These are hard contact lenses made from a material that allows oxygen to pass through it to the cornea. These lenses were typically the first lens of choice in patients with high degree of astigmatism although with todays special design soft contacts we can typically use softs lenses. Since the material is rigid it can correct for the difference in curvatures of the cornea that cause astigmatism. These lenses as a general rule typically will last longer than soft contact lenses, are easier to care for (clean and disinfect) and will offer slightly better visual acuity. They are generally more difficult to fit than soft contact lenses in that the fit is more critical and the adaptation time is usually longer. They cannot be used to change someones eye color (since they are smaller than the colored part (Iris) of the eye. The lens designs can vary dependant upon the Doctors fitting philosophies and experience. A toric or bitoric lens design is usually used in patients with high degrees of astimatism in which the contact lens is made with two different curvatures.
These are pliable contact lenses made from materials that incorporate a percentace of water content in the lens (hydrated) that makes the lens soft in nature. These are typically the lens of choice in basically myopic (nearsighted) or hyperopic (farsighted) patients. The basic soft lens does not correct astigmatism so in cases of astigmatism there are toric soft lens designs that are used. The toric soft lens designs currently available are very good. As stated above a Gas Permeable lens will probably produce a slightly better visual result and stability. The soft lens designs are typically easier to adapt to than the Gas Permeable designs. Since the lens is hydrated (from 38% water content on up) disinfection and cleaning techniques are more critical.
Soft lenses are used on a daily wear usage (remove every night), flexible wear (sleep 1-2 nights) or extended wear (sleep a maximum of 6 nights). The lenses types as a general can be classifed as Traditional (one pair used approx. 1-2 years before replacing), Planned Replacement (replace very 1-3 months), or disposable (replace every 1-2 weeks or even daily). They can be used to change somones eye color . The type of lens and wearing schedule are determined by your Doctor.
The lenses come in a variety of colors if the patient desires to change their eye color. The eye color changeable soft contact lenses are now available for astigmatism in addition to the non-astigmatism corrections. Wesley Jessen has a new colored lens called Color blends which incorporates three separate steps to produce a natural looking lens. See sample below:
In presbyopia the patient has basically two different prescriptions, first is the distance prescription and second is the reading prescription. In glasses this is corrected with the use of multifocal designs. In contact lenses there are various types of Bifocal contact lenses. The most common approach to the correction of presbyopia is either reading glasses on top of the contact lenses or Monovision which involves fitting one eye (dominate) for the distance and the other for reading.
last updated 2/15/05