With the advancement of technology, contact lenses are available with sophisticated designs, with better oxygen permeability and better comfort and are available for extended wear.[break]
For the first time, contact lenses were fabricated and worn in the eyes in the beginning of the 19th Century. Now it has been estimated that 125 million people use contact lenses worldwide.
A contact lens is a corrective, cosmetic or therapeutic lens usually placed on the cornea of the eye. When compared with spectacles, contact lenses are less affected by weather, do not steam up, and provide a wider field of vision. They are suitable for a number of sporting activities.
A corrective lens is designed to improve vision when there is a mismatch between the refractive power of the eye and the length of the eye leading to a refractive error. Bandage contact lens protects an injured or diseased cornea from the rubbing of blinking eyelids thereby allowing it to heal. Contact lenses that deliver drugs to the eye have also been developed. Colored contact lenses can be used by those with color deficiencies to distinguish colors better. A cosmetic contact lens is designed to change the appearance of the eye.
These lenses also may correct the vision, but some blurring or obstruction of vision may occur as a result of the color or design. Scleral lenses cover the white part of the eye (i.e. sclera) and are used as theatrical lenses, primarily in the entertainment industry, to make the eye appear confusing and arousing in appearance, most often in horror movies where lenses can make one’s eye demonic, cloudy and lifeless, or to make the pupils of the wearer appear dilated to stimulate the natural appearance of the pupils under the influence of various illicit drugs.
Contact lenses other than cosmetic variety become almost invisible when inserted in the eye. Most corrective contact lenses come with a light ‘handling-tint’ that may render the lens slightly more visible on the eye. Contact lens wearers must usually take their contact lenses out every night or every few days, depending upon the material and design.
Rigid contact lenses can provide good level of vision in people who have astigmatism and distorted corneal shapes. Due to their non-porous nature, they do not absorb chemicals or fumes. But they require a period of adaptation before full comfort is achieved. In the 1960s, soft (hydrogel) lenses were developed, which are immediately comfortable when worn. Hybrid rigid/soft lenses are also available. In 1999, Silicone hydrogel became available which have both extremely high oxygen permeability of Silicone and the comfort and clinical performance of the conventional hydrogels.
An extended-wear contact lens is designed for continuous overnight wear, typically for six or more consecutive nights. But wearers have the increased risk of corneal infections and corneal ulcers, primarily due to poor care and cleaning of the lenses, tear film instability and bacterial stagnation. Single-use (daily disposable) lenses which are disposed of each night are thinner and lighter and are most comfortable. They are best for patients with ocular allergies, for infrequent contact lens users, or for sporting activities (e.g. swimming) where losing a lens is likely. Most commonly, contact lenses are disposed of on an annual basis. Rigid contact lenses are very durable and last for several years without the need for replacement.
The prescribing of contact lenses is usually restricted to appropriately qualified optometrists (vision specialists). An optometrist typically determines an individual’s suitability for contact lenses during an eye examination. Corneal health is verified. Ocular allergies may affect a person’s ability to wear contact lenses successfully. Various measurements are needed to ensure that the contact lenses fit properly.
Before touching the contact lens or one’s eyes, it is important to thoroughly wash and rinse hands with a soap that doesn’t contain moisturizers or allergens such as fragrances. The technique for removing or inserting a contact lens varies slightly depending upon whether the lens is soft or rigid. In all cases, it requires some training and practice on the part of the user in order to overcome the instinctual hesitation against actually touching the eyeball with one’s fingertips. While daily disposable lenses require no cleaning, other types require regular cleaning and disinfecting in order to retain clear vision and prevent discomfort and infections by notorious microorganisms. Patient non-compliance is a major issue that can lead to contamination of the lens, storage case, or both.
In Nepal, contact lens practice is still in the nascent stage. Lack of awareness among the general population and lack of optometrists or trained contact-lens practioners are the major factors hindering the development of contact lens in Nepal. Consumers should be aware of the malpractice that is prevalent here and hence should visit proper contact-lens practioners and should use branded contact lenses. As the contact lens market is growing, the government should monitor for the quality and cost uniformity.
The writer is a final-year B. Optometry student at the Institute of Medicine, Tribhuvan University.
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