Astigmatism

We just learned about the Far Sightedness.

Another type of refractive error that makes the eye not see as well is Astigmatism.

This happens when the cornea at the front of the eye is not shaped right, causing light to get focused in the wrong place and not where it is supposed to go on the back of the retina.


(from: wikipedia - astigmatism)


Kid Facts - Blast from the past: Labial Commissure of Mouth

Far Sightedness

We just learned about the Near Sightedness.

Another type of refractive error that people can have is called Far Sightedness, also called hypermetropia.

If someone is far-sighted that means they can see far away very well, but they can't see up close very well.
An easy way to remember that is that if you are "far-sighted" you are good at seeing far away.

A lot of people become far sighted when they get older, and they can not see up close as well as they used to.
This is one of the reasons that old people will hold something out in their hand with their arm stretched out as far as it can go, because they can see far but not up close.

Older people will also get what are called "reading glasses" meaning that they only wear them when they need to look at something up close like when reading a book.

If someone is young and far sighted then it usually means there is a problem with the shape of their eyeball, or their lens or cornea are not the right shape.
This makes the light coming into the eye not focus on the retina, but focus past it, so it doesn't send the right signals to the brain.

For old people it is because the eye muscles are weaker and can't focus the lens as well as they used to.


(from: wikipedia - far-sightedness)


Kid Facts - Blast from the past: Frenulum of Lower Lip

Near-Sightedness

We just learned about the Refractive Error.

One of the types of refractive errors is Near-Sightedness, also called myopia.

If someone is near-sighted that means they can see up close very well, but they can't see far away very well.
An easy way to remember that is that if you are "near-sighted" you are good at seeing nearby.

Of all the types of eye problems, more people are near-sighted than any other problem, about 1.5 billion people!

When light comes into the eye, the lens is supposed to try and make it focus right on the retina.
The lens is like a magnifying glass, and if it doesn't focus just right then it won't get a clear enough picture.

If the lens is focusing all of the light into a point before the retina, then this causes near-sightedness.
An eye doctor can make glasses to change the direction of the light coming into the eye so that it focuses right on the retina and helps the eye see near and far.


(from: wikipedia - near-sightedness)


Kid Facts - Blast from the past: White Roll

Refractive Error

We just learned about the Myokymia.

Another part of how the eye works is a Refractive Error.

Some people have better vision than others and can see farther, closer or more clearly.

The reason some people have problems seeing is because the shape of the eyeball is not perfect, or because a person is old and their eye muscles aren't working as well as they used to.

The eye needs to be able to focus on things far away or up close, and switch between the two.
If you use a camera sometimes you can see that it is blurry at first and then focuses.

Refraction means how the eye changes the direction and size of the light coming into the eye.

All of the different parts of the eye have to work together to get the picture right and send it to your brain.
If one of them is not right, then your eyes have a refractive error and you can wear glasses to see better.


(from: wikipedia - refractive error)


Kid Facts - Blast from the past: Philtrum

Myokymia

We just learned about the Rheum.

Another part of the eye is a Myokymia, which is a type of eye spasm where the eyelid twitches.

Sometimes without doing it on purpose the upper or lower eyelid might twitch a little.
It usually goes away after a while, and is usually caused by not getting enough sleep or not drinking enough water.

If it is really bad and doesn't go away for months, then it is called a blepharospasm.


(from: wikipedia - blepharospasm)


Kid Facts - Blast from the past: Vermillion Border

Rheum

We just learned about the Eyelash.

Another part of the eye is Rheum.

This is what some people call sleep, sleepy seeds, sleepy bunds, sleepy sand, eye goop, sleep dust or sleepy dirt.

Sometimes when you wake up in the morning there is some hard crusty thing by the inside corner of your eye.
It is hard almost like a piece of sand, and you can wipe it away.

This is called rheum, and it is just the oils that come from your glands building up and drying by your eye.
These oils are coming out all day long, but when you blink they get spread out on your eye or they dry up.
When you sleep you aren't blinking so it dries up and gets crusty.

In the old days people made up a person called the Sandman that comes around and sprinkles sand on the eyes of kids to bring them good dreams.
When you wake up in the morning, that's the leftover sand from the sandman.


(from: wikipedia - sandman)


Kid Facts - Blast from the past: Cupid's Bow

Eyelash

We just learned about the Bulbar Conjunctiva.

Another part of the eye is the Eyelash, also called the cilium.

The hair on the eyelids helps protect the eyes from dust and other things that might fly into it.
There are three layers of eyelids on the edge of the eyelids.

Eyelashes grow on the body even before a person is born.
They do not keep growing forever, they stop after growing out a little.
These hairs take about 7 to 8 weeks to grow, and after a while they will fall out and new ones will grow in the same place.


(from: wikipedia - eyelash)


Kid Facts - Blast from the past: Lips

Bulbar Conjunctiva

We just learned about the Lacrimal Lake.

Another part of the eye is the Bulbar Conjunctiva.

This is a very thin layer of skin on top of the white sclera that helps bring tears to the eye, and also has blood vessels coming into the eye.


(from: wikipedia - conjunctiva)


Kid Facts - Blast from the past: Palatine Raphe

Lacrimal Lake

We just learned about the Canthus.

Another part of the eyes is the Lacrimal Lake.

This is in the inside corner of the eyes, where the tears pool up before they spill over onto the cheeks.


(from: wikipedia - lacrimal lake)


Kid Facts - Blast from the past: Incisive Papilla

Canthus

We just learned about the Meibomian Gland that helps keep your eyes wet.

Another part of the eye is the Canthus, or canthi for both of them.

This is the inner and outer corners of your eyes, where your upper and lower eyelids meet.

Remember the eyelids are called the palpebra, and another name for the canthus is the palpebral commissure.
The inner canthus is the "medial" palpebral commisure, and the outer canthus is the "lateral".


(from: wikipedia - canthus)


Kid Facts - Blast from the past: Palatal Rugae

Meibomian Gland

We just learned about the Epicanthic Fold.

Another part of the eye is the Meibomian Gland.

Just inside the top and bottom eyelids are some small glands that help keep your eyes wet.
They let out a little bit of oily liquid called meibum that helps spread around the water tears that come out, help keep the tears from spilling over onto your face, and help keep the water from just evaporating.

If someone is having problems with their meibomian glands they can get really dry eyes.
The word "meibomian" was named after the person who discovered the glands, Heinrich Meibom.

(from: wikipedia - meibomian gland)


Kid Facts - Blast from the past: Soft Palate

Epicanthic Fold

We just learned about the Eyelids.

Another part of the eye is the Epicanthic Fold.

The skin above the eyelid for some people is folded over and lays over the top of the eyelid.

This happens more for some people depending on where they come from.
Asian people from countries like China or Japan usually have a bigger epicanthic fold than people form North America or Europe.


(from: wikipedia - epicanthic fold)


Kid Facts - Blast from the past: Hard Palate

Eyelids

We just learned about the Nasolacrimal Duct.

Another part of the eye is the Eyelid, also called the palpebra, or palpabrea for both eyelids.

The upper eyelid is called the palpebra superior, and the lower is the inferior.

The job of the eyelids is to help protect the eye from wind, dirt or liquids, to help spread tears around the eye, and to close so that we can sleep at night.

Some people put makeup on their eyelids to color them, and some people even have plastic surgery on their eyelids to make them look higher or lower.


(from: wikipedia - eyelid)


Kid Facts - Blast from the past: Sublingual Caruncle

Nasolacrimal Duct

We just learned about the Lacrimal Sac.

Another part of how the eyes work is the Nasolacrimal Duct.

Remember tears in the eye go into the lacrimal punctum, through the lacrimal duct and then to the lacrimal sac.
After that they drain out into the nasal cavity through the nasolacrimal duct.

If you cry too much and there are too many tears, the nasal cavity will overflow, giving you a runny nose.
This is why sometimes if you cry a lot it makes your nose run.


(from: wikipedia - nasolacrimal duct)


Kid Facts - Blast from the past: Fimbriated Fold

Lacrimal Sac

We just learned about the Lacrimal Ducts which take the tears from the lacrimal punctum that drain from the eye.

The tears next go into the Lacrimal Sac.

This is a small place like a balloon that fills up with tears from the eye, before they are drained out.


(from: wikipedia - lacrimal sac)


Kid Facts - Blast from the past: Frenulum

Lacrimal Ducts

We just learned about the Lacrimal Punctum.

Another part of the eye is the Lacrimal Ducts, also called the lacrimal canals or lacrimal canaliculi.

When the water in your eyes from tears goes into the lacrimal punctum hole in your eyelid, it goes into the lacrimal ducts.
These are like little tubes that bring the water away from your eyeball.


(from: wikipedia - lacrimal canaliculi)


Kid Facts - Blast from the past: Foramen Cecum

Lacrimal Punctum

We just learned about the Lacrimal Gland.

Another part of the eye is the Lacrimal Punctum.

When tears come out of the lacrimal gland, they help keep the eye nice and wet.
If the tears do not run down your face, they will actually drain out through a hole in your lower eyelid called the lacrimal punctum.


(from: wikipedia - lacrimal punctum)


Kid Facts - Blast from the past: Sulcus Terminus

Lacrimal Gland

We just learned about the Depth Perception.

Another part of the eye is the Lacrimal Gland, also called the caruncula lacrimalis.

The word lacrimal comes from the latin word for tears like when you cry.
This gland is up above your eye, right behind the bone where your eyebrow is.

When you cry, this gland makes the tears that flow into your eyeball and make it all wet.


(from: wikipedia - lacrimal gland)


Kid Facts - Blast from the past: Median Sulcus

Depth Perception

We just learned about Rapid Eye Movement.

Another part of how eyes work is Depth Perception.

Because humans have two eyes that are set apart from each other, they can look at the world and tell if something is close and if something is far away.

With just one eye it is very hard to tell that, but because two eyes are looking at something from different angles, the human brain can use those two different pictures and figure out if something is close or far.


(from: wikipedia - depth perception)


(from: wikipedia - binocular vision)


Kid Facts - Blast from the past: Foliate Papillae

Rapid Eye Movement

We just learned about eye movement of Smooth Pursuit.

Another part of eye movement is Rapid Eye Movement also called REM.

Sometimes when a person is sleeping, their eyes will move around quickly in a bunch of different directions over and over again for a while.
The quick or rapid eye movement also happens at the same time as a lot of activity in the brain even while you are asleep.
Some scientists think that REM is what happens when you are having very active dreams.


(from: wikipedia - rapid eye movement sleep)


Kid Facts - Blast from the past: Foliate Papillae