Autofocusing reading glasses of the future Nitish Padmanaban
Transcriber: Leslie Gauthier
Reviewer: Joanna Pietrulewicz
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 billion 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 in refocusing ability
leading up to presbyopia.
As a newborn, you would have
been able to focus
as close as six and a half centimeters,
if you wished 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 affecting 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
necessarily 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 in contact lenses
or LASIK surgeries,
and it’s called monovision.
It works by 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 leave us?
We’ve come up with a lot of 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-shifted Alvarez lenses,
deformable liquid lenses
and electronically-switched,
liquid crystal lenses.
Now these have their own trade-offs,
but what they don’t skimp on
is the visual experience.
Full-field-of-view vision that can be
sharp at any desired 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 need are glasses
that, when you’re looking far,
far objects are sharp,
and when you look near,
near objects come into focus
in your field of view,
without you having to think about it.
What I’ve worked on
these last few years at Stanford
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 tell
what direction our eyes are focused in.
Using two of these, we can
triangulate your gaze direction
to get a focus estimate.
Just in case though,
to increase reliability,
we also added a distance sensor.
The sensor 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
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.
To 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 into 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 outperforming
traditional forms of static correction.
So it’s only a matter of time.
It’s pretty 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.
Thank you.
(Applause)