0:00:00.875,0:00:02.809
Every single one of us will lose

0:00:02.833,0:00:06.684
or has already lost something[br]we rely on every single day.

0:00:06.708,0:00:09.518
I am of course talking about our keys.

0:00:09.542,0:00:11.184
(Laughter)

0:00:11.208,0:00:12.476
Just kidding.

0:00:12.500,0:00:16.309
What I actually want to talk about is one[br]of our most important senses: vision.

0:00:16.333,0:00:19.143
Every single day we each lose[br]a little bit of our ability

0:00:19.167,0:00:20.476
to refocus our eyes

0:00:20.500,0:00:22.809
until we can't refocus at all.

0:00:22.833,0:00:24.809
We call this condition presbyopia,

0:00:24.833,0:00:27.351
and it affects two billion[br]people worldwide.

0:00:27.375,0:00:29.518
That's right, I said billion.

0:00:29.542,0:00:31.268
If you haven't heard of presbyopia,

0:00:31.292,0:00:34.101
and you're wondering,[br]"Where are these two billion people?"

0:00:34.125,0:00:36.226
here's a hint before[br]I get into the details.

0:00:36.250,0:00:39.518
It's the reason why people wear[br]reading glasses or bifocal lenses.

0:00:39.542,0:00:42.400
I'll get started by describing[br]the loss in refocusing ability

0:00:42.424,0:00:43.934
leading up to presbyopia.

0:00:43.958,0:00:46.184
As a newborn, you would have[br]been able to focus

0:00:46.208,0:00:48.351
as close as six and a half centimeters,

0:00:48.375,0:00:49.643
if you wished to.

0:00:49.667,0:00:52.809
By your mid-20s, you have about[br]half of that focusing power left.

0:00:52.833,0:00:54.101
10 centimeters or so,

0:00:54.125,0:00:56.684
but close enough that you never[br]notice the difference.

0:00:56.708,0:00:57.976
By your late 40s though,

0:00:58.000,0:01:00.351
the closest you can focus[br]is about 25 centimeters,

0:01:00.375,0:01:01.643
maybe even farther.

0:01:01.667,0:01:03.768
Losses in focusing ability[br]beyond this point

0:01:03.792,0:01:06.018
start affecting near-vision[br]tasks like reading,

0:01:06.042,0:01:07.643
and by the time you reach age 60,

0:01:07.667,0:01:10.018
nothing within a meter[br]radius of you is clear.

0:01:10.042,0:01:12.309
Right now some of you[br]are probably thinking,

0:01:12.333,0:01:15.643
that sounds bad but he means[br]you in a figurative sense,

0:01:15.667,0:01:19.101
only for the people that actually[br]end up with presbyopia.

0:01:19.125,0:01:23.559
But no, when I say you, I literally mean[br]that every single one of you

0:01:23.583,0:01:26.809
will someday be presbyopic[br]if you aren't already.

0:01:26.833,0:01:28.226
That sounds a bit troubling.

0:01:28.250,0:01:31.934
I want to remind you that presbyopia[br]has been with us for all of human history

0:01:31.958,0:01:34.768
and we've done a lot[br]of different things to try and fix it.

0:01:34.792,0:01:38.684
So to start, let's imagine[br]that you're sitting at a desk, reading.

0:01:38.708,0:01:40.059
If you were presbyopic,

0:01:40.083,0:01:42.143
it might look a little[br]something like this.

0:01:42.167,0:01:45.059
Anything close by,[br]like the magazine, will be blurry.

0:01:45.083,0:01:46.434
Moving on to solutions.

0:01:46.458,0:01:48.101
First, reading glasses.

0:01:48.125,0:01:50.184
These have lenses[br]with a single focal power

0:01:50.208,0:01:52.601
tuned so that near objects[br]come into focus.

0:01:52.625,0:01:55.226
But far objects[br]necessarily go out of focus,

0:01:55.250,0:01:57.726
meaning you have to constantly[br]switch back and forth

0:01:57.750,0:01:59.518
between wearing and not wearing them.

0:01:59.542,0:02:00.809
To solve this problem

0:02:00.833,0:02:04.101
Benjamin Franklin invented[br]what he called "double spectacles."

0:02:04.125,0:02:06.226
Today we call those bifocals,

0:02:06.250,0:02:09.684
and what they let him do[br]was see far when he looked up

0:02:09.708,0:02:11.434
and see near when he looked down.

0:02:11.458,0:02:14.434
Today we also have progressive lenses[br]which get rid of the line

0:02:14.458,0:02:17.059
by smoothly varying the focal power[br]from top to bottom.

0:02:17.083,0:02:18.518
The downside to both of these

0:02:18.542,0:02:21.143
is that you lose field of vision[br]at any given distance,

0:02:21.167,0:02:23.768
because it gets split up[br]from top to bottom like this.

0:02:23.792,0:02:25.184
To see why that's a problem,

0:02:25.208,0:02:28.059
imagine that you're climbing[br]down a ladder or stairs.

0:02:28.083,0:02:31.684
You look down to get[br]your footing but it's blurry.

0:02:31.708,0:02:33.101
Why would it be blurry?

0:02:33.125,0:02:36.559
Well, you look down[br]and that's the near part of the lens,

0:02:36.583,0:02:39.143
but the next step was past arm's reach,

0:02:39.167,0:02:41.268
which for your eyes counts as far.

0:02:41.292,0:02:44.184
The next solution I want to point out[br]is a little less common

0:02:44.208,0:02:46.601
but comes up in contact lenses[br]or LASIK surgeries,

0:02:46.625,0:02:47.976
and it's called monovision.

0:02:48.000,0:02:50.518
It works by setting up[br]the dominant eye to focus far

0:02:50.542,0:02:52.143
and the other eye to focus near.

0:02:52.167,0:02:54.976
Your brain does the work[br]of intelligently putting together

0:02:55.000,0:02:56.976
the sharpest parts from each eye's view,

0:02:57.000,0:02:59.268
but the two eyes see[br]slightly different things,

0:02:59.292,0:03:01.934
and that makes it harder[br]to judge distances binocularly.

0:03:01.958,0:03:03.351
So where does that leave us?

0:03:03.375,0:03:05.226
We've come up with a lot of solutions

0:03:05.250,0:03:07.851
but none of them quite restore[br]natural refocusing.

0:03:07.875,0:03:09.934
None of them let you[br]just look at something

0:03:09.958,0:03:11.434
and expect it to be in focus.

0:03:11.458,0:03:12.809
But why?

0:03:12.833,0:03:14.101
Well, to explain that

0:03:14.125,0:03:16.851
we'll want to take a look[br]at the anatomy of the human eye.

0:03:16.875,0:03:20.101
The part of the eye that allows us[br]to refocus to different distances

0:03:20.125,0:03:21.684
is called the crystalline lens.

0:03:21.708,0:03:25.559
There are muscles surrounding the lens[br]that can deform it into different shapes,

0:03:25.583,0:03:27.684
which in turn changes its focusing power.

0:03:27.708,0:03:30.184
What happens when someone[br]becomes presbyopic?

0:03:30.208,0:03:32.434
It turns out that[br]the crystalline lens stiffens

0:03:32.458,0:03:35.143
to the point that it doesn't[br]really change shape anymore.

0:03:35.167,0:03:38.893
Now, thinking back[br]on all the solutions I listed earlier,

0:03:38.917,0:03:42.643
we can see that they all have[br]something in common with the others

0:03:42.667,0:03:44.143
but not with our eyes,

0:03:44.167,0:03:46.184
and that is that they're all static.

0:03:46.208,0:03:49.101
It's like the optical equivalent[br]of a pirate with a peg leg.

0:03:49.125,0:03:52.268
What is the optical equivalent[br]of a modern prosthetic leg?

0:03:52.292,0:03:55.559
The last several decades have seen[br]the creation and rapid development

0:03:55.583,0:03:58.268
of what are called "focus-tunable lenses."

0:03:58.292,0:03:59.976
There are several different types.

0:04:00.000,0:04:01.809
Mechanically-shifted Alvarez lenses,

0:04:01.833,0:04:03.268
deformable liquid lenses

0:04:03.292,0:04:05.851
and electronically-switched,[br]liquid crystal lenses.

0:04:05.875,0:04:07.684
Now these have their own trade-offs,

0:04:07.708,0:04:10.309
but what they don't skimp on[br]is the visual experience.

0:04:10.333,0:04:13.601
Full-field-of-view vision that can be[br]sharp at any desired distance.

0:04:13.625,0:04:15.768
OK, great. The lenses we need[br]already exist.

0:04:15.792,0:04:17.684
Problem solved, right?

0:04:17.708,0:04:19.143
Not so fast.

0:04:19.167,0:04:22.143
Focus-tunable lenses add a bit[br]of complexity to the equation.

0:04:22.167,0:04:26.018
The lenses don't have any way of knowing[br]what distance they should be focused to.

0:04:26.042,0:04:27.351
What we need are glasses

0:04:27.375,0:04:29.934
that, when you're looking far,[br]far objects are sharp,

0:04:29.958,0:04:31.268
and when you look near,

0:04:31.292,0:04:33.726
near objects come into focus[br]in your field of view,

0:04:33.750,0:04:35.601
without you having to think about it.

0:04:35.625,0:04:38.143
What I've worked on[br]these last few years at Stanford

0:04:38.167,0:04:40.768
is building that exact intelligence[br]around the lenses.

0:04:40.792,0:04:44.393
Our prototype borrows technology[br]from virtual and augmented reality systems

0:04:44.417,0:04:45.934
to estimate focusing distance.

0:04:45.958,0:04:49.601
We have an eye tracker that can tell[br]what direction our eyes are focused in.

0:04:49.625,0:04:52.434
Using two of these, we can[br]triangulate your gaze direction

0:04:52.458,0:04:53.768
to get a focus estimate.

0:04:53.792,0:04:55.976
Just in case though,[br]to increase reliability,

0:04:56.000,0:04:57.559
we also added a distance sensor.

0:04:57.583,0:04:59.976
The sensor is a camera[br]that looks out at the world

0:05:00.000,0:05:01.601
and reports distances to objects.

0:05:01.625,0:05:04.601
We can again use your gaze direction[br]to get a distance estimate

0:05:04.625,0:05:05.893
for a second time.

0:05:05.917,0:05:07.893
We then fuse those two distance estimates

0:05:07.917,0:05:10.393
and update the focus-tunable[br]lens power accordingly.

0:05:10.417,0:05:13.351
The next step for us was[br]to test our device on actual people.

0:05:13.375,0:05:16.518
So we recruited about 100 presbyopes[br]and had them test our device

0:05:16.542,0:05:18.351
while we measured their performance.

0:05:18.375,0:05:21.643
What we saw convinced us right then[br]that autofocals were the future.

0:05:21.667,0:05:25.018
Our participants could see more clearly,[br]they could focus more quickly

0:05:25.042,0:05:28.059
and they thought it was an easier[br]and better focusing experience

0:05:28.083,0:05:29.559
than their current correction.

0:05:29.583,0:05:31.643
To put it simply, when it comes to vision,

0:05:31.667,0:05:34.893
autofocals don't compromise[br]like static corrections in use today do.

0:05:34.917,0:05:36.851
But I don't want to get ahead of myself.

0:05:36.875,0:05:39.601
There's a lot of work[br]for my colleagues and me left to do.

0:05:39.625,0:05:41.893
For example, our glasses are a bit --

0:05:41.917,0:05:42.934
(Laughter)

0:05:42.958,0:05:44.309
bulky, maybe?

0:05:44.333,0:05:47.684
And one reason for this[br]is that we used bulkier components

0:05:47.708,0:05:50.518
that are often intended[br]for research use or industrial use.

0:05:50.542,0:05:52.809
Another is that we need[br]to strap everything down

0:05:52.833,0:05:56.643
because current eye-tracking algorithms[br]don't have the robustness that we need.

0:05:56.667,0:05:57.976
So moving forward,

0:05:58.000,0:06:00.476
as we move from a research[br]setting into a start-up,

0:06:00.500,0:06:02.434
we plan to make future autofocals

0:06:02.458,0:06:05.018
eventually look a little bit more[br]like normal glasses.

0:06:05.042,0:06:08.393
For this to happen,[br]we'll need to significantly improve

0:06:08.417,0:06:10.559
the robustness[br]of our eye-tracking solution.

0:06:10.583,0:06:14.768
We'll also need to incorporate smaller[br]and more efficient electronics and lenses.

0:06:14.792,0:06:16.976
That said, even with[br]our current prototype,

0:06:17.000,0:06:19.726
we've shown that today's[br]focus-tunable lens technology

0:06:19.750,0:06:23.309
is capable of outperforming[br]traditional forms of static correction.

0:06:23.333,0:06:24.976
So it's only a matter of time.

0:06:25.000,0:06:27.059
It's pretty clear that in the near future,

0:06:27.083,0:06:30.143
instead of worrying about which pair[br]of glasses to use and when,

0:06:30.167,0:06:32.708
we'll be able to just focus[br]on the important things.

0:06:33.667,0:06:34.934
Thank you.

0:06:34.958,0:06:36.583
(Applause)