Everyone Loves a Good Debate
BY JASON J. NICHOLS, OD, MPH, PHD, FAAO
This month's issue features our second Point/Counterpoint article on the topic of "Silicone Hydrogels and Lens Comfort." This new department focuses on timely — and sometimes controversial — unanswered clinical questions. We received a lot of positive feedback about our first Point/Counterpoint topic, "The Clinical Impact of Corneal Staining," which was written by Dr. Lyndon Jones ("Solution-Induced Corneal Staining Does Matter") and Drs. Philip Morgan and Carole Maldonado-Codina ("Putting Solution-Induced Staining into Perspective").
In this issue, Drs. Robin Chalmers and Noel Brennan have taken up the debate on the general impact of silicone hydrogel lenses on patient comfort. This controversy has loomed since the introduction of silicone hydrogel materials almost 10 years ago. Many practitioners feel that in general, silicone hydrogel materials do provide overall improvements in patient comfort. If this is indeed true, the most obvious difference in silicone hydrogels compared to their predecessors is their increased oxygen permeability. However, those on the opposite side of the fence are quick to point out that it is more biologically plausible for a hypoxic environment to be more comfortable because the hypoxia could induce a mild anesthesia of the ocular surface, for example.
Another potential difference between silicone hydrogels and their predecessors is that silicone hydrogel materials generally demonstrate reduced rates of dehydration compared to many older materials. But some studies have shown that material dehydration may not play a role in discomfort.
Others believe that differences in silicone hydrogel materials and manufacturing result in different characteristics that might positively or negatively impact comfort. For example, characteristics such as the propensity of some materials for certain types of deposition, the unique surface characteristics used to mask silicone expression of some materials, and the addition of wetting agents or technologies used in this regard could impact comfort. Much of this debate has led to discussion that silicone hydrogels deserve their own Food and Drug Administration classification, apart from Group I where most now generally reside.
We hope you appreciate this month's debate. We look forward to your feedback on this and future topics.