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The colored part of the eye is called the iris. It is composed of two muscles. The constrictor and the dilator. The black circle at the center of the iris is called the pupil and is actually just an opening to allow light into the eye. The pupil appears black because the inside of the eye contains pigment to absorb all of the light that enters it, not allowing any of it to reflect back out.

When light enters your eye there is a muscular reflex in your iris to regulate the amount of light that hits the retina. Too much light and constrict muscles tighten to making your pupil smaller to limit the amount of light entering your eye. Not enough light and the dilator muscles contract allowing your pupil to get bigger.

During a comprehension eye exam, your eye doctor might want to dilate your pupils to evaluate the back of each eye under high magnification. Without dilation, the bright exam light automatically causes your pupils to constrict, making a much smaller opening to look through.

Dilating drops cause your pupils to enlarge by inhibiting the constrictor muscles from reacting to light., then the doctor can use a bright exam light combine with a magnification lens for an unobstructed view of the internal structure of each eye, including the retina, macula and optic discs.

Dilation drops typically cause blurred near-vision and light sensitivity lasting about 4 to 6 hours. Sunglasses are usually worn afterward to relieve glare discomfort, but you should be safe to drive with caution.

Keratoconus is an eye disease in which the cornea deforms from its normally curved dome shaped and becomes cone shaped. Sometimes there is a flaw in the collagen, the material of the cornea that weakens and allows the cornea to stretch into an irregular cone shape.

The cornea is the clear tissue located at the front of the eye and it refracts and focuses light as it enters the eye. Therefore abnormalities of the corneal surfaces can severely distort vision.

Symptoms usually start in the teen years with near-sighteness and astigmatism which can often be treated with contact lenses or glasses. At the onset it can be difficult to detect.

It is first diagnosed when the cornea starts reveal progressive irregular distortion and eventually becomes to advance for conventional glasses or contact lenses to correct. At this critical point it is often treated with specially designed contact lenses to provide a smooth optical surface to focus light rays and impede progression of the bulging cone shape.

In some case keratoconus can progress to the point that corneal replacement surgery is needed. This usually occurs around the age of 35.

There are some evidence to suggest allergy suffers and people with rigid contact lenses that rub their eyes may contribute to the progression of the symptoms and cause scratches on the surface of the cornea.

If you feel you are at risk or your prescription is changing rapidly make certain your eye care professional checks for Keratoconus during your next eye health and visual examination.