Poem 1 = entire grid
Poem 2 = inner circle, central vision that’s left
Poem 3 = Blind Ring
Poem 1
Before, al I remembered from science class was the strange image of an inverted tree entering upright then shrinking and flipping around. I didn’t remember the retina or that it is a thin layer of tissue lining the back of the eye or that at its center is the macula where the most important cells reside waiting to convert light into signals that travel through the optic nerve to the visual cortex. After, I began learning about the fovea and the number of cone cells in it and when the blind spot was first written about and how the brain guesses when it lacks visual data and why some people in the early stages of vision loss hallucinate floating faces and little folks in costumes.
Poem 2
here the
cells
convert light
travel
Poem 3
I never thought about blind spots or tried to find mine or wondered about how much of what I saw was real or illusion but when my brain could no longer hide the effects of diminishing cones–missing moons disappearing cars shifting lines absent faces–I began to pay attention.
Resources and Additional Thoughts
the strange image of the inverted tree
Things I learned after I discovered my vision loss (as mentioned in the poem):
- The fovea is a tiny pit in the macula that provides the clearest vision. A healthy fovea contains about 200,000 cone cells (source).
- The blind spot was first presented on and written about in 1668 by Edme Mariotte for the Royal Society.
- “Without visual data coming in through the eyes, the brain fills the void and makes up images or recalls stored images for you to see” (source).
- And people who hallucinate during the early stages of vision loss, might have Charles Bonnet Syndrome (CBS):
The exact cause of Charles Bonnet Syndrome is not presently known, but the popular theory suggests that the brain is merely attempting to compensate for a shortage of visual stimuli. Consider that each human eye normally receives data at a rate of about 8.75 megabits per second, a higher bandwidth than many modern Internet connections. The visual cortex is the most massive system in the human brain, and it is packed with pathways which manipulate the rush of visual data before handing it over to the conscious mind. When disease begins to kink this firehose of information, a legion of neurons are left standing idle
Alan Bellows
Discovered in 1760 by Swiss naturalist, Charles Bonnet, when his grandfather began experiencing very strange hallucinations.
CBS usually affects people in the early stages of vision loss, and the hallucinations usually begin while their vision is still present but slowly diminishing.
CBS Hallucinations
- surfaces covered in patterns, shapes
- a nonexistent man sitting and relaxing in a real life recliner
- men, leering, on the edge of bed, or a man looming over the bed, leaning down and staring into your eyes
- waterfalls coming out of tall buildings
- (as experienced by Bonnet’s grandfather, Charles Lullin): a carriage that kept growing in size until it was 2 stories tall
- floating, disembodied faces
- an excerpt of a musical score–unplayable with too many staffs and notes, and impossible key signatures
- texts with letters that are unreadable
- a stage, and when the curtain opens, roman letters dressed in medieval costumes appear
- charging rhinos
- animals, children, little people
These hallucinations are usually pleasant. A defining characteristic of CBS: the person experiencing them understands that they are not real.
A good source: Oliver Sacks has a chapter on CBS in his book, Hallucinations.