The topic of a session and debate at the recent Global Specialty Lens Symposium (GSLS) in Las Vegas was: “Do specialty lenses need special care?”

The reason for a session devoted to this topic is that contact lens care, maintenance, and safety are highly undervalued. Much attention in our specialty lens field is paid to the fitting process and the indications—but a large part of the success, or failure, of specialty lenses pertains to contact lens solutions, hygiene, and handling. A distinguished global panel from Hong Kong, the United Kingdom, and the United States covered orthokeratology (ortho-k), scleral lenses, and specialty soft lenses in the general session “Safety & Contact Lens Compliance.”

How contact lenses can be a friend, and sometimes a foe, was illustrated by a recent case. A 22-year-old white female in perfect health, wearing soft disposable contact lenses, developed an Acanthamoeba corneal infection. While Acanthamoeba is not our biggest concern in contact lens practice in terms of “volume” (that is Pseudomonas, the gram-negative bacteria), it can lead to a severe and difficult-to-treat corneal infection. More on the parasite Acanthamoeba later.

But while any contact lens-wearing modality poses some risk of corneal complications, contact lenses can come to the rescue when it comes to restoring eyesight. For patients, it can be worrisome and frightening to have to return to lens wear after a corneal infection. However, in many cases—with scleral lenses, for example—visual acuity can be restored quite remarkably.

Scleral lenses require a rigorous lens care regimen, as hygiene and compliance play a crucial role in maintaining safe and successful lens wear.

ORTHOKERATOLOGY

One of the biggest debates in our industry is about the safety issue surrounding ortho-k. Some practitioners have advised against using this modality for children for myopia control (i.e., in the Netherlands), putting an important pillar in myopia management partly off to the side for eyecare practitioners.¹

In his opening presentation in the GSLS session, Mark Bullimore, MCOptom, PhD, explored the topic of safety of contact lens wear and ortho-k, putting things in perspective. His conclusion was that serious contact lens complications are rare. But statistics are complicated, and Dr. Bullimore even stated, “Statistics is never having to say you’re certain.”

The first problem is that large sample sizes are needed to be able to present confirmatory results on the risk of infection. If the incidence of a corneal infection is 1 in 100,000, then information from hundreds of thousands of lens wearers is needed. For specialty lens modalities this is even more problematic, given that there are fewer wearers of specialty lenses. Chance plays an important role in any numbers that are generated if sample size numbers are smaller.

According to a study by Stapleton and coworkers,² the incidence of microbial keratitis (MK) with loss of visual acuity in daily wear of silicone hydrogel soft lenses was 0.00011%. This is more easily interpreted as: the chance is 1.1 per 10,000 patient-years. The 95% confidence interval (CI) with this is between 0.9 and 1.4. Dr. Bullimore reported in his presentation that not every case of MK leads to loss of vision; only 15% of MK cases have that result.

To compare the relative risk of MK (not leading to vision loss) per lens modality, the annualized incidence per 10,000 wearers was determined: for daily-wear rigid corneal lenses 1.2 (CI 1.1-1.5); daily wear soft 1.9 (CI 1.8-2.0); daily disposable 2.0 (CI 1.7-2.4); silicone hydrogel soft 11.9 (CI 10.0-14.6); overnight wear soft 19.5 (CI 14.6-29.5); and overnight wear silicone hydrogel 25.4 (CI 21.2-31.5).² It is clear that daily wear of lenses is the safest wear modality, occasional overnight wear increases the risk, and regular overnight wear increases that risk further. Daily disposable lens wear seems to be associated with the lowest risk of severe MK, although the latter is not always an option in specialty lens practice.

Back to ortho-k then: In overnight wear modality, the lenses are only worn during the night and the wearer is lens-free during the day. What are the risks?

Bullimore et al³ reported a survey involving 1,317 patients (640 adults and 677 children), which resulted in 2,599 patient-years of data (1,164 in adults, 1,435 in children). Fifty cases of painful red eye were reported, eight cases of corneal infiltrates, and two cases of MK. The study reported an incidence per 10,000 years of wear of 7.7 (CI 0.9-28). For children, the MK risk was 13.9 per 10,000 patient-years (CI 1.7-50.4), while for adults the estimated incidence was 0 per 10,000 patient-years (CI 0-31.7).

Dr. Bullimore also reported on a retrospective study of safety of ortho-k.⁴ All episodes of infiltrative keratitis from a children’s hospital in Moscow were recorded and adjudicated by three ophthalmologists, which resulted in 139 cases of infiltrative keratitis in children, of which 45 were MK (32%). Five of them were overnight ortho-k wearers.

The annual incidence thus reported was about 5.0 (CI, 2.1-12.4). One final finding of the studies that Dr. Bullimore presented was that the group with the biggest risk of MK was not the younger age group (8- to 12-year-olds), but rather the 13- to 17-year-olds, while the highest risk is in the 18- to 25-year-old group.

My belief is that practices that do the most with ortho-k take the care that the modality deserves very seriously. In these situations, informed consents are used for the parents and for the children, hygiene and compliance protocols are reconfirmed on all follow-up visits, and it is made very clear that the patient should exclude any tap water from the care regimen.

In some of the larger ortho-k practices, for example, patients are informed that if they do not show up for follow-up care they are excluded from further lens purchases and eye care, to show the seriousness of eye and lens assessment.

In summary, the risk with overnight ortho-k may be increased compared to daily wear (certainly compared to daily rigid corneal lens wear) but does not seem to exceed that of soft lens overnight wear. Ortho-k lens wearers have been reported to show small amounts of corneal staining, which may or may not pose a small increased risk for corneal infection, although in rigid corneal lens wear—with the lowest rates of corneal infection—corneal staining (especially 3 and 9 o’clock staining) is not uncommon either.⁵

The overnight aspect of ortho-k and the higher risk of MK needs to be weighed against the benefits that ortho-k can have in terms of myopia progression reduction. Work by Gifford⁶ showed that this balance can be favorable for lens wear if myopic retinal pathology is considered, and a recent paper by Bullimore and coworkers also showed that the benefits of myopia control outweigh the risks.⁷

SCLERAL LENSES

Since the introduction of scleral lenses, there has been a debate about physiological situations posterior to the lens and the potential for MK and other complications. Oxygen delivery to the cornea is impacted by the fact that a scleral lens is much thicker than a rigid corneal lens (by about a factor of three), and the post-lens tear fluid is yet another thick barrier to oxygen flow to the cornea (with an estimated Dk of 80).

Furthermore, there seems to be minimal tear film exchange possible behind a scleral lens, which is obviously different from a rigid corneal lens, where the tear film is estimated to be replenished every three to five minutes.⁸ However, scleral lenses do not seem to pose an exceptionally large risk of MK, as reported at GSLS by Melissa Barnett, OD, who quoted from the recently published British Contact Lens Association (BCLA) Contact Lens Evidence-based Academic Report (CLEAR) papers on scleral lenses.⁹

Damien Fisher, BAppSc, PhD, presented his dissertation finding in the scleral lens supersession at GSLS that, as opposed to earlier beliefs, if the Dk of a scleral lens exceeds 100 units, then the oxygen delivery to the cornea needed for normal functioning in daily wear is met in most cases. Scleral lens thickness and lens reservoir variations help in providing more oxygen, but only if large steps are taken. Lens fenestration, although potentially helpful in other ways, did not add much in terms of oxygen delivery to the cornea. In cases of compromised corneas (such as post-corneal transplant, post-radial keratectomy, etc.) oxygen issues can arise, but not typically in normal corneas.

While special attention to lens care is warranted in any lens modality, care for scleral lenses is of critical importance. In other words, hygiene in lens handling is crucial to improve scleral lens safety, perhaps even more important than the exact Dk with premium lens materials. Dr. Barnett also reported that difficulty with lens handling is greater in scleral lens wear (63%) compared to rigid corneal lens wear (40%) and that handling issues are the primary reason for scleral lens wearers to drop out.^10-12

It is not easy to put a hard number on the incidence rate of MK in scleral lens wear, no matter how desirable it would be to communicate that to patients in practice. Despite the success of scleral lenses, the large sample sizes needed to give any serious numbers on incidence rates involving hundreds of thousands of lens wear years are simply not attainable.

And the complicating factor in this category is that underlying pathology is often the indication for scleral lens wear. The balance of risks versus benefits in scleral lens wear almost always turns out in favor of the modality—as patients simply have inferior vision without them.

SPECIALTY SOFT LENSES

James Wolffsohn, PhD, from Aston University in Birmingham, UK, discussed how the risk of infection can be reduced by identifying and differentiating non-modifiable risk factors from modifiable risk factors.¹³ Nonmodifiable factors including male sex and country (presence of Acanthamoeba due to water storage and legal requirements) were identified, while poor hand washing, overnight wear, improper use of solution (such as topping off), expired lens care products, extending lens use beyond the replacement interval, inadequate case cleaning, failure to rub and rinse lenses, use of tap water/sports water, and online purchasing were identified as modifiable factors. Online purchasing may not be conclusive, but unregulated purchasing behavior was identified to be associated with ocular complications.

The modifiable factors should potentially be considered in relation to contact lenses that are custom-made because of design or prescription needs (contact lenses that have higher or lower sagittal heights, for instance, and/or contact lenses with high or low prescriptions). These lenses are typically lathe-cut and are by default (much) thicker than molded lenses, which have a negative impact on Dk/t values even when they are made of silicone hydrogel materials (including both high plus- and high minus-powered contact lenses).

As for bandage lenses, in most cases molded disposable lenses are used, unless the shape of the ocular surface is abnormal (either flat, such as after a corneal transplant, or steep, such as in severe keratoconus). Standard molded contact lenses typically have good oxygen delivery, especially in the silicone hydrogel category. However, bandage lenses are used for eyes that have compromised corneas, and extra vigilance regarding safety should be exercised. A complicating factor may be that frequent disposal of bandage lenses is not always possible, daily disposables are not always an option, and overnight wear is often needed to promote epithelial healing, despite the known risks.

In summary, extra emphasis on safety seems warranted with specialty lenses, as more challenging oxygen delivery and the potential presence of underlying pathology may make the eye more vulnerable.

ACANTHAMOEBA

Acanthamoeba is almost solely a contact lens-related infection. It has even been called “a preventable disease.”¹⁴ The biggest issue is exposure to tap water, where the microorganism can reside. It is not a virus, not a bacterium—not even a yeast or a fungus. It is a free-living parasite, which is hard to disinfect. Exclusion of all tap water from any contact lens care regimen is warranted. Special “no water” stickers are available now from various professional associations around the globe. The exclusion of tap water in the contact lens regimen includes rigid corneal lens wear (in which, for a long time, it was customary to rinse with tap water) and the use of a lens storage case.

Tap water should never be used to rinse or clean the lens case. Even after hand washing, it is important to thoroughly dry the hands with a clean towel before handling the lenses.

THE CASE OF THE LENS CASE

In the GSLS session, Pauline Cho, PhD, focused specifically on lens safety in ortho-k. She was very clear about one thing: the lens case has proven to be an important source of contamination. Replacing the lens case monthly is advised.

Mark Willcox, PhD, found in his studies that using lens cases that are different from the ones that the solution manufacturer recommends is a risk for having more microbes grow in cases, with a potential increase in the risk of MK or inflammation during lens wear.¹² The use of novelty lens cases (e.g. “fun” lens cases) that can be purchased in many countries should be discouraged, as they have not been evaluated for compatibility with disinfecting solutions or approved by regulatory agencies.

Contact lens cases should be dried and cleaned regularly. At the very least, all solutions should be discarded from cases and the cases should be dried (as should the lens basket in hydrogen peroxide cases). Flat lens cases used with multipurpose solutions should also be wiped with a clean tissue prior to air drying and stored upside down. Dr. Cho also specifically advised against the use of lens cases with ridges in the compartments, as they are difficult to clean.

Apart from the lens case, special attention should be given to proper disinfection of the plunger/applicator/suction holder, according to Dr. Cho’s lecture. Disinfection with peroxide is warranted, and monthly replacement advised. In fact, when it comes to various rigid lens modalities, including ortho-k, Dr. Cho recommends using fingers for lens application and removal instead of devices. For scleral lenses, this may be more difficult to accomplish.

In-office disinfection of both GP (scleral and corneal) and hybrid and soft lenses involves 3% peroxide exposure in a non-neutralizing case for at least three hours straight before neutralization (soft and hybrid) or dry storage (rigid corneal lenses and scleral lenses), per the American Academy of Optometry and the American Optometric Association recommendation, in conjunction with the Contact Lens Manufacturers Association (CLMA) and the GP Lens Institute (GPLI) in the United States.¹⁵ Dry storage may be disadvantageous to some of the coatings on rigid lens surfaces, but for long-term storage that may be the price to pay.

CLEAN—STORE—FILL

What can be confusing to lens wearers is that on one hand we actively promote solutions that clean and disinfect their lenses while also being compatible with the ocular surface. But in lens modalities such as ortho-k and scleral lens wear, the cornea may have prolonged exposure to the care solution, and in these situations anything other than preservative-free saline solution can be problematic (Figure 1).

At the same time, patients need to understand that if lenses are stored in the saline alone, there is a risk of clinically relevant growth of microorganisms overnight. Hence, a disinfection and cleaning solution is needed to stop the multiplication of microorganisms and remove buildup of tear film proteins and lipids.

FILLING SOLUTIONS

In the GSLS Scleral Lens session, Gloria B. Chiu, OD, explained that environmental gram-negative organisms, many of which can contribute to MK, can persist for weeks once introduced into saline solutions.¹⁶ Off-label multi-dose preservative-free saline commonly used to rinse and fill scleral lenses before application to the ocular surface may become contaminated with microorganisms once the bottle has been opened.

Practitioners and patients need to be aware of possible contaminants that may increase the risk of ocular complications. Single-dose saline units don’t pose that risk. Dr. Cho specifically called for essential aftercare visits, with more frequent and more diligent aftercare for higher-risk patients. She emphasized the importance of reminding patients and reinforcing the importance of proper lens wear and care habits at each visit.

IT’S A WRAP

The choice of disinfecting solution may depend on how frequently the lenses are worn. Multipurpose solutions provide good disinfection against most microbes that are associated with infections or inflammation.¹⁶ The primary criteria for the stand-alone test include a reduction of not less than 99.9% (or 3.0 logs) for bacteria and a reduction of not less than 90% for molds and yeasts within the soaking period as recommended by the manufacturer.¹⁷ Note that other microorganisms (viruses and parasites such as Acanthamoeba) are not part of this criteria.

Hydrogen peroxide or iodine-based solutions have shown superior disinfection quality over multipurpose solutions.¹⁸ For that reason, oxidizing disinfection systems are a common and popular solution for different types of specialty lenses. These pose an extra risk, because of either the overnight nature of a modality or the underlying condition of the eye, making the eye more vulnerable. One must keep in mind, though, that as these solutions are neutralized after use, occasional lens wearers should be reminded to re-disinfect their lenses before applying them.

PARTNERS IN SLIME

In closing, to keep standard lens wear safe, it is of the utmost importance to emphasize good lens hygiene and care. Although rare, serious conditions have been reported in general contact lens wear where—oh, the irony—specialty lenses are needed to heal the situation and to restore vision. The care of specialty lenses is at least as important—but probably even more important—than that of standard lenses, as specialty lenses are often used for conditions in which the corneas are compromised.

This poses extra risk and some lens modalities may pose even more challenging risks, such as increased oxygen barriers or the need to wear the lenses overnight. To keep all these specialty lens options as safe as possible, eyecare practitioners and patients must partner to prevent buildup of debris, growth of microorganisms, and the occurrence of adverse complications. CLS

Acknowledgments: Special thanks to Lynette Johns, OD, for her help and support.

REFERENCES

1. NOG (Dutch ophthalmological society). Standpunt nachtlenzen (ortho-K) bij kinderen. 2018 Feb 16. Available at www.oogheelkunde.org/richtlijn/nachtlenzen-bij-kinderen-nog-standpunt-2018 . Accessed March 15, 2022.
2. Stapleton F, Keay L, Edwards K, et al. The incidence of contact lens-related MK in Australia. Ophthalmology. 2008 Oct;115:1655-662.
3. Bullimore MA, Sinnott LT, Jones-Jordan LA. The risk of MK with overnight corneal reshaping lenses. Optom Vis Sci. 2013 Sep;90:937-944.
4. Bullimore MA, Mirsayafov DS, Khurai AR, et al. Pediatric Microbial Keratitis With Overnight Ortho-k in Russia. Eye Contact Lens. 2021 Jul 1;47:420-425.
5. van der Worp E, De Brabander J, Swarbrick H, Nuijts R, Hendrikse F. Corneal desiccation in rigid contact lens wear: 3- and 9-o’clock staining. Optom Vis Sci. 2003 Apr;80:280-290.
6. Gifford KL. Childhood and lifetime risk comparison of myopia control with contact lenses. Cont Lens Anterior Eye. 2020 Feb;43:26-32.
7. Bullimore MA, Ritchey ER, Shah S, Leveziel N, Bourne RRA, Flitcroft DI. The Risks and Benefits of Myopia Control. Ophthalmology. 2021 Nov;128:1561-1579.
8. Muntz A, Subbaraman LN, Sorbara L, Jones L. Tear exchange and contact lenses: a review. J Optom. 2015 Jan-Mar;8:2-11.
9. Barnett M, Courey C, Fadel D, et al. CLEAR - Scleral lenses. Cont Lens Anterior Eye. 2021 Apr;44:270-288.
10. Schornack MM, Pyle J, Patel SV. Scleral lenses in the management of ocular surface disease. Ophthalmology. 2014 Jul;121:1398-1405.
11. Kreps EO, Pesudovs K, Claerhout I, Koppen C. Mini-Scleral Lenses Improve Vision-Related Quality of Life in Keratoconus. Cornea. 2021 Jul 1;40):859-864.
12. Macedo-de-Araújo RJ, van der Worp E, González-Méijome JM. A one-year prospective study on scleral lens wear success. Cont Lens Anterior Eye. 2020 Dec;43:553-561.
13. Willcox M, Keir N, Maseedupally V, et al L. CLEAR - Contact lens wettability, cleaning, disinfection and interactions with tears. Cont Lens Anterior Eye. 2021 Apr;44:157-191.
14. Carnt N, Hoffman JJ MBBS, Verma S, et al. Acanthamoeba keratitis: confirmation of the UK outbreak and a prospective case-control study identifying contributing risk factors. Br J Ophthalmol. 2018 Dec;102:1621-1628.
15. Sindt C, Bennett E, Szczotka-Flynn L, Sclafani L, Barnett M; American Academy of Optometry (AAO) Section on Cornea, Contact Lenses & Refractive Technologies, and The American Optometric Association (AOA) Contact Lens and Cornea Section. Technical Report: Guidelines for Handling of Multipatient Contact Lenses in the Clinical Setting. Optom Vis Sci. 2020 Aug;97:544-548.
16. Jeong M, Lee KL, She RC, Chiu GB. Microbiological Evaluation of Opened Saline Bottles for Scleral Lens Use and Hygiene Habits of Scleral Lens Patients. Optom Vis Sci. 2021 Mar 1;98:250-257.
17. U.S. Food & Drug Administration. Guidance for Industry—Premarket Notification (510(k)) Guidance Document for Contact Lens Care Products. 1997 May 1. Available at www.fda.gov/media/72725/download . Accessed March 7, 2022.
18. Willcox M. From Research to Practice: Do Specialty Soft Contact Lenses Need Different Care? Softspecialedition.com . 2022 Winter. Available at softspecialedition.com/winter-2022.html . Accessed March 15, 2022.