Do Specialty Soft Contact Lenses Need Different Care?

from Research to Practice

Mark Willcox

The short answer to the question above is: all contact lenses that are reused need to be disinfected between use. This is particularly true for specialty lenses, which are almost by default ‘reusable lenses’. It applies to speciality soft contact lenses such as custom soft multifocals, extended-power-range soft lenses, soft lenses for irregular corneas, prosthetic lenses and coloured lenses just as much as to more traditional soft lenses for daily wear. However, in the case of specialty lenses, sometimes a compromised ocular surface (such as dry eye or different syndromes) is present, which may make this disinfection step even more urgent.

Multipurpose Disinfection Solution vs. Multipurpose Solution

The choice of disinfecting solution may depend on how frequently the lenses are worn and on the sensitivity of wearers to excipients such as preservatives and disinfectants contained within the formulations. Most people who use reusable soft lenses use multipurpose solutions, whether those that are labelled as multipurpose disinfecting solutions (i.e., passing the ISO 14729 stand alone criteria) or a multipurpose solution (i.e., passing the ISO 14729 regimen test criteria). The primary criteria for the stand alone test are a reduction not less than 99.9% (or 3.0 logs) for bacteria and a reduction not less than 90% for mould and yeasts within the soaking period as recommended by the manufacturer. In other words, if no rub-and-rinse is applied to the lens. Note that other micro-organisms (viruses and parasites such as Acanthamoebe) are not part of this criteria. A multipurpose solution should meet the criteria as part of a contact lens disinfection regimen.

Sensitive Stuff

Multipurpose solutions generally provide excellent antimicrobial activity if used according to the manufacturers’ instructions, although some struggle against certain, albeit relatively uncommon, potential pathogens such as the Gram-negative bacteria Delftia acidovorans or Stenotrophomonas maltophilia. The solutions typically contain the disinfectants polyhexanide, polyquaternium and alexidine, either alone or in various combinations, and are not required to be neutralised before the lenses are reapplied to eyes. These solutions provide relatively long-term disinfection and thus may be most appropriate for people who wear their contact lenses irregularly and so leave lenses in their contact lens cases for extended periods of time. However, people who have sensitivities to the disinfectants may struggle with these systems. For eyes with ocular surface disease, for instance, this may become an issue.

Broad-spectrum Antimicrobials

Hydrogen peroxide is also used as a contact lens disinfecting agent. This provides excellent antimicrobial activity but must be neutralised before the lenses are worn again. These days, most hydrogen peroxide solutions are neutralised during the disinfecting cycle and are called one-step systems. Another type of oxidising disinfection system like hydrogen peroxide uses iodine. Again, this is neutralised during the disinfection cycle. These disinfectants are good broad-spectrum antimicrobials that have activity even against SARS-CoV-2, the causative agent of COVID-19, in the ISO 14729 stand alone test. The oxidising agents are also effective to a large degree against Acanthamoebe cysts, something that most multi-purpose solutions are not unless the rub-and-rinse regimen is carefully followed. Once these solutions are neutralised, lenses do not contain the disinfectant when worn and so may be useful for those who have sensitivities to disinfectants. However, as the disinfectants are neutralised, if lenses are not worn at the end of the disinfection cycle or the next day, they sit in the aqueous solutions in the cases, and any remaining microbes may re-grow. Therefore, if using these systems with occasional wearers, they should be advised to go through a re-disinfection cycle prior to wear to reduce the likelihood of microbes being transferred from the cases to the lenses and then to the eye. These neutralised solutions are therefore not to be used with trial lenses either.

The Case of the Lens Case

Speaking of contact lens cases, these need to be cared for as well. Wearers should use cases for, at the most, only three months and preferably for one month. Lens cases used with one-step hydrogen peroxide disinfectants may need to be replaced monthly to ensure that neutralisation occurs. Many contact lens disinfecting solutions come with a new case, and wearers should be advised to use these cases and to replace them when they replace their solution bottles. One of our studies found that using lens cases that are different from the ones that the manufacturer recommends (and often supplies for free) with a disinfecting solution is a risk for having more microbes grow in cases. This then increases the risk of infection or inflammation during lens wear. The use of novelty lens cases that can be purchased in many countries should be discouraged, as they have not been evaluated for compatibility to disinfecting solutions and so may also be associated with increased microbes in cases. Contact lens cases should be dried and cleaned regularly. After each use, 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 drying.

“One of our studies found that using lens cases that are different from the ones that the manufacturer recommends with a disinfecting solution is a risk for having more microbes grow in cases.”

Recommendations for ECPs

Contact lens care, maintenance & safety is highly undervalued. Much attention in the specialty lens field goes to the fitting process and to the indication range, but the success—or failure—of specialty lenses relies in large part on contact lens solutions, hygiene and handling. Most contact lens wearers prefer the convenience of using multipurpose solutions. These provide good disinfection against most microbes that are associated with infections or inflammation. For those people who struggle with these solutions because of sensitivity to the disinfectants (or other excipients), hydrogen peroxide or iodine-based solutions should be used. The latter have shown superior disinfection quality over multipurpose solutions. However, as these are neutralised during use, occasional wearers should be reminded to re-disinfect their lenses before use if possible. Wearers should be reminded to change cases regularly, to use the lens case that comes with the solution and to use a tissue to wipe cases (apart from cases for oxidising solutions) and to air dry all cases when not in use to minimise the possibility of microbes gaining access to their eyes and causing infections or inflammation.