Eyes allow species to visualise and detect others or terrains. Eye converts light from the outside world into electrical nerve impulses. These impulses then travel to the visual cortex where they are interpreted as a visual scene. For the long chronicle of history, the eyes of human and hawk, Buteo jamaicensis, were used for their survival instincts. They find prey and avoid hazards with their eyes. Eyes do numerous functions for any species. However, there are many distinctions in the structure of species’ eyes as they adapt to different environments. 

The eyes of hawks were adapted to catch the prey while flying fastly. They have incredible hunting abilities and to endure high pressure in the sky. Different from the body size of the hawk, the size of hawk eyes are much larger than those of humans. The flatter and aspherical shape of the hawk eye allows more of the visual field to be in focus. Also, the hawk has a similar lens and corneas with humans, but the large pupil and highly curved cornea of the hawk eye admit plenty of light to keep the image on the retina bright. The creation of long focal length between the flattened lens and retina of the hawk eye allows a large image to be produced. Humans have a shorter distance between the lens and retina, compared to the hawk. 

Visual acuity is the ability that enables the species to see accurately without vagueness. In the retina of the hawk, rods and cones are much tighter packed than the humans: Humans have about 200,000/mm2 while hawks possess 1,000,000/mm2. This enhanced visual acuity of the hawk and distinguished the eye ability of humans and the hawk. In hawk’s eye, 80% of the photoreceptors are cones while only 5% are cones in the human eye. The higher proportion of the cones in the retina allows hawks to perceive better colours but poor night vision. Furthermore, hawks have the ability to see colours more vividly than humans can. Their ability to see ultraviolet light and more shades of one colour made hawks to see the bodily traces left by their prey. 

In the blind spot of humans and hawks, there are no light-sensitive cells so light falling on the blind spot cannot be detected. Moreover, they both use the optic nerve to carry nerve impulse to the brain. Nevertheless, the signal processing of hawks is much more complex than humans. Their areas of the brain involved with visual processing are in fact much larger relative to humans. Although function of organisms happens due to different parts, it is undeniable that the eyes are the essential organs. Expanding the study of eyes would open up the new chapter of science which benefits the majority of mankind.

Taeyoo Noh
Taeyoo Noh

Student of NLCS Jeju
Member of NLCS Jeju Biomedical, Philosophy, Ethics (BPE) Society


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