The iris is a circular, pigmented membrane that provides the eye its color and the opening in the center is the pupil of the eye.
The iris is made up of muscular fibers that control the amount of light entering the pupil so that you can see clearly. The iris accomplishes this task by making the pupil smaller in bright light and larger in dim light.
In some people, the iris can become inflamed. This is termed iritis.
Farsightedness: Blurred vision that's present when you are looking at near objects or, more commonly, near and far objects indicates that you may be farsighted, or hyperopic.
Astigmatism: Blurry vision can occur at any distance and usually coincides with discovery of other vision problems.
Retinal detachment: An abrupt onset of flashing lights, often in combination with black floating spots in your vision, possibly combined with the sensation of a dark curtain or veil blocking a portion of your vision, suggests retinal detachment. Cover each eye separately and compare the sight in each eye.
Color blindness: Difficulty distinguishing shades or intensity of color may suggest a color perception problem. Color vision defects are usually not known to the patient until discovered on testing, and it is mainly a condition in males.
Cataracts: Because cataract development is usually a gradual process, your first symptom may be trouble passing the vision test when renewing your driver's license, or it may be identified during a routine eye exam. Symptoms include:
Hazy vision that might be worse in bright light
Weaker vision at night; difficulty in discerning movements, details, or objects (especially street signs)
Blinding or uncomfortable glare from automobile headlights or bright sunlight
A need for brighter light for reading
Colors appearing faded or yellowed
Double or triple vision (overlapping images) in one eye only
A milky white or opaque appearance to the normally dark pupil (advanced case)
Painful inflammation and pressure within the eye (very advanced case)
Strabismus:Eyes don't move together in a coordinated pattern or may be crossed inward or outward. Young children with vision problems such as this may rub one or both eyes frequently and may squint, tilt their heads, or close one eye in order to see things better.