contact lens care
Warm Up to Soft Lens Heat Disinfection
BY SUSAN J. GROMACKI, OD, MS, FAAO
As some of us endure yet another cold winter, I thought it would be a good time to write about heat. In this case, heat disinfection of soft contact lenses. As we know, heat disinfection has for the most part gone the way of the dinosaur -- or, for a more appropriate analogy, the way of PMMA contact lenses. Like the newer GP lens materials that supplanted PMMA lenses, chemical soft lens disinfection systems are more convenient for patients than heat disinfection systems while remaining efficacious.
I don't prescribe heat disinfection for new soft contact lens patients. However, what I learned way back in practice management class rings true in this case: "If it ain't broke, don't fix it." So for soft lens patients whose eyes and lenses look impeccable and who adamantly refuse to switch to a chemical lens care system, here's a review of soft contact lens heat disinfection.
It's Still Out There
Some of you may be surprised to learn that heat disinfection units still exist, but the practice of heat disinfection is still alive and well. Three companies currently supply heat disinfection units for soft lenses: Earth Eyes (Earth Eyes Electronic Disinfection Unit), Ophtecs (Bioclen Ace Presto) and LensMedic (LC-750 Ultrasonic Contact Lens Cleaner).
How Heat Disinfection Works
In general, an electrical heating unit will disinfect lenses for 10 to 30 minutes at 160 degrees to 176 degrees Fahrenheit (80 degrees Celsius) -- that's quicker than many chemical systems. In addition, it's well-documented that heat is the most efficacious disinfection system. It's highly effective against almost all micro- organisms, including Acanthamoeba, Pseudomonas and HIV. It's also the only FDA-approved, in-office lens disinfection method. What's more, heat disinfection may be less expensive for patients in the long run than chemical solutions.
Pick Your Spots
If heat disinfection works so well, why don't all patients use it? Several reasons exist for its lack of universal popularity:
- The electrical requirements of heat disinfection systems render them inconvenient for many travel circumstances
- Heat disinfection is not recommended for silicone hydrogel lenses and FDA Group II and IV hydrogel materials. Many popular lenses fall within one of these groups
- After prolonged use, heat can cause premature color fading of opaque contact lenses
- Digital rubbing with a contact lens cleaner is required before placing lenses in the unit. If not, the heat will bake on deposits not cleaned off the lenses, causing decreased lens life and complications such as giant papillary conjunctivitis. Of course, rubbing is a step no longer required for many of the simpler chemical cleaning systems.
Non-preserved saline is recommended for heat disinfection units; homemade saline, tap water and multipurpose solutions are contraindicated.
Still a Great Choice
If used properly, heat disinfection gives practitioners a good alternative for patients who have chemical solution hypersensitivities. That 160 degree temperature sounds really good right about now.
Dr. Gromacki has a specialty contact lens practice as part of a multi-subspecialty ophthalmology group in Fishkill, NY, and has served as a faculty member at the University of Michigan Department of Ophthalmology and Visual Sciences.