What to know about contact lens
Why do people wear contact lenses?
People wear contact lenses for various reasons: To correct refractive errors (poor vision that can be improved with spectacle; myopia (short-sightedness); hypermetropia (long-sightedness) and astigmatism (unequal curvature).
People with high refractive errors tolerate contact lenses better, because of some distortions they experience with high-powered spectacle lenses.
Also, some types of astigmatic errors cannot be optimally corrected with spectacles. In addition, high-powered spectacles are often heavier and less cosmetically appealing.
Some types of contact lenses can also be used to prevent worsening myopia. This is called Orthokeratology.
People also wear contact lenses for cosmetic purposes. In such a case, such people wear coloured contact lenses to alter the colour of their eyes for aesthetic reasons and also for people with unsightly scars in the eyes.
There are also medical reasons for wearing contact lenses. Tinted contact lenses can also be used for people with conditions in which the Iris (brown/black/grey circular diaphragm-like structure is partially or totally absent such as Aniridia, following trauma and in albinism to reduce glare and photophobia.
Other non-cosmetic contact lenses can as well be prescribed for pain relief, severe dry eye, promotion of wound healing, small corneal leaks, following trauma or surgery. Some eye medications can also be delivered to the eye using contact lenses. The latest is contact lens for measurement of eye pressure.
What are the types of contact lenses?
Contact lenses can be classified as follows: Based on material into hard, soft, rigid gas-permeable, hybrid contact lenses.
Based on optical design into Spherical (for long or short-sightedness), Toric (for astigmatism), Multifocal (for presbyopia). Based on wear schedule into daily disposable (disposed after one day).
Daily wear has to be removed every night, while Extended wear can be worn overnight, though usually for a maximum of two weeks.
Based on diameter into Corneal (smaller and rests on the cornea) and Scleral (larger and rests on the sclera) contact lenses.
What are the risks associated with wearing contact lenses?
These include: Infective keratitis, which is infection of the cornea. This can spread to involve the whole eyeball, and can also lead to blindness and loss of the eye.
More often than not, this results from use of inappropriate fluid/solution as storage or cleansing liquid e.g. tap water.
Unhygienic practices, such as not washing hands before insertion or removal of the contact lens, can also predispose to an infection.
There is also Toxic keratopathy, brought about due to exposure to toxic substances in the cleaning or storage solutions.
This may result into red and painful eye, and if not properly treated can lead to loss of vision. People should ensure that the right cleansing solution is used.
Then, there is Giant papillary conjunctivitis. This is allergic reaction to the presence of contact lens or lens solution. It may result in moderate/severe itching or gritty sensation (sandy sensation), and redness of the eyes.
Corneal abrasion (scratch) can occur with chipped lenses or from fingernails during insertion or removal of the contact lens. Very uncomfortable foreign body sensation pain and redness of the eye may affect vision.
Corneal warpage results from prolonged use of contact lens, and can also change the curvature of the eye. This is reversible with discontinuation of contact lens use. It can cause distortion of images.
Corneal oedema and vascularisation occurs due to poor supply of oxygen and nutrients to the cornea caused by tight contact lens and prolonged wear. The cornea swells up, can become whitish and painful with abnormal growth of blood vessels in the cornea.
Dry eyes are very uncomfortable. The situation occurs when eyes are not well lubricated by natural tears because the lens prevent adequate wetting of the cornea.
What are the signs and symptoms of contact lens problems?
Symptoms and signs of contact lens problems include, redness of the eyes, foreign body sensation, excess tearing, blurry vision, photophobia, eye discharge, pain, whitish opacity of the cornea and loss of vision.
When should medical attention be sought for contact lens problems?
Once a contact lens wearer notices any of the symptoms listed above, he/she should immediately discontinue contact lens wear and see an Ophthalmologist immediately. Preferably, he/she should take the contact lens, its container and cleaning/storage solutions along to the hospital.
Are there alternatives to contact lenses?
Alternatives to contact lenses are spectacles and Refractive surgery (Laser surgery).