Menicon Progent: the safeguard of RGP lens cleaning, especially for ortho-k lenses
Menicon always recommends use of the Progent system to remove protein deposits and biofilm from RGP lenses, either bi-weekly on top of everyday cleaning with Unique pH for daily wear, or by keeping a regular schedule of Progent treatment in the case of continuous wear. This article explains in detail why the Progent system is essential in lens care, based on qualitative and quantitative studies, and why you should always emphasize the use of Progent to wearers.
Protein deposits and biofilm on RGP lenses
RGP lenses are designed to be worn for long periods. Ideally, if the wearer uses fresh multipurpose solution (MPS) every day to rub the lenses sufficiently and soak the lenses for the indicated hours, the lenses can remain relatively clean. But wearers are not always compliant. Sometimes they don’t do lens care for one or two days, sometimes they skip rubbing or do not rub or soak the lenses long enough. As time goes by, protein deposits and biofilm start to build on the surface of RGP lenses and can be stubborn on specialty designs such as orthokeratology lenses and lenses for keratoconus. Independently or associated, protein deposits and biofilm could impair vision quality and comfort, induce intolerance, and eventually cause corneal infection.
Fig-1: inner surface of an ortho-k lens. On the right: midsagittal section of an ortho-k lens.
Orthokeratology lenses, or ortho-k lenses, have a reverse-geometry back surface design (Fig-1). This complex structure allows the reshaping of the cornea to correct refractive error but is prone to deposits, especially at the reverse curve area. Invisible to the naked eye and easily ignored by wearers, these deposits reveal themselves on microscopic photos. From 8 worn ortho-k lenses collected from wearers, deposits of up to 7.72 µm thick were measured. 
It is also suggested that deposits may increase bacterial retention on the lens surface.  Bacterial retention can lead to corneal infections, for example keratitis caused by Pseudomonas aeruginosa (PA). PA is the most common pathogen of contact lens-related keratitis. It can be highly resistant to antibiotics; corneal infection caused by PA is costly and treatment is long with limited clinical outcome. An in vitro study has shown that deposits on ortho-k lens increases adhesion of PA onto the lens surface. 
Several multipurpose solutions (MPS) are commercially available to clean RGP lenses; wearers are routinely told to use them every day to remove protein and disinfect the lenses. However, their cleaning efficacy can be limited when it comes to specialty lenses such as ortho-k lenses, or when wearers fail to rub the lens thoroughly before soaking. 
Proven efficacy of Progent against protein deposits and biofilm
Various studies have shown that the Progent system is efficient in removing protein deposits and biofilm from the lens surface. It consists of 2 compounds to be mixed upon use: a dose of Progent A, sodium hypochlorite and a dose of Progent B, potassium bromide. When mixed, the generated hypobromite disinfects the lenses against bacteria, viruses, fungi, yeasts and acanthamoeba in 5 minutes and destroys protein chains in 30 minutes. 
In the Hiraoka study, Progent completely removed the deposits of various thicknesses from an ortho-k lens, while the tested MPS only reduced the thickness.  Three worn ortho-k lenses were each cut evenly into 4 pieces: A piece, B piece, C piece and piece with the serial number; the serial number piece was discarded. All A, B and C pieces underwent different treatments before being measured for deposit thickness on the reverse curve area. All A pieces were measured without treatment, all B pieces were measured after daily cleaning and all C pieces were measured after Progent treatment. The thicknesses were 2.78 μm, 3.84 μm and 3.52 μm pre-cleaning (A pieces), 1.67 μm, 3.59 μm and 1.57 μm post-daily cleaning (B pieces), and 0.00 μm, 0.00 μm and 0.00 μm post-cleaning by Progent (C pieces). 
In the Nomachi study (Fig-2), Progent is concluded to have the highest efficacies against both protein deposits and biofilm. Progent removed the artificial protein deposits on the lenses and eliminated the biofilm, instead of leaving a mix of living and dead bacteria. 
Fig-2: LIVE/DEAD image of S. epidermidis biofilm treated with Progent and 3 commercially available multipurpose solutions (MPS). The black frame of Progent indicates no remaining biofilm. In the cases of MPS-1, 2 and 3, there was a mix of dead bacteria (red) and survivors (green).
Progent: extraordinary efficacy with a simplicity of use
The studies are focused on specialty lenses because their design makes them more difficult to clean by conventional MPS. Other RGP lenses (spherical, toric, multifocal, etc) are not deposit-free because wearers are not always compliant. As the protein deposits and biofilm accumulate, so does the risk of discomfort, intolerance, and infection. Bi-weekly use of Progent ensures protein free lenses while remaining simple to use.
Progent does not require any rubbing or long soaking. A 30 minute soak in the mixed solution is enough to achieve protein deposit removal as well as biofilm elimination. Each box of Progent contains 7 vials each of the A and B solutions, 7 vials of saline solution and a Progent case. To treat the lenses, the wearer will pour 1 vial of A and 1 vial of B in the Progent case and leave the lenses in the case for 30 minutes. After 30 minutes, rinse the lenses with the provided saline solution, then the lenses can either be worn again or stored in Unique pH.
In conclusion, several factors contribute to the buildup of protein deposits and biofilm on RGP lenses, including lack of compliance of wearers, complex design of lenses and dependence on thorough rubbing for some solutions. Progent minimizes the impact of these factors by the combining an extraordinary efficacy with a simplicity of use. It should be systematically recommended to RGP wearers to maintain a high quality of vision and protect ocular health.
Please note that Menicon Progent should not be used on lenses treated with Tangible Hydra-PEG as it may damage the coating.
Menicon France, Marketing Manager
Biyang ZHOU joined Menicon in 2019 as Product Manager and is now Marketing Manager of Menicon SAS France. Equipped with dual skills of life science and marketing, Biyang is specialized in marketing and management in health care industry, with a focus on product management. She is fluent in Chinese, English and French and enjoys public communication related to science and healthcare, both at work and in her volunteering activities for wild life conservation NGO.
 Hiraoka T, Yoshimitsu M, Santodomingo-Rubido J, Kondo H, Oshika T. A novel quantitative evaluation of deposits adhered to worn orthokeratology contact lenses. Jpn J Ophthalmol. 2021. 65(6):855-863.
 Choo JD, Holden BA, Papas EB, Willcox MD. Adhesion of Pseudomonas aeruginosa to orthokeratology and alignment lenses. Optom Vis Sci. 2009. 86(2):93-7.
 Taizo S, Chie S, Rie S, Masaki I. Effects of artificial deposits on adhesiveness of Pseudomonas aeruginosaonto orthokeratology lens. GSLS 2020
 Miya N, Osamu M, Masaki I, H. Dwight C. Efficacy of Progent system against protein deposits and Staphylococcus epidermidisbiofilm isolated from contact-lens users. AAO 2014.
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