Eye Diseases and Conditions Slideshow Pictures Pink Eye Slideshow Pictures Laser Eye Surgery Pictures Iris: The circular, colored curtain of the eye. The opening of the iris forms the pupil. The iris helps regulate the amount of light that enters the eye. From Eye Health Resources How's Your Eye Health?Diabetes and Your EyesEye Care for Diabetes Featured Centers When Prostate Cancer SpreadsEssential Tips to Manage DiabetesWhat Is Cystic Fibrosis? What Causes It? Health Solutions From Our Sponsors Kept Your Wisdom Teeth? What is TAVR?