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The delta variant and your eyes: What we know

This article will be updated as new information becomes available.

  • As of early September, nearly all new COVID-19 cases in the United States were caused by a strain of the virus known as the delta variant.

  • Like other variants of the coronavirus, delta may be able to cause certain eye-related symptoms, but we don't know for sure yet.

  • Vaccines are less effective against delta, but they're still your best form of protection.

  • An eye test may soon be able to help detect cases of long-haul COVID.

The current COVID spike will likely be America's second-largest upturn of daily new cases since the start of the pandemic. It comes at the hands of a delta variant that spreads as easily as chickenpox among people who are unprotected.

Delta cases were first seen in the U.K. and the U.S. in February 2021 after originally being spotted in India in October 2020. The CDC estimates more than 99% of new COVID cases in America are currently caused by delta infections, as of September 4.

Virtually all of these cases are caused by the original delta variant. About 2 in every 1,000 cases are caused by subtypes known as delta plus.

There were early concerns about delta plus overtaking the original delta strain. But as the rate of delta plus infections level off, delta plus doesn't appear to be any more of a threat than delta itself.

The three COVID-19 vaccines used in the United States — Pfizer, Moderna and Johnson & Johnson — will still protect you against the delta variant, but not as effectively as they did against previous strains. Fortunately, studies continue to show that these "breakthrough" cases are less common and less severe, on average.

Can the delta variant cause eye symptoms?

We don't know for sure — yet. Previous strains of COVID could cause eye-related symptoms, but there isn't enough scientific data available right now to say with certainty that delta does the same.

There have been isolated reports of delta infections causing eye symptoms, including one fully vaccinated Kentuckian who had bloodshot eyes and flu-like symptoms, and a five-year-old in Mississippi who showed signs of conjunctivitis.

Although not nearly as common as symptoms like cough and fever, other strains of the coronavirus were capable of causing:

It isn't a stretch to think that some delta infections are capable of causing similar eye symptoms, but, like other aspects of delta, we need to wait for more information.

While each infection is different, delta seems to be causing slightly different symptoms overall than earlier forms of COVID.

"It seems like cough and loss of smell are less common," said Dr. Inci Yildirim, a  pediatric infectious disease specialist at Yale Medicine, in an article about the delta variant. "And headache, sore throat, runny nose and fever are present based on the most recent surveys in the U.K., where more than 90% of the cases are due to the Delta strain."

If a set of symptoms that includes runny nose, sore throat and headache sounds familiar, it's because many delta infection symptoms resemble a bad case of hay fever — seasonal allergies — more than any other strain.

This is where eye-related symptoms could get even more confusing.

If you have bad seasonal allergies, you probably know how much allergies can affect your eyes. Red, bloodshot eyes are a hallmark symptom; itchiness, watering and even blurry vision are also common.

And while "classic" COVID symptoms are becoming less common, they can still show up. Cough, loss of taste or smell, and certain gastrointestinal symptoms still occur, but they're becoming less likely.

MIS-C: A rare but growing concern in children

As delta finds ways to infect more young people than earlier strains, a rare but serious complication of COVID is also expected to be on the rise.

MIS-Cmultisystem inflammatory syndrome in children — can cause vital organs and other parts of the body to become inflamed. It shares similarities with Kawasaki disease, a condition uncovered earlier in the pandemic.

We don't currently know why MIS-C happens to some children.

Symptoms of MIS-C can vary. It can also cause red, bloodshot eyes, but like COVID-19, it's unlikely that would be the only symptom. Additional symptoms occur alongside a fever, according to the CDC.

In addition to a fever, MIS-C symptoms can include:

  • Bloodshot eyes

  • Headache

  • Abdominal pain

  • Chest pain or tightness

  • Diarrhea

  • Fatigue

  • Neck pain

  • Low blood pressure

  • Rash

  • Vomiting

As of August 22, there have been 4,661 verified cases of MIS-C in the U.S., with others under investigation. Forty-one children have died from the complication.

While rare, the CDC recommends seeking emergency care if you notice symptoms such as difficulty breathing, chest pain or pressure, pale skin or any other severe symptoms.

The eyes could offer insight into long COVID cases

There's a lot we still don't know about long COVID, the symptoms that linger for weeks or months after the initial infection clears up. Sometimes, symptoms seem to continue indefinitely, significantly impacting a person’s quality of life.

Also known as "long-haul COVID" or "post-acute COVID," long COVID can show up as one or more of a multitude of symptoms. In addition to many others, ongoing symptoms can include:

  • Fatigue

  • Changes in taste or smell

  • Difficulty breathing

  • Brain fog

  • Cough

  • Chest pain

  • Joint pain

  • Heart palpitations

  • Worsening symptoms after physical activity

We don't yet know how often long COVID occurs after a delta infection, or among vaccinated people. One February study found that roughly 30% of people were still experiencing symptoms between three and nine months after having COVID.

About one in 12 participants reported that symptoms affected their ability to complete at least one "activity of daily living," with household chores being the most common.

Long COVID is a developing issue that will continue to affect millions of people for the foreseeable future. Standardized treatment options may not be available yet, but clues to diagnosis could lie in — of all places — the eyes.

Corneal nerve fibers in a healthy person (A), a COVID-19 patient without long COVID (B) and one with long COVID (C). [Image courtesy: British Journal of Ophthalmology]

There may be a connection between long COVID and damage to microscopic nerve fibers in the cornea, the clear layer in front of the pupil, according to a study published in July.

Ophthalmologists used a painless, noninvasive test called a corneal confocal microscopy, a procedure used to diagnose several other conditions that affect the cornea.

While the study acknowledged that more research is needed, the discovery could eventually be a stepping stone toward recovery for people affected by ongoing symptoms, especially neurological.

Getting help from a medical professional

COVID-19's symptoms can be unpredictable, and, like other illnesses, it's important not to self-diagnose. People who experience symptoms are advised to follow the latest guidance from the CDC.

If you think that you or someone you know has COVID-19 or long-haul COVID, speak with a medical professional.

If you notice emergency symptoms such as difficulty breathing, chest pain or pressure, confusion or skin discoloration, seek medical attention as soon as possible.

READ NEXT: Can COVID-19 vaccines cause eye-related side effects?

Expert reaction to cases of variant B.1.617 (the ‘Indian variant’) being investigated in the UK. Science Media Centre. April 2021.

Tracking SARS-CoV-2 variants. World Health Organization. August 2021.

About variants of the virus that causes COVID-19​​. Centers for Disease Control and Prevention. Accessed 6 August 2021.

COVID vaccines protect against delta, but their effectiveness wanes. Nature. August 2021.

Effectiveness of COVID-19 vaccines in ambulatory and inpatient care settings. New England Journal of Medicine. September 2021.

Sore eyes as the most significant ocular symptom experienced by people with COVID-19. BMJ Open Ophthalmology. November 2020.

5 things to know about the delta variant. Yale Medicine. August 2021.

Symptoms of the delta variant vs. previous COVID-19 strains. Baton Rouge General. July 2021.

Is It COVID-19 or allergies? American Academy of Ophthalmology. January 2021.

When you’ve been fully vaccinated. Centers for Disease Control and Prevention. Accessed 6 August 2021.

Health department-reported cases of multisystem inflammatory syndrome in children (MIS-C) in the United States. Centers for Disease Control and Prevention. Accessed 16 August 2021.

For parents: Multisystem inflammatory syndrome in children (MIS-C) associated with COVID-19. Centers for Disease Control and Prevention. Accessed 16 August 2021.

MIS-C and COVID-19: Rare inflammatory syndrome in kids and teens. Johns Hopkins Medicine. July 2021.

Post-COVID conditions. Centers for Disease Control and Prevention. Accessed 6 August 2021.

Sequelae in adults at 6 months after COVID-19 infection. JAMA Network Open. February 2021.

A pandemic that endures for COVID long-haulers. The Harvard Gazette. April 2021.

Corneal confocal microscopy identifies corneal nerve fibre loss and increased dendritic cells in patients with long COVID. British Journal of Ophthalmology. July 2021.

Clinical applications of corneal confocal microscopy. Clinical Ophthalmology. June 2008.

Symptoms of COVID-19. Centers for Disease Control and Prevention. Accessed 6 August 2021.

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