Recent Posts
Connect with:
Saturday / April 13.
HomemieyecareThe Cornea Staining Matrix

The Cornea Staining Matrix

Are lens solutions enough? Or do we need to encourage our patients to get ‘hands-on’ with their lenses?

The solutions manufacturer has a tough job. On the one hand, the market wants comfort, but microbial efficacy and safety must come first.

Rub and rinse…

I’m sure all practitioners have been following the ‘rub and rinse’ issue. In November 2007, the Institute for Eye Research (IER) conducted its own regimen test to evaluate the efficacy of contact lens disinfection solutions, and in particular, to test the efficacy of the ‘rub and rinse’ regimen.1

In Regimen A, lenses were neither rubbed nor rinsed before disinfection. In Regimen B, lenses were rinsed for five seconds per lens surface before disinfection and in Regimen C, lenses were rubbed and rinsed before disinfection. Solutions tested included Complete MoisturePlus, Opti-Free Replenish, AQuify and ReNu MultiPlus. Challenge micro-organisms were the standard panel of organisms which include Pseudomonas aeruginosa, Staphylococcus aureus, Fusarium solani, Candida albicans, as well as a strain of Acanthamoeba polyphaga.

It is important that practitioners are aware of the
potential issue of corneal staining with lens/solution
combinations, and they should check to ensure the
best recommendations are made to patients.

In most cases, across four solutions and three lens types, the addition of the ‘rub and rinse’ step significantly reduced the microbial load on the lens. The study demonstrated that the rub and rinse step adds a significant safety margin (up to 100,000x).

In June 2007, Mark Willcox from the Institute presented this work to the 111th meeting of the U.S. Food and Drug Administration (FDA) Ophthalmic Devices Panel of the Medical Devices Advisory Committee. He considered that the ‘rub and rinse’ combination is superior to ‘no-rub’ in disinfecting contact lenses and should be recommended to all wearers. The Panel heard similar studies and recommendations from many presenters. The FDA has now recommended the rub and rinse technique as best practice in contact lens care.

Benefits of Peroxide

While ‘rub and rinse’ is the primary recommendation, one alternative is the use of a solution with hydrogen peroxide, providing strong disinfection without preservative. Peroxide also offers another benefit, as it is currently the only solution to virtually eliminate solution-induced corneal staining with silicone hydrogel lenses.2

Corneal Staining

Corneal staining is an important inpractice tool for evaluating the state of the corneal epithelium. However, the introduction of silicone hydrogel contact lenses had an unexpected ocular consequence. Around 2004, corneal staining occurring in response to particular combinations of silicone hydrogel materials and solutions became a concern.

Unfortunately, it was found that the lens/solution interactions were not predictable from the lens, preservative type and concentration. The chemistry in each of lens materials, solutions and tears is complex, and the result of the combination of these is impossible to predict with certainty. Understanding which combinations may cause problems is important for practitioners in providing appropriate advice to their patients and the only way to develop this understanding is by testing each likely combination.

The Institute for Eye Research Matrix Study examined five leading brands of lenses used in combination with four brands of disinfecting solutions. The study was first published with four brands in September 20072, and updated in March 20083, with the addition of Night and Day lenses.

The initial work involved 640 experienced and new contact lens wearers in 16 groups of 40. They used each type of silicone hydrogel lenses bilaterally in conjunction with each type of multipurpose solution and were monitored over three months.

The Night and Day studies were completed with 40 patients in each of the four lens-solution combinations. Clinicians indicated the presence of solution-induced corneal staining or ‘SICS’. The IER Matrix Study defined SICS (in order to avoid confusion with other corneal staining phenomena) as “punctate fluorescein staining associated with lens care regime affecting at least four of five areas of the cornea, presenting as either diffuse, i.e. spread over the cornea, or as a peripheral/annular band around the limbus”.3

The studies reveal that each solutionsilicon hydrogel lens combination presents a different situation; some causing staining in a high percentage of wearers, others causing very low staining, with hydrogen peroxide causing almost none (Table 1).

It is important that practitioners are aware of the potential issue of corneal staining with lens/solution combinations and they should check to ensure the best recommendations are made to patients.

In the updated IER paper Nicole Carnt comments: “While minimal corneal staining often occurs in contact lens wear, moderate amounts of controllable staining should always be avoided, especially given the links that have been established between SICS and low grade corneal inflammation and discomfort.”

Solutions at the Summit

We come back again to the ‘Guidelines for the Safe and Effective Use of Contact Lenses’ which were developed at the 2007 Contact Lens Care Summit in Singapore.

The delegates provided seven recommendations in Contact Lens Hygiene Fundamentals that dealt with solutions. These recommendations are:

1. Contact lens disinfection systems solutions should be effective against bacteria, fungi, viruses and amoebae.

2. Every time a contact lens is handled, it should be with clean, washed and dried hands.

3. Any time a contact lens is removed from the eye, it should be properly disinfected.

4. Safety is enhanced significantly by rubbing and rinsing contact lenses both prior to and following storage. 5. Patients should never ‘top up’, i.e. add additional solution to the solution already in the case.

6. When contact lenses have been stored for more than seven days, regardless of whether peroxide or multipurpose solutions are used, lenses should be effectively re-disinfected before reuse.

7. Hydrogen peroxide is considered to be a very safe solution. However, patients using hydrogen peroxide for disinfection should be advised to use unit dose sterile saline or other sterile saline based solutions, for rinsing their lenses prior to lens insertion. We hope that all practitioners follow these and keep their patients up to date with the latest recommendations.

Professor Brien A Holden, B.App.Sc. PhD. DSc. OAM, is CEO and Director of the Institute for Eye Research, CEO of the Vision Cooperative Research Centre, founder and Director of the Cornea and Contact Lens Research Unit at the School of Optometry and Vision Science, University of New South Wales, and was Director of the Cooperative Research Centre for Eye Research and Technology.
References 1. Zhu H, Bandara M, Kumar A, Masoudi S, Wu D, Willcox MDP. Contribution of regimen steps to efficacy of multipurpose solutions used to disinfect silicone hydrogel contact lenses. XVIII International Congress of Eye Research, Beijing Sep 24-29, 2008
2. Carnt NA, Willcox MDP, Evans VE, Naduvilath TJ, Tilia D, Papas EB, Sweeney DF, Holden BA. Corneal staining with various contact lens solutions – Silicone hydrogel lens combinations and significance: The IER Matrix Study. Contact Lens Spectrum, September, 2007
3. Carnt NA, Evans VE, Holden BA, Naduvilath TJ, Tilia D, Papas EB, Willcox MDP. The IER Matrix Study update with Night and Day. Contact Lens Spectrum, March, 2008