BCLA CLEAR – Contact lens technologies of the future

doi:10.1016/j.clae.2021.02.007

Contact Lens and Anterior Eye

Volume 44, Issue 2, April 2021, Pages 398-430

https://doi.org/10.1016/j.clae.2021.02.007 Get rights and content

Abstract

Contact lenses in the future will likely have functions other than correction of refractive error. Lenses designed to control the development of myopia are already commercially available. Contact lenses as drug delivery devices and powered through advancements in nanotechnology will open up further opportunities for unique uses of contact lenses.

This review examines the use, or potential use, of contact lenses aside from their role to correct refractive error. Contact lenses can be used to detect systemic and ocular surface diseases, treat and manage various ocular conditions and as devices that can correct presbyopia, control the development of myopia or be used for augmented vision. There is also discussion of new developments in contact lens packaging and storage cases.

The use of contact lenses as devices to detect systemic disease has mostly focussed on detecting changes to glucose levels in tears for monitoring diabetic control. Glucose can be detected using changes in colour, fluorescence or generation of electric signals by embedded sensors such as boronic acid, concanavalin A or glucose oxidase. Contact lenses that have gained regulatory approval can measure changes in intraocular pressure to monitor glaucoma by measuring small changes in corneal shape. Challenges include integrating sensors into contact lenses and detecting the signals generated. Various techniques are used to optimise uptake and release of the drugs to the ocular surface to treat diseases such as dry eye, glaucoma, infection and allergy. Contact lenses that either mechanically or electronically change their shape are being investigated for the management of presbyopia. Contact lenses that slow the development of myopia are based upon incorporating concentric rings of plus power, peripheral optical zone(s) with add power or non-monotonic variations in power. Various forms of these lenses have shown a reduction in myopia in clinical trials and are available in various markets.

Introduction

Contact lenses were invented to correct refractive error and they have become a successful, convenient and widely used commodity for this purpose. However, looking forward into the not-so-distant future, the potential applications for these devices are proliferating to uses where vision correction per se is often not the main intention. Industries as far ranging as bio-sensors, pharmaceuticals, defence and the entertainment sector could all potentially apply contact lens-based technologies to achieve solutions to problems for their specific unmet needs. This review will explore some of these innovations and consider how these efforts will change the way contact lenses are used in the future.

Section snippets

Diagnosis and screening for systemic disease

Historically, the quantification of analytes in the tear film has primarily focused on the diagnosing and monitoring of ocular conditions. However, it is increasingly apparent that the tear film contains a wide range of biomarkers that may help diagnose systemic disease for a range of conditions [1]. A contact lens-based diagnostic device would allow a biosensor to be placed in close proximity to the ocular tissue and be bathed in the tear fluid, which is known to reflect pathophysiological

Intraocular pressure monitoring for glaucoma

Glaucoma is a leading cause of blindness globally and thus developments in improving intraocular pressure (IOP) monitoring are of great interest to clinicians. However, methods of measuring IOP in clinical practice are suboptimal and do not reflect its dynamic nature, including its circadian variation and short-term fluctuations [77]. Current gold standard tonometry techniques provide an estimate of the IOP only over a matter of seconds, are generally only available during typical clinic hours

Treatment and management of ocular conditions

The use of contact lenses in the treatment and management of ocular diseases is a relatively routine part of clinical practice. From providing pain relief in cases of corneal abrasion, corneal protection for trichiasis, to promotion of wound healing in neurotrophic keratitis, contact lenses are employed by clinicians for a broad variety of anterior segment conditions. However, the application of contact lenses for disease indications beyond what is currently undertaken in clinical practice has

Drug delivery to the ocular surface

Drug releasing soft contact lenses have been widely studied and continue to show promise, primarily by overcoming the current limitations associated with delivering ophthalmic medications via an eye drop.

The primary disadvantage with eye drops is their low bioavailability of less than 5% [188], which is attributed to high tear turnover rates, blinking, nasolacrimal drainage, non-productive absorption by the conjunctiva, and low permeability of the cornea [189,190]. Thus, improving

Antimicrobial contact lenses

Microbial adhesion to contact lenses is a risk factor for developing microbial keratitis, contact lens acute red eye and contact lens peripheral ulcers [370]. These adverse events occur more frequently with lenses worn on an overnight wear schedule compared to those worn on a daily wear basis. It is estimated that as many as 1 in 500 wearers per year will develop microbial keratitis while using overnight wear contact lenses [[371], [372], [373]]. Reduction in bacterial adhesion to contact

Theranostics

Theranostics is a multi-disciplinary field of medicine that combines therapeutics and diagnostics. This rapidly growing area has produced new avenues of research, facilitating discoveries in disease mechanisms as well as drug and medical device development. Theranostics applies knowledge and techniques from nanotechnology, molecular and nuclear medicine, as well as pharmacogenetics, to achieve such tasks as in vitro diagnostics and prognostics, in vivo molecular imaging and therapy and targeted

Customised optics for aberrated or diseased eyes

Aberrations within the eye are categorised as low order and higher order, with low order aberrations being those corrected with conventional optical corrections. Corneal pathology, such as keratoconus, creates significant amounts of higher order aberrations and spectacle lenses are unable to correct the aberrations created by the ectatic cornea. A standard soft contact lens simply drapes over the distorted shape and is unable to correct the high order aberrations, although customised soft

Contact Lens packaging

Microbial keratitis is the most serious complication of contact lens wear, yet its incidence and associated risks have not changed over decades [372,489,490]. Many elements of poor compliance have been linked to microbial keratitis, including hand hygiene [[490], [491], [492]], and storage case hygiene and replacement [372,491,[493], [494], [495]]. For these reasons, the contact lens storage case and primary blister-pack packaging, often overlooked, are important elements of contact lens

Storage cases

Contact lens storage cases have been implicated in microbial keratitis involving bacteria, fungi and Acanthamoeba [372,493,494,[502], [503], [504], [505]]. A population attributable risk model of microbial keratitis predicts that disease load in daily wear reusable lenses could be reduced by almost two thirds by merely attending to storage case hygiene and storage case replacement [494]. Thus, efforts to minimise the negative impact of the contact lens case should remain a priority.

Conclusion

This review demonstrates the incredible diversity of new technologies under development that will shape the future for contact lenses. The rapid growth in novel biomaterials and, in particular, the development of powered contact lenses through advancements in nanotechnology will enable the commercialisation of lenses that can both detect and treat ocular and, in some cases, systemic disease. Novel optical designs will help manage common ocular conditions such as myopia and presbyopia, in

Acknowledgements

The CLEAR initiative was facilitated by the BCLA, with financial support by way of Educational Grants for collaboration, publication and dissemination provided by Alcon and CooperVision. The authors would like to acknowledge the assistance of Carol Lakkis in supplying background materials for some sections of this paper.

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BCLA CLEAR – Contact lens technologies of the future

Abstract

Introduction

Section snippets

Diagnosis and screening for systemic disease

Intraocular pressure monitoring for glaucoma

Treatment and management of ocular conditions

Drug delivery to the ocular surface

Antimicrobial contact lenses

Theranostics

Customised optics for aberrated or diseased eyes

Contact Lens packaging

Storage cases

Conclusion

Acknowledgements

Res Vet Sci

Adv Clin Chem

Neurosci Lett

Anal Biochem

Diabetes Res Clin Pract

Anal Chim Acta

Biosens Bioelectron

Sensor Actuat B-Chem

Biosens Bioelectron

Sensor Actuator

Anal Chim Acta

Curr Opin Biotechnol

J Proteomics

Can J Ophthalmol

Med Eng Phys

Microsyst Nanoeng

Sens Actuators A Phys

Tear fluid biomarkers in ocular and systemic disease: potential use for predictive, preventive and personalised medicine

EPMA J.

Changes in the chemical barrier composition of tears in Alzheimer’s disease reveal potential tear diagnostic biomarkers

PLoS One

Lacryglobin in human tears, a potential marker for cancer

Graefes Arch Clin Exp Ophthalmol

IL-8 and IFN-gamma in tear fluid of patients with cystic fibrosis

J Interferon Cytokine Res

Elevated tear fluid levels of MIP-1alpha in patients with cystic fibrosis

J Interferon Cytokine Res

CCL4/MIP-1beta levels in tear fluid and serum of patients with cystic fibrosis

J Interferon Cytokine Res

Study of the correlation between tear glucose concentrations and blood glucose concentrations

Diabetes

Advanced glycation end product (age) modified proteins in tears of diabetic patients

Mol Vis

Changes to tear cytokines of type 2 diabetic patients with or without retinopathy

Mol Vis

Oligoclonal IgG in tears

Neurology

Silver stained isoelectrophoresis of tears and cerebrospinal fluid in multiple sclerosis

J Neurol

Exploring the human tear fluid: discovery of new biomarkers in multiple sclerosis

Proteomics Clin Appl

Levels of oligomeric alpha-synuclein in reflex tears distinguish Parkinson’s disease patients from healthy controls

Biomark Med

Changes of lacrimal gland and tear inflammatory cytokines in thyroid-associated ophthalmopathy

Invest Ophthalmol Vis Sci

Interleukin-7 expression in tears and orbital tissues of patients with graves’ ophthalmopathy

Endocrine

Contact-lens biosensors

Sensors (Basel)

Functionalized eyewear device for detecting biomarker in tears

Google Patents. US10830776B2

Blink detection system for electronic ophthalmic lens

Google Patents. US9498124B2

Interface using eye tracking contact lenses

Us9244285b2

Scleral lens sensor for ocular electrolyte analysis

Adv Mater

Finger pricking and pain: a never ending story

J Diabetes Sci Technol

A 3-μw cmos glucose sensor for wireless contact-lens tear glucose monitoring

Ieee J Solid-St Circ

Wireless powered contact lens with biosensor

Google Patents. US8608310B2

Wearable contact lens biosensors for continuous glucose monitoring using smartphones

ACS Nano