What Is 20/20 Vision? Visual Acuity Explained | Dr. Jeff Goldberg & Dr. Andrew Huberman
00:00:00.000 | - Could you define 2020 vision and a few of the variants
00:00:05.000 | so that any person could understand it?
00:00:10.520 | So we think of 2020 as perfect vision.
00:00:13.520 | What does that mean?
00:00:14.680 | What would degraded vision look like?
00:00:17.060 | Whatever those numbers are.
00:00:19.880 | And then what would above normal,
00:00:22.160 | supra normal vision look like?
00:00:25.040 | And is it true that fighter pilots have supra normal vision?
00:00:29.240 | - Yeah, that's another population like many athletes
00:00:33.320 | of people who may have sort of better than normal vision.
00:00:37.640 | 2020, we define almost everything we do
00:00:42.320 | based on kind of a average, not sick human being,
00:00:47.320 | adult, whatever it is, right?
00:00:49.680 | And so 2020 vision means that you can read
00:00:54.180 | the smallest letters at 20 feet away
00:00:58.380 | that the average healthy person can read at 20 feet away.
00:01:03.380 | So you can read at 20 what they can read at 20, okay?
00:01:07.760 | Now, if you have worse than 2020 vision,
00:01:10.520 | maybe you have 2025 vision, 2040 vision,
00:01:13.320 | maybe you have 2200 vision,
00:01:15.360 | which on the eye chart at the office
00:01:17.360 | is like the big E at the very top is 2200 vision.
00:01:22.360 | That means you can read at 20 feet
00:01:26.680 | what a normal person could read at 200 feet, right?
00:01:31.520 | So you've got pretty limited lower vision.
00:01:34.600 | We can measure down to like 2400, 2800.
00:01:38.440 | At that point, we're getting into like,
00:01:40.120 | gosh, can you count how many fingers I'm holding up?
00:01:43.240 | You know, that kind of thing.
00:01:44.320 | And then ultimately hand motion,
00:01:46.720 | can you even tell if my hand is moving
00:01:48.640 | in this side of your vision or this side of your vision?
00:01:51.440 | And then ultimately after that light perception,
00:01:54.960 | can you tell if the room lights are on or off, right?
00:01:57.720 | And that's kind of the edge of being actually fully blind.
00:02:01.560 | We call legal blindness in the United States
00:02:03.640 | typically 2200 or worse.
00:02:06.120 | - And is it true that there are people
00:02:07.760 | who are legally blind that are out there driving
00:02:10.200 | as we're having this conversation?
00:02:11.680 | - I have to imagine that that is unfortunately the case,
00:02:16.240 | but it shouldn't be because those people obviously
00:02:18.360 | are really severely impaired
00:02:20.000 | and that's obviously quite dangerous.
00:02:22.400 | So that's 2020.
00:02:24.840 | Now it gets worse, 2040, 2080, 2100.
00:02:29.200 | Can it get better?
00:02:30.040 | Yeah, it turns out that people can be sort of
00:02:32.600 | on the other end of that curve.
00:02:34.960 | And so we could have athletes and fighter pilots
00:02:37.600 | or people who have had LASIK surgery who are 2015, 2010.
00:02:42.400 | If you're 2010, that means you can see at 20 feet
00:02:47.240 | what the average person needs to be
00:02:48.760 | only 10 feet away to see, right?
00:02:51.400 | And so you've got better than normal vision.
00:02:54.080 | And people do get to that through a variety of ways.
00:02:57.200 | And so it is possible to have better than 2020 vision.
00:03:01.480 | - Does the degree of visual acuity,
00:03:05.920 | 'cause that's really what we're talking about here,
00:03:08.000 | differ dramatically between the two eyes?
00:03:10.160 | - In most healthy people, no.
00:03:13.720 | Remember we talked about you're born
00:03:16.800 | with something like 2200 vision,
00:03:18.680 | takes you a couple of years
00:03:19.880 | and it can be a little bit asymmetric.
00:03:21.760 | - 2200 vision.
00:03:23.360 | Yeah, that reminds me,
00:03:24.720 | I've seen images of what babies can see.
00:03:27.160 | Parents love looking at their child
00:03:29.000 | and thinking that their child is looking right back at them.
00:03:31.000 | And indeed, often the child is looking right back at them.
00:03:33.480 | And your face to your child,
00:03:35.640 | sorry to break this to you folks,
00:03:37.080 | is incredibly blurry, even at that close distance
00:03:40.560 | for probably the first six to eight months even
00:03:43.400 | before you come into sharp relief.
00:03:44.840 | They're not seeing the fine details of your face.
00:03:47.520 | So smile big.
00:03:48.680 | - That's right, smile big.
00:03:49.960 | Keep those eyebrows dark.
00:03:51.040 | - Right, and keep cooing at them
00:03:52.640 | 'cause they can hear pretty well.
00:03:54.160 | - That's right.
00:03:55.000 | - Yeah, the optics of newborn babies are just dreadfully bad
00:03:57.960 | but they need visuals to know.
00:03:59.560 | - Now other species, hawks, raptors, owls that hunt,
00:04:04.560 | they can naturally have 2010, 28 vision, right?
00:04:12.560 | So much better vision.
00:04:15.160 | And that's just their normal vision
00:04:17.240 | as best as has been measured.
00:04:18.800 | So there's definitely the potential
00:04:22.240 | for us to have better than 2020 vision.
00:04:24.720 | Now, all of this we call visual acuity.
00:04:26.840 | And just to be clear for everyone,
00:04:28.360 | that's the vision in the very center of your vision.
00:04:32.160 | Like when you're reading or looking,
00:04:33.880 | that's the very center of your vision.
00:04:36.600 | Our vision is actually described
00:04:37.960 | variably as a hill of vision.
00:04:40.080 | The peak is in the center.
00:04:41.920 | That's let's say 2020 in most people, right?
00:04:45.120 | But it's normal to have that slope off.
00:04:48.000 | And our visual acuity,
00:04:49.280 | your ability to read the eye chart
00:04:51.000 | on the edges of your vision,
00:04:52.640 | if you can read the big E, that's pretty normal.
00:04:55.000 | Like you would be 2200 out on the edges of your vision
00:04:58.880 | and we would feel like, yep, that's pretty normal.
00:05:01.960 | So our highest acuity vision's in the center.
00:05:05.280 | And that's a big part of why we spend a lot of time
00:05:07.520 | using those eye muscles to look around, right?
00:05:10.000 | We gotta get a little bit of a high acuity view
00:05:12.920 | of what's around us, fill in the gaps
00:05:16.280 | of what our brain is interpreting
00:05:19.160 | our peripheral world to look like.
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