Corneal Reshaping and Lens Care: Improving Compliance
BY JEROME A. LEGERTON, OD, MS, MBA, FAAO
Overnight contact lens corneal reshaping or orthokeratology is a useful vision correction modality for many patients worldwide. It's important to remember that the U.S. Food and Drug Administration once considered these lenses significant risk devices because of their use in the closed eye during sleep. The importance of contact lens care and prescribed replacement are elevated to meet the health maintenance objectives of closed eye wear.
Pellicle Formation With GPs
There is historic evidence of biofilm or pellicle formation on GP lenses. Metabolic byproducts combine with tear constituents, residue from care product components and airborne material and collect on lens surfaces. Over time these materials form a plaque or pellicle that becomes increasingly difficult to remove. The result is a loss of lens surface integrity. The pellicle can cause mechanical trauma, challenge the epithelium chemically and may be a potential antigen for an allergic response.
Clinicians have reported cases of patients who, after months of successful overnight corneal reshaping, present with acute episodes of ocular pain and central corneal abrasions (Figure 1). Lens inspection in these cases reveals areas of deposits on the posterior lens surface for the affected eyes.
Figure 1. Corneal abrasion caused by posterior surface lens deposits.
These reports suggest that maintaining the integrity of the posterior lens surface is important as a preventive measure. Cleaning or replacing the respective lens can help resolve signs and symptoms upon resuming lens wear.
Inspect Lenses as Part of Case Management
I believe it's wise for practitioners to incorporate lens inspection in their patient case management. During the first phase of corneal reshaping treatment, it's common to see patients at one week, two weeks and one month for follow up. Most often, patients report for their visits having already removed their treatment lenses that morning. It's advisable to instruct them to bring the lenses to every visit. While you examine the patient, a trained technician should inspect the lenses for cleaning regimen effectiveness.
A technique for inspection starts with gently blotting the lens with a tissue designed for contact lenses and looking through the blotted lens for clean surfaces. Avoid inadvertently cleaning the lens by using a rubbing action — such rubbing during inspection would prevent the technician from observing inadequate cleaning on the part of the patient. Gently blot the lens, hold it by the edges and look through the lens to see if the surfaces are clean.
A 5X to 7X loupe may also be useful to inspect the surfaces. The surfaces will have a clean, highly reflective appearance if the patient is adequately cleaning them (Figure 2).
Figure 2. An adequately cleaned corneal reshaping lens.
The presence of a central smudge, haze or significant pellicle (Figure 3) is an indication that you need to retrain the patient on proper lens cleaning. This is an opportunity to emphasize to patients that cleaning of the posterior surface of the lens will help them maintain clear, comfortable vision without episodes of pain and disrupted wear.
Figure 3. A corneal reshaping lens with significant pellicle formation.
Daily Cleaning and Storage
Instruct patients to clean their lenses immediately upon removal, which is when they are the dirtiest and have the most surface coating. Patients should gently rub lenses with the prescribed care solution. Some practitioners recommend the use of a clean cotton swab to clean the posterior surface of the lens (Figure 4) because the size of patients' fingers may not match the base curve of their lenses. A trained technician can demonstrate the appropriate force that will not damage the lens or its surface.
Figure 4. A cotton swab may help properly clean the posterior surface.
The swab should not be used dry against a dry lens surface. Rather, instruct patients to moisten the swab with the prescribed care solution and apply it to a lens that is also wet. Further, lenses should never be stored dry. An acute episode of corneal staining may result from biofilm that has dried on a lens that a patient did not clean and subsequently placed in a dry case.
Also instruct patients to make sure the lens is concave side up and covered with the care solution in the case. It's possible for lenses to go into the case convex side up and trap a bubble under the posterior surface. An unclean lens placed in a case that traps a bubble in this way may facilitate formation of a central pellicle.
Lens Inspection by Patients
The standard of care for overnight corneal reshaping includes periodic visits between annual comprehensive examinations. Practitioners see patients every three, four or six months for post-treatment follow up depending on their practice policies. The longer the interval between follow-up visits, the more important it is to have patients inspect their lenses for cleaning effectiveness.
You can train patients to inspect lenses in the same manner that technicians inspect them. An inspection once a week or once a month may be all that is needed. Suggest to them to inspect their lenses every Sunday morning or on the first day of each month. Seeing a clean lens surface is good feedback for patients.
Considerations for Plasma-Treated Lenses
Most lenses prescribed today for overnight corneal reshaping are plasma-treated. Some practitioners mistakenly believe that the plasma treatment used by GP lens manufacturers is a film or coating. It is not, rather, it's a surface modification conducted in a plasma chamber in which a vacuum is first created followed by the introduction of a gas (usually oxygen) that is charged and destabilized by a radio frequency to allow electrons to be released and to bind with the lens surface. These electrons change the surface silicon molecules to produce a silicate glass-like, water-loving nature rather than a silicon rubber hydrophobic nature. The result is a lens surface that is far more hydrophilic.
This modification is only surface deep. For this reason, any process that removes surface material will eliminate the improved wetting of the plasma-treated lens. Avoid in-office polishing and the use of abrasive cleaners that remove lens material. Plasma-treated lenses should always be stored wet. Silicon molecules are understood to be mobile within a lens. If the lens is allowed to dry, the air-loving silicon molecules within the lens can move to the surface to replace the modified water-loving molecules.
Prescribed Lens Replacement
Prescribed replacement is the practitioner-driven modality of prescribing the best lens for each patient and replacing it at the interval that's best for each patient. Consider prescribing at least annual lens replacement for corneal reshaping patients, who sleep in their lenses every night and handle their lenses every day. The posterior surface of the lens is in contact with the central cornea. If trauma were to occur it could be close to the visual axis.
Annual replacement was an early recommendation by Paragon Vision Sciences, the first company to receive an FDA approval for overnight treatment. Only eight Medical Device Reports have been filed against Paragon CRT in its six-year history. While this supports the overall safety of Paragon CRT, it may also support the recommendation for annual replacement of the lenses.
|TABLE 1 A Plan for Posterior Surface Integrity for CRT Lenses|
Consider offering patients an annual aftercare agreement that covers a pair of lenses and your recommended visits that are not covered by patients' annual comprehensive examination or third party coverage.
Putting it All Together
Think preventively to avoid unscheduled visits and interruption of corneal reshaping treatment. The objective is to maintain the integrity of the posterior surfaces of the lenses (Table 1). Start early in the case management of your patients by inspecting their lenses to see if their cleaning regimen is effective. Train them on posterior surface cleaning and periodic lens inspection so they can get feedback on the effectiveness of their cleaning technique.
Prescribe annual replacement of their lenses to keep patients in fresh lenses with quality surfaces. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #156.
Dr. Legerton was in private practice in San Diego for 26 years followed by 14 years in product development with Pilkington Barnes Hind, Visx, Paragon Vision Sciences and SynergEyes. He is an inventor on 18 patents for aberration blocking contact lenses, presbyopic laser refractive surgery, corneal refractive therapy, hybrid contact lenses and myopia progression control.