|PHOTOS COURTESY OF STAININGGRID.COM.|
The Staining Grid can provide a quick tool to inform practitioners as to the level of biocompatibility of various multi-purpose solutions.
From our early days in our ophthalmic training we are taught to diagnose corneal staining as an indicator of injury to the corneal epithelium. To help reduce these occurrences of corneal staining, I developed the Staining Grid as an easy-to-use reference for detailed staining assessment for many lens materials.
Publications as far back as 1993 reported that various amounts of toxicity staining were associated with PHMB-containing multi-purpose solutions. With the introduction of silicone-hydrogel lens materials, the frequency of these reports increased. Most previous studies looked at toxicity staining using one or two lens materials and just a couple of solutions. It was impossible for the eyecare practitioner to make a valid comparison of the staining induced by the many lens/ solution combinations that their patients might be using.
I decided to systemically examine these lens/solutions combinations, one by one, using the same real-world methodology for each combination. After testing about 25 combinations, I realized that I needed a concise way to report these results to fellow colleagues. I came up with the color-coded Staining Grid.
There are various causes of staining. In the Staining Grid study, I focus on corneal staining as a result of a toxic response to the preservatives used in some multi-purpose solutions. Specifically when some hydrogel lens materials are soaked in some multi-purpose solutions using PHMB as its primary preservative, we often find clinically significant corneal staining soon after lens insertion.
This occurs because the lens material absorbs the preservative during the overnight soak and subsequently releases it into the tear film when the lens is inserted. Sometimes this staining is clinically insignificant, consisting of a few dozen micropunctate spots spread across the cornea. However, in other cases thousands of spots of staining can be observed covering the entire cornea. In these instances, the patient often notices significant discomfort upon lens insertion.
In the Staining Grid study, I pair each multi-purpose solution with the leading brands of contact lenses, testing 30 subjects for each lens/solution combination. The goal is to measure the amount, or area, of corneal staining induced by the release of preservatives from the solutions two hours after lens insertion. This is reported on the Staining Grid as the percentage of corneal surface covered by this staining, the higher the percentage the more widespread the staining. In addition, to help the eyecare practitioner quickly analyze this vast amount of information, color-coding is employed for each lens/solution combination to indicate minimal, moderate, or excessive staining.
The Staining Grid is designed to make the practitioners’ multi-purpose solution prescribing decision easier. In addition, many practitioners use the Web site as a simple visual aid when explaining the importance of using a biocompatible solution to their patients.
Gary J. Andrasko is director of a contact lens research practice in Columbus, OH, and the publisher of the StainingGrid.com Web site.