Lens Care Update
Understanding Contemporary Contact Lens Care Products
An overview of current contact lens systems, their components, and standards for care and cleaning.
|Dr. Gromacki is a diplomate in the American Academy of Optometry’s Section on Cornea, Contact Lenses and Refractive Technologies and practices in Chevy Chase, Md.|
|Mr. Ward is an instructor in ophthalmology at Emory University School of Medicine and Director, Emory Contact Lens Service. You can reach him at firstname.lastname@example.org.|
By Susan J. Gromacki, OD, MS, FAAO, & Michael A. Ward, MMSc, FAAO
There has been renewed interest in contact lens care. Although unfortunate, the contact lens-related Fusarium and Acanthamoeba keratitis outbreaks of six to eight years ago taught both practitioners and patients that not all care solutions are alike—and that compliance does matter. In the last three years, we have seen the development of new contact lens care systems for both soft and rigid contact lenses. These care solutions have demonstrated distinct technological advances over their predecessors, particularly in their ability to clean and disinfect the newest generations of contact lens materials and designs.
In the following review article, we will discuss the attributes that make each contact lens care system unique and highlight what differentiates the latest technologies.
Care System Components
Each contact lens care system, whether for soft or rigid lenses, contains a variety of ingredients that are essential for ocular biocompatibility, debris removal, and microbial eradication (Table 1). They often differ in concentration and composition from care solution to care solution, making each formulation different.
• Buffers keep the pH of the solution close to natural tears. Examples include borate, phosphate, nitrate, bicarbonate, and citrate.
• The purpose of a salt is to make the solution isotonic with the tears. A common salt is sodium chloride.
• A cleaning agent (surfactant) can be a stand-alone solution or can be added to a multipurpose solution (MPS). Its function is to remove protein, lipids, mucin, and/or debris from contact lenses. Surfactants are amphiphilic surface acting agents that possess hydrophilic heads and hydrophobic tails, yielding their ability to chemically attach and solubilize various debris. Common cleaning agents include isopropyl alcohol, sodium citrate, sodium borate, sodium phosphate, polyvinyl alcohol, and poloxamer-407.
Care System Components
• Chelating agents, such as edetate disodium (EDTA), prevent calcium-bound proteins from depositing on the lens surface. This, in turn, enhances disinfection.
• A demulcent enhances comfortable contact lens application. A popular example is propylene glycol.
• Wetting agents decrease the wetting angle of a lens material by changing the surface energy. Wetting agents are surfactants. Examples include tetronics.
• Lubricants are agents that attract moisture. Examples of lubricants include hydroxypropyl methylcellulose, hyaluronic acid, carboxymethylcellulose, hydroxypropylguar, tetronic, dexpanthenol, sorbitol, and poloxamine.
• Disinfectants are antimicrobial agents. They also protect a care solution bottle’s contents from contamination. Examples include hydrogen peroxide, polyhexamethylene biguanide HCl (PHMB), polyaminopropyl biguanide, polyhexanide hydrochloride, polyquaternium-1 (PQ-1), and myristamidopropyl dimethylamine (MAPD). First-generation disinfectants such as thimerosal or chlorhexidine, when used in higher concentrations, frequently led to hypersensitivity reactions. Today’s disinfectants have higher molecular weights, and as a result, tend not to penetrate the matrices of soft contact lenses. However, some sensitive patients nevertheless can still develop allergic or toxic reactions. There still continue to be incompatibilities with certain lens-care solution combinations, particularly with silicone hydrogel (SiHy) materials (Carnt, 2009; Andrasko, 2013). As a result, it is important to carefully prescribe a care system with the lens material in mind. More specifics on some of the aforementioned disinfectants are:
• Quaternary Ammonium Compound Polyquaternium-1 (“Polyquad”) is bactericidal and acts by reducing the surface tension at interfaces and denaturing microbial cell wall proteins. A larger molecule than some of the other disinfectants, it can be less likely to penetrate soft contact lenses. With less uptake, there is less potential release of the disinfectant into the tear film and cornea (Green, 2012), where it may have deleterious effects.
• Amidoamine Myristamidopropyl dimethylamine (stearamidopropyl dimethylamine, “Aldox”) eliminates fungi and amoebae through its cationic properties.
• Biguanides PHMB, also known as polyhexanide and polyaminopropyl biguanide (“Dymed”), is a chlorhexidine derivative. It is a much larger molecule compared to chorhexidine, thus avoiding many of its tissue reactions. It is a bactericidal agent that disrupts the plasma membrane of a bacterial cell, eliminating the metabolic activity within it.
See Table 2 for a list of common multipurpose contact lens care solutions and their disinfectants.
Soft Lens Care
Hydrogen Peroxide Hydrogen peroxide (H2O2), although not by definition a preservative, is a potent disinfectant. It provides excellent antimicrobial efficacy by penetrating a hydrogel material, providing a thorough cleaning by expanding the lens matrix and oxidizing microbes. Because of its hypotonic nature and pH of 4.00, it is also able to break protein and lipid bonds and remove trapped debris (Aquavella and Rao, 1987; Janoff, 1979). Unlike many soft lens MPSs, it can penetrate and eradicate microbial biofilms. Because the hydrogen peroxide must be neutralized before lens application, it is ideal for patients who have hypersensitivities or dry eye. Neutralization is easily accomplished with use of a platinum disc or catalase tablet. Examples of current peroxide-based care systems include Clear Care (Alcon), Oxysept UltraCare Formula (Abbott Medical Optics [AMO]), and One Step (Sauflon) (Gromacki, May 2012 & Sept. 2012).
New Formulations Three novel contact lens MPSs have been recently introduced. One unique aspect is their formulation after the development of SiHy lens materials. SiHy materials are less likely to deposit protein compared to their predecessors and, in some instances, are more likely to deposit lipids (Green, 2012; Hutter, 2012). We are still learning the nuances of their on-eye performance, particularly with regard to their interactions with lens care systems (Gromacki, 2007; Gromacki, 2008). As a result, it is most prudent to recommend care solutions that were specifically developed for these materials. Private-label (“generic”) solutions, which now comprise 32.6 percent of the lens care market (Nielsen, 2012), are typically older formulations, so it is vital to educate each and every patient not to deviate from your prescribed lens care system (Gromacki, 2005).
Multipurpose Contact Lens Solutions and Their Preservatives
|Biotrue||PHMB, PQ-1, EDTA|
|Complete Easy Rub||PHMB, EDTA|
|Opti-Free Express||PQ-1, MAPD, EDTA|
|Opti-Free PureMoist||PQ-1, MAPD, EDTA|
|Opti-Free Replenish||PQ-1, MAPD|
|Renu Fresh||PHMB, EDTA|
|Renu Sensitive||PHMB, EDTA|
|RevitaLens OcuTec||Alexidine, PQ-1, EDTA|
Opti-Free PureMoist is Alcon’s newest multipurpose disinfecting solution. Like Opti-Free Express/Replenish, it contains the disinfectants PQ-1 and aldox. Additionally, it has EDTA and an increased concentration of aldox. It also contains the diblock copolymer poly(oxyethylene)-poly(oxybutylene) (“HydraGlyde”) as its wetting agent. Alcon reported that this combination reduces the surface and bulk hydrophobicity, improves the hydrophilic properties of SiHy lenses, and carries water to hydrophobic lens sites (Davis, 2010).
Biotrue (Bausch + Lomb [B+L]) was engineered to be biocompatible with the ocular system. Its pH measures between 7.4 and 7.6 to match the human tears. Its lubricating agent, hyaluronan (hyaluronic acid), is a glycosaminoglycan naturally found in the eye. Another feature of the new formulation is that it was designed to keep beneficial tear proteins active, which enhances antimicrobial efficacy. In addition to the traditional disinfectant found in other B+L MPSs—PHMB—Biotrue also has PQ-1.
RevitaLens OcuTec (AMO) has a completely revamped disinfection system as compared with its predecessor, Complete Easy Rub. Instead of PHMB, it contains another biguanide—alexidine dihydrochloride—combined with PQ-1. In addition, EDTA is present in the formulation to decrease deposit formations and to add to the antimicrobial properties. Its buffer is sodium borate. Tetronic 904—a block copolymer surfactant—provides wetting.
Specialty Soft Lens Care There are several new designs of soft contact lenses that require specific daily cleaning instructions. SynergEyes’ new hybrid lens for keratoconus and irregular corneas, Ultra-Health, combines a high-Dk (Si-150) rigid center with a silicone hydrogel skirt. After removal, SynergEyes recommends digitally rubbing the lenses with a surfactant daily cleaner and rinsing the lenses with non-preserved saline (e.g., Unisol 4, Alcon). Then the lenses should be disinfected using Clear Care.
Although Biotrue, Aquify (Alcon), Opti-Free Express and Replenish, Renu Fresh (B+L), and Complete Easy Rub are also approved for this lens, SynergEyes highly recommends Clear Care.
There are also two new contact lenses for keratoconus that require special care. KeraSoft IC (B+L, UltraVision CLPL) can be cleaned and disinfected with any MPS or hydrogen peroxide solution. However, if chemically disinfected, the lens needs to be thoroughly rinsed with fresh, sterile rinsing solution prior to placement on the eye. Although compatible with any of the contact lens care systems, Alden Optical specifies that its NovaKone lens be cleaned with a daily cleaner and disinfected with a hydrogen peroxide system. Both lens types require a digital rubbing step; the former recommends accomplishing this “in between the fingers” rather than in the palm of the hand. As always, it is important to contact the individual lens manufacturers to obtain full details on the care of their lenses.
GP Lens Care
GP (fluorosilicone acrylate and silicone acrylate) lens care includes:
• Surface cleaning and debulking of debris
• Lens surface conditioning
• Lens storage and case care
Surface Cleaning and Debulking of Debris GP contact lenses can provide the sharpest visual acuity of any vision correcting modality. However, crisp visual acuity and comfort are intimately associated with clean and smooth GP lens surfaces. GP lenses should be rubbed and rinsed daily. Rubbing removes dirt, tear debris, and cosmetics, and it prepares the lens surface for disinfection and conditioning. Inadequate surface cleaning results in irregular and hydrophobic surfaces that attract more environmental debris, thus creating a cycle of more surface irregularity and debris accumulation that negatively affects acuity, comfort, and lens wearing time.
All-in-One MPS or Multipart Lens Care System? All-in-one solutions provide the convenience of cleaning, disinfecting, storage, and surface conditioning/wetting in a single product. Unique pH (Menicon) is an all-in-one MPS for cleaning, conditioning, and disinfecting GP lenses. It is the same product formulation originally packaged by Alcon, which the company has also repackaged and relabeled as Opti-Free GP Multipurpose solution.
Unique pH/Opti-Free GP solution’s lubricant/comfort effects work by automatically adjusting product viscosity during lens wear. As the eye surface pH decreases (becomes more acidic), the solution becomes less viscous. The Unique pH/Opti-Free GP care solution is preserved with PQ-1 and EDTA. Its cushioning and viscosity are controlled by hydroxypropyl guar, polyethylene glycol, propylene glycol, and boric acid.
Boston Simplus (B+L) contains poloxamine 1107 for removing dirt and deposits and hydroxyalkyphosphonate to remove protein deposits. Its dual disinfection system contains polyaminopropyl biguanide and chlorhexidine gluconate. Glucam-20 and hydroxypropylmethyl cellulose (HPMC) provide lens cushioning and surface wetting.
One-step GP MPSs such as Boston Simplus and Unique pH/Opti-Free GP contain relatively low concentrations of cleaning agents. The surfactants in MPS products are necessarily mild because the solution goes directly onto the ocular surface. Adding an additional daily cleaner may be necessary for some patients. The necessity of a daily regimen of digital lens cleaning cannot be overemphasized. Boston Simplus instructions recommend rubbing the lens in the morning after overnight soak.
Clear Care is approved for use with GP lenses, but a digital rubbing step is required (Gromacki, 2012).
GP Lens Care Systems Most lens care systems for GPs involve the use of separate cleaners along with disinfecting/soaking and wetting/conditioning products. Although a few more steps are involved, they generally provide more thorough cleaning by providing specific agents for each lens care step.
Two of the more popular GP lens care systems are Boston Advance Comfort Formula (B+L) and Optimum by Lobob (Lobob Laboratories). Boston Advance is a two-part system consisting of a daily cleaner and a disinfecting/conditioning product. Optimum is a three-part system of an extra strength cleaner, a cleaning/disinfecting/storage solution, and a wetting/rewetting solution. Pay attention to the manufacturers’ use instructions, which are significantly different with these two systems.
Daily Lens Cleaners for GP Lenses GP lens cleaners contain surfactants and/or solvents and abrasives. Surfactants are the solubilizing chemicals in daily cleaners. Non-abrasive solvent plus surfactanttype daily cleaners include Optimum Extra Strength Cleaner (Lobob Laboratories), Sereine Extra-Strength Daily Cleaner (Optikem International), and Walgreen’s Extra Strength Daily Cleaner.
The Optimum Extra Strength Cleaner (ESC) is preservative-free and contains cocoamphodiacetate and glycols in an aqueous solution. It may be used daily or occasionally. Sereine and Walgreen’s Extra Strength Daily Cleaners’ formulations mimic Mira-flow (Ciba Vision), which was discontinued in 2010. They contain purified water, isopropyl alcohol 15.7%, poloxamer 407, and amphoteric 10. These alcohol-based cleaners are particularly good at removing lipid-based films and makeup from lens surfaces.
Abrasive daily cleaners include Boston Advance Cleaner (B+L) and Opti-Free Daily Cleaner and Opti-Clean II (Alcon). Boston Daily Cleaner uses silica gel, while Opti-Free daily cleaner uses polymeric beads as abrasives, which add to the surfactant’s physical scrubbing properties to help remove protein and mineral deposits.
Boston Advance Cleaner contains tri-quatemary cocoa-based phospholipid, ethoxylated alkyl phenol, silica gel, alkyl ether sulfate, and titanium dioxide to provide visibility tint.
Opti-Free Daily Cleaner and Opti-Clean II for soft and GP lenses are buffered, isotonic formulations containing Tween 21 and polymeric beads as cleaning agents with edetate disodium 0.1% and Polyquad (polyquaternium-1) 0.001% for disinfection.
Daily cleaners must be thoroughly rinsed from lens surfaces with saline, MPS, or tap water. The use of tap water to rinse lenses remains controversial, although the simplest recommendation is not to use it at all. In a 1990 paper, Shovlin raised the specter of Acanthamoeba keratitis associated with tap water and rigid lens use and recommended that tap water not be used following lens disinfection. This still seems reasonable. Lens cleaners must be thoroughly rinsed from lens surfaces to avoid irritation from residual surfactants, abrasives, or solvents left on the lens or transferred to the lens storage case. Salines and MPSs are unlikely to be as effective as water is at removing cleaner residues. When rinsing lenses with salines or MPSs, the tendency is to use less of the product for economy, which may result in inadequate rinsing.
Digital cleaning is well documented in its ability to enhance antimicrobial activity, comfort, and vision. Daily cleaners may be needed to augment MPS and peroxide-based disinfectants.
Conditioning/Disinfecting/Storage for GP lenses B+L has discontinued its Boston Original GP Conditioning formula and replaced it with Boston Improved Formula Conditioning Solution, which has a slightly lower salt content, a slightly higher EDTA concentration, and modified lubricant and surfactant ingredients. The company states that the new formula provides improved disinfection capability and lens wetting. The preservative content remains the same at 0.006% chlorhexidine gluconate. The increased disinfection capability is achieved through combined changes in the formula’s lubrication, tonicity, and EDTA concentration.
Optimum by Lobob Cleaning, Disinfecting and Storage Solution (CDS) and MeniCare GP CDS (Menicon) have the same formulation; Lobob manufacturers both. MeniCare is a two-part system that contains a combined CDS solution and a separate wetting/rewetting (WRW) drop. The Optimum system incorporates an additional extra strength cleaner (ESC). Optimum CDS and MeniCare GP CDS have the same ingredients: Lauryl sulfate salt of imidazoline and octylphenoxypolyethoxyethanol, with benzyl alcohol 0.3% and disodium edetate 0.5% as preservatives. The CDS products are used for rub-and-rinse as well as for overnight storage and disinfection. The solution must be thoroughly rinsed from the lens surfaces prior to lens application.
Hydrogen peroxide disinfection (e.g., Clear Care) works very well as a disinfectant and to mitigate protein buildup on GP lenses. Do not store “spare” lenses in these vials due to lack of on-going preservation.
Scleral GP and Piggyback Lens Care
Cleaning and storage of scleral lenses is similar to that of GP corneal contact lenses. The steps include:
Cleaning Alcohol-based daily cleaners, Optimum ESC, or Boston Advance Daily Cleaner are recommended for daily cleaning after scleral GP removal. Instruct patients to rinse their lenses thoroughly so that no chemical residue remains on the lens surfaces.
Disinfection and Storage Any approved GP disinfecting product may be used on scleral GP lenses.
Peroxides offer excellent disinfection without preservatives. Instruct patients to use such systems daily and to not store lenses for longer than a day. Peroxide-based systems are approved for longer storage times, but in reality they are depleted of any antimicrobial effect after only a few hours. GP lenses don’t absorb the storage solution, so patients can safely rinse peroxides or chemical disinfectants from the lens surfaces. A morning saline rinse is recommended with all forms of disinfection.
Wetting and Fluid Reservoir Patients may wet scleral surfaces by rubbing preservative-free artificial tears onto the surfaces prior to filling the lens reservoir with saline. This helps create a wettable surface and discourages attracting deposits. Gently rubbing wetting agents (e.g., Optimum WRW, Boston Simplus, Blink Contacts [AMO]) on the front (outside) lens surfaces only can similarly enhance lens wetting.
Patients should fill the lens reservoir with isotonic, preservative-free sterile saline. We’ve found unit-dose preservative-free sterile saline (0.9% NaCl) in 3ml and 5ml sizes labeled for inhalation therapy at various medical suppliers; this is simply non-preserved, sterile saline in one-time use vials, which is perfect for our purposes. Instruct patients not to use preserved salines and MPS products to fill the lens reservoir, thereby avoiding chemical irritation and possible toxicity to the corneal surface. Multi-dose, non-preserved saline containers (e.g. Unisol 4 and PuriLens [The LifeStyle Company]) are prone to contamination.
Piggyback (tandem soft/GP) lens systems require lens care solutions that are compatible with soft contact lenses to avoid contamination of the soft lens with GP care solutions. Please see Michael Ward’s Contact Lens Care & Compliance column on p. 19 for more on piggyback lens care.
Contact Lens Case Care
Contact lens storage cases must be kept clean as they are the greatest potential reservoir for harboring microorganisms. The following recommendations are for all contact lens types:
• Empty lens storage case after each use.
• Rinse case with fresh care solution and tissue-wipe the well (except for peroxide cases).
•Leave lens storage cases open to air dry.
• Scald case weekly with freshly boiled water; alternatively fill wells with 3% H2O2 for ≥ one hour, then rinse.
• Replace lens storage cases frequently (every one to three months).
Keeping Lens Wear Safe
Lens wear is not a sterile event, but it should be a clean one. Consider that our eyes are not sterile, our fingers are not sterile, and the lenses themselves are not sterile after first use. Contact lenses provide amazingly good vision, comfort, and safety with few complications given proper wear and care compliance. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #211.