Firm or rigid gas-permeable lenses (sometimes referred to as hard lenses) have improved over time right along with soft contact lenses.  In fact, they are a very viable alternative to soft contacts.  Firm lenses provide better vision, are easier to maintain and can last for years making them more cost effective.  The occurrence of eye infections and other complications to the eye among firm lens wearer's is much lower than with soft contact lens wearer's making them safer to wear.  The one disadvantage of firm lenses is that they take longer to adapt to.  Whereas it might take minutes or days for the eyelids to adapt to the presence of a soft contact, it may take weeks to adapt to a firm lens.  But once a patient gets through the adaptation period, rigid lenses  are as comfortable as soft contact lenses.

A note of caution is in order regarding the fitting and manufacture of firm contact lenses.   An experienced clinician is more important when fitting these lenses.  Equally important is the need for a well manufactured lens. Soft contacts are mass produced in a limited number of parameters.  Firm lenses, on the other hand, are custom made and can encompass an infinite number of parameters.  And every parameter of the lens should be specified by the doctor including the material from which the lens is made.  Kirkland Vision uses a laboratory which consistently produces lenses to Dr. Peters strict quality standards.

There was a time when people wore their soft contacts for as long as they could, for years perhaps.  This lead to severe consequences.  Soft contact lenses are porous.  Therefore they collect and absorb impurities over time, even when properly cleaned.  The impurities clog a lens, preventing the normal flow of oxygen to the cornea.  These impurities also irritate the cornea and the internal lining of the eyelids which leads to a sensitivity reaction to contact lens wear.  These are problems rarely seen today thanks to the popularity of disposable lenses.

Most contacts prescribed today are classified as disposable or time replacement.  The industry classifies lenses that are thrown away every day or every two weeks as "disposable".  Lenses which are thrown away or replaced monthly or quarterly are termed "time replacement".  Generally the more often a lens is replaced the better.  The ultimate disposable is the lens that is worn only once.  This provides the additional benefit of doing away with expensive and time consuming disinfection proceedures which many people fail to perform properly.

For the most part, contact lenses are powered to put the eye in focus for infinity (twenty feet and beyond).  The eye itself takes care of closer viewing distances through the act of focusing.  The focusing mechanism of the eye is located just behind the iris.  It consists of a flexible lens which is controlled by muscle tissue attached around the periphery or circumference of the lens.  As we age, the lens looses its flexibility, making it increasingly difficult for the muscles to change its shape. This progressive condition is called presbyopia and it's affect is to make focusing on near objects or fine print increasingly difficult.  We first notice this to be a problem around the age of forty. This is when presbyopia has progressed to a point where it is effecting our normal reading distance.  For most people this is around 16 inches.  The solution is to have lenses with more than one focal point.  As one might imagine, it is technologically challenging to get more than one power into an area the size of a pupil.  Nevertheless,  there are many new bifocal contact lenses on the market.  The success rate for these new products remains spotty.  The most successful method for presbyopic contact lens wearer's to achieve good vision far and near is the "monovision" technique.  With this method, the patients dominant eye is corrected for infinity and the non-dominant eye is corrected for near.  And with monovision, the doctor can choose any firm, soft, extended wear, or toric lens that is available.

Any contact lens that has a correction for astigmatism embedded in the lens is called a toric contact.  A toric may be either a firm or soft design.  Astigmatism is the term given when the degree of nearsightedness or farsightedness varies as it is measured through different meridians of the eye.  Ninety percent of astigmatism occurs as a result of the front of the eye being out of round.  The other ten percent is the result of some optical component inside the eye being out of round, probably the lens.  Astigmatism causes light to focus at an infinite number of points instead of one clear point of focus.  The result is blurred distorted vision.  Since a spherical soft contact conforms to the eye, it does nothing to correct astigmatism.  Therefore if a soft lens is used to correct astigmatism, there must be a correction for astigmatism in the lens.  Here is the problem with this approach: A correction for astigmatism must be aligned at a precise axis of rotation to do the job.  If this correction is rotated out of position the result is blurred vision.  Therefore toric lenses are designed to minimize rotation.  The most common technique for this is called prism ballasting, or adding weight or thickness to the bottom of the lens.  But the act of blinking has a rotational effect on contact lenses.  Therefore soft torics may not precicely correct astigmatism.  And because torics are inherently thicker than sperical soft contacts, there is added potential for too much oxygen cut-off to the cornea.  A more direct and precise method for correcting astigmatism is to use a simple spherical firm contact lens.  There is no correction for astigmatism in this lens, so it can rotate all it want's without affecting vision.  What corrects the astigmatism is the tear layer that forms between the lens and the cornea.  So even if the lens rotates, the tear layer remains constant.  The result is consistently clear, precisely corrected vision.  This does not hold true, however, for that ten percent of the the people with astigmatism that have internal astigmatism.  A soft toric is probably the best option for people that fall into this category. 

Any contact, whether it be soft or firm, which is not approved for overnight (extended) wear is classified as a daily wear lens.  Many people wear extended wear lenses on a daily wear basis, usually for the purpose of enhancing oxygen flow to the cornea.  But daily wear lenses are often more suitable for people with comfort related problems such as dry eye.

These lenses are approved for overnight wear.  The Focus Night and Day lenses made by Ciba, for example, are approved by the FDA for up to 30 days of continuous wear without removal from the eye.  But this is not true for everyone.  The actual length of time an individual can safely wear an extended wear lens can only be determined by clinical trial.  There are also rigid oxygen permeable lens materials approved for extended wear.  Those patients who want to sleep in their lenses require a clinical trial to insure it can be done safely.