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Contact lens-related complications are common, affecting around one third of wearers, although most are mild and easily managed. Contact lenses have well-defined anatomical and physiological effects on the ocular surface and can result in other consequences due to the presence of a biologically active material. A contact lens interacts with the tear film, ocular surface, skin, endogenous and environmental microorganisms, components of care solutions and other antigens which may result in disease specific to contact lens wear, such as metabolic or hypersensitivity disorders. Contact lens wear may also modify the epidemiology or pathophysiology of recognised conditions, such as papillary conjunctivitis or microbial keratitis. Wearers may also present with intercurrent disease, meaning concomitant or pre-existing conditions unrelated to contact lens wear, such as allergic eye disease or blepharitis, which may complicate the diagnosis and management of contact lens-related disease.
Complications can be grouped into corneal infection (microbial keratitis), corneal inflammation (sterile keratitis), metabolic conditions (epithelial: microcysts, vacuoles, bullae, tight lens syndrome, epithelial oedema; stromal: superficial and deep neovascularisation, stromal oedema [striae/folds], endothelial: blebs, polymegethism/ pleomorphism), mechanical (corneal abrasion, corneal erosion, lens binding, warpage/refractive error changes; superior epithelial arcuate lesion, mucin balls, conjunctival epithelial flaps, ptosis, discomfort), toxic and allergic disorders (papillary conjunctivitis, solution-induced corneal staining, incomplete neutralisation of peroxide, Limbal Stem Cell Deficiency), tear resurfacing disorders/dry eye (contact lens-induced dry eye, Meibomian gland dysfunction, lid wiper epitheliopathy, lid parallel conjunctival folds, inferior closure stain, 3 and 9 o'clock stain, dellen, dimple veil) or contact lens discomfort. This report summarises the best available evidence for the classification, epidemiology, pathophysiology, management and prevention of contact lens-related complications in addition to presenting strategies for optimising contact lens wear.
Contact lens-related complications are common, with one third of wearers surveyed in the USA reporting having experienced a red or painful eye requiring emergency eye care [
Strategies to better engage, educate, and empower patient compliance and safe lens wear: compliance: what we know, what we do not know, and what we need to know.
]. Forty three percent of asymptomatic wearers present with clinically observed ocular surface signs, which may predispose them to contact lens-related complications [
]. Complications may result in a reduction in wear time, discontinuation from contact lens wear or a need for emergency eye care. Severe complications may result in vision loss and in significant cost and morbidity [
Contact lens-related complications differ from other ocular surface conditions in several ways. Contact lenses can have well-defined anatomical and physiological effects the ocular surface and can result in other consequences due to the presence of a biologically active material [
]. A contact lens interacts with the tear film, ocular surface, skin, endogenous and environmental microorganisms, components of care solutions and other antigens which may result in disease specific to contact lens wear, such as metabolic or hypersensitivity disorders. For the same reasons, contact lens wear may alter the epidemiology or pathophysiology of recognised conditions, such as contact lens induced papillary conjunctivitis (CLPC) or microbial keratitis (MK). Wearers may also present with intercurrent disease, meaning concomitant or pre-existing conditions unrelated to contact lens wear, such as allergic eye disease or blepharitis, which may complicate the diagnosis and management of contact lens-related disease.
This report summarises the best available evidence for the classification, epidemiology, pathophysiology, management and prevention of contact lens-related complications in addition to presenting strategies for optimising contact lens wear.
1.1 Scope of the report
This report will consider only contact lens-related complications per the definition below and where possible, recent evidence will be prioritised. The effects of contact lens wear on the anatomy and physiology of the eye and medical and speciality indications for contact lens wear are outside of the scope of the report and are covered elsewhere.
1.2 Definition of a contact lens complication
A contact lens complication is considered to be an event caused by contact lens wear, which is generally symptomatic, causing the wearer to seek care, or requiring intervention, such as an interruption to contact lens wear or pharmacological intervention.
1.3 Classification of complications
Several approaches have been proposed in order to classify contact lens -related complications, including classification based on anatomical location, presumed aetiology and severity of the condition. Each approach may be suitable for different applications.
1.3.1 Anatomical location
Contact lens complications have been classified according to anatomical location [
], which is a useful approach in systematically evaluating the physiological effect of contact lenses on each of the ocular structures. This can be helpful from a teaching perspective. However, this approach does not inform the pathogenesis and may not be helpful in managing or preventing the complication.
1.3.2 Presumed aetiology
Categorisation by presumed aetiology can be helpful for treatment as well as management and prevention of adverse events. For example, to assist in managing sterile corneal infiltrates, an approach based on presumed aetiology has been described, where corneal infiltrates were classified as traumatic, viral, allergic, preserved solution-related, contact lens fitting-related, due to coated lenses, toxic vapours or idiopathic [
]. This method has also been used in a broader range of complications, classfied as patient-, contact lens - or care-related events, in an attempt to support their management [
A similar approach was used in a series of epidemiological studies where complications were classified as either ‘ulcerative’ (microbial keratitis) or ‘non-ulcerative’. The latter group were categorised into six divisions based on presumed aetiology: sterile keratitis, toxic and hypersensitivity, metabolic, mechanical, tear resurfacing and other contact lens related events [
]. Most recently, this has been modified to four categories, based on microbial challenge, hypoxia, mechanical and toxicity challenges to the ocular surface due to contact lens wear [
One of the difficulties with classification approach is where more than one mechanism may be involved in the pathophysiology of the condition. For example, the presentation of CLPC is thought to be primarily due to a mechanical stimulus in silicone hydrogel (SiHy) lenses and is localised to the region corresponding to the lens edge. Conversely for hydrogel contact lenses, protein deposition and subsequent denaturation, the stimulus is likely to be antigenic and the response inflammatory, manifesting as a generalised palpebral response [
While it is clear that MK and sterile infiltrates have different underlying pathophysiology, there is an argument to suggest that there is significant overlap in their clinical signs and that they form a “continuum” of conditions that includes microbial and sterile events [
]. Challenges with this approach include that a binary approach (sterile or microbial) is required to determine management strategy, and a range of clinical presentations are described by one descriptor, such as “generalized or localized conjunctival redness”, which limits the diagnostic value of this analysis. This is an inherent problem of retrospective datasets, where diagnostic criteria are not pre-defined and prospectively collected.
1.3.3 Severity
Several models of classification of sterile keratitis (or corneal infiltrative events, CIE) have been proposed based on disease severity and impact. Corneal infiltrates may be described as severe or non-severe events based on their signs and symptoms [
In summary, while multiple classification systems have been proposed, each with their respective advantages and disadvantages, for the purposes of this report an approach based on likely aetiology has been used. This supports a pragmatic approach to management and prevention. Corneal infection (microbial or ulcerative keratitis) is differentiated from the less serious non-ulcerative events “non-ulcerative” are further categorised into six sub-groups: sterile keratitis, toxic/hypersensitivity, metabolic, mechanical, tear resurfacing and other contact lens related events (Table 1).
Table 1Classification of contact lens-related disorders (adapted from Stapleton et al, 1992 [
]; infection, inflammation and necrosis of corneal tissue
Epithelial ulcer with underlying stromal infiltrate; Pseudomonas aeruginosa common and associated with fulminating course; adherent mucous; gross corneal oedema
Ciliary injection
Inflammation
Sterile keratitis
Discomfort, redness, and discharge
Inflammatory response in absence of infecting organism; factors include delayed hypersensitivity to thiomersal [
Multifactorial including: CL material, deposits, wettability, bioburden, CL movement, lens care solutions, inflammatory and other tear film components [
] Extending centripetally into cornea in a whorl shape. In late stages, superficial and deep vascularisation, scarring, conjunctivalisation, and calcification [
Symptoms of ocular irritation and intermittent blurred vision; may reduce comfortable wear time
Changes to morphological features of Meibomian glands, altered expressibility of glands, quality of meibum. Reduced tear break up time and lipid layer thickness. Mechanical trauma [
Corneal infection or MK is a rare but potentially severe complication of contact lens wear, which is associated with signficant morbidity including visual loss, societal cost and patient symptoms.
2.1 Frequency
Contact lens-related corneal infection accounts for around 35–65 % of new cases of hospital presenting MK in urban tertiary centres [
The annualised incidence of corneal infection varies with contact lens type and wear modality, and ranges from 1-2 per 10,000 wearers for daily use of soft and rigid corneal contact lenses to 20 per 10,000 for overnight wear with SiHy or hydrogel lenses [
]. In overnight wear, there is greater risk in the first six months of wear, indicating possible adaptation with time and/or persistence of survivors in this lens wear modality [
], however there have been no prospective studies of corneal infection since the mid-2000s, consequently no reliable incidence estimates with contemporary contact lenses, orthokeratology (See CLEAR Orthokeratology Report [
], with the remainder caused by pathogens including Acanthamoeba spp. and filamentary fungi (such as Fusarium spp.). The most common bacterial pathogen in most centres is Pseudomonas aeruginosa (Fig. 1). The proportions of causative organisms vary depending on the climate for example in Australia, Pseudomonas aeruginosa is more common in tropical regions, compared to the temperate regions, where Staphylococcus aureus and Serratia spp. are more commonly recovered [
]. In addition, in daily disposable contact lens wear, keratitis is more likely to be caused by endogenous bacteria, such as Staphylococcus spp. compared to reusable soft lens wearers, in which environmental bacteria, such as Pseudomonas aeruginosa predominate [
] and are thought to be the source of the pathogen in many reusable wearers with MK.
Fig. 1Pseudomonas aeruginosa keratitis in a soft contact lens wearer. Image courtesy of Mr Stephen Tuft, Moorfields Eye Hospital. Image reproduced from Carnt et al., 2017 [
Established risk factors, presenting signs, differential diagnosis, management and outcomes for different causative organisms are described in Table 2.
Table 2Risk factors, presenting signs, differential diagnosis, management, and outcomes for each type of causative organism in contact lens-related microbial keratitis.
Corneal scrape is positive in only around 50% of clinically diagnosed cases [83] SES: socioeconomic status; PCR: polymerase chain reaction; PHMB: polyhexamethylene biguanide.
and smear, PCR
Corneal epithelial biopsy, scrape and smear, PCR, in vivo confocal microscopy
Corneal scrape and smear, in vivo confocal microscopy
Management (typical)
Intensive broad-spectrum topical antibiotics, typically fluoroquinolone (15 min loading dose for first 6 hours), hrly night and day, reduce frequency according to repithelialisation then qid; optional concurrent topical corticosteroids after 2 days*
Biguanide (PHMB or chlorhexidine) monotherapy or with diamidine (brolene, hexamidine), hrly night and day 2-5 days; then qid; concurrent topical or oral corticosteroids if scleritis/ring infiltrate; Concurrent topical antibiotic if superinfection
Topical antifungal (eg natamycin), hrly for an extended period; highly invasive, so surgical intervention common
Contact lenses, like all medical devices, carry a certain degree of risk. An evidence-based approach to decrease frequency and severity of contact lens-related infection includes attention to those risk factors associated with a greater impact on disease load as follows:
The relative risk of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. A case-control study. Microbial Keratitis Study Group.
Attention to hand, lens and case hygiene. As these behaviours are common, a sense of diminished risk can result. Frequent and repeated compliance education is required. Novel reminder cues may be helpful, for example, a recent study has shown that a simple “no water” graphic on contact lens paraphernalia can reduce water exposure behaviours and environmental contact lens case contamination [
Daily disposable lenses, while not decreasing the absolute risk of contact lens infection, do result in less severe disease and fewer cases of vision loss compared with frequent replacement soft contact lenses [
For ECPs, the most important differential diagnosis for a contact lens wearer presenting with a painful red eye should focus on determining whether they have sight-threatening MK or a non-infectious or sterile keratitis, referred to as a corneal infiltrative event (CIE). Although accurately classifying ocular signs is important, understanding the incidence and risk factors for MK and CIEs helps the clinician with differential diagnosis. More importantly, knowledge of risk factors helps the clinician recommend contact lenses that will minimise risk of CIEs for patients who have non-modifiable risk factors that increase their risk.
3.1 Signs associated with CIE
Sweeney and co-workers developed a classification system for CIEs in the early 2000s that has been used in most of the larger studies of soft contact lens-related adverse events (see Section 2.3) [
]. CIEs may or may not be accompanied by symptoms, but when they are symptomatic, the wearer typically presents with discomfort ranging from none to moderate pain, and a red and watery eye. Asymptomatic CIEs are almost exclusively reported in randomised clinical trials and present infrequently in population-based studies [
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.
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.
Univariate model only, -- Data not captured in study or unable to test due to homogeneity in sample, NS Not Significant, + Hazard Ratio, Mos: months, yr: year, IRR: Incidence rate ratio, Rx: prescription.
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.
Univariate model only, -- Data not captured in study or unable to test due to homogeneity in sample, NS Not Significant, + Hazard Ratio, Mos: months, yr: year, IRR: Incidence rate ratio, Rx: prescription.
* Univariate model only, -- Data not captured in study or unable to test due to homogeneity in sample, NS Not Significant, + Hazard Ratio, Mos: months, yr: year, IRR: Incidence rate ratio, Rx: prescription.
The number of infiltrates, their size, location and presence of overlying staining help determine the differential diagnoses for the sub-categories of CIEs. In patients with CIEs, signs and symptoms typically begin to resolve as soon as lens wear is temporarily ceased. An important differential between CIEs and MK is that the discomfort/pain is not relieved by contact lens removal in MK, but the pain progressively increases [
Contact lens peripheral ulcers (CLPU) occur in the periphery or mid-periphery of the cornea, have overlying fluorescein staining and are <1 mm in diameter with regular edges (Fig. 2). CLPU events will resolve to a small scar over time. Although they are not infectious, management of CLPUs usually involves coverage by a combination antibiotic-steroid combination in countries where ECPs have access to prescribing them.
Fig. 2Left: CLPU. Right: Infiltrative Keratitis; Images courtesy of CORE.
Infiltrates seen with contact lens acute red eye (CLARE) can be diffuse, or multiple focal, much smaller and often do not have overlying staining. They are accompanied by eye redness, watering and pain on waking and are highly associated with overnight wear of lenses. These will resolve with cessation of lens wear, although coverage with antibiotic-steroid is sometimes used to manage the condition.
Infiltrative keratitis presents as single or multiple anterior focal infiltrates that sometimes show overlying fluorescein staining (Fig. 2). It presents with mild to moderate irritation, some redness and occasional discharge. Management of infiltrative keratitis depends on the degree of redness, discomfort and presence of overlying staining. It is managed similarly, with prophylactic coverage with antibiotics or combination agents.
]. Using data from the Manchester Keratitis Study, the authors propose that the various classification schemes at the time were most likely describing an infiltrative response that is actually a continuum of disease rather than distinct conditions. Most importantly for the practicing clinician, they also conclude that if a contact lens wearing patient presents with an increasingly uncomfortable red eye with an infiltrate that contact lens wear should be ceased and intensive antimicrobial treatment commenced immediately.
3.2 Incidence of CIEs
The incidence of CIEs varies widely depending on the proportion of the study population with risk factors for CIEs, the contact lens wearing schedule (daily versus overnight wear), contact lens replacement schedule (daily disposable versus reusable), contact lens material (hydrogel versus SiHy), history of prior CIEs and the age of the wearer (Table 3 and Fig. 3). It is clear that studies that included large proportions of wearers using daily disposable soft contact lens have rates that are approximately ten times lower than with reusable contact lenses, with incidence ranging from 0.0 % to 0.4 %/yr depending on daily disposable contact lens material [
CIE incidence varies depending on the presence of risk factors in the population that is being studied (Fig. 3). The most consistent risk factors, divided into those that are modifiable by different choice of wear schedule, lens replacement schedule, frequency of case replacement, disinfection system, compliance with lens care or lens material and other factors are not modifiable, such as the age of the wearer, sex, their refractive error, or general or eye health history (Table 4a, Table 4b; note that some studies did not analye all of the factors listed).
Among the modifiable risk factors, overnight wear increases risk significantly [
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.
]. In these studies the increased risk ranged from 2.5–10 times higher depending on the subgroup being studied. Use of reusable contact lenses was consistently identified, with increased risk from 3.0–12.5 times the risk compared to daily disposable use [
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.
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.
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.
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.
The clinician should consider the risk factors for each contact lens wearer to arrive at the best contact lens option for that patient. In general, use of daily disposable contact lenses and avoiding overnight wear bring lower risk for CIEs, as does use of hydrogen peroxide disinfection for wearers of reusable contact lenses. For example, a 23 year old with a history of previous CIEs or with blepharitis should be encouraged to wear daily disposable contact lenses in order to mitigate the added risk that their age and history contribute. Similarly, patients with high refractive errors or a history of a previous red eye should be steered toward daily disposable contact lenses as the safest choice for them. All daily disposable contact lenses wearers should be advised at all follow-up visits to never sleep in their contact lenses and to discard contact lenses every day.
4. Metabolic complications
Contact lens wear results in metabolic stress to the cornea, which is influenced by both the oxygen transmissibility of the contact lens as well as the degree to which tear exchange is impeded by the contact lens (See CLEAR Material Impact Report [
Although the development of recent lens materials has led to a decrease in the frequency and severity of disorders resulting from hypoxia, these complications still exist because high Dk lenses are not universally prescribed [
], and individual responses to hypoxia vary. Moreover, closed eye wear by intention (e.g. orthokeratology) or by neglect (non-compliance) further limits oxygen to the eye. Metabolic complications from hypoxia manifest as distinct clinical entities (Table 5).
Table 5Contact lens complications attributed to hypoxia.
Comparison of corneal endothelial bleb formation and disappearance processes between rigid gas-permeable and soft contact lenses in three classes of dk/l.
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