Uvea: Choroidal Dystrophies

Question 1

What are choroidal dystrophies?

Answer 1

• Group of inherited disorders affecting choroidal function
• Uncommon
• Affect RPE, choriocapillaris and photoreceptors with progressive involvement of large choroidal vessels

Question 2

What are the 3 most common types of choroidal dystrophies?

Answer 2

• Choroideremia
• Gyrate atrophy
• Progressive bifocal chorioretinal atrophy

Question 3

Describe choroideremia - symptoms, signs, management?

Answer 3

• Progressive, diffuse degeneration of choroid, RPE, and photoreceptors
• X-linked recessive – so generally affect males – v uncommon for females to be affected but they can be carriers
• Very poor prognosis
• Symptoms:
  o Usually diagnosed in adolescence
  o Nyctalopia – reduced night vision
  o Reduced peripheral vision
  o Eventual loss of central vision
• Signs:
  o RPE mottling (in female carriers)
  o Mid peripheral RPE changes, which gradually spread both centrally & peripherally – starting in mid-periphery and spreading in and out
  o End-stage:
   Choroidal vessels run over bare sclera
   Retinal arteriolar attenuation
   Optic atrophy – choroid which supplies nutrients & oxygen to retina is no longer able to do that & so retina itself stops to function & then get optic atrophy
• Treatment:
  o Supportive
  o Low Vision Assessment (LVA)
  o Blind registration
  o Gene therapy research ongoing

Question 4

Describe gyrate atrophy - symptoms, signs, treatment?

Answer 4

• Rare autosomal recessive condition
• Enzyme deficiency leading to choroidal atrophy
• Unable to break down ornithine (amino acid)
• Poor prognosis
• Legal blindness by age 50
• Symptoms:
  o Nyctalopia
  o Peripheral field loss
  o Eventually central field loss
• Signs:
  o Mid-peripheral de-pigmented spots
  o Well-defined peripheral atrophic patches with scalloped edge
  o Atrophic lesions eventually coalesce – areas of atrophy get bigger and bigger
  o Fovea lost in later stages
  o May develop ERM or CMO as complication – often don’t require tx as they are not effective in this situation
• Treatment:
  o Arginine restricted diet – reduced ornithine levels & can slow progression of disease
  o Pyridoxine supplements (Vitamin B6) – only useful in pxs who have certain gene mutation
  o Gene therapy research ongoing