Contact lens solutions will soon be required to have two new additions to their labeling. Although most manufacturers no longer label solutions “no rub” the F.D.A. will require rubbing lenses as part of disinfecting cycle on labeling for all multipurpose contact lens solutions. The other change will be to add a discard after opening date in addition to the expiration date already required..
Two separate incidences of outbreaks of serious eye infections the last several years have prompted theses changes. While the evidence points to non compliance with manufacturer recommendations of product use, it is felt that a higher error of margin needs to be built into the solutions regimens.
Testing of solutions is not as simple as you would think at first glance. Historically, the FDA has required two different methods of testing. Simplifying the process it can be viewed as primarily two different tests. The first is adding bacteria and fungal microorganisms to samples of the solutions and after the manufacturers specified time period for disinfecting they must reduce the number of bacteria by 99.9% and the fungi by 90%. The second method of testing involves soaking the contact lenses in the microorganisms and then being disinfected as the manufacturer recommends. The lenses are then used to grow the bacteria and fungus on a special type of growth media. After a specific time period the number of live organisms are counted. These are referred to as colony forming units and less than 10 gives a passing grade. Tests must also be done to show that the solutions are not toxic or irritating to the eyes.
Bacteria chosen for testing in the past include Pseudomonas aerginosa, Serratia marcescens, and Staphylococcus aureus. The first two are in a category called gram negative bacteria and the third is gram positive. Bacteria can be classified gram negative or positive by how their cell wall retains dye, and gram negative bacteria tend to be responsible for more serious infections. While most tropical and semi tropical climates show gram negative bacteria and fungal eye infections are more prevalent, temperate northern climates tend to have more gram positive bacterial infections associated with contact lens related eye infections. Pseudomonas is present almost everywhere in humid climates. While these three bacteria do cause a high incidence of contact lens related eye infections, there are numerous other bacteria that cause infections. While fungal eye infections are rare, Candida albicans and Fusarium solani are the two tested for. One of the recent outbreaks was caused by Fusarium.
We can’t test for every possible microorganism, the time and cost would be prohibitive. This is the best mix determined in the past. With Acanthamoeba being the organism resulting in the other recent outbreak it may be added to testing procedures in the future.
Reducing microorganisms to a level that the eyes immune system can handle is one assumption for test requirements. Bacteria are present at low levels at any given time in most peoples eyes. Many variables are left out of the testing protocols. The age of a lens may effect how well bacteria adhere. The condition of the contact lenses case, the wearers personal hygiene and individual variation in immune response, all factor in bacterial growth. The therapeutic dose of a disinfecting agent shows individual variation. Some bacteria mutate and become resistant to disinfectants, and also can develop coatings on the lens to render the solutions less effective. Some microorganisms may become more common, virulent, or our daily exposure to them may increase for various reasons. For example, hot tubs have increased our exposure to acanthamoeba. The use of antimicrobial hand soaps may result in mutations to bacteria that were not a problem for the eyes in the past. Incomplete use and under dosing of antibiotic treatment may result in the same problem. The microorganisms used for testing are standardized and not necessarily representative of the current existing strain of that microorganism. Even the culture media used is standardized and different from the eye contact lens environment presented for the bacteria to develop in.
Rubbing a contact lens helps remove surface films and debris and allows the disinfecting solutions to work better. In the imperfect world of solution testing it is expected to help reduce eye infections.
The second change is more questionable. Solutions do have a lifespan when the disinfecting action drops below an effective level. They also could remain unopened until close to this date and then be used, resulting in usage past the time the solution was effective. Alternatively, once opened, the solution is subject to environmental contamination from bacteria that could exceed its capacity over time. The problem is putting two different dates on a bottle can be confusing. Proper wording can help, but one glance in any refrigerator will likely reveal we all aren’t very good at the two date dilemma. Time will tell, but short expiration dates on all solutions might be a better approach. Best of all would be a solution that changes into a horrible color after it has been open for a month. Of course with teenagers, that unfortunately might be an incentive to continue using it.
Contact lens solutions will soon be required to have two new additions to their labeling. Although most manufacturers no longer label multipurpose solutions “no rub” the F.D.A. will soon require adding a rubbing step to the care instructions. The other change will be to add a discard after opening date in addition to the expiration date for multipurpose contact lens solutions.
Two separate incidences of outbreaks of serious eye infections the last several years have prompted theses changes. While the evidence points to non compliance with manufacturer recommendations of product use as the cause, it is felt that a higher error of margin needs to be built into the solutions.
Testing of solutions is not as simple as you would think, with multiple requirements specified by the Food and Drug Administration. Simplifying the process it can be viewed as primarily two different tests. The first is adding bacteria and fungal microorganisms to samples of the solutions and after the manufacturers specified time period they must reduce the number of bacteria by 99.9% and the fungi by 90%. The second method of testing involves soaking the contact lenses in the microorganisms and then being disinfected as the manufacturer recommends. The lenses are then used to grow the bacteria and fungus on a special type of growth media. After a specific time period the number of live organisms are counted. These are referred to as colony forming units and less than 10 gives a passing grade. Tests must also be done to show that the solutions are not toxic or irritating to the eyes.
Bacteria chosen for testing in the past include Pseudomonas aerginosa, Serratia marcescens, and Staphylococcus aureus. The first two are in a category called gram negative bacteria and the third is gram positive. While most tropical and semi tropical climates show gram negative bacteria and fungal infections are more prevalent, temperate northern climates tend to have more gram positive bacterial infections. Pseudomonas is present almost everywhere in humid climates. While these three bacteria do cause a high incidence of contact lens related eye infections, there are numerous other bacteria that cause infections. While fungal eye infections are rare, Candida albicans and Fusarium solani are the two tested for. One of the recent outbreaks was caused by Fusarium.
We can’t test for every possible microorganism, the time and cost would be prohibitive. This is the best mix determined in the past. With Acanthamoeba being the organism resulting in the other recent outbreak it may be added in the future.
Reducing organisms to a level that the bodies immune system can handle is one assumption for test requirements. Many variables are left out. The age of a lens may effect how well bacteria adhere. The condition of the contact lenses case, the wearers personal hygiene, individual; variation in immune response, all factor in. The therapeutic dose of a disinfecting agent shows individual variation. Some bacteria mutate and become resistant to disinfectants and also can develop coatings on the lens to render the solutions less effective. Some microorganisms may become more common, virulent, or our daily exposure to them may increase for various reasons. This is probably the case with acanthamoeba. The use of antimicrobial hand soaps may result in mutations to bacteria that were not a problem for the eyes in the past. Incomplete use and under dosing of antibiotic treatment may result in the same problem. The microorganisms used for testing are standardized and not necessarily representative of the current existing strain of that microorganism. Even the culture media used is standardized and different from the environment the eye contact lens environment presents for the bacteria to grow in.
Rubbing a contact lens help remove surface films and debris that allow a the disinfecting solutions to work better. In the imperfect world of solution testing it is expected to help reduce eye infections.
The second change is more questionable to me. Solutions do have a lifespan when the disinfecting action drops below an effective level. They also could remain unopened until close to this date and then be used, resulting in usage past the time the solution was effective. Alternatively, once opened, the solution is subject to environmental contamination from bacteria that could exceed its capacity over time. The problem is putting two different dates on a bottle is confusing. Proper wording can help, but one glance in any refrigerator will likely reveal we all aren’t very good at the two date dilemma. Time will tell, but short expiration dates on all solutions might be a better solution (pardon the pun). Best of all would be a solution that changes into a horrible color after it has been open a month. Of course with teenagers, that unfortunately might be an incentive.