contact lens solutions

FOR EVERY CONTACT LENS PROBLEM, THERE IS A SOLUTION

Follow these two steps to ensure you choose the correct lens-care solution for your individual CL wearers.

BY SUSAN RESNICK, O.D., F.A.A.O., New York.

In developing a clinical rationale for the selection of a lens-care solution for soft contact lens (CL) wearers, keep in mind that you’re “juggling” three variables: solution characteristics, ocular surface characteristics and lens material characteristics. So, the compatibility of the solution with the patient’s unique physiological profile, wearing habits and lifestyle, as well as with the CL material, are all factors that should influence your decision to recommend a specific product.

Here, I’ll discuss the two steps you should take to ensure you choose the right lens-care solution for your individual soft-lens patients.

1. Understand solution characteristics

Lens-care solution choices include both hydrogen peroxide-based (unpreserved) and chemical multipurpose (preserved) disinfecting systems. The required disinfection (soaking) times will vary depending upon the specific product. Care indications may range from a speedy ten-second rub with five-minute soak to a six-hour minimum (or overnight) soak.

Some disinfectants, the biguanides in particular, result in higher amounts of corneal staining, especially when combined with certain lens materials.

The primary function of a lens-care solution is disinfection. With the exception of hydrogen peroxide-based products, the preservatives in multipurpose solutions (MPS) serve as the biocidal agents. Secondary components, including cleaning agents (e.g. citrate, poloxamer 237) and chelating agents (e.g. hydranate) are responsible for removing debris and preventing deposit formation. Surfactants (e.g. Tetronic 1304, poloxamine) function to promote lens surface wettability along with other compounds such as hydroxypro-pylmethlycellulose (HPMC), which promote comfort by virtue of improving lens lubrication and conditioning. Because reduced comfort is often related to a sensation of dryness, solution manufacturers are redoubling their efforts to address this issue. We can expect ongoing efforts in this area given the industry’s goal to reduce patient drop-out as well as to introduce products specifically designed to enhance the sur-face wettablility of the newest generation of silicone hydrogel lenses.

Solution manufacturers seek to achieve a delicate balance between antimicrobial efficacy and biocompatibility. While it’s desirable that the components responsible for increasing wettability have an affinity for the lens surface, it’s undesirable for the pre-servatives to be either absorbed or adsorbed. This is because the binding and subsequent release of these biocides into the tear film may ultimately compromise the ocular surface.

In addition to cleanliness and enhanced comfort, solution manufacturers recognize that patients place a premium on convenience. This feature has been most notably offered among the current array of single-solution stand-alone products. And while promoting convenience has also been largely the reason that “no-rub” indications have made their way onto product labels, the reality is that you best serve your patients by instructing them to rub. While “no-rub” lens-care regimens were formulated to optimize passive protein removal, digital cleaning serves to remove the lipids, which otherwise decrease surface wettability and result in symptoms of dryness. This is especially important given the lipophilic tendencies of today’s silicone hydrogel lenses. Furthermore, rubbing in combination with rinsing has been shown to reduce pathogen load alone by 90%, providing a potentially critical component in patient protection.¹ Another aspect of convenience is storage flexibility. Lens-care solutions have different minimum soaking requirements as well as differences in long-term vs. short-term antimicrobial activity and, therefore, storage capability. By recognizing these differences, you can prescribe a regimen that most conveniently and safely meets the needs of even your marginally compliant patients.

It’s important to recognize that while we, as optometrists, may broadly categorize and separate hydrogen peroxide solutions from MPS, clinically significant differences often exist among brands in each category. To obtain the information you need to understand these distinctions:

• Seek the numerous published clinical studies, which highlight differences in attributes ranging from cleaning efficacy to enhancing comfort to compatibility. Products must pass primary stand-alone criteria to be labeled as a multipurpose disinfecting solution (MPS). In stand-alone efficacy testing, no rubbing or rinsing is involved; in fact, no lenses are involved. As all approved solutions have passed the minimum Food and Drug Administration (FDA) standards for disinfection (3 log kills for bacteria and 1 log kill for fungi), you can acquire useful insights into the the secondary strengths and weaknesses of the various lens-care solutions through additional clinically relevant and often more rigorous investigation.

For example, you might critically review published studies related to whether the disinfection efficacy of a specific lens-care solution is affected by external factors, such as the presence of CLs and/or the addition of organic soil.

• Examine the product labeling. The FDA also approves unique product labeling in some cases to signify that the results of post-new-drug-approval (NDA) testing have provided satisfactory evidence that specific claims, such as reconditioning, can be made. (Reconditioning refers to a solution’s ability to attract moisture to the lens surface even as the lens is being worn. Chemically, this is achieved by its interaction with the lens surface as well as with the tear film. This would result in patients reporting better “throughout-the-day” comfort or reporting that their lenses feel moist when using that particular solution.)

• Employ the Andrasko Cor-neal Staining Grid. This handy tool, which can be found at www.staininggrid.com, enables you to ascertain the level of biocompatibility of several CL/multipurpose solutions. The grid is comprised of solutions listed across the top and the lens materials listed in the first column. Percentages, which appear in each cell, represent the aver-age amount of corneal surface area that stains two hours post lens/solution insertion.

• Rely upon your own clinical experiences and observations. Keep your own notes on your clinical experiences with, and observations of, lens-care solutions, so you can use them for future reference.

2. Develop a clinical profile

Once you have a working knowledge of the various available lens-care solutions and their differing characteristics and interactions, develop a clinical patient profile, so you can decide which solution is best for a particular patient. Do this by performing the same three steps you carry out on a patient when deciding on a specific CL design and modality. These steps are:

• A focused case history. When examining first-time CL wearers, inquire about atopic tendencies (e.g. allergic rhinitis, asthma and atopic dermatitis), including a history of sensitivity to skin-care products or cosmetics. This is important because patients who report these tendencies and sensitivities may ultimately be more prone to exhibit sensitivities to the ingredients in certain lens-care solutions.

When examining previous and current lens wearers, inquire about a history of sensitivity to any previously used lens-care solution(s). This is important because these patients often are unaware that minor symptoms, such as transient stinging upon CL insertion, may actually be related to their lens-care solution and not the lenses themselves.

Finally, ask your first-time wearer or newly refitted patient what wearing schedule he desires or anticipates. For example, will he wear his lenses on a daily basis or just on weekends for sports or social activities? The answer to this question will enable you to determine whether he’s apt to leave his lenses in storage solutions for extended periods of time, yet expect them to be “ready to wear” at a moment’s notice. For a patient such as this, an MPS in which the disinfection activity lasts for up to a month is preferable to a hydrogen peroxide-based system, which, once neutralized, is purely an unpreserved aqueous bath.

• A careful anterior segment evaluation. When probing into dry-eye symptoms, ask current wearers or previous dropouts whether they experience any sensations of dryness, grittiness or transient blurring when not wearing their lenses. Do their symptoms vary with environment, task or time of day? Remember to question patients about end-of-day CL comfort and how frequently they use lubricating or rewetting drops. The answers to these questions may help differentiate between CL-related dry eye and physiologic dry eye. So, for patients with CL-related dry eye, in which you suspect symptoms relate to pre-lens tear film evaporation, choose a lens-care product that has a de-mulcent or lubricant and promotes tear film retention on the lens surface.

In addition, perform clinical tests that include blink pattern, tear volume and tear break-up time and vital staining of the conjunctiva, cornea and lid-wi-per epithelium. Also, be aware of the tarsal plate appearance. You may gain an impression of relative tear quantity by viewing the tear meniscus in conjunction with phenol red thread or Schir-mer testing.

Upon instillation of sodium fluorescein, measure tear break-up time, and note the location and severity of corneal and conjunctival staining. Evert the lids and examine for staining of the lid-wiper epithelium, and grade any papillary hypertrophy of the tarsal plates. The results of these objective clinical tests reveal whether the patient has pre-existing ocular surface abnormalities and/or inflammatory signs and to what degree. Because signs of solution toxicity may also be typified by these findings, have good baseline clinical data so that you can detect future problems fast. For patients with marginal pre-existing ocular surface abnormalities, it’s often best to prescribe a hydrogen peroxide-based system at the outset. (See “Matching The Solution With The Patient,” page 38.)

• Appropriate follow-up. Post-dispensing follow-up allows you to monitor for an exacerbation of pre-existing ocular surface abnormalities and/or inflammatory signs and determine the severity — alerting you to the possibility of solution-related complications. You’re well aware that certain lens materials and the preservatives (biocides) in certain lens-care solutions may create a cytotoxic environment. Clinically, a cytotoxic effect may present as corneal staining.² Studies have shown that this staining may occur without symptoms.³ Solution-related corneal staining is most easily observed (with a Wratten filter) at two to four hours after lens insertion.⁴ Given the increased potential for microbial invasion and corneal infection when the epithelium is compromised, your ultimate goal is to reduce risk in CL wearers by routinely monitoring for corneal staining and taking appropriate measures to minimize solution-related ocular stress.⁵

Because patients are repeatedly distracted from your lens-care solution prescription by coupons, generic brands and colorful displays on the retail shelves, take the time to explain and reinforce to the patient the reasons behind your prescribing a specific product. Explain to him that you’ve carefully considered his clinical profile and needs to prescribe the lens-care solution you believe will best complement his ocular health and lifestyle.

References available upon request.

DR. Resnick is in private practice in new york. She is a member of the American Optometric Association and a Diplomate of the Cornea and Contact lens Section of the American Academy of Optometry. E-mail her at susanr58@aol.com.