Do blind people know when it is day?
Plus injecting viruses to cure blindness, why an IQ score isn't the same as intelligence, and the ancient origin of the "evil eye".
Hello friend,
There is much that is wrong with the world right now. I hope that in the midst of everything, you are able to find some peace and clarity this year.
Perhaps because I’ve been going through proofs for my book on COVID-19, I’ve decided to focus on something completely different this time. How we perceive anything at all is a fascinating question. I’ve only scratched the surface of this topic in previous pieces on our “two noses” and on differences in perception.
Please excuse the Philip K. Dick styled title of this newsletter. But today, I want to talk about vision.
Can blind people detect light? Can they detect seasonal changes?
These are questions that you may not have given much thought to before. But even if you haven’t, what is probably obvious to you is that much of our health and mood depend on sunlight.
Blind people can detect light. To understand how those of us who can see and most blind people (who have intact eyes) do so, we need to understand that there is more than meets the eye—the job of our eyes is more than just image vision. There is another kind of vision—a nonimage vision that predates the formation of eyes in our ancestors. Some version of this kind of vision exists even in very simple animals that can’t see at all.
This is quite extraordinary and I’ll wager, unknown to most people.
All life on earth is subject to the cycles of day and night, lasting 24 hours that are imposed by the earth’s rotation. Very primitive organisms have evolved with systems that allow the detection of light to coordinate life cycles. For most animals (including humans), this cycle is a little over 24 hours.
But how do our eyes perceive light without seeing?
To understand this, we must throw out everything we learned in high-school biology class.
The standard model of the eye, which you and I learned in school is that there are two kinds of light receptors, and both are involved in vision. Rods help us see in dim light. Cones help us see in color. Well, into the 21st century that is also what scientists believed.
But blind people who lack both rods and cones can detect light just fine. How are they able to do this? It has to do with a second function of the eye that we never think about- light detection. The eye is not just an organ of vision, but also an organ of light detection.
Light detection is physically very different from vision. Think of vision as a movie projector. You need to move frames fast so there is continuity and fast information processing. So, images have to decay quickly, or otherwise your vision will have multiple images at once. Rods and cones that are involved in vision send fast signals, so there is no persistence of images. But fast information processing doesn't help when you want to know how much ambient light is present. For that you need a light detector to be turned "on".
Scientists first made the discovery of this third kind of receptor in rodents. These are nocturnal animals. Scientists noticed that blind lab rats that do not have functional rods and cones can detect light and it helps with their hiding patterns in daylight. There is a third receptor in mammalian eyes called retinal ganglion cells. These receptors are intrinsically light sensitive and they’re responsible for the “nonimage” vision in the eye. Yes, I know, “retinal ganglion cell” isn’t as catchy as “rod” or “cone”.
Humans— though we are much more complex than mice— have this third kind of light sensor in our eyes too. It's helps us with our 24-hour patterns- the circadian rhythm. Blind people who have this sensor, sleep when it's night and wake up in the morning, though they can't see.
What would happen if we lived in perpetual darkness? Well, we can look to a kind of cavefish that lives in isolated caves in Somalia to find out. These fish have evolved in darkness for almost two million years!
These fish have lost their eyes, coloration, and scales which they no longer require in the absence of light. But being isolated does not mean that they no longer possess a body clock, it means that their body clock is different. Instead of the normal pattern of 24-25 hours showed by creatures exposed to lights, these animals have developed a clock that cycles every two days!
Laser-like eyesight?
For thousands of years people have wondered just how it is that we see. Many ancient Greek scholars, such as Plato, Euclid, and Galen thought that the eyes emitted rays. Kind of like Homelander in Boys.
The Greek scholar Empedocles thought that there was a fire raging inside the eyes that was the source of these laser-like rays. I think if you see the shining eyes of animals at night, it's easy to jump to this conclusion. But it is still incorrect.
Of course, we know that for vision, light enters the eye and not the other way around. Indian physician-scientist Sushruta hinted at this over 2000 years ago. Arab physicist Hasan Ibn al-Haytham proved it over 1000 years ago. Still, the idea that eyes emit rays hasn't gone away among many people.
My guess is that you can trace the concept of the evil eye (Nazar) all the way back to the prescientific Greek theory of vision. Today we live in a world in which many people believe the Earth is flat: others believe eyes emit dangerous rays (sometimes out of jealousy).
An IQ score does not equal intelligence
Going through some of the papers of Nobel Laureate Joshua Lederberg, I found this wonderfully convincing passage.
Injecting viruses in an eye to cure blindness
I stumbled on a series of very interesting papers when researching the various medical uses of adenovirus vectors. Related versions of virus vectors are used in the University of Oxford/Astra Zeneca/Serum Institute of India vaccine for COVID-19, among others.
These viruses are used in experimental gene therapy to restore vision resulting from macular degeneration and certain other kinds of blindness. The idea is to inject an engineered virus into a person's eye and a few months later, they start seeing again.
The other really freaky thing about this kind of therapy is that if you inject one eye with the engineered virus, you see an improvement in vision in both eyes!
Here’s the link to the Kindle version on Amazon.com.
Here’s the link to the hardcover version on Amazon’s Indian site.
Here’s an excerpt of the book in which I talk about how so many COVID-19 vaccines were developed so quickly (and why they’re not the same).
If you enjoy the book, please do leave me a review on Amazon or on Goodreads.
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