Eye Doctor Answers Eye Questions From Twitter

I'm ophthalmologist Ashley Brissette.

Let's answer some questions from Twitter.

This is Eye Support.

[upbeat music plays]

@EvanMurphy asks, how does LASIK eye surgery even work?

Like what?

How does that just let you see?

Well, I'll tell you how it works.

I perform LASIK and I even had LASIK done on myself.

What LASIK does is it helps to remove microscopic layers

of tissue on the surface of the cornea

to better direct the light

as it enters the eye so that it's focused in your retina.

The biggest risk is risk of infection.

Although it's quite rare, less than one

in 1000 people would ever develop an infection.

@JJDGMN asks, what do eyeballs feel like?

I mean, the closest thing I can think

that it feels like is a grape.

If you peel back a layer here,

you can see how delicate this tissue is.

So if you were gonna squeeze an eye,

it would kind of have the same squishy consistency

of a grape.

It's filled with a jelly, which is called the vitreous,

and then the tissue layers of the eye are really

really thin, almost like this thin outer layer of the grape.

When we're learning how to do surgery,

sometimes we practice certain techniques

on things like grapes.

@JuniorBarnaby asks,

how do ophthalmologists know babies need glasses?

One way we can tell that babies need glasses

is their eyes are crossing, turning in, or turning out.

Another reason we can tell

that babies can't see or might need glasses

is if they're rubbing their eyes a lot.

Sometimes babies rub their eyes a ton

'cause they're trying to stimulate vision.

Another reason is if babies are tilting their heads

or if they're not fixating on objects.

Usually by about three months,

babies should be able to see a toy or an object

and kind of fixate on it and follow it

if you move it around.

@mark_swisher_ asks,

what is the anatomical purpose of eyelashes?

Eyelashes actually exist to help trap all the dust,

pollution, bacteria, allergens that exist in the environment

so that they don't hit the surface of the eye.

It's actually proven

that eyelashes should be a specific length.

If your eyelashes are too long,

it's trapping too much of that in the environment

and it can sit there and cause irritation on the eyes.

That's why it's so important to be washing

over your closed eyelids every morning

and evening to remove all that's been trapped

in the eyelids and lashes.

@TransReginaL asks,

my right eye twitches, is this anxiety or nervousness?

Twitching is what's called myokymia.

Eyelids twitch for a number of reasons.

The most common is because of lack of sleep,

too much caffeine, or stress.

The muscles that are around the eye are very delicate

and very sensitive to stressors.

@rdabdao asks, what are the dangers

of wearing contact lenses while sleeping?

I always sleep with contacts on.

I don't see any side effects so far.

I have seen terrible damage to vision

from people that sleep in their contact lenses.

Our eyes get their oxygen from the environment

and when you wear your contact lenses for too long,

you deprive the eyes of oxygen.

And that can leave You really prone

to developing an infection.

And you can develop what's called a keratitis,

which is an infection on the cornea,

which is the surface layer of your eye.

It can lead to scarring and permanent damage to your vision.

@kevinclarknw asks,

why does eyesight deteriorate with age?

Eyesight deteriorates with age mostly due to cataract.

It happens to all of us as we get older.

The cataract is the clouding of the lens

which is on the inside of the eye.

This gets more yellow, big and thick as we grow up

and that changes the prescription

and also causes a vision to be blurry.

Cataract is actually the world's leading cause of blindness,

but it's reversible With a surgery.

It's actually the most commonly

performed surgery around the world.

I go inside the eye, remove the cloudy cataract,

and then put a new lens implant

in its place that has your prescription in it.

It's an artificial lens but is really well tolerated,

it's biocompatible, and can help to restore vision.

@KielKnut wants to know what does 20/20 vision mean?

20/20 vision refers

to how we measure your vision on a vision chart.

So most vision charts are set for 20 feet away.

If you can see the 20/20 line,

that means that at 20 feet away from the eye chart,

you can read that line

and we refer to that as normal or perfect vision.

About 35% of the population can only see

that 20/20 line without glasses or contact lenses.

So say if you had 20/50 vision,

which would be this line here.

What that refers to is that

what you would be able to see at 20 feet,

being this line here,

someone with perfect vision

would be able to see at 50 feet away.

Some people can even have better than perfect vision.

So we would refer to that as 20/15 vision.

If you were standing at 20 feet from the eye chart,

the person with normal vision

would only be able to see what you see

if they stood closer at 15 feet to the eye chart.

@noamonothotties asks,

what does legally blind even mean?

Like can you be illegally blind?

Like can you get arrested for being [bleep] blind?

So legally blind refers to vision that is 20/200 or worse.

20/200 is this big E on the chart.

If you are standing 20 feet away from the vision chart,

this is the only letter that you can read.

While somebody with perfect vision

would be able to stand 200 feet away

and also be able to read this E.

This would be vision of 20/200.

@nolsy27 asks, do carrots actually improve your eyesight

or have my parents been lying to me my whole life?

Carrots actually improve your eyesight.

They have betacarotene, which is an important part

of the vitamin A pathway.

There's actually big studies that we've done

that look at nutrients and how they affect your vision.

The main nutrients that are recommended are vitamin A,

vitamin C, vitamin E, lutetium, and zeaxanthin.

These vitamins that are recommended are really important

in the metabolic pathway

of the cells that are in your retina,

which is that vision sensory organ of the inside of the eye.

@axyhus wants to know,

how do people know they're colorblind?

You might know it's not right because you'll start to sense

that there aren't as many differences in colors.

Most people who are colorblind,

it's not that they can't see color,

it's that colors are much more muted.

We can actually test it though.

These are what are called ishihara color plates.

So if you're colorblind,

you might not see this red number six in the sea of green.

Similar to this one,

you might not be able to see the green S in the sea of red.

The most rare form of colorblindness is blue colorblindness.

So you might not be able to see the 10 here

in the sea of blue.

@Ferriby14 wants to know,

Seriously though, where do eye floaters come from?

Eye floaters are a natural part of the eye's anatomy.

Your eye is filled with the jelly,

it's called the vitreous.

This jelly starts to liquefy as we grow up.

When it liquefies, you get clumps of cells and collagen

which are in this jelly that clump together

and then cast a shadow on the retina.

So the floater that you're seeing moving around

is just kind of a clump of cells

in this now liquified vitreous jelly

casting a shadow in the back of your eye.

@ms_claire18 asks, where do these tears come from?

Tears come from the lacrimal glands.

It's a gland that is

in the upper outer corner of your eyelid.

The purpose of tears is to help keep your eyes lubricated.

Our eyes need to be lubricated

for us to see clearly through.

That's why people that have dry eye

feel like their vision is blurry

and their eyes feel really uncomfortable.

@meg_stand asked,

I hate having to get my pupils dilated at the eye doctor.

What is the purpose of that

other than giving me a migraine?

The reason we need to dilate your eyes is to take a look

inside the back of your eye.

As you can tell, the pupil,

it's really hard to see through it if it's small.

So by using the chemicals phenylephrine and tropicamide,

they help to dilate that iris muscle

so that I can actually see into the back of your eye.

That's why it's so uncomfortable when you leave the office.

Your pupils are really dilated,

so much light is getting through.

The way that I can see in the back of your eye

is by using a light on a microscope device such as this,

which can then magnify the view into the back of the eye.

We can tell a lot about your total body health.

So I can learn if you have high blood pressure,

if you have diabetes,

even sometimes some autoimmune conditions.

This is showing a normal eye.

This is the retina,

which is like the back wallpaper lining layer of the eye.

These are all the blood vessels,

which look really normal and healthy.

Here is the nerve.

That's the cable that connects the eye to the brain,

that sends the visual signals to your brain.

In contrast, this is actually a photo

of an eye with diabetes.

There's some bleeding spots.

The blood vessels look what we call tortuous,

which means that they're a little bit twisted,

and all of these yellow deposits here are swelling

or what we refer to as exudates.

As you can imagine, all of this here can actually

cause damage to the vision.

@SeeParty25 wants to know,

What's the difference between an ophthalmologist,

an optometrist, and an optician?

So an ophthalmologist goes to medical school,

they perform any medical procedures,

and they do surgery on eyes as well,

such as LASIK, cataract surgery, glaucoma surgery.

Optometrists go to optometry school.

So they do general eye care, glasses prescriptions,

and contact lenses prescriptions.

And an optician is someone who makes the glasses.

@SerenaMailes asks, are eyelash extension safe?

So my answer is sometimes.

If you have the lash extensions on and they're too long,

it's keeping too much of the bacteria

and dust and pollution that gets trapped in them.

That just leads to bacterial overgrowth

and eventually infections.

I also see a lot of damage that people get

from the chemicals that are used

in terms of gluing them onto your natural lashes.

And sometimes I'm seeing people's natural lashes fall out

because of an issue With an allergy to the glue.

The lashes can grow back.

So if your eyelashes fall out

it takes about two months for them to come back.

If you're really gonna play around with beauty trends,

only do it for a special occasion

and then give your eyes a break.

@LeonPaws_FFXIV wants to know,

What's the difference between near and farsighted?

Nearsighted is when you can see up close

but it's really difficult to see far away.

That's actually the most common prescription error

that most people have.

Farsighted is when you're able to see somewhat far away

but really difficult seeing up close.

@Alexxisk97 asks,

question for optometrists out there -

Why do I see shapes and colors when I rub my eyes?

What actually is that?

The eyes filled with a jelly and when you press on the eye

the jelly then presses on the retina and it stimulates it,

similar to like if light entered the eye to stimulate it.

This is where those rods and cones,

those photo receptors are.

So it's why it's important not to be rubbing your eyes

'cause you're kind of just squishing your eyeball.

@DodgesonisHere asks,

I've never understood how marijuana can be

an effective treatment for glaucoma.

Like how is extreme paranoia supposed to help your eyes?

Marijuana is not a recommended treatment for glaucoma.

Yes, marijuana can have a very small,

very temporary effect of lowering your eye pressures.

We know that high eye pressure is a risk factor

for glaucoma, but marijuana only lowers it

for a really short period of time

and not enough that would actually be of any benefit.

@YashArchive wants to know,

how did the eye test work?

I mean, they do so many seemingly random things?!

The first thing that we test

when you come for an eye exam is the vision.

So they'll flip back and forth

between the different prescriptions

to see what prescription do you actually need.

What these lenses do is they help to focus the light

so that it lands right on the back

of the eye so that it brings everything into focus for you.

Then we test your eye pressure.

That's that puff of air test

that everybody hates having done.

When the air puff test hits the front of the eye,

it's actually measuring how much it decompresses the front

of the eye and the rebound.

And that gives us a general sense

of the pressure on the inside of the eye.

We know that high pressure

in the eye can lead to damage in the nerve.

The nerve is the cable that connects to your eye

to your brain, and that's what gets damaged in glaucoma.

The last thing that we're gonna do is look at your eyes

underneath a microscope, which is called a slit lamp.

It's this big machine, you're gonna put your chin

on the chin rest, so we can actually look

inside the back of your eye.

If the nerve is getting bigger,

that's a sign of glaucoma damage.

@phenomenal_nisa asks,

Is the blue light filter actually good for eyes?

There was no evidence

that using the blue light blockers helped

with eye strain with computer use.

It was a great marketing tool

but a big research study came out that showed no benefit

for eye strain using the blue light blockers.

Most of the eye strain occurs because of glare

so you can get an anti-glare cover

for your screen and that can help.

@dpalmer216 asks, what kind of drugs is Zuckerberg on

that his pupils are always dilated?

I never noticed that and I don't wanna get on his bad side.

But there's a few reasons why your pupils dilate,

one is if you're in dim lighting,

and that's to allow more light to enter the eye.

Another reason peoples can dilate is from some medications

or some drugs, stimulants such as cocaine,

MDMA, sometimes even some antidepressants.

It's a side effect of the medications.

Lastly, your pupils sometimes dilate

if you're in love or if you're aroused.

So if you see somebody that you love,

the pupils dilate and that's because you get a release

of dopamine and the dopamine leads to the dilation.

@JustSimplySally asks,

what happens when you look directly at the sun?

So you can sunburn your eyes.

UV damage can occur on the eyeballs.

It can cause something called photo keratitis,

which is a sun damage to the surface of the eye.

But it can also cause damage

to the retina in the back of the eye.

It damages those fine photoreceptors,

which are used for sensing vision.

If you look at the sun for say, longer than 90 seconds

that can cause this damage.

Flavor of Gabby asked,

did you know know that we actually see things upside down

but the sensors that connect

our brain and our eyes flip the image?

Yes, I did know that.

And not only does it flip the image from up and down,

it also flips it from left to right.

Thinking of the eye like a camera,

it actually travels through the entirety of the eye.

The first thing it hits is the cornea,

which is the clear cover layer of the eye.

Then it travels through the lens,

which helps to direct the light raise into the macula,

which is the back part of your retina.

This nerve here is made up of 1.3 million little axons,

which are connections that allow the image to be distributed

through the brain all the way

into the back of your brain called the occipital region.

So by having lots of different input,

lots of different connections from our visual world,

that helps to provide depth of feel, depth of focus,

and gives you really great clarity for your vision.

Next question,

is there a thing where your eyes can change color?

My eyes have never been this light before.

Your eye color is pretty set by about one year of age.

Your eyes can appear to look different colors.

It usually has to do

with the amount of lighting, colors that you're wearing.

The reason why people have different eye colors

is the amount of melanin or pigment in their iris,

which is the colored part of the eye.

So people with blue eyes have less melanin

and people with brown eyes have more melanin.

@only1lvm asks, how do people become cross-eyed?

We call this strabismus.

Strabismus means a turning in or a turning out of the eyes.

You have to be able to see clearly

for your brain to use the two eyes together.

And if one of the eyes isn't seeing very well,

then the brain starts to ignore One of the eyes,

ignores those muscles

and the eye starts to drift or turn.

So those are all the questions for today.

Those were some really great questions.

My biggest pieces of advice,

make sure you're washing over your closed eyelids,

eating well, and just stay healthy.

Thanks for watching Eye Support.