The pinhole occluder can also be used in testing visual acuity in mydriatic patients. One effect of administration of a mydriatic is intolerance to bright light (photophobia). As a mydriatic, it is available in 2.5% and 10% minims. A mydriatic is an agent that induces dilation of the pupil. Dilation can be caused by mydriatic substances such as an eye drop solution containing tropicamide. A "mydriatic" pupil will remain excessively large even in a bright environment.