Types of Contact Lenses
Vision Correcting Contact Lenses
These contacts are designed to correct a person’s vision. These conditions are myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia. Orthokeratology is a process where hard types of contact are worn at night to flatten the cornea for the treatment of myopia. The person can then see at distance during the day. This treatment has not been accepted by many eye doctors.
Therapeutic Contact Lenses
These are soft contact lenses used to treat certain medical eye conditions usually involving the cornea and are commonly called bandage contact lenses. They have been used to treat corneal abrasions, after a variety of corneal operations, recurrent corneal erosions, dry eyes, corneal damage from loss of nerve innervations to the cornea, and a variety of corneal surface dystrophies.
Cosmetic Contact Lenses
Contacts for Damaged or Abnormal Eyes
There are contact lenses designed to change the appearance of the eye. Some of these lenses are designed to match a person’s eyes as one has been damaged or abnormal and the lens is made to match the appearance of the normal eye.
Contacts to Change the Color of the Eye
There many brands of contacts designed to change the color of the eye.
Contacts to Change the Appearance of the Eye
There contacts designed to change the look of the eye such as ones used in movies. There are also these types of contacts sold by non professional stores that have caused problems as the people wearing them as they have not had any training on how to put the lenses in and out. Also, they have not been trained to properly care for the lenses.
Materials Used to Make Contact Lenses
Polymethyl Methacrylate (PMMA)
PMMA was used for many years to make hard type contact lenses. It is not used today as it had poor oxygen permeability.
Rigid Gas Permeable (RGP)
RGP lenses are hard type lenses that have excellent gas permeability. These types of lenses provide excellent vision and are used in eye with astigmatism and keratoconus.
Hydrogel or Silicone Hydrogel Lenses (Soft Contact Lenses)
These lenses provide almost instant comfort versus RGP that require a break in period to be comfortable.
Contact Lens Designs
Spherical Contact Lenses
Spherical contacts lenses are a single power correcting lens used for myopia (nearsightedness), hyperopia (farsightedness), or monovision in people with presbyopia (inability of the eye to focus up close beginning when people reach their forties).
Toric Contact Lenses
Toric contacts are designed to correct spherical conditions as well as stigmatism of the eye. These lenses are designed to sit on the eye in a specific orientation to allow the astigmatism correction to be aligned in the correct axis.
Bifocal Contact Lenses
Bifocal contacts are designed to correct the distance vision abnormality as well as provide up close or near vision. These lenses are used for people with presbyopia.
Contacts Designed for Daily or Extended Wear
Daily Wear Contacts
Daily wear contacts are removed each day. The lenses are cleaned and disinfected before use the next day.
Extended Wear Contacts
Extended wear contacts can be left in overnight. Depending on the lenses , it may be worn as long as thirty days before removal.
Replacement Schedules for Different Contact Lenses
Discard lenses every 2 weeks
Daily use lenses are discarded every day
Regular lenses can be used for 6 months to a year before discarding
Contact Lens Care
Multipurpose Cleaning Solutions
These solutions provide cleaning, disinfecting, and storing of contact lenses.
Hydrogen Peroxide Cleaning Solutions
These solutions disinfect the lenses using hydrogen peroxide. The peroxide changes to water and oxygen. These solutions are good for people who become allergic to the preservatives in the multipurpose solutions.