Month: October 2021

At one time, replacement parts for the eyes must have seemed unimaginable. Nowadays, if the inner lens of the eye becomes clouded by a cataract, a routine surgery to swap it out with a new artificial lens restores vision.

But what happens if the outer lens of the eye (the cornea) becomes damaged or diseased? You can have that replaced, too. “It’s not as common as cataract surgery, but many people get corneal diseases after age 50 and may need a corneal transplant,” says Dr. Nandini Venkateswaran, a corneal and cataract surgeon at Harvard-affiliated Massachusetts Eye and Ear.

More than 49,000 corneal transplants occurred in 2021 in the US, according to the Eye Bank Association of America.

What is the cornea?

The cornea is a dome of clear tissue at the front of each eye, covering the iris and pupil, that acts as a windshield that protects the delicate eye apparatus behind it, and focuses light onto the retina, which sends signals that the brain turns into images (your vision).

You need this combo of windshield and camera lens to focus and see clearly. But many things can go wrong within the five layers of tissue that make up the cornea. That can make it hard to see and rob you of the ability to read, drive, work, and get through other activities in your day.

How does damage to the cornea occur?

It may stem from a number of causes:

• Injuries, such as a fall. “Falls are a big reason for people to come in with acute eye trauma. The cornea can be damaged easily if something pokes it,” Dr. Venkateswaran says.
• Previous eye surgeries. “Especially for adults who’ve had several eye surgeries — such as cataract and glaucoma surgeries — the inner layers of the cornea can become damaged and weakened with age,” she adds.
• Illness. Problems like severe corneal infections, or genetic conditions such as Fuchs’ endothelial dystrophy, can cause vision loss.

What are the options for treating corneal damage?

Cornea treatment depends on the type of problem you have and the extent of the damage. “It’s a stepwise approach. Sometimes wearing a specialty contact lens or using medications can decrease swelling or scarring in the cornea,” Dr. Venkateswaran says.

When damage can’t be repaired, surgeons can replace one or a few layers of the cornea (a partial-thickness transplant), or the whole thing (a full-thickness transplant).

The vast majority of transplants come from donor corneas that are obtained and processed by eye banks throughout the US. In some instances, such as when repeated transplants fail, an artificial cornea is an option. Recovery after corneal surgery can take up to a year.

How long-lasting are corneal transplants?

There’s always a risk that your body will reject a corneal transplant. It happens about a third of the time for full-thickness transplants. It occurs less often for partial-thickness transplants. Preventing rejection requires a lifetime of eye drops.

Still, transplant longevity varies. “I’ve seen transplants from 50 or 60 years ago and now they’re starting to show wear and tear. Other patients, for a variety of reasons — immune system attacks, intolerance to eye drops, or underlying conditions — may only have a transplant for five to 10 years before they need another,” Dr. Venkateswaran explains.

Preventive eye care can help preserve the cornea

It’s crucial to get regular comprehensive eye exams to make sure your corneas and the rest of your eyes are healthy.

The American Academy of Ophthalmology recommends a comprehensive (dilated) eye exam

• at age 40
• every two to four years for people ages 40 to 54
• every one to three years for people ages 55 to 64
• every one to two years for people ages 65 and older.

You’ll need an eye exam more often if you have underlying conditions that increase your risk for eye disease, such as diabetes or a family history of corneal disease.

If you have any vision problems, such as eye pain, redness, blurred vision despite new glasses, or failing eyesight, see an eye doctor.

Fortunately, for people who do experience corneal damage, advances in surgical options are encouraging.

“Corneal transplants are a miracle,” Dr. Venkateswaran says. “I have patients whose quality of life was significantly decreased because they couldn’t see through their cloudy windshield. We can give them sight again, and we have the technology and medications to keep the transplant alive.”

About the Author

Heidi Godman, Executive Editor, Harvard Health Letter

Heidi Godman is the executive editor of the Harvard Health Letter. Before coming to the Health Letter, she was an award-winning television news anchor and medical reporter for 25 years. Heidi was named a journalism fellow … See Full Bio View all posts by Heidi Godman

Polio is a potentially life-threatening or disabling illness that spreads from person to person. Thanks to vaccination, the United States has been polio-free since 1979, and the spread of this highly contagious disease has been interrupted in most countries. Yet on June 22, the United Kingdom Health Security Agency announced that it had detected poliovirus in a most unexpected place: the sewers of London.

Over the past several months, scientists at the agency repeatedly found poliovirus in London sewer water. The viruses were genetically similar, suggesting that they were the result of limited spread within a family or close-knit community. Just how concerned should all of us be about this news?

Health clues found in wastewater

Sampling of wastewater for genetic material from viruses is a powerful tool used by epidemiologists to track outbreaks of polio and other diseases. Surges in the amount of SARS-CoV-2 RNA in Boston wastewater have been highly predictive of COVID outbreaks. Wastewater may also help to detect the spread of influenza and antibiotic-resistant bacteria.

Poliovirus infection was once a common and dreaded disease. Most people with poliovirus either had no symptoms or mild gastroenteritis (stomach flu). But one in 100 people developed paralysis, or poliomyelitis. In half of the affected patients, this paralysis was permanent.

In the UK, wild poliovirus has been eliminated since 1984. Although great progress has been made in many parts of the world, complete eradication of polio has been elusive. Pakistan and Afghanistan have never been free from wild-type polio, and outbreaks have recently taken place in Malawi and Mozambique, countries which had previously eliminated polio.

The reasons for this backsliding are complex. Some contributing factors are diversion of scarce resources toward the COVID-19 pandemic, backlogs in vaccine manufacturing, anti-vaccine agitation, and violence directed at vaccine workers.

Another problem is vaccine-derived poliovirus. In the United States and most other countries, injections containing killed viruses are used. While these vaccines are safe, they are less effective than oral vaccines at breaking the chain of polio transmission. Oral vaccines stimulate long-lived immune responses in the lining of the intestines, where polioviruses replicate. Unfortunately, oral vaccines contain weakened but live viruses, which occasionally revert to a more dangerous form. In fact, the poliovirus found in London was a vaccine-derived strain that the infected individual had likely acquired from travel abroad.

Who is at risk for poliovirus stemming from this source?

Vaccine-derived viruses pose little risk to highly vaccinated populations, but they are able to spread in communities with low polio vaccination rates. In some cases, this can even cause paralytic disease. Because of these risks, steps are being taken to gradually phase out the use of oral polio vaccines.

If you’re concerned about polio, the best protection against this disease is vaccination. Children should receive a full series of four shots of inactivated polio vaccine, given at specific intervals, that helps with developing immunity.

Nationwide, rates of childhood polio vaccination in the United States are still high (nearly 93%). However, some infectious disease experts worry that the weakening of vaccine mandates in some areas has created islands of vulnerability in this sea of immunity. Communities in the US with low childhood vaccination rates have been vulnerable to large measles outbreaks in recent years, and might also be vulnerable to polio outbreaks.

With few exceptions, adults who were fully vaccinated as kids do not need booster shots. These exceptions include travel to a country with active polio transmission, laboratory work with poliovirus, or providing health care to polio patients and their close contacts. A single lifetime booster dose of inactivated polio vaccine is adequate for these high-risk scenarios.

About the Author

John Ross, MD, FIDSA, Contributor

Dr. John Ross is an assistant professor of medicine at Harvard Medical School. He is board certified in internal medicine and infectious diseases, and practices hospital medicine at Brigham and Women’s Hospital. He is the author … See Full Bio View all posts by John Ross, MD, FIDSA

It’s an old line: everyone complains about the weather but no one is doing anything about it.

But if you’re a person with bad allergies or asthma, stormy weather can be more than an annoyance; it can be a serious threat to your health. “Thunderstorm asthma” was first reported in the 1980s in England and Australia, and cases continue to crop up. Just after severe thunderstorms passed through Melbourne, Australia in 2016, more than 9,000 people sought urgent medical care for asthma during one notable event. Medical facilities were overwhelmed and at least eight people died. That’s unusual, but if you do have asthma — or seasonal allergies, as it turns out — understanding this trigger can help you stay well.

What is thunderstorm asthma?

The term describes an attack of asthma that starts or worsens after a thunderstorm. It can occur in anyone with asthma, but it most often affects people with seasonal allergic rhinitis, which many people know as hay fever or allergies. Heralded by a runny nose, sneezing, and itchy eyes, seasonal allergies are often worst in the spring, summer, or early fall.

Rain tends to lower pollen counts by cleansing the air, and many people find that rainy weather tends to reduce asthma symptoms triggered by allergies. But thunderstorms can make asthma worse because of a unique sequence of events:

• Cold downdrafts concentrate air particles, such as pollen and mold
• These air particles are swept up into clouds where humidity is high
• In the clouds, wind, humidity, and lightning break up the particles to a size that can readily enter the nose, sinuses, and lungs
• Wind gusts concentrate these small particles so large amounts can be inhaled.

What raises risk for experiencing thunderstorm asthma?

According to a new study in the Journal of Allergy and Clinical Immunology, a whopping 144 out of 228 people with seasonal allergies reported experiencing thunderstorm asthma — that’s 65%! And many of the asthma attacks set off by thunderstorms weren’t mild. Nearly half of people who had an attack sought emergency hospital treatment.

Among people with seasonal allergies, risk factors for experiencing thunderstorm asthma include having

• poorly controlled asthma symptoms (assessed by a standard asthma questionnaire)
• a low score on a rapid exhalation test (a common breathing test for asthma)
• higher levels of a certain antibody (ryegrass pollen-specific IgE)
• higher numbers of certain blood cells (eosinophils, which tend to increase when people have allergic conditions)
• higher levels of exhaled nitric oxide (one measure of lung inflammation among people with asthma).

Not everyone with these risk factors will develop thunderstorm asthma. And even among those who do, asthma attacks won’t necessarily occur with every storm. But it may be useful to know if you’re among those at risk, especially if you live in an area where thunderstorms are common.

The bottom line

Thunderstorm asthma may seem like more of a curiosity than a serious threat to public health. But when it affects a large population area, emergency rooms can become overwhelmed, as happened during the 2016 Melbourne event. A better understanding of when these events are expected could lead to advanced warning systems, enhanced emergency room preparedness, and even preventive treatment.

In the US, 25 million people have asthma and more than 20 million have seasonal allergies. Odds are good that millions have both, which puts large numbers of people at risk for developing thunderstorm asthma.

If you’re among them, the weather forecast may be much more than just a guide on what to wear or whether to bring an umbrella. Knowing thunderstorms are headed your way may serve as an advance warning to double check that you are taking your asthma medicines properly, have a supply of rescue medicine handy, or simply plan to stay indoors until the storm has passed.

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD