Microphthalmia

From Dog
Microphthalmos in a Pomeranian pup[1]

Microphthalmia is a relatively uncommon congenital eye disease of dogs characterized by a unilateral or bilateral shrunken eye.

In some severe cases, the congenital defect presents as anophthalmia (eye is absent entirely).

Microphthlamos is defined as an abnormal reduction in ocular size and can range from a globe that is only slightly smaller than normal to one that is only vestigial[2].

Microphthalmia has been reported in merle Australian Shepherd dogs in association with coloboma, where it appears as an incomplete-penetrance recessive trait.

Other causes include intrauterine infections, vitamin A deficiency, drug toxicities[3] and concurrent genetic diseases such as encephalomyelopathy[4].

This disease is more frequently diagnosed in Akitas, Collies, Schnauzers, Australian Shepherds, and Great Dane.

Affected dogs have a characteristic shrunken orbit, narrowed palpebral fissure and poor corneal development. Blindness of the affected eye is associated with this condition.

In the Dalmatian, it appears to be associated with heterochromia and deafness[5].

Diagnosis is based on visual inspection of the eye. Histological analysis of tissue is usually confirmatory.

A differential diagnosis would include congenital orbital cysts[6], persistent hyperplastic primary vitreous[7], dermoid cysts and melanoma.

There is no treatment for this condition, and cosmetic enucleation is usually required.

References

  1. Dell M (2010) Severe bilateral microphthalmos in a Pomeranian pup. Can Vet J 51(12):1405-1407
  2. Kirk NG (2008) Essentials of Veterinary Ophthalmology. 2nd ed. Ames, Iowa: Wiley-Blackwell; 2008. pp:37–38
  3. Hyttel P et al (2010) Essentials of Domestic Animal Embryology. New York: Saunders Elsevier. pp:170–179
  4. Geiger DA et al (2009) Encephalomyelopathy and polyneuropathy associated with neuronal vacuolation in two Boxer littermates. Vet Pathol 46(6):1160-1165
  5. Stritzel S et al (2008) A role of the microphthalmia-associated transcription factor in congenital sensorineural deafness and eye pigmentation in Dalmatian dogs. J Anim Breed Genet 126:59–62
  6. Regnier A et al (2008) Congenital orbital cysts of neural tissue in two dogs. Vet Ophthalmol 11(2):91-98
  7. Bayón A et al (2001) Ocular complications of persistent hyperplastic primary vitreous in three dogs. Vet Ophthalmol 4(1):35-40