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YOUR GUIDE TO CONTACT LENSES
Everything you need to know about the function and how to use your contact lenses properly
Functions of Contact Lenses
Prescription contact lenses
Corrective contact lenses are designed to improve vision. Conditions correctable with contact lenses are myopia (shortsightedness), hypermetropia (farsightedness), astigmatism, and presbyopia.
Cosmetic contact lenses
A cosmetic contact lens is designed to change the appearance of the eye. These lenses are available with or without prescription and carry the same risk of complications as any other contact lens. This is why even zero-powered lenses are classified as medical devices and a contact lens examination is essential before first use.
Therapeutic contact lenses
Contact lenses may be used in the management and treatment of various disorders of the eye. For example, a bandage contact lens is used to prevent the eyelid from rubbing against an injured or diseased cornea.
Wearing Schedule
Daily Wear lenses are designed to be removed before sleeping.
Extended Wear lenses can be worn overnight, usually for 6 or more nights. These lenses can be worn for long periods of time because of their high oxygen permeability to the cornea, which allows the eye to remain healthy even when the eyelid is closed. However, Extended lens wearers may have an increased risk for corneal infections and corneal ulcers, primarily due to poor care and cleaning of the lenses, tear film instability, and bacterial stagnation.
Contact Lens materials
Hard lenses are made from a rigid plastic material called PMMA. Their main disadvantage is that no oxygen is transmitted through the lens to the cornea.
RGP (Rigid Gas Permeable) lenses started development during the 1980s. Their rigid structure and high oxygen transmission make them ideal for higher prescriptions and patients with keratoconus. In addition, RGP lenses are not hydrophilic and do not absorb vapours or liquids, making them suitable for use in many industrial environments.
Soft lenses are made from gel-like, water-containing plastics. Whilst rigid lenses require a period of adaptation, soft lenses are immediately comfortable.
Replacement Schedule
Daily disposable lenses – Discard after a single day of wear.
Shorter replacement cycle lenses are commonly thinner and lighter, due to lower requirements for durability against wear and tear, and may be the most comfortable in their respective class and generation. These may be best for patients with ocular allergies or other conditions because they limit deposits of antigens and protein, and are considered the healthiest wear schedule due to the most frequent replacement. Single-use lenses are also useful for people who use contacts infrequently, or for purposes (e.g., swimming or other sporting activities) where losing a lens is likely.
Disposable lenses – Discard every two to four weeks as prescribed by your practitioner.
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Frequent replacement lenses – Discard monthly or quarterly as prescribed by your practitioner.
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Traditional (reusable) lenses – Discard every six months or longer as prescribed by your practitioner.
Do you need contact lenses?
Contact Lens Designs
Many lens designs are available to correct various types of vision problems:
Spherical contact lenses are prescribed to correct myopia (shortsightedness) or hyperopia (farsightedness).
Toric contact lenses are used to correct astigmatism.
Multifocal contact lenses contain different zones for near and far vision to correct presbyopia.
Contact Lens Wear and Care
Cleaning and disinfecting contact lenses are usually carried out by storing them in multipurpose or preservative-free hydrogen peroxide solutions.
Daily disposable contact lenses do not need cleaning or disinfecting. They are stored in sterile containers and discarded after use.
Which Contact Lens is right for you?
Lenses are available in a multitude of combinations of diameter, curvature, and material. Your Optometrist will judge the best lens for you based on good vision, fit, comfort, and wearing schedule. He/she will also ensure that the final lenses prescribed will not interfere with the physiology of the eye.
Contact Lens Problems
People react differently to various lens materials and cleaning solutions. In most cases, if a problem develops, a change in lens type, material, or cleaning solution is all that is needed to provide comfort, good vision, and healthy eyes.
If you experience any discomfort, remove your lenses and consult your Optometrist.