This is the best video that I have found on how the eye focuses. I am extremely grateful to Dr. Blackwell for providing it.

My Opthalmic Tech job brought me here. The human eye is the most beautiful thing I have ever seen, magnified!

Dr. Blackwell, you have the kindest voice.

Just the right amount of information for the normal person. I also like your conversational voice. Thanks for posting.

Thanks for the nice, clear video. I love the use of a beautiful painting for showing the mechanism of tearing.

The best video I have seen on this subject for which I have to write an essay. It is really clearing things up for me thank you!

wow. great video! incredibly informative, easy to follow and understand. thank you so much for sharing. this give's me a whole new understanding of what it is to be a living organism! what an amazing device. and a flexible lens that can change shape! and how we don't have to contract and relax our iris muscles, but that they function on their own according to how much light there is! incredible. absolutely incredible.

I found this video to be very instructional. I am having cataract surgery next week and this video explained alot. Thank you for the information and I found your voice to be very calming.

This is great. I teach medical students and this really explains things well.

Thank you for such clear explanations. This video has been extremely beneficial throughout my studies.

Great Video! Wonderfully clear explanation!

Thank you for this video. It was very well explained and is the only video I need. This is the most in-depth analysis I have seen so far, good work, keep it up

You must be a passionate doctor and teacher . Thank you for your wonderful video. I could use this video to explain how to protect their eyes to the kids in my daughter's class.

Gary, don't worry, it's not scary. Measurement is painless and takes only a few seconds with a hand held ultrasound device. Corneal thickness varies from person to person just like height. It provides an important correction factor to determine the true intraocular pressure. For more information look at my videos on Glaucoma.

. . . thanks for this one doc! was looking for an animation on the physiology of eye accomodation. you video is indeed a perfect complement with Guyton's explanation.

The iris looks like an amazingly superstructure with many fibrous elements in a network arrangement. With paler eye color, these iris elements appear white. Is this the color of the smooth muscle? It is unimaginable to have different colors of these smooth muscle in different colored eyes. So the smooth muscle should be all white with different pigments that end up differently colored eyes? Are the smooth muscles are single fibers or in thin fiber bundles like the skeletal muscle?

Thanks. Guyton, one of the best books in med school. (Though my edition was an early one.)

An excellent review!

im in love with the iris

Hi Craig, That is indeed my friend's father. I did not realize the book has been such and outstanding success!

Dr, a couple of questions, if i may. 62 year old male with a cataract in left eye. i can barely pass the CA DMV eye test from the counter, which i did in April 2016. my vision is cloudy, foggy in this eye. what kind of IOL do you suggest? i am retired, don't do much vehicular driving and am not out much at night. what is a basic IOL called? any specific brand? secondly, does all cataract surgery come with a new IOL? Great videos. many thanks.

you literally just saved me. Amazing video

omg i was getting so confused on what specifically is th retinas job and this helps so much:)

Well done, 🥰👌👌🖐👋🖐👋✌✌✌👍👍

Thanks for the answer. My qustion was more geared towards how the eye reacts to focusing up close while wearing glasses(since I dont need them to see up close). You said this wont harm my eyes, but is it not true my eye will have to compensate someone for viewing up close with classes? If I wear glasses all the time could if actually cause my lens to degrade more quickly then it would normally?

Excellent video !

Makes sense, thanks for the response.

Thanks, greay way to understand how vision works.

Best video I have found in a long time. Thank you for this!

Craig, Your two introduction videos on how the eye works will be great for my AP Psychology classes. Thanks!

Good video thanks for posting! This definitely helped me in my anatomy class.

Great video. I am really glad that I found this!

Do you know why irises appear to have different structure? I have been looking at macro photos of eyes and they are fascinating.

Think about it this way. With your glasses on your focusing muscles are doing the same amount of work as someone who isn't near-sighted. With them off the muscles do a bit less work than someone who doesn't have the advantage of being near-sighted. But they are designed to do that work. No harm is expected. Lens damage comes from other things like UV exposure and diabetes.

Very instructive video. Many thanks!

I dont know if anyone one on here would known but I really need to know something. I have distance problems and just got glasses. Im trying to figure out if looking up close actually stresses my lens(im young). Since I can see up close Im a bit confused how my lens adjusts of if it does extra work since my distance visor is now magnified.

nice video. it really helped me in when i was doing surgery in Nigeria. Thanks a lot Craig Blackwell

i have got kerotoconus and im only 23. my cornea is basically like a vone instead of a dome. but i am having cxl to stp the condition

it's really nice well explained really liked it...!!

Thank you for your video sir it's so useful to understand the subject matter😎

Take my like and my subscription, very informative video. :)

thank you for your video...awesome

Question. Is it possible to focus one eye at a time? They are not mechanically linked. So it should be possible?

thanks, this helped a lot.

Is pupil is the part of or made from lens....??

Wow! Thank you Craig - bless your heart for making such an informative video! 5 Stars!

Hi Doctor, why is it that no light can enter my eye after an eye accident, is it a problem with my cornea, lens, or could it be internal blood staining of the working parts of my eye.?

Amazing how complex some so tiny as the eye is

How do people have texture in the iris when taking photos? It doesnt look I have any at all. It looks like I just have black eyes and it does not look cool to me. I have asian in me and idk if it has something to do with or not.

But why don't we see the space around the object, I mean if light rays are bouncing off randomly from all parts of the object then these rays would coincide at several points in space around the object so why don't our eyes focus these mixed rays coming from different-different parts over the retina, making those points visible? How our eye lens treats light rays from different parts seperately?

I have just been told that I have raised pressure in both eyes. I was told they will propbably do tests to determine the thickness of the Cornea. What does this involve. I was born with Nystagmus and Astigmatism, and I am in my mid 50's. I am a little apprehensive about what I might need to have done. I have had the field vision test and had Tonometrey pressure test done twice, which gave a reading of around 26, but I don't know what that means. He told me anything above 21 is considered to be high. I passed the field vision test, for peripheral vision, but my eye pressure is what he would call on the high side. Can anyone help?

fantastic video

An excellent exploration. Thank you for this most informative discussion. Billy Weprin

Our eyes are fiber optic pictures of our brains

Hi Craig, I was curious about the name of the book by Dr. Guyton. I have a friend by that name - and I think they are related! Thanks!

TC, if your vision is blurred at distance, but clear up close, then you are likely to be 'near-sighted.' Your focusing muscles and Lens are designed to work together to change focus. WS was correct, except for the eye strain. If you are young you have a lot of reserve for close focus; no harm results whether you read with or without glasses. Your optometrist was explaining that the ability of the Lens to change shape decreases (linearly) with time. Unfortunately, not much you can do about it.

awesome vid

This video is great i can learn this video for my science subject.

I like they used Renaissance paintings as examples

This is a pleasant presentation.

So your saying that when I look up close with glasses this can cause strain to my eye? Im a young guy 23 and my optometrist just said you will be fine to see up close because your lens adjusts(over 40 and you may need bifocals). When I look up close with my glasses I can see just as clear as without them but it just confuses me how my eye can do this when the glasses magnify my vision in a sense.

Where good lecture.Thank you.

Thank you sir

thanks alot , alot of thing became clearer

loss sight over night as is all is now like a 40 watt sun now. My pupils was changed to square on one eye . A diifernt size but both eyes did same of darkness over night. I saw eye fella he nice person.

study the eye study the soul

This is an awesome video.. helped me with my test. Thnx for posting this EPIC CHIZZ

i enjoyed this video though thanks doc :]

Textbook of Medical Physiology by Arthur Guyton. Now in its 11th edition, authors Guyton and Hall. (Note: Unfortunately migraine explanation is out of date.)

Can you Sir ,make some videos on the basics of slit lamp exam ,please

If you're a fairly normal case, your eyes are able to focus normally, but your cornea is oddly shaped. Glasses undo this optical variation. I'm assuming you're nearsighted, since you mention "Up Close". Your eyes do need to focus more for the same distance with your glasses on, since the glasses lens is directing focus farther out. This can easily cause eye strain. I would recommend removing your glasses in cases where you need to inspect something closely.

Thanx

Cool. You might also want to take a look at the color vision series, really interesting subject. A lot of visual physiology work is done in psychology departments.

It's not like while it was saying about distance focusing I was pulling my iPod really close to my eye. On lowest light, of course.

Thank you for the kind comment. Where do you teach?

This helped me understand my lessons thanks for vid brah

Tq sir

Sir I've visual acuity of 20/200😒 Wt shud I do

Thank you for the kind comment. How is ophthalmology in Nigeria?

if this video is accurateThat means the problem with myopic patients is their focusing muscles do not relax well enough so the lens is always rounder not flatter

Can anyone imagine how would b our creator who created this small thing??? "That's the reason today scientists are not rejecting the GOD they are rejecting the MODELS OF GOD.... Alhamdulillah (Praise be to GOD)

Cell

I think that doing surgery on your eyes are crazy. I watched a video the other day and it was fun yet disgusting to watch