A disinfection solution needs to be safe and effective, kill pathogens associated with eye infections, have minimal side effects, and be cost effective. Infection due to contact lenses may occur from bacteria, fungi, viruses, parasites, or amoebae. The most common methods of GP disinfection are hydrogen peroxide or polyhexamethylene biguanide, either alone or in combination with chlorhexidine (Choy et al, 2013). The hydrogen peroxide disinfecting process loosens dirt, debris, protein, and deposits. Multipurpose disinfecting solutions are all-in-one care systems to clean, disinfect, and store lenses.

Additionally, microbial keratitis has been associated with lens care system bottle contamination, primarily at the tip of the bottle opening or the cap covering the tip of the bottle (Szczotka-Flynn et al, 2010). Contaminated bottles can transfer microbes to contact lenses and storage cases (Szczotka-Flynn et al, 2010).

In the Scleral Lenses in Current Ophthalmic Practice: An Evaluation (SCOPE) Study, providers were asked to indicate all recommended products for disinfection and storage (Harthan et al, 2018; Nau et al, 2018). Hydrogen peroxide disinfection products were the most commonly recommended (61%), followed by GP lens conditioning solutions and GP multipurpose products at 54% and 49%, respectively.

A Novel Choice

Povidone iodine is a broad-spectrum microbicide that reacts with the mitochondrial enzymes of the respiratory chain and/or cell membrane proteins to inactivate microorganisms (Han, 2016). It has demonstrated effective in vitro antimicrobial activity (Gurwood and Myers, 2004).

It is a well-established antiseptic for skin and ocular disinfection of both patients and healthcare providers for pre- and postoperative surgical prophylaxis, minor skin wounds, ophthalmia neonatorum prophylaxis, and bacterial conjunctivitis treatment (Gurwood and Myers, 2004; World Health Organization [WHO], 2016; Nesvadbova et al, 2015). It is effective against fungi and viruses (WHO, 2016; Nesvadbova et al, 2015). Recently, a 0.6% povidone iodine formulation eye drop was faster compared to 5% povidone iodine preparation in killing gram-positive and gram-negative bacteria; this may be used prior to ophthalmic surgery and intravitreal injections (Musumeci et al, 2018).

A study by Cho et al (2018) investigated the efficacy of a novel povidone iodine-based disinfection solution for GP lenses compared to three multipurpose and hydrogen peroxide solutions. A new formulation for GP lenses uses povidone iodine as the disinfecting agent with a time-release neutralizing tablet that dissolves in approximately 30 minutes. The tablet contains 2.4mg of sodium sulfite coated with hydroxypropyl methylcellulose and a proteolytic enzyme for protein removal. The exposure time to povidone iodine is minimal because it disinfects rapidly, and the solution is neutralized before lens application to prevent ocular toxicity (Martin-Navarro et al, 2010).

The povidone iodine solution demonstrated efficacy against the required log reduction for both bacteria and fungi according to ISO regulations. All three solutions achieved more than the U.S. Food and Drug Administration requirement for solution efficacy and attained a 4-log reduction in viability of the three bacterial species tested and a 3-log reduction against both C. albicans and F. keratoplasticum (Cho et al, 2018). The povidone iodine solution reached a 1-log reduction against Acanthamoeba castellanii trophozoites and was near this level for the other solutions. Activity against cysts ranged from a 78% to an 86% reduction in viability. All solutions were stable over three months of testing.

Solutions containing povidone iodine are currently available in Japan and have the potential to be available worldwide. CLS

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