Introduction

• Iris atrophy is relatively common in dogs.
• Primary iris atrophy is usually age-related (senile iris atrophy), but iris thinning may also develop secondary to chronic uveitis Uveitis , chronic glaucoma Glaucoma or a traumatic injury.

Pathogenesis

Etiology

• Senile iris atrophy: age-related degeneration of iris sphincter (constrictor) muscle.
• Secondary iris atrophy: thinning of the iris usually following development of synechiae associated with chronic uveitis or glaucoma that involves the iris sphincter muscle.

Predisposing factors

• Age.
• Breed.

Specific

• Chronic intra-ocular disease such as chronic uveitis or glaucoma (uncommon).

Pathophysiology

• Senile iris atrophy: age-related degeneration of iris sphincter muscle leads to reduced ability to constrict the pupil, which is manifested by decreased pupillary light reflexes despite normal vision. The iris stroma may also be affected, causing dyscoria, thinning of the iris stroma, occasional color changes within iris (often iris darkening as underlying pigment is exposed) areas of iris translucency or the development of actual holes in the iris.
• Secondary iris atrophy: chronic uveitis or glaucoma may lead to thinning of the iris and degeneration of iris sphincter muscle, especially in association with synechiae. Unlike primary iris atrophy, vision may be affected in these cases, from the underlying disorder. The remaining discussion below, pertains only to senile iris atrophy.

Timecourse

• Months to years.

Epidemiology

• Increased frequency in aged populations.

Diagnosis

Treatment

Outcomes