If you are a contact lens wearer who is reaching the age of forty you should probably be asking your eye care practitioner about potential contact lens options for the correction of presbyopia. Don’t worry – we are not talking about a disease but rather the natural outcome of a lifetime of accommodative visual work performed by our eyes natural crystalline lens and the muscles that assist it in that function. During the course of our lives our daily visual requirements demand certain physical changes of this lens. Simply put, these changes are the thinning out (distance vision) and thickening out (near vision) of the lens. The physical force causing this change in form is brought to bear by way of ciliary muscles attached to either side of a sac containing our natural lens. The stretching and releasing of the muscle creates the varying degrees of thickness which enables us to see near and distant objects, as well as objects in between at various focal lengths.
This seamless magic of accommodation eventually tires out the ciliary muscles just as experienced with other muscles of the body with age. The natural lens also undergoes changes with age, changes that affect its density and opacity – all this being a direct result of a natural aging process at its molecular level. The ever-tiring muscles and the changing composition of the lens make the process of accommodation more challenging with time. The net result, from a practical standpoint, is that the decrease in accommodative power translates into a greater difficulty to focus on close objects, which includes reading. In fact you may have experienced the symptoms to some degree already. If you find yourself holding reading materials at arm’s length because reading as you knew it before is simply impossible you have begun to experience presbyopia. Moreover, pretending that presbyopia doesn’t exist and insisting on reading at a closer distance can lead to eye fatigue and even headaches.
The good news is that you are not alone. There are approximately 70 million Presbyopes in America today. The majority of these Presbyopes are in the 40+ age group. If you have been a long-time contact lens wearer and find yourself concerned about what to do to correct for presbyopia – there now are good options to consider.
Instead of further developing bifocal lens designs first introduced in the 1980’s, a couple of manufacturers have launched new multifocal lens designs. The basic difference between the two is that the classic bifocal lens design was used to provide distance and near vision but not necessarily anything in between to any satisfactory degree. Ophthalmic lens versions of this design have been marketed for decades and are illustrated by lenses that have a line or a crescent shaped portion somewhere in the lower segment of the lens. Stabilizing contact lenses produced with such a design was challenging. Physical forces within the eye, including blinking and tearing, resulted in contact lens rotation as well as up and down movement with blinking.
Progressive bifocal ophthalmic lenses normally installed in glasses inspired the multifocal contact lens solution. A couple of leading contact lens manufacturers developed relatively easy to fit multifocal lenses capable of providing visual correction throughout a series of focal lengths which basically results in a seamless flow of vision from near to distance vision. Unlike the bifocal lens designs of the past, these new multifocal lenses place the various corrective powers within a series of concentric circles existing in a specified optical zone area within the lens. In this case no visual interruption occurs with lens rotation. Up and down movements are usually limited in properly fitted contact lenses. So any distortion due to movement is extremely limited and almost unnoticeable.
So the thing to do is to seek the advice of your eye care practitioner so that you may find the best multifocal lens for you. Right now there are two market leaders: Bausch & Lomb and CooperVision. The former has the greater market share and is the one that has produced their lens design in a 38% lower water material called Soflens Multifocal and also in a Silicone Hydrogel version called PureVision® Multifocal [http://www.contactlensking.com/purevisionmultifocal.aspx]. Silicone Hydrogel materials deliver at least 6 times more oxygen to the cornea and tend to dehydrate less than the more conventional materials such as the Soflens Multifocal option. CooperVision produces the Proclear® Multifocal lens manufactured of a special dehydration resistant material that provides a comfortable all-day wear. The additional benefit to the CooperVision product is that it is also available in a version that corrects for astigmatism. Both manufacturers produce their products in a disposable lens format, each prescribed for bi-weekly or monthly replacement, depending on the eye care practitioner’s evaluation.
As you can see you do have options. Visit your eye care practitioner to learn which lens is best for you.