Although contact lenses all work on the same principle they come in many different types. The contact lenses that are prescribed for you depend on what type of vision correction you require, your lifestyle, and personal preference.
Contact Lens Materials
Soft lenses are the most commonly prescribed lenses. Made of soft and flexible plastics they are comfortable, convenient and easy to adapt to.
Rigid Gas-Permeable or RGP lenses are made of a harder, less flexible material than soft lenses but still allow oxygen transmission to the eye.
Hybrid lenses are the newest form of contact lens combining a soft material “skirt” or outer edge with a RGP centre. Currently there aren’t many of these types of contact lenses available; using plastics is still a relatively new technology, remembering that only 120 years ago contact lenses were still being made of blown glass!
Spherical lenses are used to correct myopia (short-sightedness) and hyperopia (farsightedness). The curvature of the contact lens is spherical in nature and it bends light evenly in all directions.
Toric contact lenses are used to correct astigmatism. Unlike spherical lenses they do not curve evenly. Instead they bend light differently vertically and horizontally. Due to the nature of astigmatism they must be properly orientated to work effectively. One design feature is to weigh the bottom of the lens to ensure correct orientation.
Multifocal lenses are used to correct presbyopia. Presbyopia is a condition where you are farsighted but have difficulty focusing nearby and/or reading. Multifocals have multiple focal points to correct vision for both distance and reading. Similarly to toric lenses multifocals must be properly orientated to work properly.
The wearing schedule of contact lenses varies depending on the material the lens is made from. Daily contact lenses can only be worn for a day before removal. Extended and continuous wear lenses are made from materials with a much higher level of oxygen transmission and can be slept in for consecutive nights. Extended wear can typically be worn for up to 6 consecutive nights whilst some continuous wear lenses can be worn for up to 30 nights. Replacement time for contact lenses also varies, contact lenses can be disposed of after one use or kept and reused for a period of time recommended by the manufacturer.