Rigid gas permeable lenses, or hard contact lenses, are more rigid than soft contact lenses and therefore more durable. Unlike older versions of hard contact lenses, rigid gas permeable lenses are made with silicone polymers, allowing oxygen to circulate to the cornea of the eye. Compared to soft contact lenses, hard contacts maintain their shape better and offer clearer vision for some types of corrections. They are also easy to take care of and are extremely durable. However, if you are considering this type of hard contact lens, you should know that:
There is a 10-15 times greater risk of developing corneal ulcers, a serious infection, which may damage your vision if not treated.
Sleeping in extended wear contacts may decrease flow of oxygen to the cornea.
Undesirable reshaping of the cornea may occur.
The amount of time needed to adjust to hard contact lenses is often repeated after not wearing them for as little as a day. Therefore, in order to achieve maximum comfort you have to wear the contact lenses everyday.
Bifocal contact lenses are designed to give good vision to people who have a presbyopia . These contact lenses work much like bifocal eyeglasses, having two powers on one lens one to correct distant vision and another to correct near vision. Bifocal contact lenses come as both soft and rigid gas permeable lenses.
Toric contact lenses are special lenses for people with astigmatism. Toric contact lenses are made from the same material as other contact lenses and come in soft or rigid gas permeable forms. Like bifocal lenses, toric lenses have two powers, one for the astigmatism and another for nearsightedness or farsightedness if either of these conditions is also present.
A sty (sometimes spelled stye) is a tender, painful red bump located at the base of an eyelash or on, inside, or under the eyelid, which is the result of an acute infection of the oil glands of the eyelid. Complications of a sty can be blepharitis and chalazion.
A subconjunctival hemorrhage is bleeding under the eye's conjunctiva. There is usually no obvious cause for a subconjunctival hemorrhage, but it may be caused by sneezing, vomiting, infections on the outside of the eye, coughing, and clotting disorders. Symptoms and signs include blood in the white of the eye and a sense of fullness under the lid. No treatment is needed.
Eye allergy (or allergic eye disease) are typically associated with hay fever and atopic dermatitis. Medications and cosmetics may cause eye allergies. Allergic eye conditions include allergic conjunctivitis, conjunctivitis with atopic dermatitis, vernal keratoconjunctivitis, and giant papillary conjunctivitis. Dry eye, tear-duct obstruction, and conjunctivitis due to infection are frequently confused with eye allergies. Eye allergies may be treated with topical antihistamines, decongestants, topical mast-cell stabilizers, topical antiinflammatory drugs, systemic medications, and allergy shots.
Blepharitis is inflammation of the eyelids. Acne rosacea, Staphylococcal bacteria, allergies, sensitivities to makeup or contact lens solutions, head lice, or other conditions may cause blepharitis. Symptoms and signs include itchy eyelids, burning sensation in the eyes, crusting of the eyelids, light sensitivity, red, swollen eyelids, loss of eyelashes, and dandruff of the lashes and eyebrows. Proper eyelid hygiene and a regular cleaning routine controls blepharitis.
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.
Astigmatism is a common eye condition that's easily corrected by eyeglasses, contact lenses, or surgery. Symptoms of astigmatism are headaches, fatigue, eyestrain and blurred vision.
A corneal ulcer is an open sore on the cornea. Infection is a common cause of corneal ulcer. Symptoms and signs of corneal ulcer include redness, eye pain and discharge, blurred vision, photophobia, and a gray or white spot on the cornea. Treatment depends upon the cause of the corneal ulcer.
Blindness is the state of being sightless. Causes of blindness include macular degeneration, stroke, cataract, glaucoma, infection and trauma. Symptoms and signs may include eye pain, eye discharge, or the cornea or pupil turning white. Treatment of blindness depends upon the cause of the blindness.
Myopia, or nearsightedness, makes it difficult to focus on objects that are far away. The condition runs in families and occurs because light focuses in front of the retina, instead of directly on it. Headaches, eye strain, and fatigue are symptoms of myopia. The condition is diagnosed by having an eye exam and can be treated by wearing glasses or contact lenses or by having refractive surgery.
Presbyopia is the age-related loss of the ability to focus on objects that are close up. The condition generally affects people over 45 years of age and causes blurred vision, headaches, and the need to hold reading material at arm's length. Presbyopia cannot be cured. Prescription contact lenses and glasses can help those who have presbyopia to see more clearly.
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