What is iridodonesis?

What is iridodonesis?

• A. Trembling of the iris due to iris atrophy
• B. Trembling of the iris due to pupil dilation
• C. Trembling of the iris due to inflammatory changes in the iris
• D. Trembling of the iris due to lens instability

Answer: (C)

Iridodonesis is the tremulous movement of the iris caused by instability of the lens-iris diaphragm. When the lens is displaced (as in lens subluxation or ectopia lentis) or absent (aphakia) due to weak or broken zonules, the iris loses posterior support. As the eye moves, the unstable lens lets the iris “wobble,” producing a visible tremor. Inflammatory changes in the iris don’t produce this tremor point; instead, they cause signs like flare and cells in the anterior chamber, photophobia, and iris changes from inflammation, not a dynamic iris tremor. Likewise, pupil dilation alone doesn’t create true iris trembling, though it can alter appearance. A related concept is phacodonesis, which is the tremor of the lens itself, whereas iridodonesis refers to the iris tremor due to lens instability.

Iridodonesis is the tremulous movement of the iris caused by instability of the lens-iris diaphragm. When the lens is displaced (as in lens subluxation or ectopia lentis) or absent (aphakia) due to weak or broken zonules, the iris loses posterior support. As the eye moves, the unstable lens lets the iris “wobble,” producing a visible tremor.

Inflammatory changes in the iris don’t produce this tremor point; instead, they cause signs like flare and cells in the anterior chamber, photophobia, and iris changes from inflammation, not a dynamic iris tremor. Likewise, pupil dilation alone doesn’t create true iris trembling, though it can alter appearance.

A related concept is phacodonesis, which is the tremor of the lens itself, whereas iridodonesis refers to the iris tremor due to lens instability.