Putting Research into Practice: Contact Lens Associated MK

Lisa Keay1, 2 B Optom, UNSW, Australia Research Optometrist

Katie Edwards1, 2 B App Sci (Optom), QUT, Australia Research Optometrist

A/Prof Fiona Stapleton1, 2, 3 MSc PhD MCOptom DCLP FAAO Program Director of Academic Education Director of the Australian and New Zealand Microbial Keratitis Study

Vision CRC1, School of Optometry & Vision Science, UNSW2, Institute for Eye Research3

Microbial keratitis is the most serious complication that can arise from contact lens wear. Fortunately contact lens related microbial keratitis is relatively rare affecting approximately 5 in 10,000 contact lens wearers annually.  Amongst these cases approximately 10-15% of patients lose 2 or more lines of visual acuity.  However, this is not the only measure of morbidity of this condition.  Changes to a patient’s quality of life, distress during acute phases of the disease and treatment, costs to the patient in time off work and to the health care system for treatment should also be considered in describing the severity of this disease.   Prevention of infection, early detection and effective treatment are key to reducing the impact of this condition.


Australia and New Zealand Studies: 

A large-scale collaborative research project involving the Vision Cooperative Research Centre, the School of Optometry and Vision Science at the University of New South Wales, and the Institute for Eye Research has just concluded.  These studies involved surveillance of all cases of lens-associated keratitis presenting to private and hospital based ophthalmic practitioners and a population based telephone survey of 30,000 households in Australia and 7500 in New Zealand to gather information on contact lens wearers in the community.  This research has provided a unique opportunity to develop evidence-based guidelines on a rare but important complication of contact lens wear.
The microbial keratitis surveillance study commenced on October 1st 2003 and concluded on 30th September 2004.  All practicing ophthalmologists (n=718) and optometrists (n=3697) in Australia and New Zealand were invited to participate in this research.  Active surveillance techniques were used to prompt the response from practitioners.  The response rates for ophthalmology (96%) and therapeutically licensed optometrists were high (91%).  Supplementary case reporting was sought through other practicing optometrists and through medical records reviews at large hospital clinics yielding a dataset of 389 cases.   

The data from the telephone survey forms the denominator in estimates of incidence.  Results indicate that contact lenses are worn by 5.1% of the Australian population aged between 15 and 64 years and a higher proportion in New Zealand.  Detailed information about contact lens care practices were collected via these surveys for comparison to the contact lens wearers who developed microbial keratitis from the surveillance study.

To ensure the highest quality research, an international steering committee was formed involving experts in the epidemiology of contact lens related microbial keratitis.  They have advised on research methodology and reviewed the methods for interpretation of data.  The current study findings are interpreted in the context of previous [1-4] and recent research [5] into contact lens related infections. 


Importance of research:  

In the past, similar studies of corneal infections secondary to contact lens wear have provided evidence, which has led to changes to health policy. In 1989, a surveillance study [2] of 5 states in the north of America found a five-fold increase risk of infection with overnight contact lens use.  A case control study in the US [6] published in 1989 also found increased relative risk of infection with overnight contact lens use.  It was this evidence which led to the Food and Drug Administration in the USA reducing their approval of disposable contact lens use from 30 nights continuous wear to 6 nights extended wear in 1990.  In the UK, similar findings led to the Department of Health requirement of signed consent for extended wear of soft contact lenses. These changes in health policy were also reflected in prescribing behaviour; overnight contact lens use which was commonplace in the 1980’s was largely disbanded in the Australia, New Zealand, United Kingdom and many other markets prior to use of silicone hydrogel contact lenses [7].


Contact lens wear: high risk behaviour?

Many studies of microbial keratitis secondary to contact lens wear have shown increased risk with overnight contact lens use [2, 3, 6, 8-11].  An important finding of recent studies is that overnight wear persists as a risk factor no matter which soft lens type is worn [5, 12, 13].  
Published case reports of infection with daily disposable and silicone hydrogel lenses have highlighted a number of potential risk factors of infection.  While lens and case cleaning [9, 14, 15], smoking [6, 9] socioeconomic status [8] and male gender [15] have all been identified as specific risk factors for infection, no study to date has considered the effect of water exposure, climate from either swimming or showering on the risk of infection.  A number of reports of infection with silicone hydrogel lenses have been associated with swimming prior to the event [16], and the link between domestic water supply and Acanthamoeba keratitis is well established [17, 18].  Also, studies have found that there is an increased number of infections during summer months [19].  However, due to most incidence studies being of 3-4 month duration [2-4], seasonal variances have not been considered. 
The Australia and New Zealand studies found that contact lens hygiene was of vital importance in preventing infection.  The study also found that those who developed infections were more likely to have purchased their contact lenses over the internet, highlighting the importance of professional advice and education on contact lens prescribing.


Severity:

Our analysis suggests that over 50% of cases of contact lens related microbial keratitis present to optometrists.  Treatment delays after presentation to a health care provider affected visual outcome, associated costs and duration of disease and this is a modifiable factor.  Better education of primary health care providers about timely diagnosis, treatment and appropriate referral are indicated.  Previous hospital population studies of microbial keratitis have also shown that delays in initiation of appropriate therapy is related to eventual need for penetrating keratoplasty [20] and increased severity [21]. 


Dissemination of research results:

Disseminating research findings to the health care community allows practitioners to make informed decisions about the care of their patients.  The Oxford Centre for Evidence Based Medicine defines evidence-based medicine as the ‘conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients’.  The conclusions drawn from clinical research are of limited value unless they are made available to practitioners.

The Microbial Keratitis Study Group was recently awarded the British Contact Lens Association Dallos Award for the development and evaluation of evidence based clinical guidelines on contact lens associated microbial keratitis.  It is planned to publish these clinical guidelines both as colour brochures and electronically via links on various websites, which offer practitioners information on contact lens practice.  The Internet is a medium for obtaining technical information used by a growing number of practitioners.

As part of a public health campaign with Sydney Eye Hospital, Australia the ‘Take Care With Contacts’ website has been developed by the Vision CRC.

This research has involved optometrists as well as ophthalmologists for the first time in studies of contact lens related microbial keratitis.  The involvement of contact lens practitioners in the development stages of these guidelines promotes ownership of the guidelines and will enhance the likelihood of implementation [22].  Optometrists are the target for implementation of these guidelines as they provide the majority of contact lens care in Australia and New Zealand and in many other countries. 

It is hoped that this research will generate information, which is of relevance to contact lens prescribing, patient advice, differential diagnosis and referral.  The goal of these guidelines will be to reduce the total incidence of contact lens related microbial keratitis and the severity of this condition in both costs of treatment and visual outcome.

Take home messages:

Recent studies have confirmed that microbial keratitis is a rare but serious complication associated with contact lens wear.  Silicone hydrogel lenses have provided certain ocular health benefits, however increased risk of infection in overnight wear persists despite the advances in material technology.  Patients should be informed of risks and benefits and discuss these with their eye care practitioner when considering continuous wear.

To reduce the risk of infection, wearers must comply with stringent lens care and cleaning regimens, particularly when travelling, and must remove their lenses and contact a practitioner at the first signs of red and painful eyes.

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