There are several conditions and disorders known to alter the iris and cornea functionality, increasing the light sensitivity, which has a negative effect on visual performance. Other conditions also lead to photophobia, but their origin is not related to iris dysfunctionality.
These conditions include, among others, the following ones:
Iris disorders (aniridia, coloboma), ocular albinism, high-order aberrations like keratoconus. Also, neurologic disorders where patients develop photophobia, like Chronic Migraine, Dry Eye Syndrome, or Traumatic Brain injury.