Autofocusing reading glasses of the future

Every single one of us will lose,

or has already lost something
we rely on every single day.

I am of course talking about our keys.

(Laughter)

Just kidding.

What I actually want to talk about
is one of our most important senses:

vision.

Every single day we each lose
a little bit of our ability

to refocus our eyes

until we can't refocus at all.

We call this condition presbyopia,

and it affects two billion
people worldwide.

That's right, I said billion.

If you haven't heard of presbyopia,

and you're wondering, "Where are
these two billon people?"

here's a hint before
I get into the details.

It's the reason why people
wear reading glasses

or bifocal lenses.

I'll get started by describing the loss
of refocusing ability

leading up to presbyopia.

As a newborn,

you would have been able to focus
as lose as six-and-a-half centimenters

if you wish to.

By your mid-20s, you have about
half of that focusing power left.

10 centimeters or so,

but close enough that you never
notice the difference.

By your late-40s though,

the closest you can focus
is about 25 centimeters,

maybe even farther.

Losses in focusing ability
beyond this point

start effecting near-vision
tasks like reading,

and by the time you reach age 60,

nothing within a meter
radius of you is clear.

Right now some of you
are probably thinking,

that sounds bad but he means you
in a figurative sense,

only for the people that actually
end up with presbyopia.

But no, when I say you, I literally mean
that every single one of you

will someday be presbyopic
if you aren't already.

That sounds a bit troubling.

I want to remind you that presbyopia
has been with us for all of human history

and we've done a lot of different
things to try and fix it.

So to start, let's imagine
that you're sitting at a desk reading.

If you were presbyopic,

it might look a little
something like this.

Anything close by,
like the magazine, will be blurry.

Moving on to solutions.

First, reading glasses.

These have lenses
with a single focal power

tuned so that near objects
come into focus.

But far objects necessary go out of focus,

meaning you have to constantly
switch back and forth

between wearing and not wearing them.

To solve this problem,

Benjamin Franklin invented
what he called "double spectacles."

Today we call those bifocals,

and what they let him do was see
far when he looked up

and see near when he looked down.

Today we also have progressive lenses
which get rid of the line

by smoothly varying the focal power
from top to bottom.

The downside to both of these
is that you lose field of vision

at any given distance

because it gets split up
from top to bottom like this.

To see why that's a problem,

imagine that you're climbing
down a ladder or stairs.

You look down to get
your footing but it's blurry.

Why would it be blurry?

Well, you look down, and that's
the near part of the lens,

but the next step was past arm's reach,

which for your eyes, counts as far.

The next solution I want to point out
is a little less common

but comes up a lot in contact lenses
or Lasik surgeries,

and it's called monovision.

And it works but setting up
the dominant eye to focus far

and the other eye to focus near.

Your brain does the work of intelligently
putting together the sharpest parts

from each eye's view,

but the two eyes see slightly
different things,

and that makes it harder
to judge distances binocularly.

So where does that all leave us?

It seems like we've come up with
a lot of different solutions

but none of them quite restore
natural refocusing.

None of them let you
just look at something

and expect it to be in focus.

But why?

Well, to explain that, we'll want
to take a look at the anatomy

of the human eye.

The part of the eye that allows us
to refocus to different distances

is called the crystalline lens.

There are muscles surrounding the lens
that can deform it into different shapes,

which in turn changes its focusing power.

What happens when someone
becomes presbyopic?

It turns out that the crystalline
lens stiffens to the point

that it doesn't really change
shape anymore.

Now, thinking back
on all the solutions I listed earlier,

we can see that they all have something
in common with the others

but not with our eyes,

and that is that they're all static.

It's like the optical equivalent
of a pirate with a peg leg.

What is the optical equivalent
of a modern prosthetic leg?

The last several decades have seen
the creation and rapid development

of what are called "focus-tunable lenses."

There are several different types.

Mechanically-shifting Alvarez lenses,

deformable liquid lenses

and electronically-switched,
liquid-crystal lenses.

Now these have their own tradeoffs,

but what they don't skimp on
is the visual experience.

Full field-of-view vision that can be
sharp at any desirable distance.

OK, great.

The lenses we need already exist;

problem solved, right?

Not so fast.

Focus-tunable lenses add a bit
of complexity to the equation.

The lenses don't have any way
of knowing what distance

they should be focused to.

What we really need are glasses
that, when you're looking far,

far objects are sharp,

and when you're looking near,

near objects come into focus

anywhere in your field of view
and without you having to think about it.

What I've worked on these last
few years at Stamford

is building that exact intelligence
around the lenses.

Our prototype borrows technology
from virtual and augmented reality systems

to estimate focusing distance.

We have an eye tracker that can help tell
what direction our eyes are focused in.

Using two of these,

we can directly triangulate
your gaze direction

to get a focus estimate.

Just in case though,

to increase reliability we also added
a distance censor.

The censor is a camera that looks
out at the world

and reports distances to objects.

We can again use your gaze direction
to get a distance estimate

for a second time.

We then fuse those two distance estimates

and update the focus-tunable
lens power accordingly.

The next step for us was of course
to test our device on actual people.

So we recruited about 100 presbyopes
and had them test our device

while we measured their performance.

What we saw convinced us right then
that autofocals were the future.

Our participants could see more clearly,

they could focus more quickly

and they thought it was an easier
and better focusing experience

than their current correction.

Put it simply:

when it comes to vision,

autofocals don't compromise
like static corrections in use today do.

But I don't want to get ahead of myself.

There's a lot of work for my colleagues
and me left to do.

For example, our glasses are a bit --

(Laughter)

bulky, maybe?

And one reason for this is that we used
bulkier components

that are often intended
for research use or industrial use.

Another is that we need to strap
everything down

because current eye-tracking algorithms
don't have the robustness that we need.

So moving forward,

as we move from a research
setting to a start-up,

we plan to make future autofocals

eventually look a little bit more
like normal glasses.

For this to happen,

we'll need to significantly improve

the robustness
of our eye-tracking solution.

We'll also need to incorporate smaller
and more efficient electronics and lenses.

That said, even with
our current prototype,

we've shown that today's
focus-tunable lens technology

is capable of out-performing
traditional forms of static correction.

So it's only a matter of time.

It's clear that in the near future,

instead of worrying about which pair
of glasses to use and when,

we'll be able to just focus
on the important things.

(Applause)

Thank you.

(Applause)