The grandkids staged tantrums to accompany him for his eye check-up, a year after BELT cataract procedure. The children, hinging their hopes on grandpa to forgive their ‘screenplay of a horror movie’ comment and banked on a visit to their favourite ice-cream parlour. They did not relent. To enjoy alone time from Grandpa and his three thieves, she chose to remain at home.
In the waiting hall, different pictures of eyes, with different stories to tell, kept a careful watch on them with or without glasses. The kid interested in marine life, started a mental list of questions to test his grandpa’s knowledge and patience. He encouraged the other two also to make additions to his list. He whispered into their ears, “it will be our tit for tat” for that arboretum trip, which really left us stung!
Unaware of this wily trap, grandpa completed the check-up, collected the medicines and came out to the waiting hall. He saw the kids engrossed in an animated discussion. He had no clue what so ever that final touches are being given to their attack plan. A detour to the ice cream parlour and back home for lunch completed the round trip.
At home, they saw the dining table standing bare, with nothing on it except the cloth. It only added fuel to the ravenous appetite already gnawing at their digestive tracks. From another part of the house, the grandmother made a dramatic entry with a mischievous smile. Since this act did not get her the desired response, she just went back to where from she had come. With ‘hunger cum suspense’ knocking about in their heads, they sent questioning looks at the grandfather just shrugged his shoulders to convey a “I too don’t know!”.
Then, the buzzer rang and broke
the ‘questions cum suspense’ laden silence. Grandmother hurried to open the
door, overtaking them all. Peeping from behind her back, the kids noticed the
person from Swiggy. The ‘hunger cum suspense’ and ‘questions cum suspense’
ended the moment when plates and cutleries appeared as if by magic. Their
luncheon has arrived! Unable to hold it anymore, they asked “what is the
special occasion today?” The grandma, beaming with another mischievous smile
replied, “It is the kitchen’s birthday!”
After the lunch, she said, “Children,
heavy or light lunch, it is siesta time for the old man. Disturb him, he will
behave like a grumpy old bear." Like ‘Shaun the sheep’ they all
nodded their heads with no such plan to allow the old man his siesta. One of
them silently murmured the tit for tat mantra.
Following him in to the bedroom, they sat by his side without speaking a word. The old man got the message that his siesta has already started walking southwards. Pre-empting them he asked, " Now out with it, whatever you people want to ask."
"Grandpa, we know how easily you would drift off in to sleep while telling bedtime stories. Don't do what you did to your children, to us, now!"
Feeling royally cornered, he agreed, “Ok. If your questions are interesting, I will keep my eyes open."
In the arboretum, you explained about the compound eyes of the honeybees. Tell us about our eyes?
Ok. I will give only the general picture. You will have to refer to books or use search engines in the net to get more intricate details.
You had the
BELT thing on your eyes, why?
When the natural lens in the eye becomes cloudy or yellow, it becomes difficult to see things clearly. This cloudy thing is a cataract. During cataract surgery, a new artificial lens is placed to restore sharp vision.
Why people
young and old have to wear various types of spectacles, even without a cataract?
Any one of the following could be the reason. Myopia (near-sightedness), hyperopia (farsightedness), astigmatism (distorted vision), and presbyopia (age-related close-up difficulty). Vision blurs as the light entering the lens are prevented from being properly focused on the retina. The prescribed corrective lenses or glasses overcome these deficiencies, to give a clear vision.
Why don't
we fit animals, having poor eyesight with glasses?
They do suffer from near-sightedness and cataract. As most of them do not perform tasks requiring 20/20 vision, glasses are unnecessary for them.
Do we dream
in colour and how do we see colours?
Most of us do but people from older generations who have seen mostly black and white pictures, rarely have dreams in colour. Our eyes have 6 to 7 million cone cells. Most people have three types of cone photoreceptors called trichromacy comprising of short cones (blue), medium cones (green) and long cones (red).
We can distinguish up to 1 million colours. Some have a fourth type of cone (tetrachromacy). People with a strongly developed tetrachromacy can detect up to 100 million colours, but this happens very rarely. Weakly developed tetrachromacy will be a useless addition as the brain ignores the signals from these cones. In addition, there are about 100 to 125 million rod cells to help us see in dim light but missing out on colour & finer details.
Do animals dream?
Yes. Many animals have dreams but are incapable of sharing their experience with us!
In what ways the eyes of animals differ from human eyes?
Humans have spherical, globelike shape, with a slight bulge in the front. We have round pupil. We see the world right-side up and in high detail. Generally, we get a horizontal vision spanning 200 ⁰ 220⁰ and in the vertical direction we can see objects lying in the range of 130⁰ to 135⁰.
Animals have spherical, specialised tubular, cylindrical shaped eyes and compound eyes. Some have vertical slits in the pupil; some have horizontal slits. Animal brain processes only visual information, by filtering out unimportant data. They rely on panoramic view from about 330⁰ wide vision to detect predators from any side. But have blind spots directly behind them.
In the wild, animals with poor vision cannot see prey or predators and cannot survive long enough and rarely able to pass on their genetic trait of bad eyesight. They depend on other reliable senses like smell and hearing to overcome weak eyesight. Animals don’t need to see fine, high-resolution details as they have to focus only on objects close to them rather than at a distance or to rely on environmental familiarity instead of keen visuals. Their ability to detect motion and to see in the dark, or to use ultraviolet light for visuals is sufficient for survival.
Will we be able to see underwater? How marine animals manage to see even under abysmal depths?
No. Our
eyes are designed to receive light travelling through air and not water.
Something to do with how light is bent or not bent (refractive index). Pay
attention to reflection, refraction and refractive index in Physics lessons,
then you will fully appreciate their importance in our life.
The ocean surface
is bright, and the deep sea is in pitch-black darkness. To maximise vision in
low light & high-pressure environment, the sea animals have special lens
shapes, light-gathering layers and unique pupil structures. In the abyssal
zone, where sunlight barely penetrates, their eyes are adapted to detect
bioluminescence and the faint, downwelling blue light. Marine creatures have
almost perfectly spherical, dense lenses with high-powered focusing
capabilities. To capture the maximum number of photons, their eyes are massive
relative to their body size
Tapetum Lucidum, a reflective layer behind the retina acts as a mirror to reflect light back through the retina to increase light absorption, enabling them to see in dark or murky water. Tubular and upward-facing eyes act like binoculars to identify silhouette of prey against the faint light from the surface. Their eyes, have retinas packed with rod cells, which are highly sensitive to light and have few or no cone cells as colour vision is not important for survival in deep-sea.
They have focusing structures to shape the eyes to work with refractive index of air and water. Their corneas can withstand pressure and function in water, often using a flatter shape to minimise distortion and compensates for the lack of refraction. Some have very flexible, muscular eyes that can dramatically change the shape of the lens or move it to focus at various distances.
Their eyes can regulate light to deal with high-intensity light at the surface and absolute darkness of deep sea. Some species possess a fleshy structure that hangs down to create an omega-shaped pupil that can expand or contract to manage the highly varying lighting conditions.
Why such a complicated anatomy for the eye of a typical marine animal?
The salt water absorbs, scatters and filters the light rapidly. This is a harsh and unforgiving environment teeming with predators and survival is not a given but won and to be protected. Their multifocal refractive index capability allows them to survey multiple depths at once. The rod pigments in the eye are highly sensitive to blue and green light, which is the only light that penetrates deep water. Efficiently combining all these extra features, a marine life does its best to survive and reproduce.
In space, will our eyes function
properly?
Yes. We can clearly see things in space. To avoid vacuum and radiation hazards, we must wear protective gears while in space.
He rounded off it all with some interesting facts, without answering for whom!
A watched kettle boils over only when you blink your eyes! (his own ‘grandverb’ a la proverb)
Marine animals in coastal & murky waters have a nictitating membrane (blinking third eyelid) that allows some light transmission while protecting the eyes from suspended particles. Some have mottled skin to blend in with a specialised iris that breaks up the outline of the eye as camouflage.
The land mammals have flatter lenses and near-sightedness is more common in animals like dogs & cats. They do not rely on perfect vision to survive as they are protected by humans. Because of this reason, their defective genes causing poor eyesight gets passed-on.
Rods and cones are special development in the eyes of vertebrates and are not universal to all life. Unlike humans, other vertebrates have varying number of rods and cones depending on their environment.
Some insects do not have rods
& cones but still manage with other senses. Plants & microbes depend on
photopigments or photochromes.
Humans, animals, birds and insects all have exactly the same DNA
(deoxyribonucleic acid) as their genetic blueprint. All life on Earth uses the
same fundamental genetic code in the double helix structure, based on the same
four chemical bases such as Adenine, Thymine, Guanine, and
Cytosine. The specific sequence of this A, T, G and C differs,
thus making all of them as unique species.
At the end, the kids asked, “Grandpa, how could you recollect so much information and answer all our questions without slipping into your siesta?”
The grandfather calmly replied, “I have been preparing the material since last summer. Otherwise, how could I keep you all away from mischiefs? I am like the legendary General Zhang Fei who lived in the late 2nd or early 3rd century BCE. He slept with his eyes open and with practice now I too can!”
Having heard all the eye related information, the kids were in a quandary - to take him at face value or to take everything he said his with spoonsful of salt. They tactfully refrained from asking “how then he heard and answered their questions?”. Fearing another outlandish story, they just nodded their heads and left, only to come face to face with their grandma.
She asked, “How did it go?” They replied in unison, “We asked for a
bucketful of water and he managed to dunk is in the Ocean, that is how horrible
it went. Are you happy now?” She left the spot wondering, “What happened to
these kids and why give me such a reaction? If at all they had to vent anger,
it should have been dumped on their tormentor’s head and not on me?
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