letters to the editor
Silicone Hydrogels are Underrated
In your July Readers' Forum column titled "Are Silicone Hydrogels Overrated?" Dr. Brian Chou urges practitioners to be cautious in refitting patients into silicone hydrogels, citing a number of anecdotal reports of patient issues.
Based on my own experience refitting hundreds of patients into silicone hydrogels, a more appropriate conclusion might be that silicone hydrogels are underrated, not overrated. By improving ocular physiology, they represent a superior alternative for the vast majority of patients.
Silicone hydrogel lenses have been the most thoroughly researched contact lens material ever, with thousands of patients having participated in clinical studies to establish their safety and efficacy. This vast body of scientific evidence conclusively shows that refitting patients from low-Dk/t lenses into silicone hydrogels often results in rapid and dramatic reduction in the signs and symptoms associated with corneal hypoxia.
I refer Dr. Chou to an excellent summary article by N. Rex Ghormley, OD, FAAO, in the March issue (Contact Lens Materials, "How Much Oxygen is Enough for Safe Lens Wear?") in which four independent researchers all confirmed the need for higher-Dk/t lenses, specifically above a Dk/t of 125, for different indicators related to daily and extended wear.
In my experience, patients refit into silicone hydrogels not only exhibit improved corneal health, but also are able to wear their lenses for longer periods, making these patients enthusiastic converts. Clinical studies have also demonstrated that silicone hydrogel lenses reduce contact lens-related symptoms of dryness, both during and at the end of the day, for patients as well.
A second generation of silicone hydrogel lenses has appeared, and hyper-Dk/t lenses are now available that are suitable for either daily wear or up to six nights of extended wear. Three of the major manufacturers are actively encouraging upgrades of their wearer bases to the new materials. As Dr. Chou notes, all the major manufacturers are devoting much of their R&D efforts to these new materials, recognizing that they represent the future of soft lenses.
I encourage practitioners who remain cautious about silicone hydrogel lenses because of reports that a small minority of patients cannot successfully adapt, to take another look. Waiting for the "fail-safe" lens is never a good strategy, because there will never be such a lens. It's our professional obligation to offer patients the very best lenses available, and I believe silicone hydrogels represent the very best lenses we can offer today.
Dr. Roy A. Kline, Glens Falls, NY
Soft Torics: How Design Would Really Matter
In response to Rhonda Robinson, OD's July 2005 article "Soft Toric Lenses: Design Matters," I agree that the design of such lenses does matter. However, the biggest design flaw with disposable soft toric contact lenses is the lack of base curves, specifically, steep base curves.
Almost all new lenses to enter the market recently are one-base-curve lenses, usually 8.6mm or 8.7mm. While this may fit the majority of patients, it significantly limits choices. There's only one steep-fitting disposable soft toric lens available, the Cooper Vision Frequency 55 Toric in 8.4mm. The B&L Soflens 66 Toric does seem to drape some corneas and can serve as a medium-steep lens, but it doesn't fit as well on steeper corneas (46.00D and above) as does the 8.4mm Frequency 55. Unfortunately, the Frequency 55 lens also doesn't fit really steep corneas. These patients are left with no option in disposability.
Manufacturers seem to follow the leader; whatever base curve one produces, the others follow. They seem intent on competing directly against each other and every other toric. When I question company representatives, they all insist that their lens can fit the majority of patients, so there's no need for other base curves. Some company needs to produce lenses with steeper base curves to really give us a choice and to make design really matter. Plus, that company would virtually have the market to itself until somebody follows the leader.
Jeffrey Bronsof, OD, Philadelphia, PA
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