Uvea: Congenital Abnormalities

Question 1

Describe the anatomy of uvea?

Answer 1

• Uvea is pigmented layer of eye – usually middle layer – includes iris, ciliary body & choroid
• Iris
  o Determines diameter of pupil
  o Separates anterior and posterior chambers
• Ciliary body
  o Produces aqueous humour
  o Changes shape of lens and hence focus
• Choroid
  o Provides oxygen and nutrients to outer retina

Question 2

What are the main congenital abnormalities of uvea?

Answer 2

• Aniridia
• Axenfield-Rieger Syndrome
• Coloboma

Question 3

Describe aniridia (congenital uveal abnormality)?

Answer 3

• Rare bilateral disorder of iris hypoplasia – iris has not grown way it should
• Mutation of PAX6 gene
• Range from mild defect of iris stoma to complete absence of iris
• Can be associated with foveal hypoplasia and nystagmus
• Can be associated with WARG syndrome:
  o Wilms tumour – renal tumour
  o Aniridia
  o Mental Retardation
  o Genitourinary malformations
• Glaucoma in 75%
• Treatment:
  o Treat the glaucoma – usually presents in infancy & early childhood & needs treated
  o Painted contact lens – helps cosmesis – reduces amount of light going into eye – reduces photophobia & nystagmus
  o Prosthetic iris implant - surgical
  o Cataract surgery

Question 4

Describe Axenfield-Rieger Syndrome (congenital uveal abnormality)?

Answer 4

• Umbrella term for group of disorders involving iris and angle malformations
• Axenfield Anomaly:
  o Posterior embryotoxon – prominent & anteriorly placed Schwalbe’s line
  o Peripheral iris strands attached to cornea
• Riegers Anomaly:
  o Posterior embryotoxon
  o Iris stromal hypoplasia – stroma not formed way it should be
  o Ectropion uvea – iris pigment on anterior iris surface
  o Corectopia – pupil displacement – pupil can be off to side
  o Full thickness iris defects
• Rieger’s Syndrome:
  o Riegers anomaly + systemic features
   Dental abnormalities
   Facial abnormalities
   Other abnormalities too
• Management:
  o Glaucoma develops in 50%
  o Surgical interventions for iris abnormalities
  o Supportive

Question 5

Describe coloboma (congenital uveal abnormality)?

Answer 5

• Defect resulting from failure of closure of embryologic fissure – when globe forms embryologically, it forms from the top and forms down into a circle and bottom edges join up
• Can affect any layer from discs to eyelids
• Typically inferonasal portion of iris
• Can be associated with CHARGE syndrome:
  o Coloboma
  o Heart defects
  o Choanal Atresia – abnormalities of nose
  o Retardation of growth
  o Genital abnormalities
  o Ear abnormalities