Sclera is not a well known term. If soldiers were to be told not to shoot until they could see the sclera of their enemy's eyes, they would be at a loss and not know what to do. But if they are told not to shoot, until they can see the whites of the enemy's eyes (a common command during the Civil War), the meaning becomes clear - wait till the enemy gets close to you before firing! Yes, the sclera is nothing more than the technical term for the whites of your eyes.
Nearly all animals have white sclera, although some, like horses and lizards, can have black sclera. The sclera is the opaque strong fibrous, outer layer of the eyes that acts as a shield to protect it from injury. The thickness of the sclera increases with age which is why children with their thin sclera often appear to have slightly blue tinted eyes. In the elderly, the sclera often takes on a yellowish hue. This is because of a time related collection of fatty deposits that develop there. Both the blue and yellow tints are harmless and not cause for worry.
Although soft, flexible and sensitive - if you have ever had a finger accidentally poked in your eye you will understand that - it is still the strong outer layer that contains all the other parts of the eyes and the liquid matter. The sclera is what gives the eyes their shape.
The sclera is where the muscles that cause our eyes movements are connected and when we look left or right, up or down, it is the sclera that is moving.
The sclera is perhaps the most unglamorous and underappreciated part of the eye. It does not widen and narrow like the pupil. It does not have the bright colors of the iris that can add so much to the physical appeal of a person. It is just a white mass that does not seem to do much and to which nothing seems to happen. The first impression is completely wrong, while the second is mainly correct.
Without the sclera, there would be no eye. It is the sclera that holds the internal organs of the eye in place, so that they can function properly. Perhaps, nowhere else in the human or even animal body, does the precise alignment of muscles, nerves and tissues become so important. It's all a matter of physics. The ability to see is based on the ability to focus light correctly. The better the focus, the more clearly we can see. And focus brings up the issues, as every photographer will know, of focal length.
The eye is full of liquid that creates a pressure. It is the sclera that contains this pressure and at the same time, keeps the iris, the pupil the retina and all the other parts of the eyes exactly in position so that the exact focal length needed for clear vision is always maintained.
The sclera needs to be strong to hold all the internal parts of the eye in place. At the same time it must be soft and flexible so that the eyes can move comfortably in the eye socket. If the sclera were to be hard as bone, any movements within the eye socket would result in a grating effect and friction. And when you consider the millions of movements and adjustments our eyes make each day, the problems that would cause becomes obvious.
So, the sclera has to be strong and yes soft and well lubricated. The sclera also needs to be strong enough to anchor the muscles that are attached to it that cause eye movement. And finally, the sclera needs to accept being perforated by the various nerves and vessels that enter and exit from it.
The sclera is the most often ignored part of the eye because it is so tough and suffers from few infections and rarely gives any problems. However, that can be dangerous since, if the sclera should get infected or damaged in any way, it requires immediate medical attention so that the damage or infection can be contained before it spreads to other parts of the eye. Irritation of the sclera is most often caused by a small particle of dirt getting lodged in the eye. When this happens the eye should be immediately rinsed out with saline, and if saline were not available to you, then use clean water. If the irritation persists, an eye specialist should be consulted.
TThe appearance of brown or gray spots on the sclera is fairly common. The technical name for this is scleral melanocytosis. Despite its impressive sounding name it is not in any way harmful and is nothing to worry about. And treatment that may be given for this condition will be for purely cosmetic purposes.