An OD's Guide to Epidemic Keratoconjunctivitis (EKC)

Epidemic keratoconjunctivitis (EKC) is a highly contagious form of viral conjunctivitis that arises from inflammation of the conjunctiva.¹ Individuals who have contracted EKC are usually asymptomatic during the incubation period and may unintentionally infect multiple others, causing the infection to significantly spread.¹

Adenoviruses are a group of viruses that are responsible for conjunctival inflammation, and EKC is frequently linked to adenovirus serotypes 8, 4, 19, and 37.²

Eyecare providers need to provide a precise diagnosis of EKC in order to carry out the appropriate safety measures, disinfection techniques, and reduce the overall transmission of infection.

Signs and symptoms of EKC

There are both ocular and systemic signs related to EKC.

Ocular signs and symptoms of EKC include:³

Ocular itchiness and irritation
Photophobia
Foreign body sensation
Clear or yellow ocular discharge
Follicular reaction
Conjunctival hyperemia and erythema of the bulbar and palpebral conjunctiva
Chemosis
Epithelial keratitis
Subepithelial infiltrates (SEIs)
Blurred vision
Palpebral conjunctiva membranes or pseudomembranes
Symblepharon

Systemic signs include:³

Swollen preauricular lymph nodes
Headache
Fatigue
Fever

Diagnosing epidemic keratoconjunctivitis

Since the early signs and symptoms of EKC are sometimes nonspecific and make it difficult to determine the precise origin of the ocular inflammation, an EKC diagnosis is dependent on a detailed case history and ocular examination.⁴ Before clinical symptoms and signs appear in one eye, there is typically a week-long incubation period.

Days later, the second eye is frequently afflicted, though less severely.^4,5 EKC can spread to others from the end of the incubation period to as long as 2 weeks following the start of the viral conjunctivitis.⁵

Figure 1: Slit lamp image of pseudomembranes on the conjunctiva due to the inflammatory response following viral shedding in EKC.

^{Figure 1: Courtesy of Cory Lappin, OD, MS, FAAO.}

After the initial onset of EKC, viral shedding occurs and is a process by which the virus is progressively removed from its host.^5,6 During this period, the conjunctiva's inflammatory response may worsen to the point where pseudomembranes, like those seen in Figure 1, and symblepharon can develop.^5,6

The presence of unilateral or bilateral epithelial keratitis and SEIs, which are usually concentrated in the central cornea, such as in Figure 2, distinguishes EKC from other conjunctival inflammatory diseases.^4,5,6

SEIs can result in decreased visual acuity and are usually observed 7 to 10 days after the first signs of infection appear.^4,5,6 SEIs can potentially linger for weeks to years afterwards.⁷

Figure 2: Slit lamp image of SEIs concentrated in the central cornea.

^{Figure 2: Courtesy of Cory Lappin, OD, MS, FAAO.}

PCR as the gold standard

Cell culture, immune assays, and polymerase chain reaction (PCR) are the gold standards for diagnosing EKC since they can detect adenovirus serotypes 8, 4, 19, and 37 that cause the viral conjunctivitis.⁸ It has been demonstrated that PCR is more accurate than immunoassays and cell culture.⁸

Rapid Pathogen Screening (RPS) introduced AdenoPlus, an adenovirus detector, now known as the QuickVue Adenoviral conjunctivitis Test Kit (Quidel), that provides a point-of-care antigen-based immunoassay for diagnosing adenovirus infections within 10 minutes and was FDA approved in 2012.⁸

Data on the sensitivity and specificity of PCR

In 2013, Sambursky et al. published the results of a masked clinical trial of 128 patients with clinically diagnosed adenoviral conjunctivitis to compare the sensitivity and specificity of the adenovirus detector with a cell culture and immunoassay combination (CC-IFA) and PCR.⁸

The study demonstrated that the adenovirus detector had a sensitivity and specificity of 93% and 98%, respectively, compared with both CC-IFA and PCR.⁸ However, in 2015, Kam et al. also reported a high specificity with the adenovirus detector, but a much lower sensitivity of 39.5% compared to PCR.⁹

Many consider PCR to be the new gold standard for diagnosis because it is very specific and has been shown to be more sensitive than CC-IFA and the adenovirus detector.⁹ Despite PCR being the most precise means of determining the etiology of conjunctivitis, these diagnostic techniques are costly and not often accessible in optometry clinics.⁸

Therefore, in order to take the appropriate disinfection measures and reduce the general spread of infection, eyecare providers must make an accurate initial diagnosis based primarily on clinical signs and symptoms.

How should we treat EKC?

There are currently no approved treatments specifically for EKC as it is considered to be self-limiting.¹⁰ Therefore, management is typically focused on reducing symptoms through the use of palliative treatments, such as cold compresses and preservative-free artificial tears.¹⁰

Although topical corticosteroids help reduce inflammatory symptoms, when used in isolation as a monotherapy, they do not significantly shorten the recovery times of EKC. Some research suggests that they may prolong EKC by preventing the immune system from eliminating the adenovirus and enhancing viral replication and shedding.

For these reasons, using topical corticosteroids as a monotherapy should not be considered a first-line treatment for EKC.¹⁰ Patients should be continuously monitored for the development of symblepharon, conjunctival pseudomembranes, and central corneal SEIs.

In cases of acute EKC where there is a possibility of visual loss from persistent SEIs, conjunctival pseudomembranes, and iridocyclitis, the use of topical corticosteroids can be considered justified.⁷ To reduce scarring, conjunctival pseudomembranes should be removed, and topical corticosteroids can be prescribed to the patient.¹¹

Disinfection with povidone-iodine solution

Studies have indicated that disinfection with povidone-iodine (PVP-I) can shorten the duration of EKC.¹¹ PVP-I is considered to be off-label for the management of adenoviral conjunctivitis and should be an in-office procedure only.¹² Initially, gloves should be worn by the eyecare professional to avoid contamination and spread of disease.

Since PVP-I can cause moderate ocular irritation, a topical anesthetic is instilled first. The anesthetic is typically followed by a drop of a topical NSAID and then several drops of 5% PVI-I in both eyes.¹² The patient can then close their eyelids and move their eyes around for 2 minutes to ensure widespread coverage and a higher kill rate of organisms.¹²

After 2 minutes, a sterile irrigating solution can be used to thoroughly rinse the eyes. Another drop of a topical NSAID can be instilled and the patient can continue the NSAID for a few days.¹² When PVP-I is used with a topical steroid, it has been demonstrated to reduce the chance of developing SEIs.^11,13

In a randomized controlled trial, PVP-I 1.0% / dexamethasone 0.1% reduced symptoms and expedited recovery among patients with adenoviral keratoconjunctivitis.¹³ Ophthalmic formulations of PVP-I / dexamethasone are promising treatment options for acute conjunctivitis and are currently under investigation.¹³

By addressing both infectious and inflammatory components of infectious conjunctivitis, appropriate concentrations of PVP-I / dexamethasone have the potential to treat adenoviral conjunctivitis, which currently does not have any approved treatment options.¹³

A pound of prevention

Since there are currently no approved treatments for EKC, prevention is the best proactive course of action.² Contact with contaminated objects or surfaces can spread the virus, which can linger on surfaces for more than a month.²

When a patient rubs or touches their eyes and then touches anything else, they can spread EKC. It can also enter the body through the nose, throat, or conjunctiva, and spread by respiratory secretions.²

When determining whether to return to work or school, it is important to keep in mind that a person may remain contagious for at least 2 weeks following the onset of clinical symptoms.² Many EKC epidemics originate in the office or hospital environment of an eyecare professional, thus precautions should be taken there.¹⁴

Research has indicated that cleaning chemicals like hydrogen peroxide and isopropyl alcohol have varying degrees of efficacy in getting rid of adenovirus.¹⁴ Because there are no general criteria for disinfecting or sterilizing ophthalmic instruments, it has been proposed that one should consult the manufacturer's recommendations.¹⁴

EKC infections do not need to be reported to health authorities, meaning the majority of cases go unreported.¹⁴ Nonetheless, the relevant local health department should be notified of any suspected EKC infection outbreaks in communities and healthcare facilities.¹⁴ Although it is not required, reporting EKC infections can aid in infection control efforts and stop the spread of the virus.¹⁴

Key takeaways

Adenovirus serotypes 8, 4, 19, and 37 are often associated with EKC.
PCR has been shown to be more accurate than cell culture and immunoassays for diagnosing EKC. However, access to PCR can be limited, and ECPs should be prepared to make the diagnosis of EKC based upon clinical signs and symptoms.
There are currently no FDA-approved treatments for EKC. As it is self-limiting, most treatments are palliative in nature.
Although topical steroids should be used with caution in EKC, as they can potentially prolong viral shedding, their use can be warranted in cases where significant inflammation, visually-significant SEIs, and / or potentially scar or symblepharon-forming membrane / pseudomembranes are present.
When topical steroids are used in the treatment of EKC, it is also best to pair the use of steroids with an anti-infective agent, such as PVP-I, when possible, to provide anti-infective coverage.
The off-label use of PVP-I, either in isolation or with a topical steroid, can potentially help improve symptoms and resolution.
- The combination of PVP-I and dexamethasone specifically has been shown to improve symptoms and speed resolution of adenoviral conjunctivitis without increasing viral shedding.
Preventing the spread of EKC is the most proactive treatment and depends on the eyecare practitioner making the correct diagnosis, adhering to basic infection control measures, and implementing enhanced outbreak control measures.