Heterochromia iridis

This is another physical sign where a good observation can pay dividend at the beginning of the examination. 
The heterochromia is usually best seen in a well-lit environment. There are many causes of heterochromia iridis, 
however, if the heterochromia forms the main part of the examination (for example 'Look at this patient's eye and do 
the necessary examination') the most likely case is siderosis bulbi. Remember that the abnormal eye can be the eye 
with either the darker as in siderosis bulbi or the lighter iris for example congenital Horner's syndrome or Fuchs' 
heterochromic iridis.

The patient has heterochromic iridis. 

Further examination 
(if you can choose the type of examination then choose pupillary examination or slit-lamp examination. In pupillary 
examination look .for congenital ptosis or siderosis bulbi; in slit-lamp examination look for siderosis bulbi in which 
there are usually signs of penetrating injury or Fuchs' heterochromic iridis):

  • look for any signs of mild ptosis or anisocoria on the side of the lighter iris for congenital Horner's syndrome
  • mention that you like to test the patient's visual acuity and pupil response (in siderosis bulbi the darker

  • eye has poor vision and the pupil is usually dilated and does not react to light). Also mention that you like to
    examine the eye for any retained foreign body or signs of previous penetrating injury. The optic disc may 
    show glaucomatous damage.
  • slit-lamp examination for diffuse keratitic precipitate, flare and posterior subcapsular cataract in Fuchs' 

  • heterochromic iridis.


1. What are the causes of heterochromic iridis?

2. What is the feature of ERG in siderosis bulbi?

3. What are the signs of siderosis bulbi?

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A patient with left-sided siderosis bulbi. Note the dark iris and dilated pupil.
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Heterochromic iridis in a patient with congenital Horner's syndrome. Note the
miosis and mild ptosis on the side with lighter iris.
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