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Good Chemistry

Are you up to date on pairing GP lenses and solutions? Here's a look at what makes a perfect match.
By Robert Ensley, OD, and Heidi Miller, OD

2/15/2016

Gas permeable (GP) contact lens performance is highly dependent on the quality of the lens surface. A clean, wettable lens allows for both a higher degree of vision clarity and better patient comfort. Accordingly, proper care of GP lenses is instrumental in ensuring successful wear.  

With the variety of cleaning products available, however, it’s no wonder many patients become confused regarding which solutions to use. To help differentiate, let’s take a moment to review the fundamental components of successful GP lens care: surface cleaning and disinfection.  




Deposits on a hybrid contact lens.

Surface Cleaning
Early GP lenses were manufactured with silicone/acrylate copolymers to increase oxygen permeability, resulting in negatively charged hydrophobic lens surfaces that attract positively-charged proteins and lipids. Modern GP lenses added fluorine (fluorosilicone/acrylate) to the mix, resulting in a lower surface tension that reduces deposit adherence and increases surface wettability for greater ease of lens cleaning.1 

Most GP cleaners incorporate surfactants, compound molecules with a hydrophilic head and hydrophobic tail that surround lens contaminants like proteins, lipids and cosmetic-related debris to form a micelle. This molecule is then solubilized in solution and rinsed away in combination with digital pressure and friction.  

GP cleaners that contain abrasive surfactants like the Original Formula Boston Cleaner (Bausch + Lomb) and the now-discontinued Opti-Clean II (Alcon) are traditionally more effective when used with lower-Dk, early-generation GP lenses that bind more protein. Newer cleaners including Boston Advance Cleaner (Bausch + Lomb) and Opti-Free Daily Cleaner (Alcon) use smaller-diameter abrasive particles; however, these are still classified as mildly abrasive and should be used with caution on higher Dk GP lenses, as they can scratch the surface and induce minus power to the lens by reducing center thickness.2 Abrasive cleaners are also contraindicated for use with any GP lens that is plasma treated. If a non-abrasive daily cleaner is required, Optimum Extra Strength Cleaner (Lobob Laboratories), a preservative-free formula, can be used. 

Other daily cleaners include the isopropyl alcohol-based Sereine Extra Strength Cleaner (Optikem International) and Walgreens Extra Strength Daily Cleaner. Both contain the same ingredients as the MiraFlow (Alcon) daily cleaner that was discontinued in 2010. Note, the original MiraFlow formulation was recently purchased by an independent practitioner and is distributed online only through a direct-to-consumer website.  

What is Plasma Treating?
Plasma is a gas that is ionized into a mixture of highly reactive negatively and positively charged particles. During treatment, GP lenses are placed in a vacuum chamber, where oxygen plasma breaks up and removes surface contaminants including grease, lipids and other residues. This process improves the lens’ initial wettability and comfort by reducing the wetting angle.  

Plasma treating should be thought of as a “deep clean” process rather than a coating treatment. Lenses with a plasma treatment are shipped hydrated, so excessive handling should be avoided prior to dispensing. Although the plasma treatment will wear off over time, abrasive cleaners are not recommended for use to avoid accelerating the breakdown. Most laboratories recommend cleaning the lens with Boston Simplus (Bausch + Lomb), Unique pH (Menicon) or a hydrogen peroxide-based solution. 

 

Patients who are heavy protein depositors may benefit from an additional enzymatic or solvent cleaner that can be used periodically. Current enzymatic cleaners come in liquid form, allowing them to be added directly to a storage solution. Boston One-Step Enzymatic Cleaner (Bausch + Lomb) is recommended for weekly use, while SupraClens Daily Cleaner (Alcon) is recommended for every day use. 

Formerly an in-office cleaner only, Progent (Menicon) incorporates a mixture of sodium hypochlorite and potassium bromide to remove proteins and is recommended for use on a biweekly basis. Because this formulation is essentially bleach, it is recommended only for patients who fully understand how to use it properly. 

In general, lenses should not soak in any of these liquids for more than 30 minutes, to avoid discoloration. Less frequent use of an enzymatic cleaner or Progent may be sufficient for lenses containing fluorosilicone/acrylate materials.    

Following use of daily cleaners, GP lenses should be rinsed thoroughly prior to lens insertion. While many GP wearers rinse with tap water, this is controversial. To reduce the risk of microbial exposure, rinsing with a sterile saline or multipurpose solution is typically recommended.  

Disinfection and Storage
Once the lens surface has been cleaned, a GP lens should be soaked overnight. Depending on the storage method, the lens is disinfected using either preservatives or hydrogen peroxide. There are several preservatives used in GP solutions that are either bactericidal or bacteriostatic in nature. These typically have larger molecular weights, limiting their ability to bind to a GP lens. Common preservatives include clorhexidine gluconate, benzyl alcohol, polyquaternarium-1 (polyquad) and biguanides. 

The Boston Conditioning Solution and Boston Advance Formula Conditioning Solution (Bausch + Lomb) are both packaged independently, but are part of a two-bottle system with their daily-cleaning counterparts. Both solutions use clorhexidine gluconate 0.003% as a preservative, and contain polyvinyl alcohol (PVA) and a cellulosic viscosifier to coat the lens surface, providing both moisture and a cushioning effect for added comfort. The Advance Formula Solution has an added preservative, polyaminopropyl biguanide 0.0005% (PAPB), and derivatized polyethylene glycol as an additional wetting agent.  

Other solution options for cleaning, disinfecting and storage (CDS) include Optimum CDS (Lobob) and MeniCare CDS (Menicon). Both solutions use the same formulation with lauryl sulfate salt of imidazoline and octylphenoxypolyethoxyethanol to clean the lens, and are preserved with benzyl alcohol 0.3% and edetate disodium 0.5%. Both CDS solutions recommend a rub and rinse prior to overnight soak, and should be thoroughly rinsed prior to lens insertion. Optimum CDS can be purchased independently or as part of a combined care system kit with the Optimum ESC and Optimum wetting/rewetting drops.    

If a patient develops a preservative sensitivity, hydrogen peroxide-based solutions can be used as an alternative. Solutions containing a 3% hydrogen peroxide concentration are particularly effective against multiple pathogens, including bacteria, viruses, fungi and protozoa, as peroxide produces free radicals that can penetrate a microbe’s cell membrane and destroy its DNA. However, the solution’s pH of 4.0 means that a neutralization step is also required prior to lens placement on the ocular surface. Additionally, because hydrogen peroxide cannot penetrate the matrix of GP lens, as it can a soft hydrogel, GP lenses still require a rubbing step for proper cleaning. Current peroxide-based solutions on the market include ClearCare Plus (Alcon), PeroxiClear (Bausch + Lomb), and OxySept UltraCare Formula (AMO). 

Multipurpose Solutions 
For some patients, cleaning and disinfecting a GP lens with two separate solutions can be burdensome or confusing. A multipurpose solution (MPS) may be a more convenient and appropriate choice for these patients. Boston Simplus (Bausch + Lomb) contains the surfactant poloxamine 1107 and hydroxyalkylphosphonate to remove protein deposits, clorhexidine gluconate and PAPB preservatives to disinfect the lens, and glucam-20 and hydroxypropylmethylcellulose (HPMC) for cushioning and wetting. Product guidelines recommend that lenses be removed every night and directly in solution; in the morning, the lens should be rubbed gently on either side for 20 to 30 seconds and rinsed prior to lens insertion.

Unique pH multipurpose solution (Menicon) is the same formulation as the former Opti-Free GP (Alcon). Preserved with polyquad and EDTA, Unique pH also contains hydroxypropyl guar, polyethylene glycol, tetronic 1304, boric acid and propylene glycol to aid in cushioning and wettability. The formula also allows the solution to adjust viscosity based on the pH of the ocular surface. While no rinsing is typically required, if the SupraClens (Alcon) enzyme is added to the solution, the lens should be rinsed thoroughly prior to insertion.

With any lens/solution combination, practitioners should inform patients regarding proper use and potential problems to watch for. Always be sure to remain up to date on the latest research to ensure your recommendations are the best option for your patients.  

1. Cannella A. Polymer Chemistry. In: Bennett ES, Weissman BA, ed. Clinical Contact Lens Practice. 4th Ed. Philadelphia, PA: Lippincott, Williams & Wilkins; 2005: 235-242.
2. Bennett ES, Wagner H. Gas-permeable lens care and patient education. In: Bennett ES, Henry VA, ed. Clinical Manual of Contact Lenses. 4th Ed. Philadelphia, PA: Lippincott, Williams & Wilkins; 2014: 157-186.



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