An Umpire is No Hawkeye
Baseball season is upon us again, along with occasional disgruntled suggestions from the stands that the umpire is either blind, or in need of a good optometrist.
The latter recommendation may have occasional merit, according to Philadelphia optometrist Arthur Seiderman, who examined a random sampling of umpires and referees of college, high school, and other amateur sports events.
Of the 40 umpires and referees tested, just 29 demonstrated 20/20 vision or better, and fully 12 of them had difficulties with depth perception or spatial localization (the ability to judge an object's movement through space). Seiderman suggests that all umpires and referees should have eye examinations, and steps be taken to improve the visual acuity of those who do not meet specified standards.
What, exactly, does 20/20 vision imply? As applied to humans, it means that a person is capable of discerning, at 20 feet, letters of different sizes that the majority of people can identify at the same distance. The test is usually carried out on a "Snellen" eye chart, which can either be hung from a wall or viewed through the stereoscopic devices found in an optometrist's office or in a driver's license testing line. By this standard, a rating of 20/50 means that a person sees at 20 feet what most people can make out at 50 feet, and in the United States, a rating of 1/lOth the normal acuity, or 20/200, is considered as the definition of being legally blind.
In fact, what most humans consider to be "perfect" eyesight is rather limited when the abilities of some other species are taken into account.
Consider, for instance, the hawk. With millions of "cones" compressed into an area of retina the size of the ball in a ball-point pen, the hawk has eight times the visual acuity of a sharp-sighted human, and can spot a dime on the sidewalk of the Empire State Building while perched on top. This permits it to search for small prey while circling from far aloft.
Other examples of specialized eyesight abound in the animal kingdom. The lowly frog would starve to death in a field of dead bugs, but if something moving should happen by, a highly developed set of cells in the frog's eye responds, the tongue whips out, and dinner is served. Because of this peculiarity of a frog's vision, it perceives things about it only as a constant motion picture, and blocks out anything stationary.
The bee's "compound" eye has 15,000 facets, dividing what the insect sees into a pattern of dots. With this type of vision, it sees the sun as only a single point of reference which it uses in navigation. In addition, the bee's eye provides a measure of flight speed so accurate that aeronautical engineers have designed a system based on it.
Animals can have multi-purpose eyes. For instance, humans may see perfectly well in the air, but they are far-sighted underwater. The kingfisher is a bird that needs acuity in both environments for scanning the water below in search of fish and for pursuing its prey once it has dived below the surface. The kingfisher is endowed with two foveae, areas of the eye which permit this visual distinction.
Still, there is much to be said for human sight. Although it may lack some niceties such as the bee's capability of seeing ultraviolet light, of all the mammals, only man and a few primates enjoy the pleasures of color vision.
