To access all features and enjoy the full functionality of this site, please ensure your browser is up-to-date. For IE8 users, the most recent version is IE11.

Safety & Hygiene

Contact Lens Practice in the Time of COVID-19

Published on Dec 1, 2020
20 Minutes Read

For Eye Care Professionals, the year 2020 was supposed to be “our year” and “the year of the eye exam”… and even though colleagues in the rest of the world have made the decision to go metric, 20/20 still evokes that feeling of getting to a good place. We were looking forward to a renewed focus on eye care and visual wellbeing fueled by new research and products in areas like myopia and dry eye management.  COVID-19 changed all that, bringing unprecedented change to all areas of our lives – not just our practices. But as 2020 moves on, more and more practitioners will be returning to patient care while the pandemic remains a viable threat to health and economics around the world. The good news is that while there is still much we don’t know about this novel coronavirus (SARS-CoV-2), we do know that measures can and must be taken to do our best to prevent the inadvertent transmission of the virus in our practices.

Background on Disease

The disease COVID-19 is caused by a novel strain of coronavirus, SARS-CoV-2, and currently has neither a vaccine nor a universally safe and effective treatment. The World Health Organization (WHO) declared it a global pandemic on 11 March 2020 and it has since spread to virtually every country around the world.1 The virus is highly contagious and can be spread through coughing, sneezing or even talking, (droplet transmission) particularly in confined environments and/or prolonged exposure,2 or via contact with a surface containing the virus (fomite transmission). The morphology of the virus helps explain both the different disease profiles seen to date, and the recommendations surrounding protection recommendations.

The corona virus designation comes from the morphology with includes a “crown” of glycoprotein spikes on the surface (Figure 1). The virus uses these spike proteins (S-proteins) to enter host cells and bind with high affinity to the angiotensin-converting enzyme 2 (ACE2) and TMPRSS-2 (transmembrane protease serine 2) receptors, prevalent in the lungs and small intestine.3 One good piece of news is that the virus also has an outer protective envelope made up of phospholipids which help with both entry and exit from host cells, but this structure also explains why washing with soap and water is such an effective approach. As depicted in Figure 2, detergent monomers in soap have a polar or hydrophilic head and non-polar or lipophilic tail and are able to interact with these lipid bilayers to break them up, ultimately rupturing the virus cell wall. In addition, when the hydrophobic tail interacts with the viral cell membrane, the hydrophilic head can orient outward and interact with the water, forming a micelle with the virus trapped in the middle. It can then be washed away with water during rinsing.4 Thus the importance of the recommended 20 second hand wash that includes a potent combination of plenty of soap, friction, time and flowing water. In the alcohol rub, the flowing water component is missing to flush viral particles away, but used in sufficient quantities it is more effective when hands are free of soil, offering an alternative method of hand hygiene.5

The disease has variable virulence but more severe disease is seen in the elderly6 and those with underlying conditions such as obesity,7,8 diabetes, and hypertension—conditions which inherently or due to therapy may increase expression of ACE2.9–11 Children were originally thought to be much less affected but still possible vectors for transmission, but new data is now emerging that in rare cases, children can experience a hyperinflammatory condition similar to Toxic Shock Syndrome or Kawasaki disease following COVID-1 infection or exposure.6,12,13


 Figure 1: Coronavirus structure cross section

Figure 1: Coronavirus structure cross section
The virus uses the spike proteins (S-proteins, shown as blue projections on the surface) to enter the cell and binds with ACE2 receptors. The lipid membrane (dark blue outer ring) is composed of a lipid bilayer of phospholipid. Amphiphilic (water- and lipid-loving) molecules such as soap are able to substitute into the bilayer and disrupt the cell wall

Figure 2: How soap kills the SARS-CoV-2 virus

Figure 2: How soap kills the SARS-CoV-2 virus

  • Soap works on the virus in 3 ways: by disrupting the cell wall, by forming micelles to surround the virus, and by helping wash the virus away with water.
  • Soap molecules are amphiphilic – having both water and lipid-loving ends. They can insert themselves into the lipid bilayer of the envelope surrounding the virus, disrupting the cell wall.
  • The inserted soap molecules reorient to form micelles around the virus, much like soap surrounds grease, allowing the viral particles to be carried away by water during rinsing. Virus Micelles


Ocular Involvement

Current research suggests that the eye is neither a preferred organ of human COVID-19 infection nor a preferred gateway of entry for humans for infecting the respiratory tract.14 Although conjunctivitis has been observed in COVID-19 cases,15 it is rare, and most evidence regarding SARS-COV-2 transmission through ocular tissue is anecdotal.16 Willcox conducted a comprehensive review of 287 citations in the Scopus database relating to SARS-CoV-2 and the ocular surface and provided several key points of information for practicing professionals in eye care.17

  • While there is preliminary evidence for ACE2 expression on corneal and conjunctival cells,18 most of the rest of the receptors to which coronaviruses bind appear to be found under the epithelia of the ocular surface or are otherwise not available.
  • The evidence suggests coronaviruses are unlikely to bind to ocular surface cells to initiate infection, nor is there evidence that the virus could travel to or from the ocular surface via the nasopharynx or through conjunctival capillaries.
  • Conjunctivitis and isolation of the virus from the ocular surface occur only rarely, and overwhelmingly in patients with confirmed COVID-19 infection elsewhere in the body. On examining all the studies attempting to isolate live virus or viral DNA from ocular samples, only 9/178 (5%) were positive for viral RNA at any stage of the disease and no sample yielded growth of the virus in culture when attempted.
  • However, due to person-to-person nature of the transmission of the virus and the close proximity required for eye care, practitioners, their staff and patients are advised to take strict precautions to protect themselves during necessary eye care.

In response to concerns around contact lens wear specifically, researchers from around the globe as well as the US Centers for Disease Control have issued statements confirming that contact lens wear is no more risky during the pandemic than wearing spectacles provided patients practice appropriate hand hygiene, follow wear and care guidelines, avoid touching any part of their face and cease contact lens wear while unwell.19,20

Return to Practice Considerations

In most parts of the world, routine patient care in ophthalmic was cancelled or significantly reduced during the height of the initial outbreaks of the epidemic. As the benefits of some of the protective measures have played out and new cases of the disease slow, practitioners are now returning to practice. But in the age of COVID-19, experts agree it won’t go away quickly or easily, it is essential for practitioners to consider new or augmented practices for hygiene, social distancing, sanitization and communication of such efforts to patients. The following is a compilation of advice, recommendations and practices of governmental, professional and individuals for managing patients, staff, examinations and processes in the ophthalmic practice, with a focus on contact lens care, until such time as the COVID-19 threat is deemed to be a far less significant threat to public health and safety. As these guidelines are constantly changing, it is essential that eye care professionals seek the guidance of their local governmental, medical and professional organizations to remain abreast of the latest developments.

In addition to the widely adopted essential preventive measures for COVID-19 that are recommended for everyone by most health authorities around the world (Figure 3), the World Health Organization (WHO) outlined three categories of controls that have relevance in all publics setting, but particularly in the close environments involved in patient care.

  • Administrative controls include ensuring resources for infection prevention and control (IPC) measures.
  • Environmental and engineering controls aim at reducing the spread of pathogens and the contamination of surfaces and inanimate objects.
  • Personal Protective Equipment (PPE) covers the use of physical barriers to lower the chances of exposure to the virus from person to person via droplets or airborne transmission.

By walking through these three checklists, practitioners should be confident in caring for their contact lens patients in a safe and efficient manner. With adjustments to your fitting and training areas and procedures, even new contact lens patients may be accommodated. Remember that particularly for those wearing masks or other PPE, contact lenses may offer a higher level of convenience with minimal additional risk. 

Administrative Controls in the Practice

To get a feel for what changes you will require in your own practice, experts suggest doing a “walk-through” of one patient’s journey through your office, starting from the most exterior entrance of your facility, taking note of every area of potential touch and/or interaction. As much as possible, engage your staff in evaluating options and make sure they are well trained on the changes. And don’t forget to communicate changes early and often to your patients as well.

The first decision to be made is how many and what types of patients can be accommodated while instituting other safety measures. You’ll probably find that you’ll need more time than before and will need to do some prioritization of scheduling In a recent survey of 71 diplomates and section members of the Cornea & Contact Lens Section of the American Academy of Optometry, 90% said they would schedule a contact lens patient reporting issues in the early stages of returning to practice, but fewer (56-58%) said they would prioritize exams for 

a COVID-19 patient or who care for COVID-19 patients, and both time and distance play into the equation of the critical levels of viral load contact lens patients with no current issues.21 Most also said they’d extend contact lens expirations for 3 to 6 months during the time offices were closed or not working to capacity.

Table 1 contains a checklist for key steps in developing administrative controls.

Table 1: Administrative Controls Checklist (based on direction from external resources listed)

Patient Scheduling, Flow and Triage
Determine how many patients and staff the space can accommodate while following social distancing recommendations
Create prioritization and scheduling system for managing available capacity
Develop triage schema to accommodate restricted patient flow (Figure 3)22
Create policies around who can enter practice
Key risk review (prior to arriving at office if possible)
  • Symptoms
    • Cough, shortness of breath or difficulty breathing, fever, chills, muscle pain, sore throat, recent loss of taste or smell23
  • Exposure assessment (past 14 days)
    • Diagnosis of COVID-19
    • Travel (out of home or local area)
    • Occupation with increased potential exposure (front line worker) – Contact with suspected infected person or cluster
Procedures for screening for potential infection on arrival (temperature, oximetry)
Establish patient mask/face covering policy
Eliminate or limit accompanying persons unless critical
Develop or modify recall system to accommodate schedule changes
Revisit/revise policies regarding refills/prescription extensions
  • Contact lenses, supplies, medications
  • Associated follow-up appointment policies
For new contact lens fits, devise plan for socially distant training
  • Online videos, remote 1:1 or group trainings, video check ins
  • Strongly consider daily disposable options when available
  • Encourage annual supply orders and direct to patient delivery options
    • Update exchange policy if needed
Evaluate compliant telemedicine options for routine aftercare visits
Map patient movement and touchpoints for each visit type
  • Limit “backtracking” and “traffic jams”
  • Add directional arrows, mark queueing positions if needed
  • Install hand hygiene stations at entry to practice and key patient areas
  • Implement restroom access and sanitization protocols
Staff Training, Screening & Scheduling
Involve staff in problem solving
Screening processes for staff wellness
  • Key symptom review & Diagnosis, Travel, Occupation, Contact risk assessment as for patients
Reassess dress code
  • Scrubs or hygiene protocols
    • Scrubs should not be worn for daily activities before/after work
Clarify mask requirements (cloth, hand-made, surgical, reuse and sanitization)
Formal staff training
  • Clear accountabilities and documentation
Procedural checklists for all new/modified procedures
Contingency plans for staff absences
Infection Control Protocol Updates
Institute protocol for dealing with episode of potential exposure in practice
  • Testing options available & access
  • Accurate record keeping for contact tracing
  • Office protocol for self-quarantine/isolation
  • Return to work process
Determine discontinued procedures or products (e.g., non-contact tonometry)
Update new/changed procedures (single use solutions, devices, disposal methods)
Follow ISO in-office disinfection protocols for multi-patient use contact lenses24
  • GPs: Soak in 3% hydrogen peroxide for 3 hour minimum, rinse with multipurpose solution, pat dry, store dry
  • Hybrid and Soft: Soak in 3% hydrogen peroxide for 3 hour minimum, neutralize as directed, rinse & store using multipurpose solution in disinfected case
Disinfection protocols for all areas of practice
  • Daily opening procedures
  • Pre- and post-patient encounter cleaning and disinfection procedures
  • Signage to clearly identify disinfected areas
  • End of day closing procedures
Patient Communication
Ensure that COVID-19-related changes are widely and frequently communicated (in-office signage, website, social media platforms)

Environmental Controls

The people most at risk of infection are those who are in close contact with required to cause an infection.2 The most critical area of environmental control is social distancing, with proper disinfection of surfaces also being a key consideration. Social distancing guidelines range from spaces from 1 to 2 meters (3 to 6 feet) and are intended to minimize the mixing of susceptible and infectious people, and may remain in place in some form for an extended period of time due to three factors: the extended incubation period of COVID-19 infection (2 to 14+ days), unanswered questions about immunity, and unknown seasonality.25

 Figure 3: Sample Triage Plan

Figure 3: Sample Triage Plan

Table 2: Environmental Control Checklist (based on direction from external resources listed)

Social Distancing
Provide 1-2 meters (3 to 6 feet) of distance between individuals throughout office
Avoid face to face seating in all seating areas
Social distancing should be practiced in addition to any personal protective equipment (PPE) utilized
Place plexiglass/perspex barriers at reception, contact lens training areas and other areas where distance cannot be assured
Ventilation & Filtration
Clean/service all air filtration systems; turn off air conditioning if feasible
Ensure well-ventilated rooms (open doors/windows when feasible)
Strictly adhere to frequent and effective hand washing procedures and ask patients and staff to do the same
Position hand sanitizer stations (contactless ideally) where sink access isn’t available
Minimize contact with surfaces (open doors, contactless processes when possible)
Remove all periodicals, brochures and non-disposable items
Use disposable supplies whenever possible
Perform complete room sanitization every time a patient leaves the room or area
  • Thoroughly spray, soak or wipe with approved disinfectant per IPC protocol
    • Cough, shortness of breath or difficulty breathing, fever, chills, muscle pain, sore throat, recent loss of taste or smell23
    • Chair & stand components
    • Counters, tables, instruments, instrument shields, desk shields
    • Phones, computers, tablets, mice, screens
    • Patient worn/handled frames or other equipment
Discard used bottles, lenses, wipes, cases in closed container
Use approved disinfectant recommended for coronavirus
  • 1:20 bleach solution,26 biguanides, alcohol, etc.
    • The US EPA maintains a list of disinfectants for surfaces that have been shown to be effective against SARS-CoV-2.27 Check with your country or region equivalent for a similar list
Approved, medical grade UVC disinfection with caution and adequate UV protection
  • UVC dangerous; single pass processes (<20 seconds) ineffective28

Personal Protective Equipment (PPE)

Perhaps the most contentious area of preventive and protective measure recommendations is the wearing of face coverings or masks. While it is certain that the virus can spread through droplets, which can be effectively blocked by a variety of materials, there is debate about aerosol spreading, which mandate a higher level of filtration afforded only by high quality PPE.29  And though there is little hard science in the area, scientists across multiple disciplines, as well as global health authorities maintain that the widespread usage of masks is essential to keep this highly contagious virus in check. Santarpia provided a cogent analysis of data from a university hospital that airborne transmission may be possible.30 Cheng proposed that community-wide mask wearing may contribute to the  control of COVID-19 by reducing emission of infected saliva and respiratory droplets from clinical and subclinical cases31 and De Kai provided a very compelling mathematical model demonstrating the benefit of large-scale mask wearing early in the growth phase of the pandemic.32 A large group of scientists all maintain that community mask wearing, even of home-made masks is an effective form of source control in conjunction with other hygiene, distancing and contact tracing strategies,33 while also maximizing availability of N95/FFP2 masks for medical professionals. Konda evaluated aerosol filtration efficiency of common fabrics used in cloth masks and concluded that filtration efficient could be improved to levels close to an N95 by using mixed fabrics (tightly woven cotton paired with silk, flannel or chiffon) that combine mechanical and electrostatic-based filtration (Figure 5).34  And finally, Eikenberry modeled the potential for mask wearing by the general public to curtail the COVID-19 pandemic, and used scenarios from New York and Washington states in the United States to illustrate the effects in different scenarios.35 Their models showed that immediate near term universal (80%) adoption of moderately effective (50%) masks could prevent 17-45% of projected deaths over two months in New York.

In Washington state, where the baseline transmission is much less intense, 80% adoption could reduce mortality by 24-65%. The model shows that even very weak masks (20% effective) can still be useful if the underlying transmission rate is relatively low or decreasing. In short, asking everyone in your practice to wear a mask is a widely supported recommendation.

However, fit and compliance with other protective measures are critical to the overall ability to provide significant protection against the transmission of aerosol particles. Konda showed that gaps in fit resulted in leakage that could result in over a 60% decrease in the filtration efficiency, and Howard discussed concerns raised regarding the improper use of masks, or a false sense of security from wearing a mask. Proper fit and instructions on how to don and remove a mask is essential to recognize the benefit of protection (Figure 4). While donning or removing a mask and while wearing it, it is important to handle it only by the straps or ties and not touch the front or back surfaces. The mask or covering must fit close to the face and cover the nose and mouth with minimal gaps around the edges. Reusable masks should be washed at least daily and after any event that would potentially contaminate the mask. Note also that masks are intended to be an adjunct to good hand hygiene and social distancing measures.

An additional relevant concern for ophthalmic offices is protective shields for equipment and procedures that require being within one meter (3 feet) of a patient. All such equipment should be fitted with some form of transparent shield that still allows visibility and maneuverability, but that can block breath and droplets. Many instrument manufactures and professionals have fashioned make-shift solutions out of flexible plastic materials. Slit lamp shields that wrap back around the examiner’s face offer good maneuverability but can create optical distortions. Solutions have ranged from plastic document folders to custom designed lucite/Perspex screens with cutouts to accommodate the oculars of a slit lamp (Figure 5).

Mask Wearing Essentials Figure 4. Mask wearing essentials.
Mask must cover nose, mouth and chin with no gaps at top, bottom or sides. Home-made masks that combine mechanical filtration (finely woven cotton) and electrostatic filtration (silk, chiffon, flannel) can achieve better filtration than two layers of cotton.34

Table 3: Personal Protective Equipment Checklist (based on direction from external resources listed)

Advise/require patients and staff should wear face coverings in the office
  • Children under 2 and those with breathing difficulties should not wear masks
  • Determine whether office will supply masks & what varieties are
Provide N95/FFP2 masks to be worn around potentially infective patients when performing procedures which could result in aerosolization
Provide surgical masks for when working in close proximity to possible or confirmed cases and when dealing with high risk group or those in contact with high risk individual
Determine policy on fabric/home-made masks for staff
Train office on proper handling, wear, cleaning and storage of masks
Eye and Face Protection
Fit all slit lamps, binocular indirect ophthalmoscopes and other instruments used within 1 meter with transparent shields large enough to block droplets from patients
Add procedures for disinfection and/or replacement after each use
Barriers/Booths for Teaching Area
When possible, utilize at home on-line or video-based instructions
Install plexiglass barriers around contact lens training area in office
Patient and trainer should wear masks during training if possible
Thorough handwashing by both staff and patient before and after training
Ask patient to clean face prior to training
Provide single-use or take-home solutions and cases
Patient and technician should not share items during training (lenses, solutions, sinks, etc)
Gloves, Gowns
Provide single use disposable gloves for disinfecting procedures and instruct on proper use
Strict hand hygiene for routine care when gloves not used
Single use disposable gloves and gowns/aprons are recommended for use with confirmed or possible infection

Figure 5 A

A. Custom made flat shield. Images courtesy of Fire and Pine.

Figure 5 B

B. Home-made curved shield adapted from head mounted full face shield. Image courtesy of David Czerny, OD, Rapid City, South Dakota, USA

Figure 5. Slit lamp/Instrument Shields.
Shields can be flat or curved but must be large enough to prevent passage of breaths, coughs, sneezes, but small enough to maneuver around. Shields can also be adapted to phoropters, pupillometers, indirect ophthalmoscopes, and other equipment that requires close proximity.

External Resources for Additional Information

Organization Website Materials
WHO – World Health Organization Consumer materials, workplace readiness, general information
CORE – Centre for Ocular Research & Education Consumer materials, information for professionals, journal articles & summaries
CDC – Centers for Disease Control Consumer materials, workplace readiness, general information
American Academy of Optometry Practice reactivation webinars, evidence-based guidelines for CL wear, resources for practitioners, research summaries, information for public, industry partner updates
American Optometric Association News, general information, detailed practice reactivation guide, patient materials, legislative advocacy
GPLI (Gas Permeable Lens Institute) Consolidated information from across multiple CL-related websites with links, videos, webinars
BCLA – British Contact Lens Association ECP & Consumer guidance on COVID-19; returning to practice guidance
EUROMCONTACT – The European Association of the Contact Lens and Lens Care Products Manufacturers Professional and consumer materials in multiple languages


For patients and practitioners, the good news is that for some this pandemic can help reinforce the benefits of contact lenses even for new patients. For glasses wearers, we also have a chance to start reinforcing the need for the same good hygiene habits that we teach with contact lenses.

With appropriate precautions, contact lens practice can continue and thrive. And above all, we have academic, professional and government groups supporting us in our desire to return to delivering high quality ocular and contact lens care to our patients which can be achieved by following the five key recommendations by experts and health care authorities summarized below.

Tips for safer contact lens practice

 Practice good hand hygiene icon

Practice good hand hygiene before and after every touch of the eye, face or surfaces

Wash with soap and water for at least 20 seconds and dry or use plenty of alcohol-based hand sanitizer and rub until evaporated (~ 30 seconds)

Virus in tears is rare and in small quantities when present; Soap and alcohol kill the virus and is likely to be effective against low viral loads

 COVID Mask Icon

Require masks for everyone in practice, including patients

Make sure the mask fits securely to the face & covers the nose, mouth & chin

The primary route of transmission is via respiratory emissions & masks reduce droplet transmission

Social Distance Icon

Keep your distance and install barriers in reception and training area

A minimum of 2 meters/6 feet is recommended or install a physical barrier

Infection requires a significant viral load; increased distance and barriers reduce transfer of virus

Disinfect Icon

Disinfect surfaces frequently or use single use items

Spray &/or wipe surfaces between every encounter & use single use bottles, cases, etc.

Though fomite (surface) transmission is a minor route, virus can still be transferred via contact with exposed surfaces

 Digital Temperature Icon

No contact lenses for sick or patients at high risk or with recent exposure

Take good pre-visit history and digital temperature prior to entry

High viral loads are found on infected individuals & even asymptomatic patients exposed to virus can transmit it

IMPORTANT NOTICE: This article is intended as an overview of currently accepted practices and thinking in the area. It is essential that the reader follow all local guidelines/requirements and consult their local health authorities with questions.

Acknowledgements: This publication was funded by Johnson & Johnson Vision and the author was compensated for her work

Author Info:
Dr. Cristina Schnider is the sole proprietor of C Schnider Insights & More. She spent over 20 years in the contact lens industry, and 15 years in contact lens education and research. She can be reached at [email protected]

1. Sohrabi C, Alsafi Z, O’Neill N, Khan M, Kerwan A, Al-Jabir A, Iosifidis C, Agha R. World Health Organization declares global emergency: A review of the 2019 novel coronavirus (COVID-19). International Journal of Surgery. 2020 [accessed 2020 May 15];76:71–76. doi:10.1016/j.ijsu.2020.02.034 

2.     Bromage E. The Risks - Know Them - Avoid Them. Erin Bromage PhD: 2020 May 6 [accessed 2020 May 14].

3.     Zheng J. SARS-CoV-2: an Emerging Coronavirus that Causes a Global Threat. International Journal of Biological Sciences. 2020 [accessed 2020 May 19];16(10):1678–1685. doi:10.7150/ijbs.45053

4.     Chaudhary NK, Chaudhary N, Dahal M, Guragain B, Rai S, Chaudhary R, Sachin KM, Lamichhane-Khadka R, Bhattarai A. Fighting the SARS CoV-2 (COVID-19) Pandemic with Soap. 2020 May 7 [accessed 2020 May 19].

5.     Healthcare Infection Control Practices Advisory Committee, HICPAC/SHEA/APIC/IDSA Hand Hygiene Task Force. Guideline for hand hygiene in health-care settings. MMWR. Morbidity and Mortality Weekly Report. 2002 [accessed 2020 May 20];51(2).

6.     CDC COVID-19 Response Team, CDC COVID-19 Response Team, Bialek S, Boundy E, Bowen V, Chow N, Cohn A, Dowling N, Ellington S, Gierke R, et al. Severe Outcomes Among Patients with Coronavirus Disease 2019 (COVID-19) — United States, February 12–March 16, 2020. MMWR. Morbidity and Mortality Weekly Report. 2020 [accessed 2020 May 15];69(12):343–346. doi:10.15585/mmwr.mm6912e2

7.     Lighter et al. - 2020 - Obesity in patients younger than 60 years is a ris.pdf. [accessed 2020 May 15].

8.     Sattar et al. - 2020 - Obesity a Risk Factor for Severe COVID-19 Infection.pdf. [accessed 2020 May 16].

9.     CDCMMWR. Preliminary Estimates of the Prevalence of Selected Underlying Health Conditions Among Patients with Coronavirus Disease 2019 — United States, February 12–March 28, 2020. MMWR. Morbidity and Mortality Weekly Report. 2020 [accessed 2020 May 19];69. doi:10.15585/mmwr.mm6913e2

10.   Muniyappa R, Gubbi S. COVID-19 pandemic, coronaviruses, and diabetes mellitus. American Journal of Physiology-Endocrinology and Metabolism. 2020 [accessed 2020 May 16];318(5):E736–E741. doi:10.1152/ajpendo.00124.2020

11.   Fang L, Karakiulakis G, Roth M. Are patients with hypertension and diabetes mellitus at increased risk for COVID-19 infection? The Lancet. Respiratory Medicine. 2020 [accessed 2020 May 15];8(4):e21. doi:10.1016/S2213-2600(20)30116-8

12.   Qiu H, Wu J, Hong L, Luo Y, Song Q, Chen D. Clinical and epidemiological features of 36 children with coronavirus disease 2019 (COVID-19) in Zhejiang, China: an observational cohort study. The Lancet Infectious Diseases. 2020 Mar [accessed 2020 May 14]:S1473309920301985. doi:10.1016/S1473-3099(20)30198-5

13.   Riphagen S, Gomez X, Gonzalez-Martinez C, Wilkinson N, Theocharis P. Hyperinflammatory shock in children during COVID-19 pandemic. The Lancet. 2020 May [accessed 2020 May 14]:S0140673620310941. doi:10.1016/S0140-6736(20)31094-1

14.   Sun C, Wang Y, Liu G, Liu Z. Role of the Eye in Transmitting Human Coronavirus: What We Know and What We Do Not Know. Frontiers in Public Health. 2020 [accessed 2020 May 15];8. doi:10.3389/fpubh.2020.00155

15.   Cheema M, Aghazadeh H, Nazarali S, Ting A, Hodges J, McFarlane A, Kanji JN, Zelyas N, Damji KF, Solarte C. Keratoconjunctivitis as the initial medical presentation of the novel coronavirus disease 2019 (COVID-19). Canadian Journal of Ophthalmology. 2020 Apr [accessed 2020 May 15]:S0008418220303057. doi:10.1016/j.jcjo.2020.03.003

16.   Seah I, Agrawal R. Can the Coronavirus Disease 2019 (COVID-19) Affect the Eyes? A Review of Coronaviruses and Ocular Implications in Humans and Animals. Ocular Immunology and Inflammation. 2020 [accessed 2020 May 15];28(3):391–395. doi:10.1080/09273948.2020.1738501

17.   Willcox MD, Walsh K, Nichols JJ, Morgan PB, Jones LW. The ocular surface, coronaviruses and COVID-19. Clinical and Experimental Optometry. [accessed 2020 May 26];n/a(n/a). doi:10.1111/cxo.13088

18.   Lange C, Wolf J, Auw‐Haedrich C, Schlecht A, Boneva S, Lapp T, Horres R, Agostini H, Martin G, Reinhard T, et al. Expression of the COVID-19 receptor ACE2 in the human conjunctiva. Journal of Medical Virology. [accessed 2020 May 19];n/a(n/a). doi:10.1002/jmv.25981

19.   Jones L, Walsh K, Willcox M, Morgan P, Nichols J. The COVID-19 pandemic: Important considerations for contact lens practitioners. Contact Lens and Anterior Eye. 2020 Apr [accessed 2020 May 14]:S1367048420300552. doi:10.1016/j.clae.2020.03.012

20.   CDC. Protect Your Eyes. Centers for Disease Control and Prevention. 2020 Apr 9 [accessed 2020 May 19].

21.   aao-015-survey-of-contact-lens-practitioners-summary-3.pdf. [accessed 2020 May 20].

22.   Lai THT, Tang EWH, Chau SKY, Fung KSC, Li KKW. Stepping up infection control measures in ophthalmology during the novel coronavirus outbreak: an experience from Hong Kong. Graefe’s Archive for Clinical and Experimental Ophthalmology. 2020 [accessed 2020 May 15];258(5):1049–1055. doi:10.1007/s00417-020-04641-8

23.   CDC. Coronavirus Disease 2019 (COVID-19) – Symptoms. Centers for Disease Control and Prevention. 2020 May 13 [accessed 2020 May 19].

24.   aao-008-disinfection-of-contact-lenses-chart.pdf. [accessed 2020 May 19].

25.   Hagen A. The science of social distancing. American Society for Microbiology. 2020 Apr 9 [accessed 2020 May 20].

26.   Anderson E, Li J. COVID-19 – Disinfecting with Bleach. Michigan State University Center for Research on Ingredient Safety. 2020 Mar 13 [accessed 2020 May 19].

27.   US EPA O. List N: Disinfectants for Use Against SARS-CoV-2. US EPA. 2020 Mar 13 [accessed 2020 May 20].

28.   International Ultraviolet Association. IUVA Fact Sheet on COVID-19. [accessed 2020 May 20].

29.   Leung NHL, Chu DKW, Shiu EYC, Chan K-H, McDevitt JJ, Hau BJP, Yen H-L, Li Y, Ip DKM, Peiris JSM, et al. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nature Medicine. 2020 [accessed 2020 May 20];26(5):676–680. doi:10.1038/s41591-020-0843-2

30.   Santarpia JL, Rivera DN, Herrera V, Morwitzer MJ, Creager H, Santarpia GW, Crown KK, Brett-Major D, Schnaubelt E, Broadhurst MJ, et al. Transmission Potential of SARS-CoV-2 in Viral Shedding Observed at the University of Nebraska Medical Center. Infectious Diseases (except HIV/AIDS); 2020. doi:10.1101/2020.03.23.20039446

31.   Cheng VC-C, Wong S-C, Chuang VW-M, So SY-C, Chen JH-K, Sridhar S, To KK-W, Chan JF-W, Hung IF-N, Ho P-L, et al. The role of community-wide wearing of face mask for control of coronavirus disease 2019 (COVID-19) epidemic due to SARS-CoV-2. Journal of Infection. 2020 Apr 23 [accessed 2020 May 16]. doi:10.1016/j.jinf.2020.04.024

32.   Kai D. Agent-Based Model for COVID-19 Masking. [accessed 2020 May 14].

33.   Howard J, Huang A, Li Z, Tufekci Z, Zdimal V, Westhuizen H-M van der, Delft A von, Price A, Fridman L, Tang L-H, et al. Face Masks Against COVID-19: An Evidence Review. 2020 Apr 12 [accessed 2020 May 19]. doi:10.20944/preprints202004.0203.v1

34.   Konda A, Prakash A, Moss GA, Schmoldt M, Grant GD, Guha S. Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks. ACS Nano. 2020 Apr 24 [accessed 2020 May 14]. doi:10.1021/acsnano.0c03252

35.   Eikenberry SE, Mancuso M, Iboi E, Phan T, Eikenberry K, Kuang Y, Kostelich E, Gumel AB. To mask or not to mask: Modeling the potential for face mask use by the general public to curtail the COVID-19 pandemic. Infectious Disease Modelling. 2020 [accessed 2020 May 20];5:293–308. doi:10.1016/j.idm.2020.04.001