Aniridia is the absence of the iris. This generally bilateral condition is trans-mitted as an autosomal dominant trait or occurs sporadically. Aniridia mayalso be
traumatic and can result from penetrating injuries. However, periph-eral
remnants of the iris are usually still present so that ciliary villi and zonule
fibers will be visualized under slit-lamp examination (Fig. 8.2).
In sporadic aniridia, a Wilms’ tumor of the
kidney should be excluded.
Vision is severely compromised as a result of the foveal hypoplasia. The dis-order is
frequently associated with nystagmus, amblyopia, buphthalmos, and cataract.
Visual acuity will generally be reduced in the presence of
Another congenital anomaly results from incomplete fusion of the embry-onic optic cup, which normally occurs in about the sixth
week of pregnancy.These anomalies are known as colobomas. They are directed medially and inferiorly and can
involve the iris (Fig. 8.3), ciliary
body, zonule fibers, choroid, and optic nerve (Fig. 8.4). Bridge colobomas
exhibit remnants of the iris or choroid. Involvement of the choroid and optic
nerve frequently leads to reduced visual
Surgical iris colobomas in cataract and glaucoma surgery are usuallyopened superiorly.
In this manner, they are covered by the upper eyelid so the patient will not
usually experience blinding glare.
Traumatic iris colobomas are caused by avulsion of the iris