Hard/GP contact lenses can provide the sharpest visual acuity of any vision correcting modality. A rigid lens with over-refraction is still the gold standard for assessing the visual potential of an eye in cases of ectasia or other corneal irregularities. This is because rigid lenses provide a regular, smooth anterior refractive surface, and tears fill the gaps between the irregular anterior corneal surfaces and the smooth posterior contact lens surfaces to create an optical bridge, thus allowing light to be fully focused onto the retina.

Hard (PMMA) contact lenses dominated the market from the early 1950s to the early 1970s, at which time soft hydrogel (HEMA) contact lenses were introduced. GP lens materials were also introduced in the 1970s and eventually replaced PMMA lenses except in rare circumstances. GP materials have reached a sophisticated level of chemistry and performance, allowing good oxygenation, wettability, and deposit resistance. However, crisp visual acuity and comfort are intimately associated with clean and smooth GP lens surfaces.

Sight-threatening microbial keratitis (MK) is the most significant adverse event associated with contact lens wear. The reported incidence of contact lens-associated ulcerative keratitis ranges from approximately 1.2 to 5.5 cases per 10,000 for daily wear soft lenses and from 19.5 to 25.4 cases per 10,000 patients for overnight lens wear.¹ Although the lowest reported incidence of MK is among daily wear GP lens wearers (2/10,000), any extended/overnight lens wear remains the most significant risk factor for infection.² We can make lens wear and care even safer by utilizing best practices and best products along with proper practitioner education and patient instruction.

CORNEAL GP LENS CARE

All-in-One MPS Systems All-in-one multipurpose solutions (MPSs) provide the convenience of cleaning, disinfection, storage, and surface conditioning/wetting in a single product. One 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. This MPS care solution is preserved with polyquaternium-1 (PQ-1) and ethylenediaminetetraacetate (EDTA). Its cushioning and viscosity are controlled by hydroxypropyl guar, polyethylene glycol, propylene glycol, and boric acid.

Another GP MPS solution contains poloxamine 1107 for removing dirt and deposits and hydroxyalkyphosphonate for removing protein deposits. Its dual-disinfection system contains polyaminopropyl biguanide and chlorhexidine gluconate. Glucam and hydroxypropyl methylcellulose (HPMC) provide lens cushioning and surface wetting.

One-step GP MPSs such as the two described here 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 to control surface environmental debris.

The necessity of a daily regimen of digital lens cleaning cannot be overemphasized. The instructions for the second GP MPS described above recommend rubbing the lens in the morning after an overnight soak.

GP Lens Care Component Systems Some lens care systems for GPs involve the use of separate components, typically daily cleaners along with disinfecting/soaking solutions and wetting/conditioning products. Although a few more steps are involved, these systems generally provide more thorough cleaning because they use specific agents for each lens care step.

One popular component systems is a two-part system consisting of a daily cleaner and a disinfecting/conditioning product. Another is a three-part system with an extra-strength cleaner (ESC), a cleaning/disinfecting/storage solution (CDS), and a wetting/rewetting solution (WRW). Pay attention to the manufacturers’ use instructions, which are significantly different with these two systems.

Daily Lens Cleaners GP lenses should be cleaned (rubbed and rinsed) daily upon removal. Digital rubbing removes dirt, tear debris, and cosmetics and prepares the lens surfaces 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. GP daily cleaners are often recommended to augment MPSs and peroxide-based cleaning/disinfecting products. When used together, they provide cleaner lens surfaces.

The availability of daily cleaners for both hydrogel and GP materials has diminished significantly. Only a few remain, and there are no new entries of which I am aware. Daily use cleaners contain a combination of surfactants and sometimes abrasives; they may be either chemically preserved or self-preserved. Surfactants are a class of chemicals that possess both hydrophobic and hydrophilic components within the same molecule; this enables them to quickly attach and solubilize different types of debris.³ Surfactants are the solubilizing chemicals in daily cleaners; they may act as detergents, wetting agents, emulsifiers, and/or dispersants.

There are abrasive and non-abrasive daily cleaners, including several non-abrasive, solvent-plus-surfactant-type daily cleaners. One of these extra-strength cleaners is surfactant-based, self-preserved, and contains cocoamphodiacetate and glycols in an aqueous solution. It may be used daily or occasionally.

A popular extra strength daily cleaner was discontinued by the original manufacturer in 2010. Fortunately, identical formulations are available. Many practitioners felt that the original, discontinued cleaner was unsurpassed in removing lipid-based films and makeup from lens surfaces. The formula contained purified water, 15.7% isopropyl alcohol, poloxamer 407, and amphoteric 10. It was self-preserved and could be used with all types of soft and hard lenses. It was noted for its lipolytic properties and for its significant antimicrobial activity. Fortunately, two branded extra strength cleaners offer the same formula, which is substantially equivalent to the discontinued original cleaner.⁴ Look for the 15.7% isopropanol ingredient on the label.

One abrasive-type daily cleaner uses silica gel. Abrasives add to the surfactant’s physical scrubbing properties to remove protein and mineral deposits. This abrasive daily cleaner for GP contact lenses contains tri-quaternary cocoa-based phospholipid, ethoxylated alkyl phenol, silica gel, alkyl ether sulfate, and titanium dioxide for visibility tint.

Daily cleaners feature a red container tip under the cap to signal to patients that the product does not go directly onto the eye.

Saline, MPS, or Water Rinse? Daily lens cleaners must be thoroughly rinsed from lens surfaces with saline, MPS, or water to avoid irritation from residual surfactants, abrasives, solvents, or solubilized debris left on the lens. Salines and MPSs are unlikely to be as effective as water is at removing cleaner residues due to water’s ionicity and hypotonicity. Lens rinsing requires adequate force and volume to remove surfactant-solubilized debris. When rinsing lenses with salines or MPSs, the tendency is to use less of the product for economy, which may result in inadequate rinsing.

The use of tap water to rinse GP contact lenses remains controversial, although the simplest recommendation is to just not use water at all. In a 1990 paper, Shovlin commented on Acanthamoeba keratitis associated with tap water and rigid lens use and recommended that tap water not be used following lens disinfection.⁵ This still seems reasonable. Water should never be used with soft contact lenses. Do GP lenses deserve different considerations? At least three major GP lens care products have U.S. Food and Drug Administration (FDA)-approved labeling for use with a tap water rinse. If used, tap water should be used only prior to lens disinfection.⁶ Some lens care product manufacturers are actively working with the FDA to remove water from their regimen instructions.

GP Storage and Disinfecting Solutions These component products are for conditioning, disinfecting, storage, and wetting of fluorosilicone acrylate and silicone acrylate GP lenses.

A longstanding conditioning solution has been updated and now contains a slightly lower salt content, a slightly higher and modified lubricant, and surfactant ingredients relative to its original formula. The company states that the new formula provides improved disinfection capability and lens wetting. It is preserved with chlorhexidine gluconate (0.006%) and EDTA (0.05%). The increased disinfection capability is achieved through combined changes in the formula’s lubrication, tonicity, and higher EDTA concentration.

Another conditioning solution by the same manufacturer is an aqueous, buffered, slightly hypertonic solution containing a cationic cellulose derivative polymer, a cellulosic viscosifier, and polyvinyl alcohol and a derivatized polyethylene glycol as wetting and cushioning agents; preserved with chlorhexidine gluconate (0.003%), polyaminopropyl biguanide (0.0005%), and edetate disodium (0.05%). It is a GP lens conditioning solution for disinfecting, storage, and wetting that is meant to be used in conjunction with the same brand’s daily cleaner.

Cleaning/disinfecting/storage solution products are usually combined with a separate wetting/rewetting product, available with and without a separate extra-strength cleaner. Both systems are manufactured by the same company. Both cleaning/disinfecting/storage solution products have the same ingredients: lauryl sulfate salt of imidazoline and octylphenoxypolyethoxyethanol, with benzyl alcohol 0.3% and disodium edetate 0.5% as preservatives. The cleaning/disinfecting/storage solution 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 Hydrogen peroxide (H₂O₂) disinfecting systems offer antimicrobial efficacy without the use of preservatives. Microfiltered, stabilized, and buffered 3% H₂O₂ is the active ingredient in peroxide-based systems. It is effective against a wide variety of organisms: bacteria, fungi (including spores and yeasts), viruses, and some protozoa. It destroys pathogens by oxidation, which results in protein denaturation, and by damaging microbial cell membranes and DNA. Approximately 10 minutes at full strength exposure is necessary to eliminate most bacteria.⁷ Fungi and protozoa require longer contact times at full 3% H₂O₂ strength. Unlike MPS disinfectants, H₂O₂ is unaffected by the presence of organic matter or salts and can penetrate some established microbial biofilms.⁸

The H₂O₂ in these systems must be neutralized prior to lens wear, as unneutralized peroxide is toxic to the ocular surface. The two current methods of peroxide neutralization are catalase enzyme and catalytic disc.

One system type uses a platinum-coated plastic disc to catalyze the breakdown of the H₂O₂ to oxygen and water. Catalytic disc peroxide systems are the most common type, with many generics on the market. Depending on the age of the disc, the neutralization may occur in a few minutes or in several hours. A fresh disc neutralizes the peroxide quickly, thus providing less antimicrobial activity, but a more thorough neutralization; an old disc provides a longer contact time with higher concentrations of peroxide, but with less effective neutralization.

One brand also has a newer formulation available with an added wetting agent. This formulation contains H₂O₂ 3%, phosphonic acid as a stabilizer, sodium chloride 0.79% to create an isotonic saline solution, a phosphate buffer to control pH, Pluronic 17R4 as a surfactant cleaning agent, and EOBO-21 (polyoxyethylene-polyoxybutylene) as a wetting agent. This formulation represents a product line extension and is not meant to replace the original H₂O₂-based product.

Another product in this category is a two-step peroxide system that uses the enzyme catalase to neutralize the H₂O₂. In this system, a catalase-neutralizing tablet is added to the lens case at the same time as the peroxide disinfectant solution. The catalase-enzyme-containing neutralizing tablet is encapsulated with HPMC, which time-delays the neutralizer, thus allowing a controlled exposure time for the disinfectant. HPMC also acts as a lubricant dissolved in the storage solution. A pink hue created by cyanocobalamin (vitamin B12) indicates that the neutralizing tablet has been added to the system.

There are two potential pitfalls for patients using peroxide-based lens disinfection: toxic burn of the ocular epithelium and contamination of the unpreserved storage solution. It is not uncommon for patients using peroxide-based systems to place a lens that has been bathed in unneutralized peroxide on the eye. Fortunately, this type of chemical burn, although painful, is superficial and self-limiting.

The other concern is the potential for contamination of lenses stored in neutralized, unpreserved solution following the neutralization step. Although H₂O₂ systems have high antimicrobial efficacies at full strength, once neutralized they become unpreserved aqueous bathing solutions capable of supporting microbial growth. Nonpreserved peroxide systems work fine if used on a regular, preferably daily, basis. However, if lenses have been soaking in the neutralized solution for longer than one day, I recommend that the disinfecting/neutralization procedure be repeated prior to lens wear.

Attention should also be paid to the inside of the lens case cap as little or no disinfection occurs on these surfaces. The inside cap can be disinfected by inverting the lens case with fresh peroxide; follow the instructions of the individual system.

H₂O₂ lens disinfection systems work very well as both a disinfectant and to mitigate protein buildup on GP lenses. However, patients should not store “spare” lenses in peroxide vials due to lack of preservation in the neutralized aqueous solution.

SCLERAL LENS CARE

Scleral lenses are just large GP lenses; sclerals therefore are handled similarly to corneal GP lenses, but with more attention to detail. The same basic steps include daily cleaning, overnight disinfection, and sterile saline rinse/wetting prior to lens wear.

Daily cleaners, alcohol-based daily cleaners, or extra-strength cleaners are all recommended for daily cleaning after lens removal. Thorough rinsing is required so that no chemical residue remains on the lens surfaces.

For disinfection, any approved GP disinfecting product may be used on scleral GP lenses. Personally, I prefer peroxides, which offer excellent disinfection without preservatives. Be careful with large lenses because most peroxide systems can only accommodate up to about 16.5mm diameter scleral lenses.⁹ Larger lens disinfection/storage cases are available from some manufacturers. Instruct patients to use these systems daily and only with fresh peroxide solution. Peroxide-based systems are approved for up to seven days of storage, but in reality they are depleted of any antimicrobial effect after only a few hours.

GP lenses don’t absorb lens storage/disinfecting solution; however, a morning rinse with sterile saline is important to remove any residual storage products.

Only nonpreserved sterile saline should be used to rinse lenses after disinfection and before wearing. Patients may also 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 debris attraction. Gently rubbing wetting solutions on the front (outside) lens surfaces (only) can similarly enhance lens wetting.

Patients should fill the lens reservoir with isotonic, preservative-free sterile saline. Although the fluid-filled reservoir under the scleral lens is dynamic, the bathing solution will typically be in contact with the cornea for many hours. Therefore, single-use, unit-dose sterile saline is recommended. There are two unit-dose salines that are specifically labeled for scleral lens use. Patients should never use preserved saline or MPS products to fill the lens reservoir due to the possibility of ocular surface toxicity. Multi-dose, nonpreserved saline containers are prone to contamination and are not recommended.

The growing popularity of scleral GP lenses has highlighted our need for powerful daily cleaners, sterile non-toxic rinsing solutions, and scleral lens-designed peroxide disinfecting products.

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 the lens storage case after each use.
• Rinse the case with fresh care solution and tissue-wipe the well (except for peroxide cases).
• Leave lens storage cases open to air dry.
• Replace lens storage cases frequently (every one to three months).

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GP DIAGNOSTIC LENS MAINTENANCE

GP diagnostic lens sets will last for years with proper care and storage. Some trial lens sets will receive regular use, while others may be used only rarely. Regardless of their frequency of use, diagnostic lens sets must be properly cleaned, disinfected, and maintained to ensure safety and lens parameter accuracy.

Regularly Check Lens Parameters Unlike soft lenses, GP contact lens parameters can be accurately measured with standard office instrumentation. A magnifying loupe may be used to inspect contact lens surfaces for scratches and debris and to verify optic zone and overall lens diameters.

A lensometer can be used to check GP lens power (for high powers, front versus back vertex becomes important) and optical quality. A radiuscope can accurately measure the base curves of spherical and toric lenses as well as detect any lens warpage or posterior surface lens deposits. Periodically inspect all GP diagnostic lenses to ensure that each is in its correctly labeled container.¹⁰

Preventing Microbial Contamination Diagnostic GP contact lenses are best stored dry. If GP lenses are stored wet in conditioning/disinfecting solution, they will require regular maintenance to ensure an aseptic state. No contact lens disinfecting solution is approved for lens storage for greater than 30 days. Diagnostic lenses (and storage cases) must be re-cleaned and disinfected at least every 30 days if stored in a wet state. Solution evaporation, drying film formation, and chemical aging may alter the composition of the storage solution, which can compromise its antimicrobial efficacy.

All diagnostic contact lenses must be cleaned and disinfected prior to their reuse. The Centers for Disease Control and Prevention (CDC) recommends using ophthalmic grade 3% H₂O₂ for disinfection of rigid diagnostic contact lenses. Specifically, contact lenses used in trial fittings should be disinfected after each fitting by using an H₂O₂ contact lens disinfecting system for at least 10 minutes.^8,10 The last CDC recommendation was published in 1985 and specifically dealt with hard lenses and human immunodeficiency virus (HIV) contamination.¹¹ Author’s note: To my knowledge, there are no updated U.S. government guidelines for disinfection and storage of in-office, reusable GP diagnostic contact lenses. However, the International Organization for Standardization (ISO) issued recommendations (these are voluntary standards) earlier this year.¹²

The 2018 ISO document recommends that GP lenses be cleaned before and after each use according to the manufacturers’ instructions. Manufacturers shall specify the methods of disinfection to be used on their product(s). Two disinfection procedures are described: moist heat, which is appropriate for reusable hydrogel lenses but not for GPs; and H₂O₂, which can be used on both hydrogel and GP lenses. The recommended peroxide disinfection procedure calls for a three-hour soak in 3% ophthalmic H₂O₂ solution followed by neutralization. GP lens materials are not harmed by long soaks in 3% H₂O₂. The ISO document states that one-step peroxide systems are not considered appropriate.

See the sidebar on the right for my recommendations for diagnostic GP lens care.

CLEAN LENSES PROVIDE THE BEST VISION AND COMFORT

GP lens fitting and care requires more attention to detail compared to commodity soft lens fitting. However, GP lens fitting can be the most rewarding to practitioners and can maximize patients’ visual potential with even with the most irregular corneal surfaces.

Difficult-to-fit corneal topographies and ocular surface disease irregularities are often best managed with GP lenses. Scleral contact lenses provide therapeutic and vision rehabilitative properties that can overcome the therapeutic gaps encountered with traditional rigid and soft lenses. Just remember that crisp visual acuity and comfort are intimately associated with clean and smooth GP lens surfaces. CLS

MY (SIMPLE) RECOMMENDATIONS FOR DIAGNOSTIC GP LENS CARE

• Clean GP diagnostic contact lenses after each use with a GP daily lens cleaner and rinse thoroughly.
• Peroxide disinfection is recommended, followed by a sterile saline rinse and drying with a soft, lint-free paper tissue (lens paper).
• Store dry for long-term storage.
• Prior to reuse, clean the diagnostic lenses again with an approved cleaner, then rinse and wet with sterile saline for scleral lenses or with an appropriate wetting/conditioning solution for corneal GP lenses.

REFERENCES

1. Stapleton F, Keay L, Edwards K, et al. The incidence of contact lens–related microbial keratitis in Australia. Ophthalmology. 2008 Oct;115:1655-1662.
2. Liu YM, Xie P. The safety of orthokeratology—A systematic review. Eye Contact Lens. 2016 Jan;42:35-42.
3. Ward, MA. We Need Daily Lens Cleaners. Contact Lens Spectrum. 2012 Feb;27:21.
4. FDA 510 (k) Summary of Safety and Effectiveness # K071203, June 13, 2007.
5. Shovlin JP. Acanthamoeba keratitis in rigid lens wearers: the issue of tap water rinses. ICLC. 1990 Jan-Feb;17:47-49.
6. Ward MA. In Defense of Water: Another Look at Lenses and Water. Contact Lens Spectrum. 2009 May;24:27.
7. Lever AM, Sutton SVW. Antimicrobial Effects of Hydrogen Peroxide as an Antiseptic and Disinfectant. In: Handbook of Disinfectants and Antiseptics. Ascenzi, JM ed. CRC Press, 1995.
8. Linley E, Denyer S, McDonnell G, Simons C, Maillard JY. Use of hydrogen peroxide as a biocide: new consideration of its mechanisms of biocidal action. J Antiicrob Chemother. 2012 Jul;67:1589-1596.
9. Ward MA. GP Contact Lens Care Pearls. Contact Lens Spectrum. 2012 Oct;27:23.
10. Ward MA. In-Office Care and Disinfection of Diagnostic GP Lenses. Contact Lens Spectrum. 2011 Sep:26:25.
11. Centers for Disease Control and Prevention. Current Trends Recommendations for Preventing Possible Transmission of Human T-Lymphotropic Virus Type III/ Lymphadenopathy-Associated Virus from Tears. MMWR. 1985 Aug:34(34);533-534. Available at http://wonder.cdc.gov/wonder/prevguid/m0000602/m0000602.asp .
12. International Standards Organization (ISO) document: ISO 19979:2018(E).