July 11th, 2009
Persons with eyesight problems prefer wearing contact lens for its some specific advantages over glasses. Lenses are not independent of disadvantages. They provide coverage and protection for the cornea. The cornea is the most important part of the eye. It is the thin, clear tissue like watch glass on the frontage of the eye. It leaps over the iris that is the colored tissue in the eye. Oxygen is a primary need of the cornea as no blood vessels are there to supply it with oxygen. Oxygen enters the cornea through the tear film. Contact lenses when put on the eyes block the oxygen supply to the cornea.
This problem does not occur when contact lenses are new and fresh. Oxygen supply to the cornea remains intact with the use of new lenses. Lenses in use get usually coated with tear oils and proteins. Air cannot easily pass through these lenses. Lenses used for several months at a stretch become coated. Therefore, lens replacement after certain intervals is vital for the corneal health of the eyes. Sleeping with contactlens on the eyes has detrimental effect on a person’s vision. It keeps oxygen out of the reach of the cornea. The quality of contact lenses varies with materials that they are made of.
3-4% swelling of the cornea overnight when the eyelids block air transmission is common. Adding to the percentage of swelling is lenses that are made of average materials. However, the silicone hydrogel contact lenses are an exception in this regard. The new version of super permeable contactlenzen lets the cornea be supplied with oxygen and thereby reducing swelling to some extent. Therefore, it is mandatory to make purchase of contact len on condition of a consideration of its material.