Reader and Industry Forum
Daily Disposables and Infections: Why So Many?
By Charles W. McMonnies, MSc
The comprehensive review of daily disposable (DD) lens use by Dr. Renee Reeder in the April issue (“Daily Disposable Lenses: A Look Back and Ahead”) raises some additional matters regarding infection risk. There is no doubt that DD lens wear should reduce infection risk compared to other types of lens use. The contact lens case has been shown to be the most frequently and heavily contaminated accessory (Wu et al, 2010), although hand contamination may rival the case as a source of infection. Nevertheless, as mentioned by Dr. Reeder, eliminating the use of cases should help greatly.
Although DD lenses are recommended as the healthiest modality, a surprising number of infections with this lens type have been recorded (Stapleton et al, 2008; Dart et al, 2008; Fleiszig and Evans, 2010). There may be many factors contributing to this disappointing outcome.
One reason may be the tendency for practitioners to refit patients into DD lenses when they develop problems wearing other types of soft lenses. Similarly, practitioners may prescribe DD lenses (and possibly occasional use) for new wearers who are assessed as being more likely to have tolerance problems. Consequently, people who have reduced tolerance to contact lens wear in general, whether they are new fits or refits, may be over-represented in the DD lens-wearing population. Marginal tolerance patients (e.g., those who have dry eyes or those who have already experienced significant red eye events) may be more likely to acquire infections notwithstanding being prescribed or switched to DD lenses.
Epidemiological studies have identified other DD lens use risk factors including: overnight use, smoking, Internet purchases, less than six months wearing experience, and higher socio-economic class (Cho et al, 2009; Wu et al, 2010). To some wearers, a description as the healthiest form of contact lens wear may imply a greater margin of safety for breaking the rules.
Infection rates are much higher with overnight wear (Stapleton et al, 2008). Obviously, overnight wear should not be an option for patients who have a history of or a potential to have problems with daily wear. In addition, overnight wear is a risky option for any DD lens wearers who have not been monitored for their responses to this modality. Overnight wear may not always be intended, but when it occurs it is usually without any associated professional monitoring. Factors such as high end-of-day comfort levels, fatigue, and the effects of alcohol or other drugs may cause wearers to forget (or not bother) to remove their DD lenses before they sleep.
Other forms of noncompliance may be involved (Cho and Boost, 2010). For example, patients who wear contact lenses only occasionally may not feel that they are getting good value if they dispose of the lenses after a single use. This could be more likely if the period of lens wear is just a few hours. In addition, occasional use of DD lenses attracts some people who want to wear contact lenses at the lowest possible cost and who simply can't afford regular DD lens use. Unfortunately and obviously, lens storage and re-use eliminates the biggest potential safety feature of DD lenses. However, the risk of infection can be increased even further by compounding factors.
For example, re-use may involve lens handling in non-ideal locations, such as the locker room after a sporting activity, back stage after a theatre performance, or in the bathroom at a function where a speech is made. There are many other similar scenarios that could combine occasional reuse with inappropriate lens handling situations and practices.
Unfortunately, occasional use and re-use combine to provide longer incubation periods for mi-crobial contamination to develop between uses, with the possibility of an increased microorganism colony size, virulence, and associated risk of infection. The incubation period could run to weeks or even months in some “cases.”
DD lens wearers may never have been instructed on lens maintenance. The dilemma for practitioners is that to provide such instruction is tantamount to endorsing re-use. Consequently, re-users may end up using inappropriate storage products or using otherwise suitable products incorrectly. Occasional re-use inevitably means that a bottle of storage solution remains in use for far too long. Re-use of DD lenses has been identified as a risk factor for infection (Niyadurupola and Illingworth, 2009), but estimates of re-use frequency are hard to determine. Honest acknowledgement of re-use may not be easy to extract from patients, especially those who have or have had an eye infection related to contact lens wear.
The DD lens appeals to a lot of wearers who want to have the lowest level of time and bother possible with contact lens handling. With this mind set, such patients could be less likely to wash their hands effectively and routinely prior to application and removal. Again, honest acknowledgement of this failing may not be easy to extract from patients. In addition, prior to instruction, it is rare to see patients wash their hands effectively. Many need advice and a demonstration.
The blame for the unexpectedly high rate of DD lens infections may lie with patients who fail to follow instructions, or even with a practitioner who fails to provide adequate guidance on correct use. For example, some practitioners may not provide information on the risks associated with incorrect use. Some practitioners may only tell patients what to do (“just throw them away when you take them off”) without making it clear which specific practices are contraindicated. In addition, some practitioners may fail to place sufficient emphasis on why certain habits are contraindicated.
To make matters worse, Internet sales are the basis for a major breakdown in the frequency of patient-practitioner communications. Unfortunately, people who re-use lenses may actually prefer to avoid contact with their practitioner if they suspect that their very infrequent lens purchases might be noticed. The Internet provides this option and may be a reason why internet purchases are a risk factor for DD infection.
In addition, practice-based supply and re-supply of DD lenses may be less intensively managed when occasional use is intended.
Provide the Proper Education
As a lot of noncompliance can occur because patients don't realize what shouldn't be done, better education about the potential dangers of occasional lens wear and lens re-use may be required. Something like the following advice (as a handout) might be usefully issued (in different formats perhaps) every time DD lenses are supplied. The information is intended to help redress some of the issues described above. The unexpectedly high infection rates for DD lens wearers make it clear that many patients need reminding of what they should and shouldn't be doing. Rather than being simply a prescriptive account of what to do, this handout attempts to explain why and how infections can be associated with incorrect use.
The following text (as a Word file) is available from firstname.lastname@example.org, and can be adapted to suit individual practices. It is titled, “Correctly Used, Daily Disposable Contact Lenses are the Safest Form of Contact Lens Wear”:
“However, these guidelines will help you to avoid the costs and inconvenience associated with infections, which occur too frequently when daily disposable lenses are used incorrectly.
“1. Do not sleep in daily disposable lenses unless you have been specifically advised by your practitioner that you are a suitable candidate for that type of lens wear. For many people, sleeping in contact lenses is contraindicated because their eyes are not tolerant of the extra physiological demands of sleeping when lenses are on the eyes. The infection rate is much greater for people who sleep in their lenses.
“2. Do not re-use lenses. The greatest single advantage of daily disposable lenses is being able to avoid using storage cases and solutions. Apart from the additional expense, storage cases are easily contaminated with germs and are frequently associated with contact lens-related infections. In addition, storage solutions lose their germ killing ability when the same bottle remains in use over a long time. Infections related to storage cases and solutions can be completely eliminated by not reusing lenses.
“3. Always wash your hands carefully with soap and rinse thoroughly before inserting or removing lenses. Preferably wipe your fingers with disposable lint free paper. Germs from fingers easily contaminate lenses and are carried onto the eye with insertion of the lens. Germs trapped under the lens have a much better chance of causing infection. Similarly, germs from fingers can contaminate the eye during lens removal. The eyes can more easily become infected in this way after lens wear. Unfortunately, sleep that follows lens removal provides ideal conditions for germs to multiply and cause an infection.
“4. As much as is possible, avoid cigarette smoke. Even passive smoke reduces the defensive properties of your tears making it easier for germs to cause an infection. Sleeping in contacts after a night of exposure to cigarette smoke can involve a much greater risk of infection.
“5. Maintain regular assessments of the health of your eyes; firstly from a contact lens point of view, but equally importantly, from the perspective of maintaining good general eye health. Waiting until your eyes don't feel comfortable before re-assessment increases risk because many problems are symptom-free but can be detected in the early stages.” CLS
For references, please visit www.clspectrum.com/references.asp and click on document #182.
Charles McMonnies is a Professorial Visiting Fellow, School of Optometry and Vision Science, UNSW. He conducted a contact lens practice for over 40 years and has published more than 100 papers and articles.