What Are Cataracts?

This question came up because my son’s babysitter is fostering a blind dog – an adorable little black poodle with milky white eyes named Rosie.

Seriously. How cute is that?

My son and his babysitter’s two children love her and spoil her and carry her around, and they describe her as having “moon eyes” because they sort of look like full moons. The Peppermint Pig Animal Rescue was going to get her eyes operated on to remove the cataracts, but it turns out she also has detached retinas. So the surgery wouldn’t really change anything for her.

We were talking about the dog, and the news, and my son asked “what are cataracts?” Because we’d used the word and he didn’t know it.

“It’s what makes Rosie’s eyes white,” my wife replied.

“But what are they?” he replied.

“It’s…” My wife thought for a second. ‘It’s like a film on her eyes, that she can’t see through.”

“But why are they called that?” my son persisted.

So. What are cataracts?

This. This is a cataract.

I’ll be honest, here. I don’t actually know. My wife’s explanation seemed as good as any, and I think I always sort of assumed that they were something like scar tissue. But, like with so many other things, I’ve never really stopped to ask what they were or what causes them. So, since my son asked, it’s time to change that.


Merriam-Webster, my go to for dictionaries thanks to a handy app, gives two definitions for “cataract“:

  1. [Middle English, from Medieval French or Medieval Latin; Medieval French catharacte, from Medieval Latin cataracta, from Latin, portcullis] : a clouding of the lens of the eye or of its surrounding transparent membrane that obstructs the passage of light
  2. a obsolete : waterspout
    b : waterfall; especially : a large one over a precipice
    c : steep rapids in a river the cataracts of the Nile
    d : downpour, flood cataracts of rain cataracts of information

I’m guessing that the medical term is used explicitly because of the “portcullis” meaning in Latin, since cataracts more or less block light from entering the eye. The Online Etymology Dictionary seems to agree, so that makes me feel better.

The medical condition

Multiple online sources (the Mayo Clinic and the American Academy of Ophthalmology to name just two) agree with the Merriam-Webster definition. Cataracts are a clouding of the lens of the eye. This can result in blurry vision, seeing double, light sensitivity, having trouble seeing well at night, needing more light when reading, seeing “halos” around lights, and seeing bright colors as faded or yellowed. They are the most common form of vision loss in people over the age of 40, and the single most common cause of blindness in the world (in the US alone, more than 22 million people have cataracts).

Aging is the most common cause of cataracts, because the proteins in the lens of your eye will denature over time. This is not a good thing, because your lens is made of living cells and denatured proteins disrupt the cells and can even kill them. Diabetes and high blood pressure can accelerate the process, as can ultraviolet light (UVB, specifically) and other radiation and blunt trauma to the eye. There is a genetic component to the development of cataracts as well, particularly if someone develops them in childhood or as young adults. These aren’t the only causes, of course. Just the most common.

The most common forms of cataracts are subcapsular, nuclear, and cortical. Subcapsular cataracts start at the back of the lens, and are most common in diabetics and people taking medical steroids. Nuclear cataracts start in the center of the lens, and are most commonly associated with aging. Cortical cataracts start at the edge of the lens and work inwards ina “spoke-like fashion”. There are also congenital cataracts, which you are born with or develop during childhood – usually due to your genes or some form of infection or trauma.


Ultimately, the only treatment for cataracts is to remove the existing lens and replace it with an artificial lens called an intraocular lens that matches the prescription (if any) that you need for your glasses. The intraocular lenses come in a wide variety of different types, and if you need one you should consult with your ophthalmologist to see which ones make the most sense for you.

Surgery is generally considered a last resort, though. As long as the cataract symptoms aren’t bothering you, and the problems with your vision can be corrected with glasses, there generally no need to undergo surgery. Cataract surgery is considered pretty routine, but the only really risk-free surgery is one that you don’t have.

Hang on, hang on. This is all about people. Didn’t this start with a dog?

Yep. But cataracts aren’t limited to humans. It’s a condition caused by disruption and damage to the lens of the eye, so any animal with an eye with lenses can develop cataracts. There’s a lot of information on the internet about dog cataracts, and mentions of cats. One veterinarian stated that they are “the most common cause of blindness in dogs, and can also affect people or any species of animal”. Like humans, animal cataracts can develop from age, diabetes, trauma, genetics, or something called Progressive Retinal Atrophy – the name for a cluster of generic disorders that cause the retina to degenerate. Animal cataracts can be treated in the same way as human cataracts. Progressive Retinal Atrophy has no treatment, though.

Impaired vision and even blindness aren’t a death sentence for a house pet, though. Rosie gets around just fine, as long as you don’t move her food and water dishes and rearrange the furniture a whole lot. So if you live in the Cincinnati area and want to adopt an adorable little blind dog (or another animal), contact the Peppermint Pig Animal Rescue. They’ve got a lot of animals looking for a loving new home.

Why Do We Get Boogers?

It’s winter, and the temperature has been really strange. Up and down, up and down. One day I can walk around outside, thinking my light jacket is too much coat. Two days later, it’s snowing. It’s been that kind of season, and I think that’s why my son has the sniffles. He’s not sick, per se, but he’s sniffling and sneezing and his nose is running. So recently, he goes and grabs a tissue and wipes his nose. “Dad,” he asks, “why do we get boogers?”

Well, I did say I’d answer his questions…


What is a booger?

Let’s be honest here. You know what a booger is. You were a kid once, even if you haven’t been around any recently. Still, let’s do this right. Merriam-Webster gives two different definitions for the word “booger“:

  1. Bogeyman
  2. a piece of dried nasal mucus.

Clearly, in the contex of my son’s question, we’re talking about the second definition. I’ve never told him about the “bogeyman”, and I don’t think any of his friends have told him about that character. He’s six, and he’s feeling scared of the dark, so I think it would have come up if he had. So, let’s focus on the dried nasal mucus. The Online Etymology Dictionary gives the following explanation for the word

“nasal mucus,” by 1890s; earlier bugger. Also boogie.

So, yeah. No Greek or Latin or Proto-Indo-European here.

What is mucus?

Going back to Merriam-Webster, mucus is defined as “a viscid slippery secretion that is usually rich in mucins and is produced by mucous membranes which it moistens and protects”. It’s a fairly common fluid produced by the human body – heck, by nearly every animal, not just us humans. The respiratory system produces mucus in the nose, the airways (i.e. your sinuses and throat), and the lungs, as a way of trapping foreign particles. What foreign particles, you ask? Dirt. Dust. Bacteria. Pollen. Allergens. You name it, your mucus traps it. And the more your respiratory system needs to trap, the more mucus it produces. That’s why you generate more mucus (and then cough) when you get exposed to allergens or you get sick. Your body is trying to trap more of the foreign particles and expel them before they can cause you more problems.

Your respiratory system isn’t the only place that makes use of mucus, however. Your digestive system uses it for the whole length – from the esophagus into the stomach and the intestines and into the colon – as a way of lubricating your food in its journey through your body. It also shows up in the reproductive system, functioning as a lubricant and a means of transporting sperm and eggs through the body. Your eyes generate mucus as well, lubricating and protecting sensitive cells and keeping them moist.

So. How does mucous become boogers?

Bear in mind that mucus isn’t just water. It’s full of proteins and antibodies (because it isn’t just a passive defense) and electrolytes, not to mention all the dust and dirt and bacteria and such that it has trapped. As the water in the mucus evaporates or gets absorbed by the body, these solids get left behind, sticking and clumping together until – if not disturbed – they form masses of noticeable size.

I can’t believe I’m going to ask this, but… why the nose? Why not eye boogers?

Actually, those can happen. Eye crust, also known as rheum, is essentially eye boogers.

Great. Anything else?

Yeah. You know how your mom said you shouldn’t pick your nose and eat it?

Do I want to know this?

Hey, you’re the one still reading.

It turns out that there’s a hypothesis that boogers have a sugary taste that is meant to entice you to eat them. Because the act of doing so helps introduce weakened pathogens from the environment to your immune system, building up your defenses. This is rather controversial (not to mention nauseating), and it has not been tested. A number of scientists als point out that you swallow mucus all the time, just by living. This still serves to introduce the pathogens to your body. So don’t take this as a license to go to town on your nose, please.

I wasn’t planning to. Also, I hate you so very, very much right now.

Look, the human body is endlessly fascinating. Even the bits that we find culturally repugnant. Besides, you’re the one reading the article about boogers. What did you expect?

A Little More On The Purple Eye

The day I posted “Do I Have A Purple Eye?“, a friend of mine made the following comment on Facebook:

Aha! You, sir, are incorrect. You forgot cerebral contusions which don’t leak into skin tissues but into surrounding brain tissue.

Well, this got my attention (and made my skin crawl). More importantly, it got me looking deeper into this whole ‘contusion’ thing. Buckle in, folks: this will be uncomfortable.

Not all hematomas are created equal

To begin with we’ll need to revisit some definitions, because I wasn’t entirely correct. Broadly speaking all bruises are hematomas, but not all hematomas are bruises. This is because a hematoma is just (“just”) a collection of blood outside the blood vessels, which can be caused by trauma, illness, or just the blood vessel tearing from weakness. Contusions are a specific subset of hematoma caused by blunt trauma.


According to Wikipedia, hematomas come in several flavors. These include:

  • Subdermal, which is a hematoma beneath the skin.
  • Skull/brain, which are hematomas where blood pools either within the brain itself or in the cerebrospinal fluid that cushions your brain within your skull. Subdermal hematomas of the scalp also get classified as skull/brain hematomas.
  • Breast, which is a hematoma within the breast tissue – meaning that women are much more prone to these than men.
  • Myocardial, which is a hematoma in your heart muscles.
  • Pulmonary, which is a hematoma in your lung tissue.
  • Subconjunctival, which is a hematoma of the conjunctiva – the tissue that lines the inside of your eyelid and covers the whites of your eyes.
  • Perichondral, which is a hematoma of the ear. Specifically, it is blood pooling in such a way that the ear cartilige seperates from the perichondrium (the connective tissue that surrounds the cartilige of developing bone). This is where so-called “cauliflower ear[https://en.wikipedia.org/wiki/Cauliflower_ear]” comes from.
  • Perianal, which is a hematoma of the anus. This is also known as a hemorrhoid.
  • Subungual, which is a hematoma beneath a fingernail or toenail, and is sometimes known by names such as “runner’s toe” or “skier’s toe”.

Hematomas are also classified by degree. A petechiae is less than 3 mm in diameter, a purpura (which I mistakenly thought was a type of hematoma, instead of a degree) is between 3 mm and 1 cm in diameter, and an ecchymosis is larger than 1 cm in diameter. So a petechiae subdermal hematoma is a tiny thing on your skin, while a perianal ecchymosis is no diagnosis you ever want to have.

Now, a contusion is just (just?) a hematoma caused by our old friend blunt force trauma. So, really, any type of hematoma can be a contusion. Myocardial contusion? Sure. Perianal contusion? Yep. Perichondral ecchymosic contusion? Why not.

So there you have it. Anything that has blood vessels in or near it can suffer a hematoma. Skin, heart, lungs, eyes, whatever.  And now I’m going to pack myself in cotton for a while.  Just until the skin crawling and the paranoia wears off.

Why Do I Have Crust In My Eyes?

A while back one morning, my son came wandering out into the living room rubbing his eyes and complaining that they felt funny. So I had him sit on the couch, and had a look. “Well, you’ve got some crust in your eyes,” I said, starting to (carefully) pull it off his eyelids.

“Why do I have crust in my eyes?” he asked.

“You know,” I answered, “I don’t know.” And I really don’t. I mean I’ve had it, you’ve had it, we’ve all had it. Usually just from normal sleep, when you wake up with dried little eye booger nuggets on your lashes. The worst I ever got it was the time I came down with conjunctivitis in college, and had to apply a damp cloth to my eye for several minutes in order to rehydrate the crust enough to [i]open my eye[/i] – a slightly terrifying experience, let me tell you. But I never gave it much thought, beyond assuming it was dried tears mixed with dirt, or mucous, or the like.

Kids. They make you think.

What is this eye crust stuff?

Eye crust, also known as “sleep” or rheum, is “a combination of mucus, oil, skin cells and other debris that accumulates in the corner of your eye while you sleep. It can be wet and sticky or dry and crusty, depending on how much of the liquid in the discharge has evaporated”. Which means that, for a change, my initial guess was correct. It’s dried “eye boogers”.

Wait, mucus? I thought that was a nose and/or sinus thing?

To tell the truth, so did I. Mostly, if pressed I’d have defined “mucus” as “that stuff I cough up, choke on, and sneeze out when I’m sick”. It certainly wouldn’t have associated it with eyes. So, what is mucus? Well, according to MedicineNet.com, mucus is “a normal, slippery and stringy fluid substance produced by many lining tissues in the body. It is essential for body function and acts as a protective and moisturizing layer to keep critical organs from drying out. Mucus also acts as a trap for irritants like dust, smoke, or bacteria. It contains antibodies and bacteria-killing enzymes to help fight off infections.”

The article also notes that on average our bodies produce between 1 and 1.5 liters (roughly 4 to 6.25 cups) of mucus per day and says that we “don’t tend to notice mucus at all unless its production is increased or the quality of mucus has changed, as may happen with different illnesses and conditions.”

So, yeah. That’s a lot of mucus.

Eye Mucus

Technically, eye mucus is called “mucins”, and are produced by the conjunctiva, a thin, semi=transparent mucus membrane (much like the membranes that line your nose and sinuses) that covers the white of the eyeball (known formally as the sclera).


The mucins work with tears to keep the eye moist and lubricated, so that you don’t scratch your eye up simply by blinking or looking around.

Should I be concerned about my eye crust?

Generally speaking, no. It’s a perfectly normal thing, caused by your tear ducts and conjunctiva [i]doing their jobs[/i] and then by evaporation. It might be a little uncomfortable to clean out once in a while, but as long as you don’t drive it into your eyeball and scratch things up the crust isn’t an issue.


It can be an indicator of problems, though. Particularly if abnormally thick crust or discharge is combined with green, white, or yellow eye mucus. This can be a sign of such things as conjunctivitis, blepharitis, a stye, or a corneal ulcer or a blocked tear duct. In this case you should see your family doctor for a diagnosis and treatment. You don’t want to be taking chances with your eyes.

Lovely. Anything else?

Yeah. Have you ever woken up with a crust at the corner of your mouth? That’s also rheum.

Is the Earth bigger than the Sun?

All week, in honor of the summer solstice, I’ve been writing about the sun and about astronomy. Why? Because my son unleashed a torrent of questions, once we started talking about Monday having been the longest day of the year. So far I’ve answered questions about why the sun doesn’t melt, what the hottest star is, and what would happen if the sun turned into a black hole. So now, we’re on to the final question:

“Is the Earth bigger than the Sun?”

This one made me chuckle, just a little. “No,” I told him, “the sun is lots bigger.”

“Well,” he said thoughtfully, “my friend says the Earth is bigger.”

“It isn’t,” I assured him. “It just looks bigger, because we stand on the earth and the sun is really far away.”

He thought about that for a minute. “But it could be bigger!”

No. It really couldn’t.

This is a clear cut answer. The sun has an equatorial diameter of 1,391,400 kilometers and masses 1.988 x 10^30 kg, while the Earth has an equatorial diameter of 12,756.2 kilometers and masses 5.972 x 10^24 kg. Put another way, the Sun’s diameter is about 109 times that of earth, and it is 333,000 times as massive. There is no way the sun could be smaller than the earth.

So why does it look so small in the sky?

I’ll be honest here:  this is not something I ever recall stopping to ask.  Not until I started writing this article.  Like so many things, I just took it for granted that things that are close look bigger than things that are far away.  It never occurred to me to ask “why”, before.  (Which is one of the cool things about writing these articles – I end up answering questions I never thought to ask.)

Researching this, I ended up on a couple of different physics forums, and both of them agreed with Cognition and the Visual Arts:

The size of the retinal image varies in inverse proportion to the distance of an object.  Near objects appear larger than far objects because they occupy more space on the retina.  In the perception of real world stimuli, an object 5 feet away casts an image on the retina twice the size as the same object viewed from 10 feet away.


The object on the left is an eye, and the two stick figures are identical.  However, the stick figure closer to the eye occupies a greater percentage of that eye’s field of vision, and so will appear larger.  Likewise, a small object held close can appear to be the same size (or even larger) than a large object that is far away.

The sun, on average, is 93 million miles away.  As a result, even though it’s more than a hundred times as wide as the Earth, it appears small enough that you could make your own solar eclipse by holding a quarter (or similar coin) at arm’s length in front of it.

Don’t try that, though.  You could really damage your eyes.