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'
The patient has heterochromic iridis.
(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'
1. What are the causes of heterochromic iridis?