To have an idea of different types of contact lenses, read on:
- Contact lenses can be classified by their material characteristics – soft silicon hydrogel lenses and rigid lens (made of flexible plastic).
- Lenses are of different types by their wear schedule – Daily disposable, monthly and extended wear lens.
- They can be categorized by their life span – daily disposable, monthly disposable, etc.
- By the visual problem, they correct – Spherical, toric or astigmatic, or bifocal.
When it comes to understanding what type of lenses are used in contact lenses, the answer has a very broad scope. However, by ‘type’ we generally tend to mean, what is the material that is used to make contact lenses and how this lens can be categorized according to the different types of material used throughout the years.
In earlier times, rigid materials were used in contacts that did not support sufficient oxygen permeability to the eyes. This caused a lot of exertion and exhaustion to the eyes and they could not be worn for long hours at a stretch. However, research in ocular science gave way to newer findings and advanced materials were developed for making softer contact lenses.
1. Soft Contacts
Soft contacts have high oxygen permeability as compared to their predecessors. It rests on the iris of the eye with the edges resting on the sclera (the white part of the eye). Contact lens users swear by soft contact lenses as they provide more comfort than rigid contacts. Nowadays, soft contact lenses also come as colored contact lenses that can be used purely for cosmetic purposes. You can change the color of the iris of your eyes to whatever color you fancy with soft colored contact lenses.
Soft contact lenses with prescription come in different varieties – daily, weekly biweekly, monthly or extended wear lenses.
2. Rigid Gas Permeable (RGP)
Rigid gas permeable contact lenses are named after the type of material that goes into making them. The RGP lens is smaller than soft lenses. However, due to their rigidity, hardly any oxygen permeability is possible. Thus, users take a longer time to adjust to these types of contacts. The RGP lenses rest over the pupil and the edges rest on the iris of the eye. Some optometrists believe that, though people take longer to get adjusted to RGP lenses, they are healthier and more durable than a soft lens.
3. Silicone hydrogel
Silicone hydrogel contact lenses are the result of mixing hydrophobic silicone with hydrophilic PHEMA. This material provides an improved level of comfort and has a high oxygen permeability.
Silicon hydrogel lenses differ from conventional hydrogel lenses in their higher oxygen permeability. However, the hydrogel contact lens has high water content (with low hydrogels having12-30% water content while moderate hydrogels range has 40-70% water; high hydrogels have 90-99.5% water content while superabsorbent hydrogels have more than 99.5% water content!)
4. Intraocular Contacts
These lenses, made of inflexible material known as PMMA or Polymethylmethacrylate and are planted in the eye. With time, scientists have researched to make this intraocular lense softer and healthier for your eyes. Nowadays, intraocular lenses are made of soft foldable materials like silicone or acrylic and are easily implanted in the eyes.
5. Acrylic Contacts
Acrylic contacts are usually expensive though they are not very popular among the users. This new-age contact lens may have advanced square-edge design, non-glare edge design or blue light filtering for UV rays to combat vision problems.
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