Incidence of contact-lens-associated microbial keratitis and its related morbidity

Scoping review: Reporting characteristics for the safety of contact lenses in the pediatric population

SIGNIFICANCE

Contact lenses are an increasingly popular option for correcting pediatric refractive error due to increased awareness of interventions to slow myopia progression. With limited information on the safety profiles of contact lenses in children, it is important to characterize the current understanding and promote this device's safe and effective use.

PURPOSE

This scoping review evaluates characteristics of the current literature that have examined the safety of contact lenses in pediatric patients. It provides future directions for systematic reviews and identifies any gaps in the current literature or areas for future research.

METHODS

Literature searches in MEDLINE via PubMed, EMBASE, The Cochrane Library, trial registries, and U.S. Food and Drug Administration clinical trial documentation were performed. Included studies (i.e., experimental and quasi-experimental studies; observational studies including prospective and retrospective cohort, case-control, and analytical cross-sectional studies, and case series of 30 or more participants) reported safety and/or complications of the use of any contact lens for correcting refractive error in children (0 to 18 years). Two independent reviewers first screened the titles and abstracts, and then full-text reports for eligibility. Conflicts in eligibility were resolved by discussions with a third reviewer. Two independent reviewers extracted data, including details about the participants, context, study methods, and key findings relevant to the review question.

RESULTS

This scoping review included 73 studies from 10 countries using different contact lens modalities, primarily orthokeratology and soft contact lenses, in children (6 to 18 years). The most common adverse event reported by the studies was corneal staining (60% orthokeratology, 45% soft contact lens).

CONCLUSIONS

The need for uniform reporting standards for adverse events poses challenges for comprehensive data synthesis. However, this scoping review identified a sufficient number of studies for a future systematic review to quantify the risks associated with orthokeratology and soft contact lens use in children.

Long circulating liposomal platform utilizing hydrophilic polymer-based surface modification: preparation, characterisation, and biological evaluation

Liposomes are one of the most important drug delivery vectors, nowadays used in clinics. In general, polyethylene glycol (PEG) is used to ensure the stealth properties of the liposomes. Here, we have employed hydrophilic, biocompatible and highly non-fouling N-(2-hydroxypropyl) methacrylamide (HPMA)-based copolymers containing hydrophobic cholesterol anchors for the surface modification of liposomes, which were prepared by the method of lipid film hydration and extrusion through 100 nm polycarbonate filters. Efficient surface modification of liposomes was confirmed by transmission electron microscopy, atomic force microscopy, and gradient ultracentrifugation. The ability of long-term circulation in the vascular bed was demonstrated in rabbits after i.v. application of fluorescently labelled liposomes. Compared to PEGylated liposomes, HPMA-based copolymer-modified liposomes did not induce specific antibody formation and did not activate murine and human complement. Compared with PEGylated liposomes, HPMA-based copolymer-modified liposomes showed a better long-circulating effect after repeated administration. HPMA-based copolymer-modified liposomes thus represent suitable new candidates for a generation of safer and improved liposomal drug delivery platforms.

Benefits and risks of orthokeratology treatment: a systematic review and meta-analysis

BACKGROUND

This meta-analysis reviews the evidence for the risks and benefits associated with orthokeratology (OK) treatment compared with other methods of myopia control in children and adults.

METHODS

A systematic search of Cochrane Central Register of Controlled Trials, Pubmed, Embase and Ovid was conducted from database inception to 22nd August 2021. Studies that reported on risks, visual and ocular biometric effects of OK in patients > 5 years of age with myopia (- 0.75 to - 6.00D) were included. Main outcomes are change in axial length and any adverse event.

RESULTS

Fourty-five papers were included in this systematic review and meta-analysis. The quality of data was variable and of moderate certainty, and selection bias likely skewed the results towards a relative benefit for OK. The rate of axial elongation in children was lower for OK treatment compared to other treatment modalities at one year (MD - 0.16 mm, 95% CI - 0.25 to - 0.07). Rate of change in axial length in children rebounded after OK discontinuation compared to participants who continued treatment (MD 0.10 mm, 95% CI 0.06 to 0.14). Adults and children wearing OK were up to 3.79 times more likely to experience an adverse event when compared with conventional contact lenses (OR 3.79, 95% CI 1.24 to ll.), though this evidence base is underdeveloped and requires additional well-designed studies for substantial conclusions to be drawn.

CONCLUSIONS

OK arrests myopia progression while in use, however, there remain unanswered questions about the optimal duration of treatment, discontinuation effects and long-term risk for adverse events.

Infectious keratitis associated with contact lens wear: REGINFECOR multicenter study

This 32-centre multicentre study addresses the lack of knowledge about the prevalence and significance of microbial keratitis (MK) associated with contact lens (CL) wear in Spain. A total of 304 cases recruited from 32 hospitals were studied and showed that infectious keratitis associated with contact lens wear mainly affects young women during the summer months. In this study, soft lenses with monthly replacement and single solution cleaning were most commonly used, purchased and fitted in opticians' shops. Common risk factors were identified among users, such as topping off solutions, prolonging the life of lenses, and frequently sleeping, swimming and showering with lenses. Overnight lens wear was significantly associated with a higher incidence of corneal opacities, and the presence of Pseudomonas aeruginosa in bacterial cultures was associated with more severe sequelae and a greater need for corneal transplantation. Although most cases were benign, the time taken to heal was long, which poses a problem for working patients. This study provides valuable epidemiological, microbiological and risk factor information and estimates the incidence of CL related MK in Spain to be approximately 1 case per 30,000 inhabitants per year.

Cosmetic Contact Lenses in the United Kingdom: Assessment of Online Regulation and Quality of Consumer Health Information

OBJECTIVES

To determine the compliance of online vendors to the UK Opticians Act 1989 Section 27 requirements and safety regulations for cosmetic contact lens (CCL) sales and the quality of online CCL health information.

METHODS

The top 50 websites selling CCLs on each three search engines, namely Google, Yahoo, and Bing, were selected. Duplicates were removed, and the remaining websites were systematically analyzed in February 2023. UK legal authorization for CCL sales was assessed using the Opticians Act Section 27 and safety regulations determined by the presence of Conformité Européene (CE) marking. The quality and reliability of online information was graded using the DISCERN (16-80) and JAMA (0-4) scores by two independent reviewers.

RESULTS

Forty-seven eligible websites were analyzed. Only six (12.7%) met the UK legal authorization for CCL sales. Forty-nine different brands of CCLs were sold on these websites, of which 13 (26.5%) had no CE marking. The mean DISCERN and JAMA benchmark scores were 26 ± 12.2 and 1.3 ± 0.6, respectively (intraclass correlation scores: 0.99 for both).

CONCLUSIONS

A significant number of websites provide consumers with easy, unsafe, and unregulated access to CCLs. Most online stores do not meet the requirements set out in the Opticians Act for CCL sales in the United Kingdom. A significant number of CCLs lack CE marking, while the average quality of information on websites selling CCLs is poor. Together, these pose a risk to consumers purchasing CCLs from unregulated websites, and therefore, further stringent regulations on the online sales of these products are needed.

Mesenchymal stem cell-based adjunctive therapy for Pseudomonas aeruginosa-induced keratitis: A proof-of-concept in-vitro study

PURPOSE

Pseudomonas aeruginosa-induced keratitis is one of the most severe and challenging forms of corneal infection, owing to its associated intense inflammatory reactions leading to corneal necrosis and dense corneal scar with loss of vision. Since mesenchymal stem cells (MSCs) are reported to possess antimicrobial and immunomodulatory properties, they can be tested as an adjuvant treatment along with the antibiotics which are the current standard of care. This study aims to investigate the anti-bacterial and immunomodulatory roles of human bone marrow MSC-derived conditioned medium (MSC-CM) in P. aeruginosa-infected human corneal epithelial cells (HCECs) in vitro.

METHODS

The effect of MSC-CM on the growth of clinical isolates of P. aeruginosa was evaluated by colony-forming unit assay. The expression of inflammatory cytokines (IL-6 and TNF-α) and an antimicrobial peptide (Lipocalin 2) in lipopolysaccharide-treated MSCs and HCECs was analyzed through ELISA. Corneal epithelial repair following infection with P. aeruginosa was studied through scratch assay.

RESULTS

Compared to control (P. aeruginosa (5*105) incubated in DMEM (1 ml) at 37 °C for 16 h), MSC-CM significantly: i) inhibits the growth of P. aeruginosa (159*109 vs. 104*109 CFU/ml), ii) accelerates corneal epithelial repair following infection with P. aeruginosa (9% vs. 24% closure of the wounded area after 12 h of infection), and iii) downregulates the lipopolysaccharide-induced expression of IL-6, TNF-α and Lipocalin 2 in HCECs. A combination of MSC-CM with an antibiotic, Ciprofloxacin moderately regulated the expression of IL-6, TNF-α, and Lipocalin 2.

CONCLUSION

MSC-CM holds promise as an adjunctive therapeutic approach for P. aeruginosa-induced corneal epithelial damage.

Differentiation of acanthamoeba keratitis from other non-acanthamoeba keratitis: Risk factors and clinical features

INTRODUCTION

Infectious Keratitis is one of the most common ocular emergencies seen by ophthalmologists. Our aim is to identify the risk factors and clinical features of Acanthamoeba Keratitis (AK).

METHODS

This retrospective chart review study was conducted at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia, and included all the microbial keratitis cases, male and female patients of all ages. The main outcome is the differentiation between various microbial keratitis types.

RESULTS

We included 134 consecutive eyes of 126 persons. We had 24 cases of acanthamoeba keratitis, 22 bacterial keratitis, 24 fungal keratitis, 32 herpetic keratitis, and 32 bacterial co-infection. Contact lens wear was found in 33 eyes (24.6%). Among acanthamoeba keratitis patients, 73% were ≤ 39 years of age, and 73% were females (P <0.001). Also, in AK cases, epithelial defect was found in all cases (100%), endothelial plaques were found in 18 eyes (69.2%), 12 cases had radial keratoneuritis (46.2%), and ring infiltrate was found in 53.8% of AK cases.

CONCLUSIONS

We determined the factors that increase the risk of acanthamoeba infection and the clinical characteristics that help distinguish it from other types of microbial keratitis. Our findings suggest that younger females and patients who wear contact lenses are more likely to develop acanthamoeba keratitis. The occurrence of epitheliopathy, ring infiltrate, radial keratoneuritis, and endothelial plaques indicate the possibility of acanthamoeba infection. Promoting education on wearing contact lenses is essential to reduce the risk of acanthamoeba infection, as it is the most significant risk factor for this infection.

Myopia control: Seeing beyond efficacy

SIGNIFICANCE

The availability of a range of effective myopia control modalities enables the clinician to exercise judgment when discussing the treatment plan with the patient and their parents. This article outlines important considerations beyond efficacy.Clinically meaningful myopia control may be attained with some spectacle lenses, select soft contact lenses, some concentrations of atropine, and overnight orthokeratology. Given that satisfactory efficacy can be achieved with a range of modalities, other factors should be considered when deciding upon the best intervention for a given child. Four key factors-compliance, quality of vision, quality of life, and safety-are discussed in this review. Compliance directly impacts efficacy regardless of the modality and is the most important consideration, as it is influenced by quality of vision and comfort. Daily disposal myopia control contact lenses and overnight orthokeratology are generally associated with high compliance, provide better vision-related quality of life than spectacles, and carry a very low risk when used appropriately. A further benefit of overnight orthokeratology is the elimination of a need for optical correction during the day.

Optical interventions for myopia control

A range of optical interventions have been developed to slow the progression of myopia. This review summarizes key studies and their outcomes. Peer-reviewed, randomized controlled clinical trials of at least 18 months duration were identified. Randomized clinical trials were identified and summarised: 13 for spectacles, 5 for overnight orthokeratology, 5 for soft contact lenses, and 3 for orthokeratology combined with low concentration atropine. Overnight orthokeratology trials were the most consistent with 2-year slowing of axial elongation between 0.24 and 0.32 mm. Other modalities were more variable due to the wide range of optical designs. Among spectacle interventions, progressive addition lenses were the least effective, slowing axial elongation and myopia progression by no more than 0.11 mm and 0.31 D, respectively. In contrast, novel designs with peripheral lenslets slow 2-year elongation and progression by up to 0.35 mm and 0.80 D. Among soft contact lens interventions, medium add concentric bifocals slow 3-year elongation and progression by only 0.07 mm and 0.16 D, while a dual-focus design slows 3-year elongation and progression by 0.28 mm and 0.67 D. In summary, all three optical interventions have the potential to significantly slow myopia progression. Quality of vision is largely unaffected, and safety is satisfactory. Areas of uncertainty include the potential for post-treatment acceleration of progression and the benefit of adding atropine to optical interventions.

Advances in Contact Lens Care Solutions: PVP-I Disinfectant and HAD Wetting Agents From Japan

ABSTRACT

Half of the individuals who wear contact lenses use reusable lenses that require proper care. Improper contact lens (CL) care and using inadequate disinfecting solutions can lead to lens contamination, CL-related microbial keratitis, and Acanthamoeba keratitis. Oxidative disinfecting solutions, such as hydrogen peroxide, show higher efficacy than multipurpose solutions. Povidone-iodine (PVP-I), an oxidative disinfectant used in ophthalmic surgery, has been proven to be safe and effective. The PVP-I system, a CL disinfecting solution developed in Japan, has demonstrated excellent antimicrobial and antiviral properties. Although CL discomfort does not have a risk of ocular disorders with poor visual prognosis, such as keratitis, CL discomfort can still lead to lens dropout and thus needs to be addressed. To mitigate CL discomfort, it is essential to use disinfecting solutions containing surfactants and wetting agents that improve wettability of the lens surface. A CL solution containing hyaluronic acid derivatives (HADs) as wetting agents that permanently adhere to the lens surface to improve wettability of the lens surface was developed in Japan. There is potential for HAD to be integrated into various solutions. This article reviews the efficacy of novel PVP-I-based disinfecting solution and HAD wetting agents.

Remote Measurements of Tear Electrolyte Concentrations on Both Sides of an Inserted Contact Lens

In this paper, a method is described to perform ion concentration measurements on both sides of an inserted contact lens, without physical contact with the eye or the contact lens. The outer surface of an eye is covered with a tear film that has multiple layers. The central aqueous layer contains electrolytes and proteins. When a contact lens is inserted, it becomes localized in the central layer, which creates two layers known as the pre-lens tear film (PLTF) and the post-lens tear film (PoLTF). The PoLTF is in direct contact with the sensitive corneal epithelial cells which control electrolyte concentrations in tears. It is difficult to measure the overall electrolyte concentration in tears because of the small 7 μL volume of bulk tears. No methods are known, and no method has been proposed, to selectively measure the concentrations of electrolytes in the smaller volumes of the PLTF and the PoLTF. In this paper, we demonstrate the ability to localize fluorophores on each side of a contact lens without probe mixing or diffusion across the lens. We measured the concentration of sodium in the region of the PoLTF using a sodium-sensitive fluorophore positioned on the inner surface of a contact lens. The fluorescence measurements do not require physical contact and are mostly independent of eye motion and fluorophore concentration. The method is generic and can be combined with ion-sensitive fluorophores for the other electrolytes in tears. Instrumentation for non-contact measurements is likely to be inexpensive with modern opto-electronic devices. We expect these lenses to be used for measurements of other ions in the PLTF and the PoLTF, and thus become useful for both research and in the diagnosis of infections, keratitis and biomarkers for diseases.

It's all relative: analyzing microbiome compositions, its significance, pathogenesis and microbiota derived biofilms: Challenges and opportunities for disease intervention

Concept of microorganisms has largely been perceived from their pathogenic view point. Nevertheless, it is being gradually revisited in terms of its significance to human health and now appears to be the most dominant force that shapes the immune system of the human body and also determines an individual's predisposition to diseases. Human inhabits bacterial diversity (which is predominant among all microbial communities in human body) occupying 0.3% of body mass, known as microbiota. On birth, a part of microbiota that child obtains is essentially a mother's legacy. So, the review was initiated with this critical topic of microbiotal inheritance. Since, each body site has distinct physiological specifications; therefore, they contain discrete microbiome composition that has been separately discussed along with dysbiosis-induced pathologies originating in different body organs. Factors affecting microbiome composition and may cause dysbiosis like antibiotics, delivery, feeding method etc. as well as the strategies that immune system adopts to prevent dysbiosis have been highlighted. We also tried to bring into attention the topic of dysbiosis induced biofilms, that enables cohort to survive stresses, evolve, disseminate and infection resurgence that is still in dormancy. Eventually, we put spotlight on microbiome significance in medical therapeutics. We didn't merely confine article to gut microbiota, that is being studied more extensively. Numerous community forms at diverse body sites are inter-related, and being exposed to awfully variable perturbations appear to be challenging to evaluate perturbation risks holistically. All aspects have been elaborately discussed to achieve a global depiction of human microbiota in order to meet urgent necessity for protocol standardisation. Demonstrates that environmental challenges (antibiotic use, alterations in diet, stress, smoking etc.) might cause dysbiosis i.e. transition of healthy microbiome composition to the one in which pathogenic microorganisms become more abundant, and eventually results in an infected state.

Current microfluidic platforms for reverse engineering of cornea

According to the World Health Organization, corneal blindness constitutes 5.1% of global blindness population. Surgical outcomes have been improved significantly in the treatment of corneal blindness. However, corneal transplantation is limited by global shortage of donor tissue, prompting researchers to explore alternative therapies such as novel ocular pharmaceutics to delay corneal disease progression. Animal models are commonly adopted for investigating pharmacokinetics of ocular drugs. However, this approach is limited by physiological differences in the eye between animals and human, ethical issues and poor bench-to-bedside translatability. Cornea-on-a-chip (CoC) microfluidic platforms have gained great attention as one of the advanced in vitro strategies for constructing physiologically representative corneal models. With significant improvements in tissue engineering technology, CoC integrates corneal cells with microfluidics to recapitulate human corneal microenvironment for the study of corneal pathophysiological changes and evaluation of ocular drugs. Such model, in complement to animal studies, can potentially accelerate translational research, in particular the pre-clinical screening of ophthalmic medication, driving clinical treatment advancement for corneal diseases. This review provides an overview of engineered CoC platforms with respect to their merits, applications, and technical challenges. Emerging directions in CoC technology are also proposed for further investigations, to accentuate preclinical obstacles in corneal research.

Incidence of Corneal Adverse Events in Children Wearing Soft Contact Lenses

OBJECTIVES

There is increasing interest in fitting children with soft contact lenses, in part due to the increase in prescribing of designs to slow the progression of myopia. This literature review summarizes large prospective and retrospective studies that include data on the incidence of microbial keratitis and corneal infiltrative events (CIEs) in children wearing soft contact lenses.

METHODS

Peer-reviewed prospective and retrospective studies that report contact lens-related complications in children with at least one year of wear and at least 100 patient years of wear were identified.

RESULTS

Seven prospective studies published between 2004 and 2022 were identified representing 3,752 patient years of wear in 1,756 children, nearly all of whom were fitted at age 12 years or younger. Collectively, they report one case of microbial keratitis and 53 CIEs, of which 16 were classified as symptomatic. The overall incidence of microbial keratitis was 2.7 per 10,000 patient years (95% CI: 0.5-15), and the incidence of symptomatic CIEs was 42 per 10,000 patient years (95% CI: 26-69). Two retrospective studies were identified representing 2,545 patient years of wear in 1,025 children, fitted at age 12 years or younger. One study reports two cases of microbial keratitis giving an incidence of 9.4 per 10,000 patient years (95% CI: 0.5-15).

CONCLUSIONS

Accurate classification of CIEs is challenging, particularly in retrospective studies. The incidence of microbial keratitis in children wearing soft lenses is no higher than in adults, and the incidence of CIEs seems to be markedly lower.

Epidemiology of Contact Lens-Related Emergency Department Visits: Data From Nationwide Emergency Department Sample

PURPOSE

The purpose of this retrospective longitudinal cohort study was to determine the epidemiology of contact lens-related visits to the emergency department at a national level and identify high-risk groups.

METHODS

National emergency department (ED) sample, a representative sample of all US EDs, was used to determine the incidence and characteristics of keratitis in contact lens users presenting to the ED from 2006 to 2017. ICD-9-CM and ICD-10-CM codes for corneal disorder due to contact lens use (371.82 and H1882) were used to identify the patients.

RESULTS

A total of 149,716 ED visits were recorded with a diagnosis of corneal disorder due to contact lens use. Incidence of ED visits with contact lens-related corneal disorder declined steadily from 2010 to 2016. In total, 67% of the patients were female, 68.9% were adults aged 19 to 44 years, and 56.3% had a private insurance provider. The most common diagnosis at the time of discharge was "eye discharge" or "redness" (10.9%), followed by "corneal ulcer" (3.6%). Patients of highest income quartiles were more likely to present to the ED with contact lens-related corneal disorders (adjusted odds ratio, 1.21, 95% confidence interval 1.15-1.27) compared with low-income quartile. Among those who were discharged from the ED, the average charge per patient was $1051.4 (SD = 795.4).

CONCLUSIONS

Women, young adults, and patients belonging to higher socioeconomic status were found to have higher prevalence of contact lens-related corneal ED visits. Identification of high-risk groups will help in the prevention of further corneal complications and the associated vision loss.

Urgent unmet needs in the care of bacterial keratitis: An evidence-based synthesis

Bacterial corneal infections, or bacterial keratitis (BK), are ophthalmic emergencies that frequently lead to irreversible visual impairment. Though increasingly recognized as a major cause of global blindness, modern paradigms of evidence-based care in BK have remained at a diagnostic and therapeutic impasse for over half a century. Current standards of management - based on the collection of corneal cultures and the application of broad-spectrum topical antibiotics - are beset by important yet widely underrecognized limitations, including approximately 30% of all patients who will develop moderate to severe vision loss in the affected eye. Though recent advances have involved a more clearly defined role for adjunctive topical corticosteroids, and novel therapies such as corneal crosslinking, overall progress to improve patient and population-based outcomes remains incommensurate to the chronic morbidity caused by this disease. Recognizing that the care of BK is guided by the clinical axiom, "time equals vision", this chapter offers an evidence-based synthesis for the clinical management of these infections, underscoring critical unmet needs in disease prevention, diagnosis, and treatment.

The epidemiology of infectious keratitis

Infectious keratitis is a rare but potentially severe sight-threatening disease, associated with considerable societal burden, cost and morbidity. This review summarises the most recent evidence for the incidence, risk factors and impact of disease, all of which vary widely according to region, access to health care, socioeconomic and environmental factors, predisposing conditions and causative organisms. The frequency and societal impact of infectious keratitis are significantly higher in low-income countries. In non-viral infectious keratitis, bacterial causes predominate in most regions. Fungi, particularly linked with agricultural trauma, are more frequently associated with infectious keratitis in low-income regions, particularly in India and certain African countries. The disease impact is compounded by poverty and limited access to services and treatment. Early diagnosis, access to appropriate treatment, prophylaxis in ocular trauma, availability of eye protection, awareness of risk factors may be associated with reduced disease severity and vision loss. Evidence for the incidence and burden of disease is lacking in certain regions and well-designed epidemiological studies to identify independent risk factors for the disease and those associated with more severe outcomes may better identify causation and guide resource allocation and preventative strategies.

The global epidemiology and clinical diagnosis of Acanthamoeba keratitis

Acanthamoeba keratitis is a rare parasitic infection of the cornea that can lead to permanent blindness if not diagnosed and treated promptly. We collected data on the incidences of Acanthamoeba keratitis from 20 countries and calculated an annual incidence of 23,561 cases, with the lowest rates in Tunisia and Belgium, and the highest in India. We analyzed 3755 Acanthamoeba sequences from the GenBank database across Asia, Europe, North America, South America, and Oceania and genotyped them into T1, T2, T3, T4, T5, T10, T11, T12, and T15. Many genotypes possess different characteristics, yet T4 is the most prevalent genotype. As efficient treatment against Acanthamoeba remains lacking, prevention from early diagnosis via staining, PCR, or in vivo confocal microscopy (IVCM) becomes significant for the condition's prognosis. IVCM is the most recommended approach for the early detection of Acanthamoeba. If IVCM is unavailable, PCR should be used as an alternative.

Post photorefractive keratectomy (PRK) infectious keratitis; six-year experience of a tertiary eye hospital

BACKGROUND/OBJECTIVES

As an essential development in the new century, surface ablation procedures have attracted increasing attention. There exists a concern regarding the risk of infectious keratitis. Hence, we aimed to investigate the rate and predisposing factors of infectious keratitis after photorefractive keratectomy (PRK).

SUBJECTS/METHODS

This retrospective study was designed in two phases. First, the rate of post-PRK keratitis of Farabi Eye Hospital was investigated. In other words, the targeted population was the patients who developed keratitis after performing procedure at Farabi Eye Hospital. In the second phase, all the patients with the diagnosis of post-PRK keratitis were studied regardless of the centre where surgery was performed. Patients with the diagnosis of infectious keratitis between 2014 and 2020 were enrolled and following information was analyzed: demographics, presentation time after surgery, perioperative medications, culture results, risk factors, medical treatment, complications, and final visual acuity.

RESULTS

The total number of PRK procedures in our centre was 24,986 (13,253 patients), in which 6 eyes of 5 patients developed keratitis. Beside these 5 patients, 24 referred patients (24 eyes) from the other centres were enrolled. Finally, a total number of 29 patients (30 eyes) were included. Our analysis revealed that manipulation of contact lens, dry eye, and blepharitis were the essential predisposing factors for keratitis development.

CONCLUSION

The overall post-PRK keratitis occurrence rate of our study was 0.02%. Our observation highlighted the importance of preoperative examination and treatment of the lids and dry eye disease.

Defining Daily Disposable Contact Lens Wear in a Clinical Study

SIGNIFICANCE

The U.S. Food and Drug Administration regulates contact lenses as prescription medical devices and defines daily disposable lenses for single use; however, safety comparisons between daily disposable and reusable lenses rely on the lens-wearing regimen. When inappropriately discerned, studies may erroneously report replacement regimen, resulting in inaccurate risk rates.

PURPOSE

This study aimed to explore different measures for defining daily disposable wearers in the context of a clinical study.

METHODS

A secondary analysis of data from five multisite fieldings (n = 1059) from the Contact Lens Risk Survey was performed. Descriptive statistics were used to examine self-reported lens replacement, use of lens case, and manufacturer's recommended replacement frequency as defined by the participants' selection of their habitual lenses using a photographic aide. Daily disposable wearers were identified as reporting daily replacement (by self-report and lens identification) and not using a lens case. If there was a discrepancy among these three factors, the lens assignment was assessed as a majority response (two of three) or as missing if conflicting information was reported.

RESULTS

The cohort was approximately two-thirds (68.7%) female and ranged from 12 to 33 years of age. A total of 154 participants (14.5%) were classified as daily disposable wearers and 896 (84.6%) as reusable wearers. Congruence was observed among all three daily disposable assignment factors for only 106 wearers (68.8%). The greatest discrepancy among daily disposable wearers was the report of using a lens case (n = 32 [20.8%]). In contrast, reusable lens wearers were more likely to report agreement across all three factors (n = 798 [89.1%], P < .001).

CONCLUSIONS

This analysis suggests that the report of not using a lens case is a more conservative surrogate for true single-use lens wear, as one in five may be storing and reusing their daily disposable lenses.

Contact Lens-Associated Keratitis-an Often Underestimated Risk

BACKGROUND

Millions of people in Germany wear contact lenses every day. Deficient contact lens hygiene can lead to corneal infection. Contact lens-associated keratitis usually has a highly acute presentation and can cause long-term visual loss.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed, as well as on relevant metaanalyses, Cochrane reviews, and reports by national and international health care authorities.

RESULTS

23-94% of contact lens wearers report associated discomfort and eye problems. The annual incidence of contact lens-associated keratitis is 2-4/10 000. It is due to bacteria in 90% of cases, and much less commonly to acanthamoebae and fungi. The pathogens generally arrive with the contact lens on the surface of the eye and can penetrate into the corneal tissue because the tear film under the lens is not swept away from the ocular surface by the eyelids, and corneal epithelial changes are often present as well. Corneal infiltration that is diagnosed early is often self-limited, but advanced bacterial infection usually requires intense topical antibiotic treatment. Some severe infections can only be eradicated by emergency corneal transplantation; this is the case in 20-30 % of fungal and acanthamoebic infections.

CONCLUSION

The wearing of contact lenses, particularly soft ones, is associated with a risk of microbial keratitis if proper contact lens hygiene is not exercised. Contact lens-associated keratitis very rarely causes permanent damage to eyesight (0.6 cases per 10 000 contact lens wearers per year). The use of contact lenses always calls for meticulous care.

Microbial Keratitis Associated With Penetrating Keratoplasty and Scleral Lens Wear: A Case Series

OBJECTIVES

To report on microbial keratitis (MK) in three scleral lens (SL) wearers who had undergone penetrating keratoplasty (PKP).

METHODS

This retrospective case series describes 3 cases of MK in patients who wore SLs after PKP.

RESULTS

All three patients wore SLs for visual rehabilitation for corneal irregularity induced by PKP; all three also had concurrent ocular surface disease (keratoconjunctivitis sicca and corneal exposure). Cultures identified the causative organism in two patients, and septated hyphae suggestive of fungal infection were identified in tissue removed during therapeutic PKP in the third patient. All three patients were receiving either topical or systemic immunosuppressive therapy before the infection developed.

CONCLUSIONS

Scleral lenses are often used to manage complex ocular disease, which can make it difficult to determine the precise cause of complications that arise after wearing the lenses. Multiple factors, including SL wear, may have contributed to the initial development of MK in the three patients in this case series. Patients who wear SLs after PKP should be monitored closely.

Severe Ocular Complications Associated With Wearing of Contact Lens in Japan

OBJECTIVES

To examine the severe ocular complications associated with contact lens wearing in Japan.

METHOD

A questionnaire was sent to 964 ophthalmologist training facilities inquiring for cases of contact lens-associated complications from April 2016 to March 2018. The inclusion criteria were as follows: (1) corrected distance visual acuity ≤0.1 decimal after treatment for 3 months, (2) corneal perforation observed during follow-up, and (3) requiring surgery. A secondary analysis was conducted, inquiring for further information on the type of contact lens, clinical manifestations, and course of treatment.

RESULTS

Forty-two patients with infectious keratitis met the inclusion criteria. Eight patients were users of rigid gas-permeable contact lens, and 34 were users of soft contact lens. Microbiological tests were positive in 73.0%. The organisms isolated in microbiological culture were bacteria in 11 patients (Pseudomonas aeruginosa in 9 patients), fungi in 2 patients, and Acanthamoeba in 14 patients. Ten patients were treated with local antibiotics, 11 with a combination of systemic antibiotics, and 21 with a combination of surgical approaches, including 13 with corneal transplantation.

CONCLUSIONS

The major cause of serious contact lens-associated ocular complications was microbial keratitis, and P. aeruginosa and Acanthamoeba were the major pathogens in Japan.

The role of Type III secretion system in the pathogenesis of Pseudomonas aeruginosa microbial keratitis

Pseudomonas aeruginosa is the most commonly isolated Gram-negative pathogen causing sight-threatening microbial keratitis (MK). Contact lens wear is the most significant risk factor associated with pseudomonal MK. Understanding the pathogenesis of MK due to P. aeruginosa and its interactions with contact lenses is crucial in preventing these often rapidly progressive and highly antibiotic-resistant infections. Bacterial virulence factor Type III secretion system (T3SS) has significant interplays between contact lens material, antibiotic sensitivity, disinfectant selectivity, and bacterial cell invasion. Depending on the T3SS exotoxins produced, P. aeruginosa strains are divided into cytotoxic or invasive strains. Cytotoxic strains are relatively resistant to commercial disinfectants, while invasive strains are more antibiotic resistant. Therefore, contact lens wearers are more predisposed to cytotoxic P. aeruginosa infections, and patients with trauma or previous surgery are more prone to infection by invasive strains. Previous studies with mutant P. aeruginosa strains unable to produce T3SS exotoxins were more susceptible to disinfectants and less able to adhere to soft contact lenses, indicating an essential role of T3SS in bacterial virulence. Invasion of P. aeruginosa intracellularly was found to be associated with control of scaffold protein IQ-domain GTPase-activating protein 1 (IQGAP1) and human corneal epithelial cell tight junctions. Knockdown of IQGAP1 strengthened tight junctions that prevented intracellular survival of invasive P. aeruginosa strains and enhanced corneal epithelial cell survival. These novel findings of the vital role of T3SS in the pathogenesis of pseudomonal MKs will provide new guidelines in both prevention and treatment of this common eye-blinding infection.

Bacterial keratitis: identifying the areas of clinical uncertainty

Bacterial keratitis is a common corneal infection that is treated with topical antimicrobials. By the time of presentation there may already be severe visual loss from corneal ulceration and opacity, which may persist despite treatment. There are significant differences in the associated risk factors and the bacterial isolates between high income and low- or middle-income countries, so that general management guidelines may not be appropriate. Although the diagnosis of bacterial keratitis may seem intuitive there are multiple uncertainties about the criteria that are used, which impacts the interpretation of investigations and recruitment to clinical studies. Importantly, the concept that bacterial keratitis can only be confirmed by culture ignores the approximately 50% of cases clinically consistent with bacterial keratitis in which investigations are negative. The aetiology of these culture-negative cases is unknown. Currently, the estimation of bacterial susceptibility to antimicrobials is based on data from systemic administration and achievable serum or tissue concentrations, rather than relevant corneal concentrations and biological activity in the cornea. The provision to the clinician of minimum inhibitory concentrations of the antimicrobials for the isolated bacteria would be an important step forward. An increase in the prevalence of antimicrobial resistance is a concern, but the effect this has on disease outcomes is yet unclear. Virulence factors are not routinely assessed although they may affect the pathogenicity of bacteria within species and affect outcomes. New technologies have been developed to detect and kill bacteria, and their application to bacterial keratitis is discussed. In this review we present the multiple areas of clinical uncertainty that hamper research and the clinical management of bacterial keratitis, and we address some of the assumptions and dogma that have become established in the literature.

IL-36α Enhances Host Defense against Pseudomonas aeruginosa Keratitis in C57BL/6 Mouse Corneas

The IL-36 cytokines are known to play various roles in mediating the immune response to infection in a tissue- and pathogen-dependent manner. The present study seeks to investigate the role of IL-36R signaling in C57BL/6 mouse corneas in response to Pseudomonas aeruginosa infection. IL-36α-/-, IL-36γ-/-, and IL-36R-/- mice had significantly more severe keratitis than wild-type mice. At six hours postinfection, IL-36α pretreatment augmented P. aeruginosa-induced expression of IL-1Ra, IL-36γ, LCN2, and S100A8/A9. At one day postinfection, exogenous IL-36α suppressed, whereas IL-36α deficiency promoted, the expression of IL-1β. At three days postinfection, exogenous IL-36α suppressed Th1 but promoted Th2 immune response. IL-36α stimulated the infiltration of IL-22-expressing immune cells, and IL-22 neutralization resulted in more severe keratitis. IL-36α alone stimulated dendritic cell infiltration in B6 mouse corneas. Taken together, our study suggests that IL-36R signaling plays a protective role in the pathogenesis of P. aeruginosa keratitis by promoting the innate immune defense, Th2, and/or Th22/IL-22 immune responses. Exogenous IL-36α might be a potential therapy for improving the outcome of P. aeruginosa keratitis.

Contact Lens Associated Bacterial Keratitis: Common Organisms, Antibiotic Therapy, and Global Resistance Trends: A Systematic Review

Introduction

Contact lens wearing has been increased globally during recent decades, which is one of the main risk factors for developing microbial keratitis. Microbial keratitis is a severe and dangerous condition that causes cornea inflammation. It can lead to corneal scarring and perforation or even endophthalmitis and visual loss if it remains untreated. Among bacterial, fungal, protozoal, and viral agents which can cause microbial keratitis, bacteria are the most common cause. Therefore, in this study, we aim to find common causative bacteria, sensitivity, and resistance to antibiotics and the outcome of antibiotic therapy in contact lens-related bacterial keratitis.

Methods

A systematic search was carried out in PubMed/Medline, EMBASE, and Web of Science for published studies and medRxiv for preprints up to February 30, 2021, and May 14, 2021, respectively. A combination of the following keywords was used: "Infection", "Corneal infection", "Keratitis", "Microbial keratitis", and "Contact lens", Also, we used the "Contact lenses" MeSH term. Lists of references for each selected article and relevant review articles were hand-searched to identify further studies.

Results

Twenty-six articles were included. From 1991 to 2018, 2,916 episodes of contact lens-related microbial keratitis) CLMK(with 1,642 episodes of proven bacterial keratitis have been reviewed in these studies. Studies were conducted in 17 countries with different geographical regions, and four studies were conducted in Iran, which is the highest number of studies among these countries. According to 20 studies, the mean age of patients was 30.77 years. Females with 61.87% were more than males in 19 studies. A percentage of 92.3% of patients used soft contact lenses, and 7.7% of patients used hard contact lenses (including RGP), according to 16 studies. Pseudomonas aeruginosa, Staphylococcus spp., and Serratia marcescens were the three most common bacteria isolated from samples of patients with contact lens-related bacterial keratitis. Overall, isolated bacteria were most sensitive to fluoroquinolones and aminoglycosides, especially ciprofloxacin and gentamicin respectively, and most resistant against penicillin and cephalosporins especially cefazolin and chloramphenicol. Almost all patients responded well to antibiotic therapy, with some exceptions that needed further surgical interventions.

Conclusion

Antibiotics are efficient for treating almost all patients with contact lens-related bacterial keratitis if they are appropriately chosen based on common germs in every geographical region and the sensitivity and resistance of these germs against them. In this regard, Pseudomonas aeruginosa is the most common causative germ of contact lens-associated bacterial keratitis all over the world and is almost fully sensitive to ciprofloxacin. Because of some different results about the sensitivity and resistance of germs against some antibiotics like gentamicin, vancomycin, and chloramphenicol in the Middle East region, especially Iran, more in vitro and clinical studies are suggested.

Antimicrobial Efficacy of Contact Lens Solutions Assessed by ISO Standards

Microbial keratitis (MK) is an eye infection caused by opportunistic bacteria or fungi, which may lead to sight-threatening corneal ulcers. These microorganisms can be introduced to the eye via improper contact lens usage or hygiene, or ineffective multipurpose solutions (MPSs) to disinfect daily wear contact lenses. Thus, the patient’s choice and use of these MPSs is a known risk factor for the development of MK. It is then critical to determine the efficacy of popular MPSs against ubiquitous ocular microorganisms. Therefore, we compare the efficacy of nine major MPSs on the global market against four different microorganism species, and with four different common contact lenses. In accordance with International Standards Organization protocol 14729 and 18259, the microorganisms were inoculated into each MPS with and without contact lenses, and held for the manufacturer’s disinfection time, 24 h, and 7 days after challenge with Serratia marcescens or Fusarium spp. Plates were incubated for 2–7 days and plate counts were conducted to determine the number of surviving microorganisms. The majority of MPSs demonstrated significantly higher disinfection efficacies without contact lenses. Broadly, among the microorganisms tested, the OPTI-FREE products (Puremoist, Express, and Replenish) maintained the highest disinfection efficacies at the manufacturer’s stated disinfection time when paired with any contact lens, compared with other MPSs. These were followed closely by RevitaLens and renu Advanced. MPSs containing dual biocides polyquaternium-1 and myristamidopropyl dimethylamine possessed the highest disinfection efficacy against multiple ocular pathogens.

Retention, Bacterial Adhesion, and Biofilm Formation between Anionic and Zwitterionic Bandage Contact Lenses in Healthy Dogs: A Pilot Study

This study aimed to compare the in vitro and in vivo retention, bacterial adhesion, and biofilm formation between anionic and zwitterionic bandage contact lenses (BCLs) in healthy canines. BCL retention and tolerance were evaluated in 10 healthy canines via a single-masked, crossover study for 7 days. To compare in vitro bacterial adhesion and biofilm formation, four Staphylococcus strains were incubated with the BCLs at 37 °C for 2 or 24 h, and the bacterial colony forming units (CFUs) adhering to the BCLs were counted. Next, to compare in vivo bacterial adhesion, the CFUs of bacteria adhering to the BCLs worn by canines for 24 h were counted. Anionic lenses significantly retained and reduced in vitro bacterial adhesion than in the zwitterionic lenses. However, the amount of in vitro biofilm formation was more likely to be higher on anionic lenses than on zwitterionic lenses. In vivo bacterial adhesion was not significantly different between the two types of BCLs. Nevertheless, both BCLs were well-tolerated by the canines; thus, their short-term use in dogs can be recommended as safe.

Cosmetic Contact Lens-Related Corneal Infections in Asia

PURPOSE

To explore demographics, disease characteristics, and wear habits in cosmetic contact lens (CL)-related corneal infections in Asia.

DESIGN

Prospective multicenter cross-sectional study.

METHODS

Cases of CL-related corneal infection presenting over a 12-month period were prospectively identified from 11 centers in 8 countries in Asia. Case demographics, clinical features, microbiology, and compliance characteristics were compared between wearers using CLs for cosmetic purposes and those using CLs for the correction of refractive errors.

RESULTS

Six hundred and ninety-four CL wearers with corneal infection presented: 204 cosmetic CL (29.4%) and 490 (70.6%) refractive CL wearers. Cosmetic CL infections comprised 7%-54% of cases across the region. Compared with noncosmetic CL wearers, cosmetic CLs wearers were significantly more likely to be female (90% vs 59%), young (aged <25, 68% vs 44%), and to have a shorter period of wear experience. Lenses worn by cosmetic CL wearers were more likely to be hydrogel materials and manufactured with the pigment located on the back surface of the CL. Presenting disease characteristics and visual outcomes were similar in both groups. Causative organisms were similar between the 2 groups; however, there was a higher rate of Acanthamoeba disease (9%) in cosmetic wearers, compared with refractive wearers (1%; P < .005).

CONCLUSIONS

Cosmetic CL infections represent a significant proportion of CL-related infections in Asia. Cosmetic CL users with corneal infections are generally young, female, and wearing hydrogel CLs. Internet supply, quality control, and regulation of the sale of these products provide significant challenges in managing this population of vulnerable wearers.

Comparative Analysis of the Clinical Aspects and Treatment Outcomes of Stenotrophomonas maltophilia Keratitis and Pseudomonas aeruginosa Keratitis

OBJECTIVES

We analyzed the clinical aspects and treatment outcomes of Stenotrophomonas maltophilia (SM) keratitis and Pseudomonas aeruginosa (PA) keratitis.

METHODS

Medical records of 55 inpatients with culture-proven SM (n=21) and PA (n=34) keratitis were retrospectively reviewed. Predisposing factors, clinical characteristics, and treatment outcomes were compared between the SM and PA groups.

RESULTS

The mean symptom duration was longer in the SM group than in the PA group (10.4:4.3 days; P=0.012). The most common predisposing factor was corneal trauma (47.6%) in the SM group and contact-lens wear (38.2%) in the PA group. There were no differences in the mean epithelial defect size (12.7:11.9 mm2; P=0.861), hypopyon (33.3%:44.1%; P=0.428), surgical treatment (4.8%:14.7%; P=0.390), or poor clinical outcomes (26.8%:30.3%; P=0.760) between the SM and PA groups. In multivariate logistic regression, risk factors for poor clinical outcomes were hypopyon (odds ratio [OR], 52.00; P=0.010) in the SM group and symptom duration≥7 days (OR, 44.32; P=0.015), age≥60 years (OR, 21.13; P=0.019), and hypopyon (OR, 15.20; P=0.038) in the PA group.

CONCLUSION

Compared with PA keratitis, SM keratitis had slower progression, and its clinical characteristics and treatment results were not worse. In both groups, hypopyon was the risk factor for a poor clinical outcome.

Foundational concepts in the biology of bacterial keratitis

Bacterial infections of the cornea, or bacterial keratitis (BK), are notorious for causing rapidly fulminant disease and permanent vision loss, even among treated patients. In the last sixty years, dramatic upward trajectories in the frequency of BK have been observed internationally, driven in large part by the commercialization of hydrogel contact lenses in the late 1960s. Despite this worsening burden of disease, current evidence-based therapies for BK - including broad-spectrum topical antibiotics and, if indicated, topical corticosteroids - fail to salvage vision in a substantial proportion of affected patients. Amid growing concerns of rapidly diminishing antibiotic utility, there has been renewed interest in urgently needed novel treatments that may improve clinical outcomes on an individual and public health level. Bridging the translational gap in the care of BK requires the identification of new therapeutic targets and rational treatment design, but neither of these aims can be achieved without understanding the complex biological processes that determine how bacterial corneal infections arise, progress, and resolve. In this chapter, we synthesize the current wealth of human and animal experimental data that now inform our understanding of basic BK pathophysiology, in context with modern concepts in ocular immunology and microbiology. By identifying the key molecular determinants of clinical disease, we explore how novel treatments can be developed and translated into routine patient care.

Effect of Antimicrobial Contact Lenses on Corneal Infiltrative Events: A Randomized Clinical Trial

Purpose

To determine whether Mel4-coated antimicrobial contact lenses (MACLs) can reduce the incidence of corneal infiltrative events (CIEs) during extended wear.

Methods

A prospective, randomized, double-masked, single-center, contralateral, extended contact lens wear clinical trial was conducted with 176 subjects. Each participant was randomly assigned to wear a MACL in one eye and an uncoated control contact lens in the contralateral eye or an extended-wear biweekly disposable modality for 3 months. The main outcome measures were the incidence of CIEs per 100 eye-months, identification of the microbial types colonizing the contact lenses or eyes at the time of the CIEs, and their susceptibility to Mel4.

Results

Nine participants (5.1%) experienced unilateral CIEs; six participants had contact lens acute red eye, and three participants had infiltrative keratitis. The incidence rate for CIEs (0.4 events per 100 participant months; 1.7%) in the Mel4-coated lenses (test) was 69% less than that of the control lenses (1.3 events per 100 participant months; 3.4%; P = 0.29). All Gram-negative bacteria isolated from lenses and lids of participants with CIEs (Citrobacter diversus, Acinetobacter haemolyticus, and Acinetobacter lwoffii) were susceptible to Mel4 peptide; minimum inhibitory concentrations ranged from 15.6 to 62.5 µg/mL. Reduction of adhesion of these bacteria by Mel4-coated lenses ranged from 2.1 to 2.2 log10 colony-forming units/lens.

Conclusions

MACLs had the capacity to reduce CIEs by at least 50% compared with uncoated control lenses during extended wear over 3 months; however, due to the relatively low rates of CIEs, the reduction was not statistically different compared with control lenses.

Translational Relevance

This study provides evidence that antimicrobial contact lenses have the potential to reduce the incidence of corneal infiltrative events during extended wear.

Eye Infections Caused by Filamentous Fungi: Spectrum and Antifungal Susceptibility of the Prevailing Agents in Germany

Fungal eye infections can lead to loss of vision and blindness. The disease is most prevalent in the tropics, although case numbers in moderate climates are increasing as well. This study aimed to determine the dominating filamentous fungi causing eye infections in Germany and their antifungal susceptibility profiles in order to improve treatment, including cases with unidentified pathogenic fungi. As such, we studied all filamentous fungi isolated from the eye or associated materials that were sent to the NRZMyk between 2014 and 2020. All strains were molecularly identified and antifungal susceptibility testing according to the EUCAST protocol was performed for common species. In total, 242 strains of 66 species were received. Fusarium was the dominating genus, followed by Aspergillus, Purpureocillium, Alternaria, and Scedosporium. The most prevalent species in eye samples were Fusarium petroliphilum, F. keratoplasticum, and F. solani of the Fusarium solani species complex. The spectrum of species comprises less susceptible taxa for amphotericin B, natamycin, and azoles, including voriconazole. Natamycin is effective for most species but not for Aspergillus flavus or Purpureocillium spp. Some strains of F. solani show MICs higher than 16 mg/L. Our data underline the importance of species identification for correct treatment.

[Corneal wound healing-Pathophysiology and principles]

The cornea forms the anterior border of the eye and significantly contributes to a sharp optical image quality on the retina through its transparency, avascular nature and curvature. Because of its anatomical structure and as a barrier to the environment, the cornea is particularly exposed to various external factors, such as injuries and pathogens. A correct wound healing without the formation of light diverging scarring is therefore essential to preserve the integrity and function of the cornea. Misguided wound healing is of outstanding clinical relevance and can lead to corneal fibrogenesis. Corneal fibrosis results in scarring with a loss of optical transparency, which significantly reduces eyesight and can lead to blindness. Understanding the pathophysiological mechanisms of wound healing and fibrogenesis is of great importance for the diagnostics, treatment and evaluation of the subsequent healing process in order to prevent permanent damage as far as possible.

The role of nitric oxide in ocular surface physiology and pathophysiology

Nitric oxide (NO) has a wide array of biological functions including the regulation of vascular tone, neurotransmission, immunomodulation, stimulation of proinflammatory cytokine expression and antimicrobial action. These functions may depend on the type of isoform that is responsible for the synthesis of NO. NO is found in various ocular tissues playing a pivotal role in physiological mechanisms, namely regulating vascular tone in the uvea, retinal blood circulation, aqueous humor dynamics, neurotransmission and phototransduction in retinal layers. Unregulated production of NO in ocular tissues may result in production of toxic superoxide free radicals that participate in ocular diseases such as endotoxin-induced uveitis, ischemic proliferative retinopathy and neurotoxicity of optic nerve head in glaucoma. However, the role of NO on the ocular surface in mediating physiology and pathophysiological processes is not fully understood. Moreover, methods used to measure levels of NO in the biological samples of the ocular surface are not well established due to its rapid oxidation. The purpose of this review is to highlight the role of NO in the physiology and pathophysiology of ocular surface and propose suitable techniques to measure NO levels in ocular surface tissues and tears. This will improve the understanding of NO's role in ocular surface biology and the development of new NO-based therapies to treat various ocular surface diseases. Further, this review summarizes the biochemistry underpinning NO's antimicrobial action.

The Risks and Benefits of Myopia Control

PURPOSE

The prevalence of myopia is increasing around the world, stimulating interest in methods to slow its progression. The primary justification for slowing myopia progression is to reduce the risk of vision loss through sight-threatening ocular pathologic features in later life. The article analyzes whether the potential benefits of slowing myopia progression by 1 diopter (D) justify the potential risks associated with treatments.

METHODS

First, the known risks associated with various methods of myopia control are summarized, with emphasis on contact lens wear. Based on available data, the risk of visual impairment and predicted years of visual impairment are estimated for a range of incidence levels. Next, the increased risk of potentially sight-threatening conditions associated with different levels of myopia are reviewed. Finally, a model of the risk of visual impairment as a function of myopia level is developed, and the years of visual impairment associated with various levels of myopia and the years of visual impairment that could be prevented with achievable levels of myopia control are estimated.

RESULTS

Assuming an incidence of microbial keratitis between 1 and 25 per 10 000 patient-years and that 15% of cases result in vision loss leads to the conclusion that between 38 and 945 patients need to be exposed to 5 years of wear to produce 5 years of vision loss. Each additional 1 D of myopia is associated with a 58%, 20%, 21%, and 30% increase in the risk of myopic maculopathy, open-angle glaucoma, posterior subcapsular cataract, and retinal detachment, respectively. The predicted mean years of visual impairment ranges from 4.42 in a person with myopia of -3 D to 9.56 in a person with myopia of -8 D, and a 1-D reduction would lower these by 0.74 and 1.21 years, respectively.

CONCLUSIONS

The potential benefits of myopia control outweigh the risks: the number needed to treat to prevent 5 years of visual impairment is between 4.1 and 6.8, whereas fewer than 1 in 38 will experience a loss of vision as a result of myopia control.

Frequency of Contact Lens Complications Between Contact Lens Wearers Using Multipurpose Solutions Versus Hydrogen Peroxide in the United States and Canada

OBJECTIVES

To retrospectively compare frequency of contact lens (CL) complications in soft CL users of hydrogen peroxide (H2O2) and multipurpose solutions (MPS).

METHODS

This was a multicenter, retrospective chart review of CL records from each patient's three most recent eye examinations at academic and private practices. Patients must have used the same solution type for at least 3 years. Univariate analyses were conducted using t tests, and chi-square or Fisher's exact test for categorical measures.

RESULTS

There were 1,137 patients included, with 670 (59%) using MPS and 467 (41%) H2O2. In total, 706 (62%) experienced at least one complication; 409 used MPS and 297 used H2O2. There was no difference in the proportion of patients experiencing at least one complication between MPS (61%) and H2O2 (64%) (P=0.38). Multipurpose solutions users were more likely to report discomfort compared with H2O2 users (P=0.04). Presumed microbial keratitis was experienced by 16 MPS and nine H2O2 users (P=0.60).

CONCLUSIONS

No significant differences were found in the frequency of CL complications between MPS and H2O2. H2O2 users were less likely to report discomfort and thus switching to a H2O2 system may be an alternative in CL users with discomfort.

Quarter of a century of contact lens prescribing trends in the United Kingdom (1996 - 2020)

PURPOSE

To document contact lens prescribing trends in the United Kingdom over the past quarter of a century.

METHODS

An annual survey of contact lens prescribing was conducted each year from 1996 to 2020, inclusive, by asking a random selection of optometrists and contact lens opticians to provide information relating to 10 consecutive contact lens fits between January and March.

RESULTS

Over the 25 year survey period, 2,671 practitioners returned survey forms, reporting a total of 25,575 contact lens fits. The mean (± standard deviation) age of lens wearers was 35 ± 15 years, of which 64 % were female. Over the survey period, rigid lens new fits decreased from 22 % to 2%. The prescribing of silicone hydrogel lenses has increased steadily since their introduction towards the end of the 1990s, and now represent 80 % of soft lens fits. Soft toric lens prescribing has gradually increased to 47 % - a value at which astigmatism ≥ 0.75DC is theoretically corrected in all contact lens wearers. Daily disposable prescribing increased steadily over the survey period and now represents 63 % of lenses prescribed. Extended wear fits remain at very low levels, except for some prescribing for overnight orthokeratology. Multi-purpose lens care solutions are ubiquitous; peroxide and other systems are now seldom prescribed. Rigid lenses and monthly replacement soft lenses are predominantly worn on a full time basis, whereas daily disposable soft lenses are mainly worn part time.

CONCLUSIONS

This report documents the evolution of contact lens fitting in the United Kingdom over the past 25 years. The most likely lens fit is a spherical design silicone hydrogel daily disposable contact lens prescribed for a 35 year old female and worn on a part-time basis.

Current understanding and therapeutic management of contact lens associated sterile corneal infiltrates and microbial keratitis

Contact lenses are widely prescribed in clinical practice with multiple applications and advantages. However, contact lenses can be associated with various complications which range from innocuous to severe. Clinicians thus not only need to possess the ability to prescribe the most appropriate contact lenses for each individual patient but also be able to recognise and manage any associated complications. This review examines the existing literature on the management of corneal infiltrative events associated with soft contact lenses, including microbial keratitis, particularly in the context of practising in Australia. The definitions and diagnosis of corneal infiltrative events, as well as the current understanding of their aetiologies, will be explored. The various aspects of a successful management will be discussed, including the applications of therapeutic agents such as antimicrobial and anti-inflammatory agents, the role of microbiological investigations, and strategies to improve long-term prognosis. The currently available evidence supporting management options will be presented, highlighting the relative abundance of high-level evidence on management protocols, antimicrobial selection and treatment duration for microbial keratitis; and the relative paucity of studies and trials for sterile corneal infiltrative events, despite this condition being much more commonly encountered in clinical practice.

The impact of patient behaviour and care system compliance on reusable soft contact lens complications

Reusable soft daily wear contact lenses (CLs) remain popular and were fit to just over half of all wearers in the most recent international CL prescribing survey. Unlike daily disposable CLs, reusables require cleaning and disinfecting after every use, along with storage in a CL case. These additional requirements add a number of steps to the daily wear and care routine, increasing the opportunities for CL wearers to exhibit non-compliant behaviour. The impact of non-compliance ranges from poor lens comfort through to potentially sight-threatening infective keratitis. The coronavirus pandemic has refocused the profession on the importance of hand hygiene in particular, and the need for promoting safe CL wear in general. This review summarises typical non-compliant behaviour related to reusable CLs, and examines strategies and opportunities to better support wearers. Patient education has a central role in encouraging compliant behaviour, although patient recall of information is low, and personal belief systems may result in continuation of non-compliant behaviour despite awareness of the risks. CL care solutions are required for the daily disinfection of lenses, however misuse of multipurpose solutions (MPS) and hydrogen peroxide (H₂O₂)-based care systems can challenge their ability to be fully efficacious. Standard efficacy testing is reviewed, with consideration of how well current protocols model real-world use of CL solutions. Although some recommendations are in place for the inclusion of additional variables such as lens cases, CL materials, organic soil and efficacy against Acanthamoeba, opportunity still exists to reevaluate global standards to ensure consistency of testing in all markets. Finally, potential future innovations are discussed which may further support increased safety in reusable lens wear through novel antimicrobial additions to both CL materials and cases.

Microbiological Evaluation of Opened Saline Bottles for Scleral Lens Use and Hygiene Habits of Scleral Lens Patients

SIGNIFICANCE

Scleral lenses have become a widely used treatment option for patients with irregular corneas and ocular surface disease. Successful wear entails use of a nonpreserved saline solution to fill the lens before application on the eye.

PURPOSE

The purposes of this study were to evaluate solution from opened bottles of multidose preservative-free saline for microbiological growth and to better understand study participant hygiene habits while handling these bottles for scleral lens wear.

METHODS

Eligible study participants in this single-center prospective study were patients who routinely used multidose preservative-free saline solution for scleral lens rinsing and filling. Study participants completed a 12-question survey regarding their scleral lens hygiene habits and donated their opened multidose preservative-free saline bottle (PuriLens Plus; The Lifestyle Company, Inc., Freehold, NJ), which was processed for bacterial and fungal cultures.

RESULTS

Thirty-five participants (19 males, 16 females) with ages ranging from 6 to 81 years (mean, 47.9 years) were included. Indications for scleral lens wear included those with irregular corneas and ocular surface disease. The overall rate of microbial contamination among saline samples was 62.9% (n = 22). Twenty-one different microorganisms were identified. The survey responses did not differ significantly (P > .05) for any of the questions with regard to likelihood of positive culture. There were no significant age or sex differences between participants with positive or negative culture results. No significant differences were found between isolation of specific microorganisms and any of the survey responses.

CONCLUSIONS

This study suggests that off-label multidose preservative-free saline commonly used to rinse and fill scleral lenses before application on the eye may become contaminated with microorganisms once the bottle has been opened. Eye care practitioners and scleral lens patients should be aware of these potential contaminations and prioritize lens, hand, and environmental hygiene to minimize the risk of ocular complications.

American Academy of Optometry Microbial Keratitis Think Tank

SIGNIFICANCE

Think Tank 2019 affirmed that the rate of infection associated with contact lenses has not changed in several decades. Also, there is a trend toward more serious infections associated with Acanthamoeba and fungi. The growing use of contact lenses in children demands our attention with surveillance and case-control studies.

PURPOSE

The American Academy of Optometry (AAO) gathered researchers and key opinion leaders from around the world to discuss contact lens-associated microbial keratitis at the 2019 AAO Annual Meeting.

METHODS

Experts presented within four sessions. Session 1 covered the epidemiology of microbial keratitis, pathogenesis of Pseudomonas aeruginosa, and the role of lens care systems and storage cases in corneal disease. Session 2 covered nonbacterial forms of keratitis in contact lens wearers. Session 3 covered future needs, challenges, and research questions in relation to microbial keratitis in youth and myopia control, microbiome, antimicrobial surfaces, and genetic susceptibility. Session 4 covered compliance and communication imperatives.

RESULTS

The absolute rate of microbial keratitis has remained very consistent for three decades despite new technologies, and extended wear significantly increases the risk. Improved oxygen delivery afforded by silicone hydrogel lenses has not impacted the rates, and although the introduction of daily disposable lenses has minimized the risk of severe disease, there is no consistent evidence that they have altered the overall rate of microbial keratitis. Overnight orthokeratology lenses may increase the risk of microbial keratitis, especially secondary to Acanthamoeba, in children. Compliance remains a concern and a significant risk factor for disease. New insights into host microbiome and genetic susceptibility may uncover new theories. More studies such as case-control designs suited for rare diseases and registries are needed.

CONCLUSIONS

The first annual AAO Think Tank acknowledged that the risk of microbial keratitis has not decreased over decades, despite innovation. Important questions and research directions remain.