Chemical systems [also called multipurpose solutions (MPSs)] that combine cleaning, rinsing, and disinfection are extremely popular with patients and practitioners because of their simplicity. MPSs consist of a combination disinfecting/cleaning/rinsing solution containing one or more preservatives. A separate surfactant cleaner, enzymatic cleaner, or both may be added; however, with disposable/frequent replacement soft lenses, these additional solutions are rarely necessary. These one-bottle care systems are very popular and are especially beneficial for those patients who tend to be noncompliant when using multiple bottles or are confused by a complicated system.

The problem that originally became apparent with chemical disinfection systems was the use of preservatives, such as thimerosal and chlorhexidine. Although both of these preservatives exhibit excellent preservative action, many patients were sensitive to them. The preservatives currently used cause less patient sensitivity. Occasionally, some patients may still
exhibit sensitivity, reporting symptoms of dryness, itching, burning, injection, decreased wearing time, and discomfort. A condition called multipurpose nonkeratitis has been reported.¹ The soft contact lens wearer using a multipurpose chemical solution presents with normal external findings, but complains of ocular dryness. Changing the patient to a preservative-free, hydrogen peroxide care regimen alleviates the dry-eye symptoms. A study with adolescents found that overall, patients on a hydrogen peroxide system show less staining and inflammatory response than those patients using a chemical care regimen.² The Andrasko Staining Grid and the Institute for Eye Research (IER) Matrix both pertained to solution-induced corneal staining. In the Staining Grid study, staining was assessed after 2 hours of wear and overnight soaking. The IER study investigators looked for the presence of staining three times over a 3-month period. Both studies found a hydrogen peroxide care regimen (ClearCare, Ciba Vision) to perform well with four silicone hydrogel materials (Acuvue Advance & Acuvue Oasys, Vistakon; O₂Optix, Ciba Vision; and PureVision, Bausch & Lomb). The three chemical care regimens resulted in inducing more corneal staining to a small extent in the Staining Grid study and even more in the IER Matrix study.³ Although the sensitivity rate may be lower with the newer preservatives, the practitioner needs to be aware that symptoms of sensitivity to them may be delayed and somewhat vague. If in doubt, changing the patient to a nonpreserved care regimen or a daily disposable contact lens modality may eliminate the symptoms.

Additionally, the preservatives in chemical care regimens are not as effective against bacteria, fungi, and Acanthamoeba as hydrogen peroxide care regimens. Chemical care regimens have been removed from the market because of cases of Fusarium (ReNu MoistureLoc) and Acanthamoeba (Complete Moisture Plus) that were linked to the use of these solutions. Although patient noncompliance may be partially responsible in these two outbreaks, it is also believed that the disinfection efficacy of these two solutions was decreased, part of the formulation facilitated the pathogen growth, and the solution caused disruption to the corneal surface creating a portal for the infection to occur.⁴ Extended wear, noncompliance, and poor lens hygiene increase the chances of a fungal infection.⁵,⁶ The risk of Acanthamoeba keratitis is increased by tap water use, swimming, use of hot tubs and showering with contact lenses on, and improper care. Recent outbreaks of Acanthamoeba keratitis may be associated with changes in water purification.⁷,⁸ Digital rubbing in these chemical regimens is important in removing Acanthamoeba from the lens.⁹ Digital rubbing and rinsing have been found to remove up to 99% of Acanthamoeba found on a lens before chemical disinfection.¹⁰ As would be expected, one study found that the care regimen (chemical or oxidative) is most effective when all steps are performed (i.e., rubbing, rinsing, and disinfecting).¹¹ The effects of chemical disinfection alone on Acanthamoeba and the human immunodeficiency virus (HIV) are minimal.¹² Other wearer tips to minimize the risk for Acanthamoeba keratitis include if lenses are worn during swimming, airtight goggles should be worn and, if not, the lenses should be disposed immediately after swimming.¹³ For more information on diagnosis and treatment of Fusarium and Acanthamoeba, see Chapter 21.

Chemical disinfection may be used on all types of lenses and has little effect on lens life. At minimum, 5 minutes to 4 hours are required for a chemical disinfecting cycle; however, as most patients perform disinfection overnight, this is rarely a disadvantage. Although no-rub, rinsingonly multipurpose solutions have been promoted to lens wearers, rubbing the lens with the multipurpose solution before disinfection is an important step to prevent the preservatives from binding to deposits, thus decreasing the effectiveness of disinfection. In addition, cleaning alone has been found to remove >90% of a measured amount of bacteria placed on new and used contact lenses, thus enhancing disinfection.¹⁴ The importance of rubbing and rinsing before disinfection cannot be overemphasized, as rubbing is often the first step noncompliant patients eliminate in their lens care systems. The microbial efficacy of these systems is based on the entire regimen (rubbing, rinsing, and disinfection), and when steps are omitted, the efficacy is thus reduced.¹⁵

Aquify (Ciba Vision) is the one chemical disinfection system that can be completed in 5 minutes. To disinfect a lens in 5 minutes, the lens should be rubbed on both sides for 10 seconds with three drops of Aquify, rinsed, and then soaked in Aquify for 5 minutes. This brief disinfection time is helpful if the patient must remove a lens during the day or for in-office disinfection (e.g., during the eye examination or a lens that has been dropped during insertion).

If a patient has a reaction to the preservatives in the solution, the preferable method would be to replace the lens. This is a simple process with a disposable lens. However, if the patient is wearing a conventional replacement, custom lens that needs to be salvaged, purging the lens may remove the offensive preservative. To purge a lens, place it in a vial of distilled water for 8 hours and repeat this for a total of three cycles. An 8-hour cycle in saline followed by disinfection in a nonpreserved system will complete the purging. Purging may also be used to remove fluorescein from a lens that has been stained with this dye.

A complete listing of available chemical disinfecting solutions is provided in Table 12.1.¹⁶,¹⁷,¹⁸

Another method of disinfection, oxidative, consists of a 3% hydrogen peroxide solution, neutralizing tablet or disc, case vial, and possibly a saline. Neutralization, by the disc or tablet, takes approximately 6 hours. The neutralizing tablet with Oxysept contains cyanocobalamin, which tints the solution pink to confirm that the tablet has been added to the hydrogen peroxide.¹⁹ The case vial should be replaced every 3 months. Oxidative disinfection can be more complicated and confusing for patients; however, one-bottle oxidative systems have greatly reduced patient confusion over its use. Oxidative disinfection is safe, effective, and preservative free. Contact lens wearers who use oxidative disinfection typically are very loyal to their system. Patients, particularly those with solution sensitivities, find that oxidative disinfection can make the difference between comfortable, all-day wear and the inability to achieve comfortable wear.

Oxidative disinfection utilizes hydrogen peroxide, which, in addition to disinfection, provides a deep cleaning of the lens.⁹ Hydrogen peroxide is hypotonic and has a pH of 4, which makes it effective at removing protein, lipid, and trapped debris.²⁰ Hydrogen peroxide has long been known for its antimicrobial characteristics. A longer exposure time has been recommended to be more effective against fungi and Acanthamoeba. This is accomplished by soaking the lenses 45 to 60 minutes in the hydrogen peroxide solution. Hydrogen peroxide is also effective against HIV and against fungal contamination by Aspergillus on soft contact lenses.²¹

Hydrogen peroxide is very acidic and will produce a mild to moderate punctate keratitis if it comes in contact with the cornea. No severe damage results if the patient fails to neutralize the hydrogen peroxide before lens insertion or does not fully neutralize the hydrogen peroxide (e.g., old catalytic disc or too brief of a neutralization/dilution soak); however, the patient will experience stinging, moderate discomfort, and injection. Treatment for this keratitis requires proper neutralization or dilution of the residual hydrogen peroxide in the lens and discontinuing lens wear until the symptoms have disappeared (i.e., 2 to 12 hours). The use of an artificial tear drop will improve comfort and reduce symptoms for a patient with this type of keratitis. To assist in the prevention of hydrogen peroxide being used directly in the eye, the hydrogen peroxide solutions are currently packaged in bottles with red tips, and warning labels on the bottles direct the patient not to use this solution directly in the eye (Fig. 12.1).

Removing the hydrogen peroxide before lens insertion may be accomplished by one of three methods. Two of the three methods are based on a catalyst that is contained primarily in a tablet or platinum disc. Advanced Medical Optics (AMO) has a preservative-free tablet that is placed directly in the vial containing hydrogen peroxide. The neutralizing tablet is coated with a viscosity agent that prevents activation of the tablet for 20 to 30 minutes, thus allowing disinfection with hydrogen peroxide to occur before neutralization. This tablet is placed in the vial immediately with the hydrogen peroxide, Oxysept-Ultracare formula (AMO).

The AODisc (Ciba Vision) is a platinum disc attached to the lens cage that begins neutralizing ClearCare or AOSept (Ciba Vision) immediately on contact when the lens cage is placed in the vial. The entire vial with the disc should be replaced after approximately 3 months of daily use or 100 cycles if used weekly. When the disc is losing its effectiveness, it will not fully neutralize the hydrogen peroxide, resulting in a mild stinging sensation when the lenses are inserted. The vial also includes an opening in the lid, which should remain upright and unobstructed so oxygen may escape during the neutralizing step. Sauflon Pharmaceuticals also uses a neutralizing disc to neutralize its hydrogen peroxide solution (Sauflon One-Step Cleaning & Disinfection Solution).

The final method of removing hydrogen peroxide from the lens is dilution of hydrogen peroxide by osmosis with the use of saline solution. Although no commercially available care regimens utilize this method, it is still valuable for the practitioner to be aware of in cases in which the wearer may need an emergency backup method for the tablet or disc. The hydrogen peroxide is emptied from the vial after disinfection is completed. The lenses and vial are generally rinsed once with saline solution and allowed to stand in saline solution for a specified time period (e.g., 10 minutes). Studies have shown that there is no significant difference in the “sting factor” between this type of method and that of neutralization with a catalyst.²²,²³

Oxidative disinfection systems were previously categorized as one-step or two-step disinfection systems. Currently, only one-step systems are available. Two-step systems have been discontinued, as one-step systems are useful in increasing patient compliance. However, in a one-step system, the concentration of hydrogen peroxide is much reduced and may not provide a long enough exposure time. For example, past studies found that only the two-step systems were effective against Acanthamoeba.⁹,¹²,²⁴ AOSept has been found to be significantly more effective against Acanthamoeba than chemical disinfection when cleaning and rubbing of the lens were not performed before disinfection.¹¹ Proper cleaning and rinsing before all types of disinfection will enhance the effects on Acanthamoeba. Likewise, hydrogen peroxide has been found to be more effective on Pseudomonas than a multipurpose solution when cleaning and rubbing were not performed.²⁵ New evidence shows that hydrogen peroxide is effective against the trophozoite forms of Acanthamoeba.²⁶ ClearCare and AOSept have been found to demonstrate antimicrobial activity against the cyst form of Acanthamoeba castellani after 6 hours.²⁷ In the same study, a multipurpose chemical disinfection solution was shown to have no antimicrobial activity against the cyst form after 6 hours. These findings show protective benefits of hydrogen peroxide for noncompliant contact lens wearers.²⁵

MiraFlow Extra Strength Cleaner (Ciba Vision), added to the AOSept disinfection system, will enhance disinfection because it has disinfecting characteristics of its own. Caution should be taken to ensure that the patient thoroughly rinses MiraFlow from the lens before disinfection. A chemical reaction between AOSept and the catalytic disc will increase the sudsing action of any residual cleaner and may result in all of the AOSept pouring out of the opening in the vial, leaving the lenses in an empty vial with inadequate disinfection.

Three percent hydrogen peroxide is commercially available over the counter, typically in brown bottles for nonophthalmic use. The cost of this solution is much less than that of solutions used in contact lens disinfection. Although it is similar to that used for contact lens disinfection, it is not ophthalmically pure and may contain inexpensive stabilizers and/or heavy metals that may cause lens discoloration. In addition, contamination of the solution may easily occur in these wide-mouthed containers, whereas the narrow openings found in contact lens solution containers decrease the risk of contamination. Available oxidative disinfection systems are listed in Table 12.2.¹⁶,¹⁷,¹⁸,¹⁹

Because of the differences in hydrogel versus silicone hydrogel materials, not all solutions may perform as well with silicone hydrogel lenses. The solutions currently indicated by the Food and Drug Administration (FDA) for use with silicone hydrogel lenses are ClearCare and Aquify (Ciba Vision) and Opti-Free RepleniSH and Opti-Free Express (Alcon Laboratories). In addition, silicone hydrogel materials are more prone to lipid deposits; therefore, rubbing the lens before disinfection is recommended. MiraFlow Extra Strength Cleaner (Ciba Vision) is useful for removing lipid deposits if rubbing and frequent replacement of the lenses is not sufficient. In the IER Matrix study, PureVision lenses were found to exhibit more solution-induced
corneal staining with Aquify, Opti-Free RepleniSH, and Opti-Free Express than the other silicone hydrogel materials in the comparison. In the IER and Staining Grid studies, ClearCare performed well with the PureVision material.³

Thermal disinfection is the least expensive and most effective disinfection system in the short term; however, as the heat bakes on the deposits not cleaned off the lens, lens life is shortened and complications such as giant papillary conjunctivitis [GPC, also known as contact lens papillary conjunctivitis (CLPC)] or red-eye reactions may arise from the deposited lens. As a disinfectant, thermal disinfection is effective against all forms of bacteria, including Pseudomonas, both cyst and trophozoite forms of Acanthamoeba, and HIV. The solutions used with thermal disinfection can be preservative free for those patients sensitive to preserved solutions. Despite the advantages, the popularity of thermal disinfection has declined to the point where it is not used by contact lens wearers because of electrical requirements and the long-term problem of baked-on deposits. In addition, heat is contraindicated with lenses containing >55% water, and caution must be taken when switching a patient from another type of disinfection to thermal since it is not interchangeable with all systems. Manufacturers no longer support this type of disinfection with heat units for individual use. It is used for in-office disinfection of vial lenses.

Other alternative methods of disinfection that are available are ultrasonic disinfection (Lens Comfort, Best Health, Inc.) and UV subsonic disinfection (Purilens UV, Purilens/Lifestyle Co. Inc.).¹⁷

Most diagnostic soft lenses are used on a one-time basis and discarded. This is the most acceptable method of diagnostic lens use; there is no danger of ocular infection spread from one patient to the next because the lenses are packaged in sterile containers. At the present time, some diagnostic lenses are reused after being disinfected, which does not produce a sterile lens. There is no perfect method of disinfecting large numbers of lenses and keeping these large numbers of diagnostic lenses disinfected. Large thermal disinfection units are available to disinfect lenses in glass vials, which is an acceptable method of disinfection; however, some lens materials contraindicate thermal disinfection use, primarily those with >55% water content. Oxidative disinfection, although an excellent method of disinfection, is difficult to use for diagnostic lenses because of the necessity of disinfecting the lens in a special case and transferring the disinfected lens to a glass vial. The lens may become contaminated in the transfer process, or the vial may become contaminated. It is acceptable to store lenses in a glass vial in a chemical disinfecting solution; however, their effects on Acanthamoeba and HIV are questionable. In addition, it has been recommended, based on study results, that diagnostic lenses disinfected with oxidative or chemical disinfection be redisinfected at least once a month to prevent contamination.²⁸

Possibly the best type of in-office disinfection, disregarding disposable diagnostic lenses, is the combination of two disinfection systems. In the past, chemical disinfection was not compatible with thermal; however, Opti-Free Express (Alcon Laboratories), as a result of both the preservative action and the omission of a surfactant, may be used and is approved for use in heat disinfection. The other chemical disinfection systems, conversely, contain a surfactant that, after repeated thermal disinfection cycles, may result in a cloudy lens. It is acceptable to fill a glass vial with Opti-Free Express and place the vial in an in-office thermal disinfecting unit. As with any lens worn by the patient, the lens should be thoroughly cleaned and rinsed before disinfection. Lenses of >55% water content may be stored in Opti-Free Express or other chemical disinfecting solution without thermal disinfection. The practitioner must keep in mind the limitations of the systems. Thermal disinfection is effective against Acanthamoeba
and HIV; however, chemical disinfection systems are questionable. Any lens used on a known HIV-positive patient or a patient exposed to Acanthamoeba should be disposed of and not reused, even though at the present time it is thought that the risk of transmission via the tears is low.²⁹,³⁰

Another combination method is to clean the diagnostic lens with MiraFlow Extra Strength Cleaner (Ciba Vision); disinfect in one of the 3% hydrogen peroxide disinfecting solutions for 2 to 12 hours, followed by neutralization; and then store the lens in the glass vial in a chemical disinfection solution. As noted previously, the lenses should be redisinfected every month. Autoclaving will produce a lens that should be sterile for a year. A procedure for autoclaving is to clean the lens with MiraFlow cleaner, rinse with a nonpreserved saline, and put the lens in the glass vial with nonpreserved saline. The vial should be sealed and placed in an autoclave. This final method guarantees sterility of the lens.³¹