinese’
How does Autosomal Dominant drusen appear?
The extent to which it appears varies but ultimately it is drusen diposits in a ring around the macular. (See pics for different examples of px with the condition)
What are the symptoms of Autosomal Dominant drusen and at what age is the onset?
- Onset 20-30s
- Asymptomatic usually with slow gradual visual loss
- May develop CNV in which case px experiences a faster gradual visual loss
- Px May notice metamorphopsia
What is Stargardt’s Fundus Flavimaculatus?
- An Autosomal recessive disease in which there is a
- Genetic defect in visual phototransduction cycle
- Mutations in ABCA4 which causes
–Defective ATP binding cassette transporter protein in photoreceptors
–Cannot remove N-retinylidene-PE (a toxic substance) from photoreceptors. This toxic substance binds with another substance to form lipofuscin which..
- builds up in RPE (these are seen as the white flecks around the macula in the image).
What are the clinical signs of Sorsby Macular Dystrophy?
Early on normal fundus or perhaps slight mid periphery drusen but it can progress untreated to show the follwoing:
- Geographic atrophy
- Back pigmentation
- Deposits
- CNV from 5th decade
B
Abnormal EOG
D
ERG B wave
