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.
Eyes with vision problems do not focus light where they should. Eyeglass lenses change the direction of light entering the eyes so that it focuses properly on a special part of the back of the eye known as the retina.
How Often Do You Need a New Prescription for Eyeglasses?
Call your eye doctor for an exam if your vision changes. But you should also expect to have eye exams regularly as an essential part of maintaining healthy vision. This is especially important since your eye doctor also checks for eye diseases and disorders.
The Basics of Eyeglasses
Eyeglasses may be prescribed with lenses providing:
One vision correction for all distances (unifocal)
Correction for both near and distant vision (multifocal: bifocals, trifocals, progressive, or no-line lenses)
Ultraviolet (UV) light protection -- a lens coating to block the sun's damaging and invisible UV rays
Antireflective coating to lessen light reflection off your glasses, reducing daytime glare and the nighttime "starburst" effect around lights
You may want to ask your eye doctor about other lens enhancements, such as:
Photochromatic lenses, which darken in situations where you'd otherwise wear sunglasses and act as "regular" eyeglasses in normal (usually indoor) light
Scratch protection (recommended for plastic lenses)
Tints -- typically cosmetic but also useful for people whose eyes are sensitive to light
Eyeglass frame styles change with fashion. Frames may be made from:
A combination of plastic and metal
"Specialty" metals such as titanium and carbon graphite, both highly damage resistant
Eyeglass alert! Your new eyeglasses should feel -- well, almost as if you aren't wearing them! They shouldn't rub uncomfortably against your ears or nose, fall off easily, or otherwise not feel "right." Of course, allow a reasonable amount of time for getting used to them. However, if problems persist, let your eye doctor know.