Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
There are two general categories of contact lenses – soft and rigid gas permeable (RGP). All contact lenses require a valid prescription.
Soft Lenses
Soft contact lenses are made of soft, flexible plastics that allow oxygen to pass through to the cornea. Soft contact lenses may be easier to adjust to and are more comfortable than rigid gas permeable lenses. Newer soft lens materials include silicone-hydrogels to provide more oxygen to your eye while you wear your lenses.
Rigid-Gas-Permeable (RGP) Contact Lenses
Rigid gas permeable contact lenses (RGPs) are more durable and resistant to deposit buildup, and generally give a clearer, crisper vision. They tend to be less expensive over the life of the lens since they last longer than soft contact lenses. They are easier to handle and less likely to tear. However, they are not as comfortable initially as soft contacts and it may take a few weeks to get used to wearing RGPs, compared to several days for soft contacts.
Extended Wear Contact Lenses
Extended wear contact lenses are available for overnight or continuous wear ranging from one to six nights or up to 30 days. Extended wear contact lenses are usually soft contact lenses. They are made of flexible plastics that allow oxygen to pass through to the cornea. There are also a very few rigid gas permeable lenses that are designed and approved for overnight wear. Length of continuous wear depends on lens type and your eye care professional's evaluation of your tolerance for overnight wear. It's important for the eyes to have a rest without lenses for at least one night following each scheduled removal.
Disposable (Replacement Schedule) Contact Lenses
The majority of soft contact lens wearers are prescribed some type of
frequent replacement schedule. "Disposable," as defined by the FDA, means used
once and discarded. With a true daily wear disposable schedule, a brand new pair
of lenses is used each day.
Some soft contact lenses are referred to as "disposable" by contact lens
sellers, but actually, they are for frequent/planned replacement. With extended
wear lenses, the lenses may be worn continuously for the prescribed wearing
period (for example, 7 days to 30 days) and then thrown away. When you remove
your lenses, make sure to clean and disinfect them properly before reinserting.
Lens Comparison
The American Optometric Association has more detailed information about
contact lenses including a lens comparison chart.
Conventional contact lenses correct vision in the same way that glasses do,
only they are in contact with the eye. Two types of lenses that serve a
different purpose are orthokeratology lenses and decorative (plano) lenses.
Orthokeratology (Ortho-K)
Orthokeratology, or Ortho-K, is a lens fitting procedure that uses specially
designed rigid gas permeable (RGP) contact lenses to change the curvature of the
cornea to temporarily improve the eye's ability to focus on objects. This
procedure is primarily used for the correction of myopia (nearsightedness).
Many common eye disorders resolve without treatment and some may be managed with over-the-counter (OTC) products. It's important to visit a physician or ophthalmologist is the problem involves the eyeball itself or the condition hasn't improved after 72 hours of use of an eye-care OTC product.
The eyes are complex sensory organs. About 85% of the total sensory input to our brains originates from our sense of sight,
while the other 15% comes from the other four senses of hearing, smell, touch, and taste. The eyes are designed to optimize vision under conditions of varying light. Their location, on the outside of the face, makes them susceptible to trauma, environmental chemicals and particles, and infectious agents. The eyelids and the position of the eye within the bony orbital cavity are the major protective mechanism for the eye.
The eye itself has the shape of a sphere measuring about 1 inch in diameter. It consists of a clear, transparent dome at the front (the cornea) that is surrounded by the white of the eyeball (the sclera). The iris of the eye is the circular, colored portion within the eye, and behind the cornea, and the pupil is the central opening within the iris. Behind the iris and pupil is the e...
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