letters to the editor
Response to Staining Study Methodologies
I wish to thank Gary Andrasko, OD, for his letter Staining Study Methodologies that appeared in the April issue in response to my March article The New Math of Corneal Staining. There's no denying there are differences between some of the contact lens/solution combinations. Other studies have also found this.
What I was trying to point out were the wide variations in grading methods and clinical relevance. One fact is that the staining described was Grade 1 micropunctate. Garofalo's paper states, 90% of the positive staining scores were grade 1, and generally low grade and readily reversed. Grade 1 staining is usually clinically insignificant (Terry RL et al, 1993).
Dr. Andrasko correctly quoted me regarding staining and infection: a break in the epithelium is the first step for bacteria to get a foothold into the cornea. However, my views have changed since I wrote the article. Suzanne M. J. Fleiszig, OD, PhD's Glenn A. Fry award lecture (2006) casts doubt on the role of a micropunctate break and infection. She says, experiments tell us that disrupted epithelial barrier function doesn't always make the cornea susceptible to infection. To paraphrase, many other factors are involved than just staining.
And if the transient staining results from preservative release, what better protection against bacteria than a multipurpose disinfectant? To date, there's been no connection with patient outcomes.
We could go on and on with this discussion. The bottom line is the clinical implications of Grade 1 staining. Personally, I don't like the overall negative messaging in our industry. Gary, as a researcher, I do have appreciation for your work. It has brought much interest and talk back into the specialty we both love: contact lenses.
Milton M. Hom, OD, FAAO