Understanding Vision

 is a pair of eBooks in Deus Ex: Human Revolution.

Part 1: It is located in Hengsha Court Gardens. From the main entrance, guarded by two Belltower mercs, hack into the apartment immediately to the left of the door. It is sitting on the kitchen counter.

Part 2: It's on a desk in the Harvesters Hideout's surgery ward (level -2).

Transcript
Excerpt from a lecture given by Hugh Darrow at Harvard University in August 2008.

Part I

''Understanding the way the eye works normally is important to understanding the functioning of a retinal implant. So forgive me, for a moment, if I take the time to explain a lot of information most of you already know.''

''Light within our visual spectrum travels through space in the form of photons, or light waves. Our eyes are designed to receive these photons and then transmit to the brain the "visual" information coming to us from the environment. First the light passes through our pupils, then through the lens and finally to the back of the eye - where we find the retina. At the retina there are layers of photoreceptors - rods and cones. Cones are responsible for detecting different colors of light, and rods are responsible for our low light vision.''

''In a person with a degenerative eye condition, such as retinitis pigmentosa or macular degeneration, the eye's photoreceptors die off, leaving him or her no longer able to detect light or see. The areas in the brain for visual processing are still intact, however, so people are still able to imagine vision. Because these brain areas are still intact, information can still be transmitted and visual perception can occur.''

And that is where neuro-enhancement of vision can begin.

Part II

''Today's retinal implants are designed to partially restore useful vision to people who have lost their sight due to degenerative eye conditions. The device consists of an electrode array attached to the eye's retina; a digital camera worn on the user's body (usually attached to a pair of glasses); and a transmitter and receiver that converts images to electrical impulses. These impulses are then transmitted by radio frequency to the electrode array.''

''At the moment, there are two types of retinal implants available: epiretinal implants and subretinal implants. The only difference between the two is at what point the electrode array stimulates the cells that would attach to photoreceptors. The signal transmitted travels to the optic nerve and then to the brain, allowing for the perception of sight. However, the vision a person receives from these implants is very rudimentary. He or she may be able to see an image similar to a scoreboard made up of large lights, or detect something come from light that is only an arm's length away.''

''In other words, today's retinal implant gives the patient very limited vision. For a person who is going blind, it's a very good option for retaining some sense of vision. Still, we at Darrow Industries intend to improve it.''