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Idiopathic Unilateral Transient Miosis in Dogs.
Ingrid Allgoewer1, Randall H Scaglotti2,3
1Animal Eye Practice, Berlin, Germany.
Veterinary Ophthalmology
|November 27, 2025
Summary
Idiopathic unilateral transient miosis in dogs predominantly affects young Australian Shepherds with the merle phenotype. Episodes often occur after sleep, lasting about 30 minutes and recurring in over half of cases.
Area of Science:
- Veterinary Ophthalmology
- Canine Clinical Neurology
Background:
- Idiopathic unilateral transient miosis is a rare condition in dogs.
- Understanding its clinical features is crucial for diagnosis and management.
Purpose of the Study:
- To characterize the clinical presentation of idiopathic unilateral transient miosis in dogs.
- Identify breed, phenotype, and demographic predispositions.
Main Methods:
- Analysis of owner- and veterinarian-completed questionnaires.
- Inclusion criteria required dogs with unilateral transient miosis and no other abnormalities.
Main Results:
- Seventy-eight dogs were included; Australian Shepherds (ASH) and Miniature Australian Shepherds (MASH) were overrepresented.
- The merle phenotype (70%), female sex (61%), and blue eyes (76%) were common.
- Episodes occurred post-sleep (74%), lasted ~30 minutes, and recurred in 71%.
Conclusions:
- Idiopathic unilateral transient miosis predominantly affects young dogs, particularly Australian Shepherds with merle coats.
- The condition is characterized by transient, unilateral pupillary constriction, often after sleep.
- This is the first report detailing the clinical features of this condition in dogs.
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