Preservatives are capable of either killing microorganisms (bactericidal agents) or inhibiting their growth (bacteriostatic agents).² They are the active ingredients in these solutions (and all other GP care solutions) that should perform the following functions³:

There are numerous preservatives currently in common use, all differing in their mode of action and effectiveness. The most common preservatives include benzalkonium chloride (BAK), chlorhexidine, thimerosal, ethylenediamine tetraacetate (EDTA), polyaminopropyl biguanide (PAPB), polyquarternium-1 (polyquad), and benzyl alcohol (Tables 6.1 and 6.2).

Wetting/soaking solutions typically contain either polyvinyl alcohol or a methylcellulose derivative as a wetting agent.

Polyvinyl alcohol has several properties that make it a beneficial additive to GP lens solutions.² It is water soluble and is relatively nonviscous and nontoxic to ocular tissues. It has good viscosity-building properties and exhibits good spreading and wettability on the eye and lens surfaces.²⁰,²¹ Also, unlike methylcellulose, polyvinyl alcohol does not retard regeneration of corneal epithelium.²² Methylcellulose derivatives have been used successfully as wetting agents in more viscous GP solutions.

GP cleaners and traditional hard lens cleaners may contain nonabrasive surfactant (detergent) cleaning agents to remove contaminants (e.g., mucoproteins, lipids, and debris) from the lens surface. The use of digital pressure or friction during the cleaning process is important in removing deposits from rigid lenses. Optimum Extra Strength Cleaner (Lobob Laboratories, Inc.) is an example of a nonabrasive surfactant lens cleaner.

Abrasive particulate matter has been used in cleaners as an effective adjunct in removing adherent mucoproteinaceous deposits from the lens that may be resistant to use of the surfactant alone. The daily use of abrasive cleaning regimens has been demonstrated to be more effective than the use of nonabrasive cleaners.²³ However, two problems have been described with abrasive cleaners. First, small surface scratches have been observed under high magnification.²⁴ Second, inducing minus lens power while reducing center thickness can result.²⁵,²⁶,²⁷ These problems have been minimized by the introduction of small-particle abrasive cleaners; however, abrasive lens cleaners may be contraindicated for lens materials with hyper-oxygen permeability (Dk) as well as for lens materials that have been plasma treated (discussed below). Examples include Boston Cleaner and Boston Advance Cleaner (Bausch & Lomb) and Opti-Free Daily Cleaner (Alcon Laboratories, Inc.).

GP lens care systems have traditionally embraced two-bottle regimens composed of separate cleaning and soaking solutions. One-bottle GP systems, combining these procedures, are a more recent innovation. These solutions use surfactant soaking, intended to dissolve deposits during the overnight soaking cycle; therefore, little digital pressure is necessary and warpage is less likely.²⁸ Optimum Soaking Solution (Lobob Laboratories, Inc.) contains nonabrasive surfactants; it is used for both cleaning and disinfection. It should be rinsed before insertion to remove the benzyl alcohol and facilitate the mechanical removal of lens debris. Boston Simplus (Bausch & Lomb) and Unique pH (Alcon Laboratories, Inc.) are examples of multipurpose lens care products that do not require rinsing before insertion.

The lens care system should be prescribed for the needs of the patient. For example, Boston Original was formulated specifically for silicone/acrylate lens materials that are predisposed to protein deposition. Boston Advance Comfort Care was designed for fluoro-silicone/acrylate lens materials that are more likely to attract lipids. Multipurpose lens care systems may be most appropriate for patients who do not tend to deposit lenses or who are not compliant with twobottle lens care regimens. Patients who exhibit sensitivity to one formulation may be better served by a system using a different preservative.

The use of a weekly enzymatic cleaning regimen for GP lens wearers has been proven to be a beneficial adjunct to surfactant cleaning in protein removal from the lens surface.²⁹ In addition, enzyme use has not been reported to cause any adverse effects for GP lens wearers.³⁰

More recently developed protein removal products are in liquid, rather than tablet, form and may be used with the manufacturers’ accompanying storage solution. Boston One-Step Liquid Enzymatic Cleaner (Bausch & Lomb) is added to the storage solution weekly, whereas SupraClens (Alcon Laboratories, Inc.) is added to the storage solution daily. Both products should be rinsed before insertion. Boston One-Step is composed of subtilisin; SupraClens is a pancreatin derivative. Both products are designed to promote patient compliance and meet the patient’s desire for convenience.³¹,³²

The use of laboratory-approved, extra-strength cleaners such as the Boston Lens Laboratory Cleaner (Polymer Technology Corporation) or Fluoro-Solve (Paragon Vision Sciences) can be beneficial. The Boston Lens Laboratory Cleaner, a solution consisting of several surfactants, can be beneficial for in-office cleaning of lenses that either exhibit poor initial wettability or have acquired a heavy film over time. However, surface debris that is more tenacious and difficult to remove, such as pitch or wax, can be removed only with Fluoro-Solve, which is a mild solvent.
MiraFlow (Ciba Vision), not approved for routine GP use, can be an excellent restorer of lens surface wetting. Since prolonged and repeated exposure to MiraFlow may result in permanent damage because of parameter changes,³³ brittleness, and cracking caused by isopropyl alcohol,³⁴ it should be used for no more than 30 seconds and then thoroughly rinsed off. Menicon PROGENT Intensive Protein remover is a further example of lens care products intended for professional in-office use. Available GP lens cleaners are listed in Table 6.3.

Plasma treatment for GP lenses removes residue from the manufacturing process and imparts an ultra-clean lens surface. This can enhance lens wettability and patient comfort and vision, particularly upon initial dispensing and early lens wear. Certain lens materials (Menicon Z) are routinely manufactured with plasma treatment, whereas other materials (Boston and Paragon) utilize plasma treatment at the discretion of the laboratory or practitioner.³⁵

The patient’s vision should be assessed. Biomicroscopy should then be performed to evaluate lens position and surface wettability. If both good lens centration and surface wettability are present, an overrefraction can be performed to determine the necessary additional correction.

If the visual acuity is equal to the expected value, typically a spherical over-refraction only is indicated. If a reduction of one line or greater is present, a spherocylindrical over-refraction should be performed. Just as the diagnostic fitting is imperative, both for obtaining a proper fit and for enhancing patient motivation (by the knowledge that contact lenses can be tolerated), so too is the dispensing visit important in continuing this momentum toward eventual patient success by the ability to see, handle, and care for the new GP lenses.

If an uncorrected cylinder that is not residual in nature is causing reduced visual acuity, overkeratometry should be performed to determine if the lens is flexing. If the keratometry readings are not spherical, flexure is present. This induced flexure can be minimized by selecting a flatter base curve radius (e.g., 0.50 D minimum) or increasing center thickness by a minimum of 0.02 mm.³⁷

The use of a biomicroscope is essential for evaluating lens centration, lag, fluorescein pattern, and surface wettability (although a Burton lamp would be a valuable adjunct for assessing fluorescein pattern). The lens-to-cornea fitting relationship initially should be evaluated using a wide beam with low-intensity white light and low magnification to scan the lens surface. In addition, the lens can be evaluated for regions of poor wettability or hazing. If the patient experiences variable visual acuity in combination with poor initial wettability, this problem can be minimized by presoaking the lenses for at least 24 hours to precondition the surface before insertion.

If poor wettability is present after presoaking the lenses, an in-office cleaner can be used or approved laboratory solvents should eliminate the problem. Polishing the front surface of the lens also may be beneficial; however, this should be performed after the lens is initially cleaned with an in-office cleaner and only if the lens has not been plasma treated.

Comprehensive evaluation of the fluorescein pattern is also important. Is the pattern similar to that observed at the diagnostic fitting visit? The use of high illumination, low magnification, and a moderate-to-wide beam width with cobalt filter should be beneficial when observation is by biomicroscope. If there is difficulty in observing the pattern, a Wratten no. 12 or similar filter can be used, especially if the lens material contains an ultraviolet inhibitor. In addition, if lower magnification is necessary to evaluate the pattern accurately, or to view both eyes simultaneously, a Burton lamp can be used.

The key to teaching patients to handle GP lenses successfully is reassurance. No matter how frustrating it is to the person performing the instruction, that feeling of frustration must not be conveyed to the patient. The instructions must be provided slowly and one at a time. Performing group instruction is distracting and denies the patient the necessary one-on-one personal instruction. The patient should not have the perception that the eye care provider or assistants have lost confidence in the patient’s ability to learn how to handle the lenses properly; otherwise, feelings of failure and surrender may result, possibly leading to the attitude that contact lenses will never be worn again. Conversely, if the patient feels confident about handling the lenses, a perception of satisfaction and success is often present. A minimum of three successful insertions and removals is recommended, although the number depends on how confident the patient feels. If it takes two or three visits (closely spaced to maximize memory of techniques and to minimize further anxiety) for the patient to master lens handling, it is often worth the effort. This is more often a problem with presbyopic patients, who not only are experiencing blurred vision at near, but also may have lived 40 or more years without having a foreign body placed on their eye, thereby increasing anxiety.

Patients should be instructed to insert and remove the lenses over a cloth or paper towel spread on a table (not over a sink drain). In addition, patients should be asked and reminded to avoid oily substances such as hand creams, lotions, or cosmetics, and their hands should be washed and rinsed thoroughly prior to handling the lenses. It is important for both practitioner and staff members to set a good example by washing hands before handling lenses in the office and requiring patients to do likewise.