The Secret Genius of the Human Eye

Chanan asks: "Hello. The eye is undoubtedly one of creation's greatest marvels. But a friend questioned me about what seem to be imperfections in the human eye, like the blind spot (an area each eye cannot see), noting that such a spot doesn't exist in the octopus eye. He also asked why the human eye doesn't protect against ultraviolet radiation and why we need sunglasses to avoid damage. Why are there conditions like cataracts that cause blurry vision? And why do so many people need glasses? I'm sure there are good answers, but I'd love to know them. Thanks."

* * *

Hello Chanan, and thank you for your questions.

As you've noted, our eye is indeed one of creation's great marvels, proving there's a Creator to the universe. Even the most primitive eye in nature requires simultaneously having several components to see:

1. Light-sensitive cells capable of sending signals to the brain.

2. A brain capable of recognizing electrical signals, converting them into an image, and knowing how to act based on them.

3. A bowl shape preventing excess light from blinding the eye.

4. A lens capable of focusing light waves to create an image.

5. An aperture capable of dealing with varying light levels. Too much light can damage the light-sensitive cells, like film exposed to sunlight.

6. A mechanism to keep the aperture clear, as dust particles could block light from entering.

Each of these components on its own is a complex system, guided by numerous genes in DNA. This means that only a Creator could design the eye. Without all these components simultaneously present, any light receptor would be useless.

Even the simplest light-detecting organisms indicate intentional design, proving that the eye was created purposefully.

These remarks apply to even the simplest eye; the complexity of the human eye is beyond estimation. Even if all the world's scientists were to gather, they couldn't create a biological eye from scratch. No one can manufacture an eye or even an organ close to the complexity of the human eye. Even today's most advanced technology, developed with countless researchers, cannot produce a bionic eye capable of seeing more than faint shadows.

There's no doubt the eye attests to its Creator. The Complexity designed by the Creator also sets its limits and imperfections. After all, in this world, we live in physical bodies that age and die; our role here is temporary and purposeful, and thus, includes challenges and limitations that demand courage. Therefore, Hashem gave us intelligence and tools to overcome nature's harms, create advanced technology, and most importantly, the free choice to believe in Him and trust in His eternal goodness.

Now, your friend mentioned the blind spot in the human eye, which isn't found in the octopus's eye. The blind spot is a small area within the eye without light receptors, limiting the field of vision in a minor way.

However, there’s a reason for the human blind spot which isn’t present in the octopus. The connections of the retina in the human eye protect against ultraviolet radiation present in the air. The octopus doesn’t have this "blind spot" because it lives in water, which protects it from such radiation, allowing its eye to capture all light without harm. However, if the octopus lived on land, it would soon become blind due to the excess radiation in the air. The human blind spot limits radiation entering the eye.

But what's fascinating is the great intentional design to counteract the blind spot's weakness. If no one had informed us about this blind spot, we wouldn't even be aware of its existence, as everyone receives a complete picture of reality, not a limited one. So, if there's a blind spot, how can this be possible?

(Photo: shutterstock)

Well, humans utilize two eyes located at the front of the face (known as binocular vision), where the left eye captures areas the right eye misses (about 0.25% of the field of view), and vice versa. Each eye compensates for the missing field of the other, and our brain expertly creates a perfect reality image, seamlessly filling the blind spot without any void! Thus, the blind spot illustrates immense planning, where naturally, we would suffer from a natural view limitation as land creatures, yet Hashem designed human eyes and the brain in a way to perfectly complement the blind spot, so much so that one doesn't feel its presence. We should all praise: "How great are your works, Hashem, all made with wisdom" (Psalms 104:24).

Regarding your question about sunglasses: it's critical to understand that every type of eye in nature comes with an advantage that imposes a disadvantage from that very advantage. For instance, many animals see better at night but, for this reason, cannot perceive colors as well as humans can.

The human eye protects against most of the sun's ultraviolet radiation; this is why we aren't blinded in daylight (whereas an octopus would be blinded in daylight). However, the eye doesn’t shield against prolonged and excessive exposure, which is a limitation over time. Yet there's great design even in this limitation: If the human eye also protected against strong and longstanding ultraviolet radiation, it would have to be very dark, and we would all have to see the world dimly throughout the day as if sunglasses were glued to our eyes. The human eye's limitation is what allows its advantage of seeing the world clearly and brightly during the day!

To conclude, there exists in the human eye the retina's protection against regular ultraviolet radiation but not against strong and prolonged radiation – as permanent protection would result in dim vision. Thus, the design here is ideal for our needs. For this reason, we've been given the wisdom to create sunglasses, thereby enjoying all the advantages.

Cataracts are an extremely rare condition in the young and only affect a significant portion of the population after age 60. But this is merely a natural phenomenon, a clouding of the lens occurring over the years due to prolonged exposure to light. Think of it like glasses whose sharpness naturally declines over years of regular use. Every machine decreases in productivity and performance with time. Your home computer won't endure decades of heavy operation. The human eye works 16 continuous hours a day, 448 hours a month. By the time you reach 60, your eyes will have been functioning for 322 thousand hours before their performance may significantly decline. Can we point to another machine capable of working for so many years without failure? Every machine has limited working life. Even the heart is a machine working constantly, without pause all our lives, and its strength naturally declines with age.

Nevertheless, cataracts still occur only in part of the elderly population, not in the entire senior population. This means half of the people will see well even into old age. But even if the entire population suffered from cataracts, it would still not indicate a defect, as it's a natural limitation resulting from prolonged use. For this, Hashem gave us the wisdom and knowledge to create remedies and vision corrections for this condition.

The need for glasses (nearsightedness or farsightedness) derives from two reasons: one is the curvature of the cornea, and the other is the size of the eye itself. The eye's width determines the distance at which light will pass, thus affecting its focus. And here, there exists an average concept:

The average cornea size in humans radiuses at 8 millimeters, and the average thickness of an eye is 22 millimeters. However, these values naturally vary from person to person due to genetic variations, so there are quite a few people with flat corneas as well as those with long or short eyes. There, average values for these organ traits must exist. But if these average values differed, most of the world's population would have strong nearsightedness and farsightedness. However, what we see is that most people do not need glasses for distance vision, and very few require glasses for very strong near or far sight. Essentially, even those who need glasses generally don't need very high prescriptions. This is due to the average values of the human eye, suited to fit most of the human population. Had this average not been planned, most would require very high prescription glasses and wouldn't see without them. Additionally, it's noted that, for most people, eye thickness naturally increases or decreases to produce focus. In short, the need for glasses in some of the population stems from a biological limitation of the human species, since each person is born differently from another; still, this limitation (the average) was greatly planned.

It's a fact that most of the population does not need glasses. It seems the increase in glasses wear results from modern living conditions detrimental to health (like artificial lights, disrupted sleep cycles, etc.). The need for glasses grows throughout the Western world primarily due to prolonged exposure to close ranges (books or screens). The human eye is meant to function mostly in wide spaces. For instance, the increasing need for glasses among Orthodox Jews results from a lifestyle choice of reading for most of the day. In the past, learners memorized the entire Torah, but as times changed, they began learning from books. Glasses help us overcome this issue, and it's believed that even the invention of glasses in recent generations is not coincidental (a preventative measure). It's evident that the great design lies even in the technological advances: with the invention of print allowing everyday reading – glasses were invented as well. However, it seems that most observant Jews don't view glasses as a disadvantage but rather as a mark of their scholarly appearance.

(Photo: shutterstock)

In summary:

With industrial evolution came a shift from the agricultural lifestyle that accompanied us for millennia. The new lifestyle brought benefits but also health damages (such as the shift to processed foods and refined flour requiring less chewing, resulting in smaller jaws and less space for wisdom teeth), but with these damages, means emerged to overcome them (advanced dental medicine, optical discoveries, etc.). This isn't seen as a coincidence but rather as a planned correlation by the Creator, who foresees all generations ahead.

It's astounding to find how, even in the perceived limitations and shortcomings, there's inherent design intended to allow the best logical and suitable vision. Hashem granted us the best tools to deal with embedded deficiencies in creation. Still, we should recall that these deficiencies arise due to sin (e.g., Hashem provided Adam and Eve garments out of mercy, but without sin, they wouldn't need them at all). We all believe that with the coming of complete redemption, and the rectification of humanity's sin, these inherent deficiencies and limitations will transform in a world that no longer demands these challenges.