Cataract surgery is one of the most popular and commonly performed procedures in the world. The vast majority of patients have excellent outcomes with few complications.

Here are the numbers:

• By age 80, over half of all Americans have cataracts.

• Close to 4 million cataract surgeries are performed in the U.S. every year.

• Over 90% of patients have 20/20 vision with glasses after surgery, although those with other eye conditions may not do as well, including those with glaucoma, a progressive disease typically associated with elevated pressure within the eye; diabetic retinopathy, which ultimately can cause leakage in the retinal tissues; and macular degeneration, a disease that is typically related to age.

• The rate of post-surgery infection from endophthalmitis is less than 0.1%.

As ophthalmologists who have performed thousands of these procedures, we know that many patients have misconceptions about both cataracts and the surgery. For example, some think a cataract is a growth on the eye’s surface.

We like to compare a cataract with the frosted glass of a bathroom window, where light can be transmitted but details cannot. Or when turbulence from a storm causes normally clear water in the ocean to become murky. In much the same way, the eye’s once transparent lens becomes cloudy.

About the surgery

Cataract surgery removes the clouded lens of the eye and replaces it with a new, clear lens to restore your vision. Most patients report the procedure is painless.

It’s typically an elective surgery that is performed on an outpatient basis. The patient is often awake, under local anesthesia, with sedation similar to that used for dental procedures. We like to say patients receive the equivalent of three margaritas in their IV.

Numbing drops are then applied to the eye’s surface, along with an anesthetic inside the eye. Patients with claustrophobia, or movement disorders such as Parkinson’s disease, may not be suitable candidates for awake surgeries and require general anesthesia.

Before surgery, patients receive dilating drops to make the pupil as large as possible. The surgeon makes a tiny incision, usually with a small pointed scalpel, between the clear and white part of the eye to gain access to the lens capsule, a thin membrane similar in thickness to a plastic produce bag at the grocery store.

This capsule is suspended by small fibers called zonules, which are arranged like the springs that suspend a trampoline from a frame. The surgeon then creates a small opening in the capsule, called a capsulotomy, to gain access to the cataract. The cataract is then broken into smaller parts so they are removable through the small incision.

This is similar to a tiny jackhammer, breaking the large lens into smaller pieces for removal. That sounds scary, but it’s painless. Ultrasound emulsifies the lens and vacuum power then aspirates it from the eye.

Laser-assisted cataract surgery has been found to have similar outcomes to traditional cataract surgery.

Complications are rare

Serious complications, such as postoperative infection, bleeding in the eye or a postoperative retinal detachment are rare; they occur in approximately 1 in 1,000 cases. But even in many of these situations, appropriate management can salvage useful vision.

Capsular complications deserve additional discussion. According to some studies, they occur in up to 2% of cases. If a hole or tear of the posterior capsule is encountered during cataract surgery, the clear gel in the vitreous – the back chamber of the eye – may be displaced into the front chamber of the eye.

If that happens, the gel must be removed at the time of the cataract surgery. This will reduce the likelihood of additional postoperative complications, but those who have the procedure, known as a vitrectomy, have an increased risk for additional complications, including postoperative infections and postoperative swelling.

After the surgery

Patients usually go home right after the procedure. Most surgery centers require that the patient have someone drive them home, more for the anesthesia rather than the surgery. Patients begin applying postoperative drops that same day and must wear an eye shield at bedtime for a few weeks after surgery.

Patients should keep the eye clean and avoid exposure to dust, debris and water. They should try not to bend over and should avoid heavy lifting or straining in the first week or so after surgery. Lifting or straining can cause a surge of blood pressure to the face and eye. Known as a choroidal hemorrhage, it can lead to bleeding into the wall of the eye and be devastating to vision.

Things that cause only moderate increases in heart rate such as walking are OK. Routine postoperative examinations are usually completed the day after surgery, about a week after surgery and about a month after surgery.

A choice of lens

The plastic lens used to replace the cataract, or intraocular lens, requires careful sizing for optimal results and a nuanced discussion between patient and surgeon.

Early intraocular lens technologies were monofocal, and most patients with these lenses chose distance correction and used reading glasses for near tasks. This is still the preferred approach for approximately 90% of patients having cataract surgery today.

Recent advances have led to intraocular lenses that offer multifocality – the opportunity to have near as well as distance vision, without glasses. Some multifocal lenses are even in the trifocal category, which includes distance, near, and intermediate vision, the latter of which in recent years has become very important for computer and phone use.

Most patients with these advanced technology multifocal lenses are happy with them. However, a small percentage of patients with multifocal lenses can be so bothered by visual disturbances – notably night glare and halos around light sources in the dark – that they request removal of the multifocal lens to exchange it for a standard intraocular lens. These exchanges are a reasonable option for such situations and offer relief for most affected patients.

Determining who’s an ideal candidate for a multifocal intraocular lens is an area of active research. Most clinicians would recommend against such a lens for a patient with a detail-oriented personality. Such patients tend to fixate on the shortcomings of these lenses despite their potential advantages.

As with many technologies, current generation advanced technology intraocular lenses are much better than their predecessors. Future offerings are likely to offer improved vision and fewer side effects than those available today.

But these newer lenses are often not reimbursed by insurance companies and often entail substantial out-of-pocket costs for patients.

Deciding on what type of lens is best for you can be complicated. Fortunately, except in unusual circumstances, such as when a cataract develops after trauma to the eye, there is seldom a hurry for adult cataract surgery.

Allan Steigleman, Associate Professor of Ophthalmology, University of Florida and Elizabeth M. Hofmeister, Associate Professor of Surgery, Uniformed Services University of the Health Sciences

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Windstorms can seem like they come out of nowhere, hitting with a sudden blast. They might be hundreds of miles long, stretching over several states, or just in your neighborhood.

But they all have one thing in common: a change in air pressure.

Just like air rushing out of your car tire when the valve is open, air in the atmosphere is forced from areas of high pressure to areas of low pressure.

The stronger the difference in pressure, the stronger the winds that will ultimately result.

Other forces related to the Earth’s rotation, friction and gravity can also alter the speed and direction of winds. But it all starts with this change in pressure over a distance – what meteorologists like me call a pressure gradient.

So how do we get pressure gradients?

Strong pressure gradients ultimately owe their existence to the simple fact that the Earth is round and rotates.

Because the Earth is round, the sun is more directly overhead during the day at the equator than at the poles. This means more energy reaches the surface of the Earth near the equator. And that causes the lower part of the atmosphere, where weather occurs, to be both warmer and have higher pressure on average than the poles.

Nature doesn’t like imbalances. As a result of this temperature difference, strong winds develop at high altitudes over midlatitude locations, like the continental U.S. This is the jet stream, and even though it’s several miles up in the atmosphere, it has a big impact on the winds we feel at the surface.

Because Earth rotates, these upper-altitude winds blow from west to east. Waves in the jet stream – a consequence of Earth’s rotation and variations in the surface land, terrain and oceans – can cause air to diverge, or spread out, at certain points. As the air spreads out, the number of air molecules in a column decreases, ultimately reducing the air pressure at Earth’s surface.

The pressure can drop quite dramatically over a few days or even just a few hours, leading to the birth of a low-pressure system – what meteorologists call an extratropical cyclone.

The opposite chain of events, with air converging at other locations, can form high pressure at the surface.

In between these low-pressure and high-pressure systems is a strong change in pressure over a distance – a pressure gradient. And that pressure gradient leads to strong winds. Earth’s rotation causes these winds to spiral around areas of high and low pressure. These highs and lows are like large circular mixers, with air blowing clockwise around high pressure and counterclockwise around low pressure. This flow pattern blows warm air northward toward the poles east of lows and cool air southward toward the equator west of lows.

As the waves in the jet stream migrate from west to east, so do the surface lows and highs, and with them, the corridors of strong winds.

That’s what the U.S. experienced when a strong extratropical cyclone caused winds stretching thousands of miles that whipped up dust storms and spread wildfires, and even caused tornadoes and blizzards in the central and southern U.S. in March 2025.

Whipping up dust storms and spreading fires

The jet stream over the U.S. is strongest and often the most “wavy” in the springtime, when the south-to-north difference in temperature is often the strongest.

Winds associated with large-scale pressure systems can become quite strong in areas where there is limited friction at the ground, like the flat, less forested terrain of the Great Plains. One of the biggest risks is dust storms in arid regions of west Texas or eastern New Mexico, exacerbated by drought in these areas.

When the ground and vegetation are dry and the air has low relative humidity, high winds can also spread wildfires out of control.

Even more intense winds can occur when the pressure gradient interacts with terrain. Winds can sometimes rush faster downslope, as happens in the Rockies or with the Santa Ana winds that fueled devastating wildfires in the Los Angeles area in January.

Violent tornadoes and storms

Of course, winds can become even stronger and more violent on local scales associated with thunderstorms.

When thunderstorms form, hail and precipitation in them can cause the air to rapidly fall in a downdraft, causing very high pressure under these storms. That pressure forces the air to spread out horizontally when it reaches the ground. Meteorologists call these straight line winds, and the process that forms them is a downburst. Large thunderstorms or chains of them moving across a region can cause large swaths of strong wind over 60 mph, called a derecho.

Finally, some of nature’s strongest winds occur inside tornadoes. They form when the winds surrounding a thunderstorm change speed and direction with height. This can cause part of the storm to rotate, setting off a chain of events that may lead to a tornado and winds as strong as 300 mph in the most violent tornadoes.

Tornado winds are also associated with an intense pressure gradient. The pressure inside the center of a tornado is often very low and varies considerably over a very small distance.

It’s no coincidence that localized violent winds from thunderstorm downbursts and tornadoes often occur amid large-scale windstorms. Extratropical cyclones often draw warm, moist air northward on strong winds from the south, which is a key ingredient for thunderstorms. Storms also become more severe and may produce tornadoes when the jet stream is in close proximity to these low-pressure centers. In the winter and early spring, cold air funneling south on the northwest side of strong extratropical cyclones can even lead to blizzards.

So, the same wave in the jet stream can lead to strong winds, blowing dust and fire danger in one region, while simultaneously triggering a tornado outbreak and a blizzard in other regions.

Chris Nowotarski, Associate Professor of Atmospheric Science, Texas A&M University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

When U.S. President Donald Trump imposed sweeping new tariffs on imported goods on April 2, 2025 – upending global trade and sending markets into a tailspin – he presented the move as a response to a crisis. In an executive order released the same day, the White House said the move was necessary to address “the national emergency posed by the large and persistent trade deficit.”

A trade deficit – when a country imports more than it exports – is often viewed as a problem. And yes, the U.S. trade deficit is both large and persistent. Yet, as an economist who has taught international finance at Boston University, the University of Chicago and Harvard, I maintain that far from a national emergency, this persistent deficit is actually a sign of America’s financial and technological dominance.

The trade deficit is the flip side of an investment magnet

A trade deficit sounds bad, but it is neither good nor bad.

It doesn’t mean the U.S. is losing money. It simply means foreigners are sending the U.S. more goods than the U.S. is sending them. America is getting more cheap goods, and in return it is giving foreigners financial assets: dollars issued by the Federal Reserve, bonds from the U.S. government and American corporations, and stocks in newly created firms.

That is, a trade deficit can only arise if foreigners invest more in the U.S. than Americans invest abroad. In other words, a country can only have a trade deficit if it also has an equally sized investment surplus. The U.S. is able to sustain a large trade deficit because so many foreigners are eager to invest here.

Why? One major reason is the safety of the U.S. dollar. Around the world, from large corporations to ordinary households, the dollar is used for saving, trading and settling debts. As the world economy grows, so does foreigners’ demand for dollars and dollar-denominated assets, from cash to Treasury bills and corporate bonds.

Because the dollar is so attractive, the Federal Reserve gets to mint extra cash for use abroad, and the U.S. government and American employers and families can borrow money at lower interest rates. Foreigners eagerly buy these U.S. financial assets, which enables Americans to consume and invest more than they ordinarily could. In return for our financial assets, we buy more German machines, Scotch whiskey, Chinese smartphones, Mexican steel and so on.

Blaming foreigners for the trade deficit, therefore, is like blaming the bank for charging a low interest rate. We have a trade deficit because foreigners willingly charge us low interest rates – and we choose to spend that credit.

US entrepreneurship attracts global capital – and fuels the deficit

Another reason for foreigners’ steady demand for U.S. assets is American technological dominance: When aspiring entrepreneurs from around the world start new companies, they often decide to do so in Silicon Valley. Foreigners want to buy stocks and bonds in these new companies, again adding to the U.S. investment surplus.

This strong demand for U.S. assets also explains why Trump’s last trade war in 2018 did little to close the trade deficit: Tariffs, by themselves, do nothing to reduce foreigners’ demand for U.S. dollars, stocks and bonds. If the investment surplus doesn’t change, the trade deficit cannot change. Instead, the U.S. dollar just appreciates, so that imports get cheaper, undoing the effect of the tariff on the size of the trade deficit. This is basic economics: You can’t have an investment surplus and a trade surplus at the same time, which is why it’s silly to call for both.

It’s worth noting that no other country in the world enjoys a similarly sized investment surplus. If a normal country with a normal currency tries to print more money or issues more debt, its currency depreciates until its investment account – and its trade balance – goes back to something close to zero. America’s financial and technological dominance allows it to escape this dynamic.

That doesn’t mean all tariffs are bad or all trade is automatically good. But it does mean that the U.S. trade deficit, poorly named though it is, does not signify failure. It is, instead, the consequence – and the privilege – of outsized American global influence.

The president’s frenzied attacks on the nation’s trade deficit show he’s misreading a sign of American economic strength as a weakness. If the president really wants to eliminate the trade deficit, his best option is to rein in the federal budget deficit, which would naturally reduce capital inflows by raising domestic savings.

Rather than reviving U.S. manufacturing, Trump’s extreme tariffs and erratic foreign policy are likely to instead scare off foreign investors altogether and undercut the dollar’s global role. That would indeed shrink the trade deficit – but only by eroding the very pillars of the country’s economic dominance, at a steep cost to American firms and families.

Tarek Alexander Hassan, Professor of Economics, Boston University

This article is republished from The Conversation under a Creative Commons license. Read the original article.