CONTACT LENSES

 

There are Nearly 75 million contact lens wearers in the world. 

About half of them live in the United States.

If contact lenses are to replace glasses, then they need to be extremely comfortable as well as provide excellent vision with little or no adverse effects.  Otherwise, what would be the point?  Patient criteria must be met in order to have an ideal contact lens candidate.   Generally, the following considerations are taken into account when determining if someone is a good candidate for contact lenses.

            1.  Eyelids:   

                     - If lids are tight, they may cause rotational force on lens

                     - If lids are retracted, this may cause lid impact
                     - If the patient is experiencing Ptosis (drooping of the eyelid):
                       drooping lid may not move the lens sufficiently                                        
          2.  Blinking patterns:

                     -tear film must be good and general health of the eye and

                      cornea.  If the eyes are too dry, then wearing contact lenses
                      May become difficult unless you start to administer eye drops
                      frequently.

3.  Safety is very important in fitting contact lenses.  There are many occupations which will rule out the wearing of contact lenses such as:

           Welders, miners, construction workers, jobs that involve
            sandblasting  or drilling

4.  Infection--the cornea may be infected due to the environment emitting: radiation, dust, vapors, for fumes.  Profession such as plumbers, auto mechanics, furniture builder--cannot get their hands perfectly clean—this can contaminate lenses

5.  There is a saying in the opticianry profession --PATIENT SELECTION:  AVOID THE 5 D’S

           The dirty, drunk, diseased, disabled and the dumb

 GENERAL GUIDELINES FOR FITTING CONTACT LENSES

For Rigid Gas Permeable (RGP) lenses—usually fit either on K, flatter than K or steeper than K (Keratometry readings—we will get into this later)

For Soft lenses—ideally fit to obtain the three-point touch.  For the three-point touch, the contact lens must come in contact with the corneal apex and the periphery on both sides of the cornea.

Soft contact lenses are usually fit larger than the corneal diameter for centration and stability.  A well-fit contact lens should show:  good centration, adequate movement, stable vision, clear undistorted keratometry mires.

A contact lens fit may be too loose or too tight—may change the lens parameters for a better fit i.e.  change the diameter or radius of contact lens
(If you increase diameter, lens will be tighter)
(If you decrease radius, lens will be tighter)

ASTIGMATIC EYES

For Astigmatic eyes, they require special toric lenses. 

If an astigmatic eye is fit with normal soft lenses, the patient will experience fluctuating or blurred vision

WEARING SCHEDULE FOR SOFT

If new to wearing soft lenses, you must have a ‘break-in’ period in which your eyes need to adjust to the contact lens.  The first day of wear, it is recommended to keep them on for 4 hours.  The wearing time may be increased by 2 hours daily until all-day wearing schedule is achieved.  The patient should return to the office for follow-up in 1 week, then 2-week intervals for three visits.   During these visits, lenses should be evaluated and lens changes made if needed.

--keratometer:  follow-up keratometry—pay attention to mires and to changes to radius of curvature

COMPLIANCE

Deposit formation on lens surface is affected by:

          -lens material
          -the wearing time
          -lens care system used

A build up of protein, lipids, and minerals on the lens may result in the following:

       -decreased vision, red and irritated eye, a change in the fit of the lens, a decrease in oxygen transmission of the lens.  Studies have shown that surface deposits extend over 50% of a hydrogel lens within 5 minutes after the lens is worn and over 90% of the lens after 8 hours.

The protein build up on the lens may cause GPC (Giant Papillary Conjunctivitis)—corneal and bulbar conjunctival inflammation.  Methods of Cleaning:  Surfactant cleaners, Oxidative Agents, Enzyme cleaners, Ultrasound, disinfection

 

DISPOSABLE CONTACT LENSES

Disposable contact lenses are a good choice for the sake of health.  As they are being replaced daily, there is less chance of protein and bacteria build up.

A patient will save on lens cleaners and solutions as well since, contact lenses are discarded after use