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As we grow older, it can become difficult for our eyes
to focus on things at close distances.
The medical term for this is presbyopia, or age-related farsightedness.
It’s a natural process.
It happens because the lenses in our eyes thicken over time,
making it difficult for our muscles to change
the shape of the lens and focus at different distances.
Luckily, ophthalmologists have options at their disposal to correct for this,
such as glasses, contacts, and laser eye surgery.
But now there is a new tool in that kit, and it takes on a surprising form: eyedrops.
But how can a dollop of liquid improve your vision?
Well it’s all thanks to some simple optics.
Glasses work by adding a lens to refocus the light entering your eye.
However, these eyedrops work differently,
thanks to a phenomenon called the pinhole effect.
Pinhole cameras are devices that can record an image
by letting in light through a narrow aperture.
You might have used one to view the projection of a solar eclipse at some point.
And they work because a smaller opening lets in only focused light
coming from the object you’re looking at.
A wider aperture lets in more scattered light that can cause blurriness.
Scientists have long known that medications
that contract your pupils can temporarily improve vision.
This happens because as the iris closes,
it has the same effect as shrinking the aperture on a camera.
Things at a broader range of distances come into focus simultaneously.
The downside is that since the opening is so tiny, it lets in /less/ light overall,
so it’s harder to see or take a picture in the dark.
Now, we’ve actually had drugs that can do this for a while,
but in the past they haven’t been used for this reason.
Here in the US, the FDA approved a solution
of the drug pilocarpine for use in presbyopia in 2021.
This is a well-established drug that has long been used
to relieve pressure in the eye and help treat glaucoma.
The fact that it also contracted the pupil was considered a side effect.
That is, until researchers realized that could be a feature instead of a bug!
So in two clinical trials to test the vision benefits of pilocarpine,
researchers gave 750 people either the drops or a placebo for 30 days.
They found that the drops took about 15 minutes to improve near vision,
and the effect lasted for around 6 hours.
Around 30% of those who received the medication
could read 3 more lines of a near vision eye chart!
That’s compared to around 10% of those in the control group
who got drops without the drug.
One trial also tested their distance vision
to ensure that they weren’t losing the ability to see things far away.
Given the known side effects of pilocarpine,
there was some concern that the drops could make it
harder for the eye muscles to focus the lenses.
However, participants didn’t lose the ability
to read more than one line of a distance vision chart.
But this treatment does have some trade-offs.
6 hours of improved vision isn’t the whole day,
and the trials only tested the effects of one daily dose.
Headaches and red eyes were also the most common side effect.
And making your iris smaller means people might have
a challenging time seeing at night or in dim light.
So a possible strategy could be to only put the drops in one eye.
This is likely just the beginning for eye drops designed to correct vision.
Other drugs that also use the pinhole effect are in development.
Researchers are also working on eye drops
that could counteract the hardening of the lenses in our eyes as we age.
Eyedrops are not ready to replace glasses quite yet.
But one alternative is already here,
and it looks like there will likely be more options coming along in the near future!
And speaking of seeing things more clearly,
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you might enjoy a course from Brilliant.
Brilliant’s interactivity lets you learn by doing
and experimenting with things for yourself.
The guided activities always come with explanations so you can follow along.
Like Scientific Thinking, which presents nature as a puzzle
and will let you develop intuitive insights into the laws of physics as you go along.
Right now, if you sign up at brilliant.org/scishow, you can save 20% off
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So thank you for your support!
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