The iris is the colored part of the eye, controlling how much light enters the eye by adjusting the pupil’s size. While a round iris with a circular pupil is typical, variations in its shape can occur. These variations often lead to questions about their cause.
Normal Appearance and Minor Variations
While generally round, slight irregularities are a normal part of individual eye anatomy. The iris has a complex texture, with folds and crypts, which can give the impression of a non-round shape without structural issues. These minor variations are often present from birth and remain stable over time. For instance, pigmented rings or diamond-shaped crypts are typical patterns within the iris structure. Such deviations do not typically affect eye function or vision.
Congenital Conditions Affecting Iris Shape
Some individuals are born with an iris that is not round due to developmental factors. One such condition is an iris coloboma, a defect in the iris tissue. This occurs when a gap in the developing eye, called the choroid fissure, fails to close completely during fetal development. An iris coloboma often gives the pupil a distinctive “keyhole” or “cat-eye” shape, as if a piece of the iris is missing. This defect can affect one or both eyes, and its appearance depends on the amount and location of the missing tissue. While visually noticeable, it generally does not lead to significant vision loss, though it might increase light sensitivity or cause blurred vision if it allows a second image to focus on the retina.
Acquired Conditions Affecting Iris Shape
An irregular iris shape can also develop after birth due to various acquired conditions. Eye trauma is a common cause; blunt force or penetrating injuries can damage the delicate iris tissue. This can lead to tears in the iris, or even a separation of the iris from its root, a condition called iridodialysis, which can create the appearance of a second pupil.
Inflammation of the iris, known as iritis or anterior uveitis, can also alter its shape. During inflammation, the iris can swell, and adhesions, called synechiae, can form. These adhesions can pull the pupil and iris out of their normal circular shape, causing pain, redness, and light sensitivity.
Post-surgical changes, particularly after eye surgeries like cataract surgery, can sometimes affect the iris. Surgical procedures can lead to pupillary shape changes or iris depigmentation. Other less common acquired causes include abnormal new blood vessels on the iris (neovascularization) or iris tumors, which, though rare, can change the iris’s normal contour.
When to Seek Medical Attention
It is advisable to seek a professional medical evaluation from an ophthalmologist if you notice any sudden changes in the shape of your iris or pupil. This is particularly important if the change is accompanied by symptoms such as eye pain, redness, blurred vision, or increased sensitivity to light. A history of eye trauma also warrants an examination. Any new or concerning alteration in iris appearance should be checked by a medical professional. Only an eye care specialist can accurately diagnose the underlying cause and recommend appropriate management.