For many sea-dwelling animals, seeing is extremely important for hunting and defence. Accordingly, most of the sea-dwelling animals are equipped with eyes perfectly designed for underwater.
Sea-dwelling animals, unlike land-dwelling animals, have spherical lenses in perfect accordance with the needs of the density of the water they inhabit. Compared to the wide elliptical eyes of land-dwelling animals, this spherical structure is more serviceable for sight under water; it is adjusted to see objects in close-up. When an object at a greater distance is focused upon, the whole lens system is pulled backwards by the help of a special muscle mechanism within the eye.
One other reason why the eyes of the fish are spherical is the refraction of light in water. Because the eye is filled with a liquid having almost the same density as water, no refraction occurs while an image formed outside is reflected on the eye. Consequently, the eye lens fully focuses the image of the outside object on the retina. The fish, unlike human beings, sees very sharply in water.
Some animals like octopus have rather big eyes to compensate for the poor light in the depths of water. Below 300 meters, big-eyed fish need to capture the flashes of the surrounding organisms to notice them. They especially have to be sensitive to the feeble blue light penetrating into the water. For this reason, there are plenty of sensitive blue cells in the retina of their eyes.
As is understood from these examples, every living being has distinctive eyes specially designed to meet its particular needs. This fact proves that they are all created just the way they have to be by a Creator Who has eternal wisdom, knowledge and power.
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