Sitting in the exam chair Heather casually leaned on one arm, vigorously rubbed the inside corner of her right eye, and said, “My contact lenses are bothering me, Doctor.”
“What kind of contact lenses do you wear?” I asked.
“Soft.”
“Do you remove them every night?”
“Yes. I never wear them over night.”
“Are they disposable?”
“Yes.”
“How often do you actually dispose of your soft contact lenses?”
“I usually wait till they bother me,” she responded with a smile in her voice. “I really don’t have a set schedule.”
“Is that the way they were prescribed?” I asked with one raised eyebrow.
“Well, I really don’t remember what the other doctor said… two or three weeks I think. I don’t have to use nearly as many if I just wait till they cause problems. I just replaced my lenses two days ago. My eyes are just as irritated now as they were before I changed them. It really doesn’t make a difference anymore when I change them.”
I hear this same scenario at least twice a month, some months twice a week, not only from teenagers who are on tight allowances, but from college students and young parents under financial constraints which are being complicated by the current economy.
Many parents and their children cannot understand the constraints established by the eyecare industry on contact lenses. Rightfully so. Seldom are they clearly explained.
It’s difficult to understand why, just like Augmentin, there is a contact lens prescription. Has anyone ever died from a contact lenses reaction? Why shouldn’t you be able to purchase contact lenses when and where you want? If your child is having no problems, why should he dispose of them?
Even more confusing: some disposable contact lenses are exactly the same lenses which, twenty-five years ago, were worn a full year. If you think as a parent you are confused you should see the look on some of the faces of the eighteen year olds struggling financially to make it through their freshman year of college.
The evolution of contact lenses explains the recommendations made by doctors, the constraints established by law, and the problems with which we continue to struggle.
Firm Contact Lenses
The original contacts were hard lenses made out of polymethylmethacrylate or PMMA, commonly known as plexiglas. It was proven non-toxic and inert to the human body by a World War II wound when a pilot for the Royal Air Force was hit in the face by debris from the plexiglas windshield of his fighter plane. Particles of PMMA remained in his eye with no problems.
PMMA had exceptional optical qualities, and it could be molded and cut easily, but it is rarely used today because it didn’t allow the cornea, the tissue where contact lenses lie, to breathe. It was also difficult to make comfortable on the eye.
Chemists found PMMA could be altered making it air permeable. Rigid gas permeable (RGP) contact lenses came on the scene in the late 70’s. Depending on the variation, RGP’s were three to five times more oxygen permeable than soft lenses.
To the average observer RGP’s are indistinguishable from PMMA. Comfort continues to be a problem, but they are quite good at letting the cornea breathe. Although more prone to deposits than PMMA lenses, RGP wearers tend to have less inflammation and infections, better vision, and less expense than their soft lens counterparts. Exact measurements are necessary for each patient, so prescriptions are a complex must. RGP’s continue to improve. If your child is interested in contact lenses, you should not write-off rigid gas permeable contact lenses just because they require a few weeks of adaptation. Also, if you are a parent approaching the frustrating age of 40, you will find RGP’s can be nicely fabricated as a bifocal much better than soft lenses.
Soft Contact Lenses
In the mid-sixties a Czechoslovakian chemist, Otto Wichterle, discovered hydroxymethylmethacrylate (HEMA), a gel like substance that loves water thus the name hydrogel contact lenses.
Hydrogel lenses are very comfortable on the eye and require very little adaptation time. Not as easily machined as PMMA lenses, Otto, with the help of his son’s erector set, designed a way to spin cast it. With few exceptions HEMA is the base acrylic used in most of the various types and brands of soft contact lenses. Spin casting remains a common method of production.
Hydrogel lenses can be made softer by increasing their water content. So, contact lens fabricators pushed the original hydrogel material of 38% water to 79%. Unfortunately increasing the water content causes dry eyes. It sounds contradictory, but high water hydrogel selfishly robs the wearer’s eyes of natural lubrication.
Increasing the water content also increases hydrogel’s propensity to collect denatured protein which causes blurring and an autoimmune reaction called giant papillary conjunctivitis. GPC causes bumps on the lining of the eyelids, the conjunctiva, and causes problems with wearing any type of lens.
In the 80s the soft lens industry developed enzymes to pull protein from the lenses. Most contact lens saline solutions now include them. They are not a panacea.
The best way to reduce deposits is to throw away your contacts regularly. To fill the bill, disposable lenses came into common usage in the early 90s. General categories are one month, two weeks, one day. Some daily disposable lenses have even been made to slowly exude built-in lubricants – a godsend to the dry eye crowd.
By the mid-nineties, silicone, the material that forever changed the world of computers also dramatically changed the soft contact lens industry. Chemically including silicone reduces hydrogel’s water content and protein adhesion, while increasing the oxygen permeability by a factor of seven. Silicone hydrogel ( Si-hy) lenses are cutting edge and hold the greatest market share because doctors prefer the healthier alternative.
The Solution to Contact Lens Complications
Because of all of these changes in the contact lens industry your child has a myriad of alternatives and possibilities. If you insist your child use the proper material, chemicals, wear time, and disposal schedule you dramatically reduce his chances of contact lens problems. But, only your family’s eye doctor understands the proper combination: another reason for prescriptions. Usurping your doctor’s recommendations cancels all the advantages gained by years of contact lens evolution through scientific study and doctor experience.
The usual result of ignoring his recommendations is chronic inflammation which begins as nonspecific lens discomfort. It may feel as if there is dust under the lens, stinging, itching, a dry sensation or all of these. At times there may be no symptoms. Then, one day, the contacts are intolerable.
What happened?
A little protein build-up causes antibodies to develop. Solutions may add to the problem. Chemicals in some solutions, especially when the wearer is already sensitized, are another allergen. This slow indolent development of antibodies may take years. After all, the only exposure to the blood stream, where the antibodies are developing, is through the capillaries of the conjunctiva (the clear cellophane covering over the white part of the eye and the inside of the lids). Maybe your child has been practicing the same habits for four or five years, yet overnight problems begin.
How can that be?
When enough antibodies exist problems begin, posthaste. They will not quiet immediately with a new pair of contact lenses. With the Boy Scout who has an allergy to poison oak, does the reaction quiet when he drops the plant and takes a shower? In one respect it’s similar to malaria, once your child has it, he will not outlive it. You may be able to quiet the condition, but any exposure to an allergen and your child has problems again.
With early signs, though, your family eye doctor can prevent the development of the reaction, altogether. Overlooking his instructions never causes death, and only rarely causes something as severe as a sight robbing corneal ulcer: another reasons for governmental regulation. Frequently though, ignoring your doctor’s instructions takes the pleasant option of wearing contact lenses and makes it a tedious healthcare problem of ever vigilance.
If your children are being sloppy they can easily eliminate the option of contact lenses long before refractive surgery is even an option. Surgeons seldom like seeing your children before they are 22 years of age. Their only alternative? Glasses. Are you okay with that? Are your children?
Dan David, O.D.