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Evidence-based contact lens practice involves finding, appraising and applying research findings as the basis for patient management decisions. These decisions should be informed by the strength of the research study designs that address the question, as well as by the experience of the practitioner and the preferences and environment of the patient. This reports reviews and summarises the published research evidence that is available to inform soft and rigid contact lens history and symptoms taking, anterior eye health examination (including the optimised use of ophthalmic dyes, grading scales, imaging techniques and lid eversion), considerations for contact lens selection (including the ocular surface measurements required to select the most appropriate lens parameter, lens modality and material selection), evaluation of lens fit, prescribing (teaching self-application and removal, adaptation, care regimen and cleaning instructions, as well as minimising risks of lens wear through encouraging compliance) and an aftercare routine.
Evidence-based practice has developed from evidence-based medicine, a term first introduced in the early 1990s for medical students to help with clinical decision-making using the most appropriate evidence [
]. Evidence-based medicine is defined as the “conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients” [
]. Evidence-based practice involves integrating the best available, and clinically relevant, scientific research evidence with a clinician’s expertise, the practice context and individual patient values (Fig. 1). This considers the patient experience, importance of prognostic markers and the efficacy and safety of various treatment or management options. While appraising the latest knowledge and the validity of data, it may also identify key questions that are currently unanswered and highlight potential areas for future research.
Fig. 1Three fundamental elements in Evidence-Based Practice.
Evaluating scientific research findings and using them to make the best clinical decision for patients is a key aim with evidence-based practice and an important part of contact lens practice. The commonly cited hierarchical evidence model (Fig. 2) aims to assist healthcare providers categorise the quality of evidence from different sources, from systematic reviews and randomised controlled clinical trials through to case reports and expert opinion. The levels within the hierarchy have been challenged [
]; it has been suggested there may be overlap based on clinical applicability, and that the ‘critical appraisal’ levels of the hierarchy pyramid should be separated as they are limited by the difference in methodology and statistics in the studies they combine [
]. It is also important to recognise that individual studies within a given level of the hierarchy (such as randomised controlled clinical trials) may differ in their ‘quality’, due to differences in risk of bias and internal validity. Formal risk of bias tools exist to assist clinicians with appraising the quality of an individual study rather than simply relying on the evidence level [
In a PubMed search performed on January 2, 2021 (https://pubmed.ncbi.nlm.nih.gov/), “evidence-based medicine” provided 203,167 search results and “evidence based practice “152,188; when the term “contact lens or “contact lenses” was added (AND operator), the potential data sources were limited to just 65 results. However, much of the evidence relevant to contact lens practice is from clinical studies designed to test a specific hypothesis, ideally with the least bias and greatest precision. Study designs vary, ranging from randomised controlled clinical trials to retrospective case control studies, providing a range in the quality of evidence. The research question can influence the most appropriate study design; for example a randomised controlled clinical trial may be the best approach to study a clinical intervention, whereas a prospective cohort study may be employed to assess an aetiological question. Potential bias can be minimised by masking (researcher and/or the participants), randomisation (between treatment(s) and/or a control) and statistical analysis methods (such as accounting for within-participant associations such as the synergy between eyes). Some contact lens research employs study designs not explicitly described in hierarchical models or common in general medicine; cross-over, contralateral and monadic designs are important to understand the clinical performance of different brands of lenses and care products (Table 1).
Table 1Study designs commonly seen in contact lens and care product research.
Study design
Description
Strengths
Limitations
Sequencing
Parallel
Each participant receives only one product Group comparison (test versus control) or matched pairs
Shorter, simpler and easier to run Less complicated analysis No carry-over effect No need for washout period Reflects ‘real world’
Requires larger sample size Cannot determine ‘within participant’ vs ‘between participant’ variability Comparison between participant groups Cannot derive ‘preference’
Cross-over
Repeated measures - participant receive at least two products over different periods (one may be a control); all participants receive same number of “treatment” options and for same number of periods
Determine ‘within participant’ and ‘between participant’ variability Comparison of treatments undertaken within each participant Assesses effect of first treatment on second (carry-over) with higher order designs Smaller sample size
Consider carry-over effect May need wash-out period Analysis can be complex Longer to run
Contralateral
Direct comparison within participant at same time i.e. different lenses in each eye
Could switch lenses between eyes Not ‘real life’ Sympathetic effect Assumes eyes have similar characteristics Assume participants can reliably distinguish outcomes between eyes
Eyes
Bilateral
Comparison within subjects; different time points or between participants
Reflects ‘real life’ experience
Larger sample size Contact lenses/care products experienced at different time points
Monocular
Participants wear one product
Stand-alone product performance & wearer acceptance; “real world”
No comparison
Comparison
Observational
Effect of treatment in a population Analytical or descriptive (case report or series). Retrospective or prospective including registries
“Real world” Non-interventional Low resources Cohort, case control or cross-sectional study
No control, randomisation or masking, so prone to bias Hard to determine causality
Controlled trials
Interventional study with a control group for comparison
Hypothesis tested – determine causality
High resources Hard if outcome being studied is rare
Comparison trial
Intervention study with no control group
Able to compare efficacy/safety directly
Potential bias in terms of the comparison product and measures assessed
Systematic reviews such as those developed with Cochrane (www.cochranelibrary.com), seek to collate, appraise and synthesise evidence that fits pre-specified eligibility criteria to answer a specific research question. The aim is to minimise bias by using explicit, systematic methods that are documented in advance with a published protocol [
]. An analysis of 1016 Cochrane health related reviews found the intervention under review to be beneficial in 44%, was likely to be harmful in 7% and in 49% the evidence supported neither benefit nor harm; by far the majority of reviews (96%) recommended further research [
]. To date, the only Cochrane systematic review conducted in the field of contact lenses is on interventions to slow the progression of myopia in children [
]. While Cochrane reviews are regularly updated, it is important to consider studies that may have been published since the cut-off date of the last review when considering the benefit of a new treatment and that they only generally consider randomised controlled clinical trials. In recent years, a number of international, consensus-building workshops that inform elements of contact lens practice such as dry eye therapies and management options [TFOS DEWS II] [
The quality of evidence from case reports may be low, particularly for rare diseases, but in the absence of higher level evidence they can demonstrate how a management option can work for an individual patient, the clinical relevance in practice and the critical thinking over the time-course of a case [
]. Publishing atypical cases can be of interest to eye care practitioners (ECPs), and case series can be of clinical interest. The information can be linked to clinical questions to help improve patient outcomes on when and how to manage certain cases and the potential prognosis. This can be useful when considering the potential time to obtain high-quality evidence from longitudinal studies for certain treatments; it has been estimated that there is an average 17-year lag between initial clinical research and the translation of that evidence into routine clinical practice in medicine [
How long does biomedical researach take? Studying the time taken between biomedical and health research and its translation into products, policy, and practice.
]. Case reports also highlight potential gaps in the evidence, giving direction and context to possible future research and can be very useful such as in the context of the potential utility of new materials, care systems and optical designs in the specific case of contact lenses.
1.1 Patient values and preferences
Patients should be involved in their own care and decisions that determine their management. There has been a growing interest in using structured validated questionnaires to quantify patient reported outcomes to understand the perspective of the patient, quantify quality-of-life impact or benefits, and understand their experience related to contact lens wear rather than an ECP recording their perception of satisfaction [
]. However, this approach has been limited mainly to meet a research purpose, and not as a routine clinical procedure. While ECPs are expected to routinely consider patient needs in a clinical practice setting to tailor their evidence informed decisions, they are often not encouraged or well prepared to elicit and discuss them [
]. Understanding patient needs involves skills and various competencies so to help embrace this more in practice, training should include communication and critical thinking skills to help with clinical decision making.
1.2 Clinical judgement
For ECPs to apply evidence-based practice in their contact lens practice, they need to be trained in its implementation and to be lifelong, independent learners. While it is likely that few ECPs conduct their own literature searches or critically appraise research evidence, systematic reviews and peer-reviewed journal articles that appraise and summarise the literature can help provide the latest evidence. Keeping up to date can be supported by attending evidence focused clinical conferences and continuing education programs. While clinical trials can show whether an intervention is efficacious and/or safe (on average and in a particular population), they do not answer whether it will work in an individual patient to the same extent. Having reviewed the evidence and its relevance, ECPs need to exercise careful clinical judgment and critical thinking, having reviewed the subjective and objective contact lens performance, during fitting and aftercare, to ensure the management is effective and safe, and discuss the options with their patient.
1.3 Proactive lens fitting
Evidence-based practice can be employed by ECPs to help maximise the likelihood of success for lens wearers, maintain satisfaction with lens wear, retain wearers and grow their contact lens practice. With neophyte lens wearers, ECPs should ensure that handling, vision and comfort are optimised on fitting and routinely check wearer satisfaction and anterior eye health to help retain them in lens wear [
]. Established lens wearers lapse mostly due to comfort-related problems, and these tend to be product (material or care system) or ECP-related (competency or lack of encouragement) rather than being due to patient-specific problems [
]. The majority can be successfully refitted and so evidence-based practice can be employed in these cases to review the evidence, consider the patient needs and apply clinical expertise to find alternative options. Evidence-based practice can also be employed to help ECPs grow their wearer base; research shows that introducing contact lenses to non-wearers prior to spectacle dispensing is well received and encourages many to trial contact lenses in addition to optimising the dispensing process [
Enhancing the approach to selecting eyewear (ease): a multi-centre, practice-based study into the effect of applying contact lenses prior to spectacle dispensing.
2. History and symptoms: considerations for lens wear
A discussion of history and symptoms are essential to an efficient practice, highlighting issues requiring further investigation such as health, lifestyle and environment features that inform lens type or wearing frequency. The questions asked should allow efficient examination of the key issues and elicit all relevant information to inform clinical decision making and patient advice.
2.1 Reason for visit
Cosmesis, especially on social occasions, is one of the major motivators why people with refractive error decide to wear contact lenses, together with the benefits they provide in optics and performing certain activities such as sports. In two qualitative studies, contact lens wearers reported being more confident and less conscious about their appearance in social functions such as weddings and parties than spectacle wearers [
], hence daily disposables might be considered to reduce this risk. Conversely, use of soft contact lenses in young patients aged 8–15 years has been associated with a lower risk of CIEs compared with teens and young adults (15–25 years) [
Age and other risk factors for corneal infiltrative and inflammatory events in young soft contact lens wearers from the contact lens assessment in youth (clay) study.
]. Although this information does not direct the clinician to a specific recommendation for contact lens material or modality, it should prompt careful assessment of tear film quantity, quality and ocular surface condition during the clinical examination.
2.3 Ocular health
2.3.1 Ocular symptoms
The commonly reported ocular symptoms in contact lens wearers include dryness, scratchy or watery sensations, irritation, blurry vision, light sensitivity, eye soreness, sandy or grittiness and burning sensations.[
]. In established wearers, use of the Contact Lens Dry Eye Questionnaire (CLDEQ-8) provides a validated quantification of ocular symptoms when contact lenses are worn, with a score of ≥12 points proposed to identify soft contact lens wearers who may be experiencing suboptimal lens wear and could likely benefit from clinical management of their contact lens-related symptoms [
]. Further, the CLDEQ-8 can be used to monitor the response to any contact lens intervention, with a difference in score of three being established as the size of change representing a ‘clinically important difference’ [
A recent study showed the importance of a routine clinical examination even in asymptomatic contact lens wearers. More than half (52%) of the 202 wearers had at least one diagnosed complication: 70% had contact lens-related complications (such as meibomian gland dysfunction, conjunctival injection, corneal staining and contact lens papillary conjunctivitis); 54% were diagnosed with non-contact lens related ocular health issues; and 4% showed signs of undiagnosed systemic disease [
]. Seasonal allergic conjunctivitis results in uncomfortable, itchy, red eyes. Use of daily disposable hydrogel lenses has been shown to reduce ocular symptoms compared to the exposed ocular surface [
]. A history of these conditions and dry eye/ocular surface disease is relevant to enable the clinician to check if there is a need to manage the pathology prior to fitting contact lenses, and, for conditions that increase the presence of bacteria on the lid margin.
2.4 General health
Certain ocular sequelae of diabetes are relevant to contact lens wear, including the presence of ocular surface disease, recurrent corneal erosions or reduced corneal sensitivity; however, providing these contraindications are absent, a patient with diabetes can still achieve successful contact lens wear [
]. Similar considerations apply to patients diagnosed with the human immunodeficiency virus (HIV) which can make them more susceptible to infection along with a number of potentially associated ocular pathologies [
]. Ensuring that the patient is making an informed choice about contact lens wear and understands the need to remain compliant to safe handling, wear and care practices is of particular importance in these two patient groups.
In a large case series, both thyroid disease and self-reported poor health were more common in wearers with contact lens related microbial keratitis compared to age-matched controls, with the authors concluding that ECPs should consider recommending daily disposables as a lower risk lens wear schedule in these cohorts [
]. Poor health is also relevant for current contact lens wearers, with inflammatory responses such as contact lens-associated red eye (CLARE) 154x more likely to develop in subjects positive for Haemophilus influenzae [
Poor health, specifically upper respiratory tract infections, is a factor in contact lens associated corneal infiltrates and illness during the past week was a significant risk factor for developing a CIE with soft contact lenses, and so advising against lens wear is prudent advice, particularly for overnight wear [
]. Debate continues on the presence of receptors for Severe Acute Respiratory Coronavirus-2 (SARS-CoV-2) on the ocular surface, although risk of infection via this route is thought to be low [
A number of systemic medications can cause ocular surface changes leading to dryness symptoms by decreasing tear production, altering nerve input and reflex secretion, inflammatory effects on secretory glands, or direct irritation through their secretion into tears [
]. ECPs should check the side effects of medication used, prompting a thorough evaluation of tear film quantity and quality along with careful assessment of the ocular surface.
Application of topical ocular medications, such as for glaucoma management, is also important to consider. Whilst not a direct contraindication for contact lens wear, patients will need counselling about the timing, dosing and applying contact lenses. This is especially relevant for preparations preserved with benzalkonium chloride, which is known to cause signs and symptoms of ocular surface disease [
There are many systemic and ocular conditions for which family history may be of critical importance. This includes inherited conditions, such as keratoconus and corneal dystrophies [
]. For these patients, contact lens fitting can be supplemented with advice and recommendations on myopia management strategies such as myopia control contact lenses, potential pharmaceutical options and environmental considerations, such as time outdoors and time on close work and near digital devices [
]. Wearing spectacles to play contact sports can cause injuries so soft contact lenses are a good form of refractive correction for these individuals [
], but spectacles are also not a good option for water sports, so the disposal of contact lenses after swimming and/or the use of well fitted goggles over the contact lenses can reduce the bioburden and related risks [
], so it is important to ascertain whether a patient will be driving in the contact lenses prescribed. Correction of even low levels of astigmatism should be considered to optimise driving performance [
], which, if reported during the patient history, can help inform the wear modality, avoiding overnight wear and consideration of daily disposables (Table 2).
It is also important that history-taking includes questions on use of eye cosmetics [
]. Similarly, pigments in eyeliners, mascara and eye shadows can disrupt the flow of meibum from the glands, deposit on the contact lenses, and cause ocular irritation [
]. Identification of patient needs and epectations, and delivery of relevant and accessible patient education is important to achieve successful contact lens wear.
2.8 Influence of environment on successful lens wear
Certain work-environments are challenging for contact lens care. Office workers who work prolonged hours at video display terminals should be encouraged to take breaks, as both contact lens and computer use are associated with tear film instability [
]. Environmental factors such as air pollution, wind, low humidity, high room temperature, dust, smoke, and high altitude may impact contact lens wear [
]. Conversely, in some industrial settings, contact lenses have been shown to protect from mechanical injuries from high-speed particles striking the eye [
]. Low humidity and increased blink-interval while concentrating on visual tasks may cause ocular dryness in pilots, with those wearing contact lenses, significantly more likely to report use of eye drops than non-lens wearers [
The effect of senofilcon a contact lenses compared to habitual contact lenses on ocular discomfort during exposure to a controlled adverse environment.
Novel method for determining hydrogel and silicone hydrogel contact lens transmission curves and their spatially specific ultraviolet radiation protection factors.
] and loss of vision (section 6.7.2.7). Therefore, work-environments and potential hazards to contact lens wear should be discussed during history-taking.
3. Anterior eye examination
A thorough examination of the anterior eye is required prior to fitting contact lenses and at each aftercare visit. The assessment requires a combination of different slit lamp biomicroscopy techniques [
] and the health of the eye, and the use of ophthalmic dyes to monitor the eye for contact lens complications (section 7.4 and see CLEAR Complications Report) [
] and affects lens fit – more so for rigid corneal lenses (section 4.1). Central corneal radii over a 2−3 mm radius can be quantified by conventional keratometry, which measures the separation of reflected pair(s) of mires [
]. A fuller profile of the shape of the cornea can be gained by video topography where the separation of placido disc rings reflected from the smooth tear film surface across the corneal surface are analysed (hence the need to ask the patient to blink a few seconds before image capture). The limitation of the extent of the analysed area from shadows of the ocular adnexa can be minimised by ‘stitching’ together topographies captured in different positions of gaze [
]. Raster scanning, in the form of measuring the shape of a slit of light as it passes across the cornea, can be used to assess anterior and posterior surface shape of the cornea as well as scleral shape with techniques such as scanning-slit, Scheimpflug cameras or Optical Coherence Tomography (OCT) [
Standard anterior eye viewing is conducted using a slit lamp biomicroscope. Different illumination and observation techniques are used to optimize the visibility of the features of the anterior segment of the eye and contact lens [
] and corneal endothelial cell imaging 40× . The cornea should be scanned for signs of physiological compromise (section 7.4) and hyperaemia should be assessed [
]. Slit lamp biomicroscopes combined with commercial digital imaging systems adapted to the slit lamp biomicroscope, including use of smartphone cameras mounted to the eye pieces, may enhance patient record keeping and management. Appropriate database and image manipulation software is available, as well as automated intelligence systems to grade images [
]. Consequently, an appropriate examination of the tear film, the ocular surface and quantification of symptoms, is vital in contact lens fitting and aftercare [
], such as using cold light illumination (section 3.6.1). The pre-lens tear film can also be observed to assess the in vivo wettability which is affected by lens deposition [
Detailed and accurate record keeping is a necessity in contact lens practice. A worldwide survey of ECPs reported that 84.5% use a grading scale to record the anterior eye health of their contact lens patients [
There are two main approaches to generating clinical grading scales: illustrated (artist-rendered drawings) and photographs of eyes. Illustrated scales can systematically represent the severity of a feature using the same magnification and angle-of-view [
], but may lack the realism of a photographic scale. Some scales combine these approaches with a photograph of a healthy eye overlaid with the different severities of the feature of interest [
Images are typically presented to represent grades 0–4. While it is suggested that clinical action is needed for grades >2, this depends on the feature being observed and associated signs and symptoms. In theory ECPs should use these images to interpolate to 0.1 grade increments to enhance sensitivity [
]. Reference to a visible grading scale at every visit to record blepharitis, meibomian gland dysfunction, bulbar and limbal hyperemia, corneal neovascularisation and palpebral conjunctival redness under white light and palpebral roughness with fluorescein (section 3.4.1) in recommended [
]. Corneal and conjunctival staining observation recording was also recommended, but a sketch with a description of depth was advocated rather than multiple grading scales scores to record type, size, location and depth [
], the resulting images or movie clips can accurately reflect anterior eye characteristics. As well as allowing changes in physiology and pathology to be more precisely tracked over time, grading scale images and digital images/videos are also useful education tools to help explain ocular changes to patients during contact lens aftercare appointments and keep them fully informed.
3.4 Lid eversion
Eyelid eversion is a necessary component of the contact lens fitting and aftercare process to assess the eye for complications (see CLEAR Complications Report) [
]. The procedure must be quick and comfortable for the patient, while also permitting the clinician to view a large area of the palpebral conjunctiva. The optimal device for everting the upper lid is a finger-shaped everter made of silicone rubber [
]. The silicone rubber everter was rated as comfortable as using the ECP’s index finger to evert the lid, as fast as using a cotton bud, and exposed the largest amount of palpebral conjunctiva [
]. To evert the upper lid, instruct the patient to look down, and then lift up the upper eyelid to separate the base of the lashes while stretching the lid forward [
]. Clinicians need to avoid causing iatrogenic staining of the lid wiper area when everting the lids (section 3.4.2.2). Double lid eversion is useful when there is a history of a lost or displaced contact lens [
]. The lower lid can be everted by placing a cotton wool bud along the lower eyelid margin, rotating towards the eye and pressing inwards or using a curved ended plastic tool to press just below the lower lid margin [
]. The authors recommend to first evert the upper and lower eyelid to examine the hyperemia at the slit lamp with white light before instilling fluorescein [
] if fluorescein is instilled before lid eversion, the ECP can assess redness with white light and switch to blue light and insert a yellow filter to observe roughness. More advanced clinical techniques, such as confocal microscopy [
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