Museum of Vision

Vision is a complex sense. The eyes are the entry to a multilayered visual system that processes millions of bits of information every second.

In order for us to see, light rays must be bent or “refracted” so that they can focus directly on our retina, the nerve layer that lines the back of the eye.  The cornea and lens of the eye do the job of refraction while the retina receives images, modifies them and then transmits nerve impulses through the optic nerve.  The retina is actually brain tissue so it begins coding visual information, a process which is finished in the brain, allowing us to recognize objects, people and places. 

To understand how humans see in color, you have to study how the eye works.  The eye is like a tool that helps the brain to understand the world around it.  Light waves bounce off an object and are reflected into the eye’s cornea.  These light waves then pass through the iris and lens to finally rest on the retina at the back of the eye.  The retina has millions of photoreceptors called cones and rods that convert the light waves into information including color, shape and motion.  The information from the cones and rods are then sent to the brain via the optic nerve.  Our brains take all the information supplied by the cones and rods, processes it, and allows us to perceive the things around us. 

The most common form of color blindness involves poor discrimination of red and green.  Most often a person who has red/green color blindness sees only strong colors so subtle variations in shades are hard to distinguish.  Some may not see red and green at all.  More rare, are people who have yellow/blue color blindness and the most uncommon is for a person to be absolutely color blind, where they perceive the world only in shades of gray.

It may seem amazing to you, but many people who are colorblind do not realize it or simply ignore it.  Being colorblind does not limit a person's ability to do most things, which is probably why it was not studied much by scientists until the 1800s. The first instrument created to measure color perception was the colorimeter, designed by James Maxwell (1831-1879) in 1860.  However, the most widely used test was developed by Shinobu Ishihara (1879-1963) of Japan in 1916. Dr. Ishihara's color charts were designed so that they could test everyone, including children.

Eye charts measure visual acuity- the basic measurement of one's eyesight.  Herman Snellen (1834-1908) defined a test for eyesight and a formula to express how well a person sees in the form of a fraction.  First published around 1860, Snellen described a person's eyesight as a ratio comparing the test subject's eyesight to that of a "standard" person.  The ratio expresses how many chart objects can be seen at a specific number of feet, i.e. 20/20 would indicate that the test subject could see 2 chart objects at 20 feet.  The original Snellen test card used the English alphabet, but in 1868 he devised a test card for illiterates that resembled a rotating "E".  

An eye cannot simply fall out of its socket.  Eyeballs are held in their sockets by a set of six muscles attached to the eyeball and anchoring it to the skull.  There are also 3 of the 12 cranial nerves there to help the muscles contract and allow us to move our eyes in all directions.  Popping an eyeball out of its socket takes some force and rarely does it come out completely- that would require cutting all six muscles at once.  In addition the structure of the face is such that an eyeball is meant to stay in place.  Our eyelids help with that, as does the sockets themselves which are lined with a tough membrane and a pad of fat for cushion and support.

Dogs see differently than humans.  They have fewer "cones" in their retinas than humans so they are able to see only white, black, gray, blue, yellow and violet.  Dogs see very well in low light because they have a structure in their eye called a "tapetum".  The tapetum helps gather light to increase what a dog can see in the dark.  When you take a picture of a dog, often their eyes will appear to glow.  This is the tapetum reflecting light.  Humans do not have tapetums, so we see poorly in the dark.  Dogs have a larger field of view than humans.  Dogs can see approximately 200-270 degrees around them, while humans only see 160-180 degrees. Still, dogs have relatively poor visual acuity.  Their eyesight is good only in a range of about 20 feet to approximately 13 inches- much of their close vision is blocked by their muzzles.  However, dogs have exceptionally good senses of smell and hearing.  They use these in combination with their sight to help locate objects and people.  Dogs are also wired to perceive movement- which, thanks to their large field of view, they can see on all sides.  This is why dogs are so good at catching balls or Frisbees.

For information about specific eye diseases, their symptoms and where to find an ophthalmologists, go to www.eyecareamerica.org or www.geteyesmart.org

The Museum of Vision is always interested in expanding its collection.  It is the museum's policy to place all offered gifts before an acquisition committee for a formal vote.  Meetings are quarterly.  Please contact museum staff with details about your offer of donation, including a description and photos, if possible.

The American Academy of Ophthalmology is the largest national membership association of ophthalmologists, or EyeMDs, in the world.  Ophthalmologists are medical doctors who provide comprehensive eye care, including medical, surgical and optical care.  The mission of AAO is to advance the lifelong learning and professional interests of ophthalmologists to ensure that the public can obtain the best possible eye care.  In 1980, AAO created its foundation, which in turn created a museum.

In 1980 the American Academy of Ophthalmology created the Foundation of the American Academy of Ophthalmology to provide financial support and implement programs that advance ophthalmic education resulting in the best possible eye care for the public.  One of FAAO's first acts was to establish a museum.  As an educational program of FAAO, the Museum of Vision preserves the history of ophthalmology and celebrates its unique contributions to science and health. Today, FAAO also raises funds that are used to develop ophthalmic educational products and services and provided access to eye care for medically underserved communities in the U.S.