Recovery from blindness
Recovery from blindness is the phenomenon of a blind person gaining the ability to see, usually as a result of medical treatment. As a thought experiment, the phenomenon is usually referred to as Molyneux's Problem. The first published human case was reported in 1728 by the Surgeon William Cheselden. Patients who experience dramatic recovery from blindness experience significant to total Agnosia, having serious confusion with their visual perception.
Contents
As a thought experiment
The phenomenon has often been presented in empiricism as a thought experiment, in order to describe the knowledge gained from senses, and question the correlation between different senses.
John Locke, an 18th century philosopher, speculated that if a blind person developed vision, he would not at first connect his idea of a shape with the sight of a shape. That is, if asked which was the cube and which was the sphere, he would not be able to do so, or even guess.
The question was originally posed to him by philosopher William Molyneux, whose wife was blind:[1]
Suppose a man born blind, and now adult, and taught by his touch to distinguish between a cube and a sphere of the same metal, and nighly of the same bigness, so as to tell, when he felt one and the other, which is the cube, which is the sphere. Suppose then the cube and the sphere placed on a table, and the blind man made to see: query, Whether by his sight, before he touched them, he could now distinguish and tell which is the globe, which the cube? To which the acute and judicious proposer answers: ‘Not. For though he has obtained the experience of how a globe, and how a cube, affects his touch; yet he has not yet attained the experience, that what affects his touch so or so, must affect his sight so or so…’
In 1709, in “A New Theory of Vision,” George Berkeley also concluded that there was no necessary connection between a tactile world and a sight world—that a connection between them could be established only on the basis of experience. He speculated:
the objects to which he had hitherto used to apply the terms up and down, high and low, were such as only affected or were in some way perceived by touch; but the proper objects of vision make a new set of ideas, perfectly distinct and different from the former, and which can in no sort make themselves perceived by touch (sect. 95).
This thought experiment (it was a thought experiment at the time) outlines the debate between rationalism and empiricism; to what degree our knowledge of the world comes from reason or experience.
First case
There are many stories or anecdotes of the phenomenon, preceding the first documented case, including one from the year 1020, of a man of thirty operated upon in Arabia.[2]
Before the first known human cases, some tests were done rearing animals in darkness, to deny them vision for months or years, then discover what they see when given light. A. H. Reisen found severe behavioural losses in such experiments; but they might have been due to degeneration of the retina.[3]
The first known case of published recovery from blindness is in 1728, of a blind 13 year old boy by William Cheselden.[4] Cheselden presented the celebrated case of a the boy of thirteen who gained his sight after removal of the lenses rendered opaque by cataract from birth. Despite his youth, the boy encountered profound difficulties with the simplest visual perceptions. Described by Cheselden:
When he first saw, he was so far from making any judgment of distances, that he thought all object whatever touched his eyes (as he expressed it) as what he felt did his skin, and thought no object so agreeable as those which were smooth and regular, though he could form no judgment of their shape, or guess what it was in any object that was pleasing to him: he knew not the shape of anything, nor any one thing from another, however different in shape or magnitude; but upon being told what things were, whose form he knew before from feeling, he would carefully observe, that he might know them again;[5]
Examples and case studies
Virgil
In his book, An Anthropologist On Mars (1995), neurologist Oliver Sacks recounts the story of Virgil, a man who saw very little until having cataract surgery at age 50. Virgil's subsequent behavior was that of a "mentally blind" person —someone who sees but can't decipher what's out there; he would act as if he were still blind. Often confused, Virgil rapidly sank into depression. About 4 months after his surgery, he died of pneumonia.[6]
Sidney Bradford (S.B.)
In 1974, Richard Gregory described a patient, Sidney Bradford, a 52 year-old who gained vision from corneal grafts to both eyes. No experimental psychologist was informed of the case until after the corneal grafting took place. His operation was able to reveal idiosyncrasies of the human visual system. For example, not having grown up with vision, Bradford did not perceive the ambiguity of the Necker cube. Nor was he able to interpret the perspective of two-dimensional art.
Nevertheless, he could accurately judge the distance to objects in the same room, having been familiar with these distances before regaining sight by virtue of having walked them. In a similar analogy between vision and sightless (touch-only) experience, Bradford was able to visually read the time on the ward clock just after his operation. Before surgery Bradford was a skilled machinist, but upon gaining vision, he became confused and unable to work. He committed suicide 2 years after his operation.[7] The case history published in the Quarterly Journal of Psychology in 1963.
Michael May
Michael G. "Mike" May (born 1954) was blinded by a chemical explosion at the age of 3 but regained partial vision in 2000, at 46, after Corneal transplantation and a pioneering stem cell procedure by San Francisco ophthalmologist Daniel Goodman.[8] May had a stem-cell transplant in his right eye in 2001 when he was 43, after 40 years of blindness. He reportedly has adapted well to his recovered vision.
- May still has no intuitive grasp of depth perception. As people walk away from him, he perceives them as literally shrinking in size
- problems distinguishing male from female faces, and recognizing emotional expressions on unfamiliar faces.[6]
The effect of visual loss has an impact in the development of the visual cortex of the brain. The visual impairment causes the occipital lobe to lose its sensitivity in perceiving spatial processing. Sui and Morley (2008) proposed that after 7 days of visual deprivation, a potential decrease in vision may occur. They also found an increasing visual impairment with deprivation after 30 days and 120 days. This study suggests that the function of the brain depends on visual input. Michael lost his eyesight at age 3, when his vision was still not fully developed to distinguish shapes, drawings or images clearly. It would be difficult for him to be able to describe the world compared to a normal sighted person. For instance, Michel would have trouble differentiating complex shapes, dimension and orientations of objects. Hannan (2006) hypothesized that the temporal visual cortex uses prior memory and experiences to make sense of shapes, colours and forms. She proposed that the long term effect of blindness in the visual cortex is the lack of recognition of spatial cues.
At 3 years of age, Michael’s vision had still not reached the acuity of an adult person, so his brain was still not completely exposed to all possible clarity of images and light of the environment. His brain lacked the full picture of the world to be able to describe its beauty. This made it difficult for Michael to lead a normal daily life. Cohen et al. (1997) suggested that early blindness causes a poor development of the visual cortex with the result of a decrease in somatosensory development. This study proposed that Michael’s long term blindness affects his ability to distinguish in between faces of males and females, and to recognize pictures and images. In spite of the surgery on his right eye, his newly regained vision, after blindness of forty years, is not fully recovered. Thinus-Blanc and Gaunet (1997) suggest that early blinded people show limited ability in spatial representation. Michael still struggles to identify pictures or illustrations. The impairment of his visual cortex, due to the loss of his vision at a very early age, resulted in visual cortex cells that are not used to the stimuli in his surroundings. Cohen et al. (1997) proposed that in their early age, blinded subjects developed strong motivations to tactile discrimination tasks. Michael’s early blindness benefited him so far; he developed very precise senses of hearing and touch.
The fact that Michael lost his sight at an early age affected his development, critical period and played a large role in his impaired development after surgery years later thus, impairing his depth perception and visual acuity.
In 2006, journalist Robert Kurson wrote a book on May, Crashing Through, expanded from an article he did for Esquire [9], which is being adapted into a motion picture.[10] Crashing Through was released on May 15, 2007.
Shirl Jennings
Shirl Jennings (1940–2003) was blinded by illness as a young boy. Experimental surgery in 1991 partially restored his vision, but like Bradford and May, Jennings found the transition to sightedness difficult. In 1992, a pneumonia infection resulted in anoxia, and ultimately cost Jennings his vision again.
Modern history
In 1960, Maurice von Senden restored vision to 65 patients with congenital cataracts.[7] Corneal grafts are also becoming more common. More recently, another condition called aniridia has been treated with reconstructive surgery using the membrane from the amniotic sac that surrounds a fetus combined with stem cell transplantation into the eye.[11] In 2003, three people were successfully implanted with a permanent "retinal prosthesis" by researchers at the University of Southern California. Each patient wore spectacles with miniature video cameras that transmitted signals to a 4-mm-by-5-mm retinal implant via a wireless receiver embedded behind the ear.[12]
Ancient
The following account of visual agnosia from a sudden recovery of sight is from the Gospel of St. Mark, Chapter 8: "And he cometh to Bethsaida; and they bring a blind man unto him, and besought him to touch him. And he took the blind man by the hand, and led him out of the town; and when he had spit on his eyes, and put his hands upon him, he asked him if he saw ought. And he looked up, and said, I see men as trees, walking. After that he put his hands again upon his eyes, and made him look up: and he was restored, and saw every man clearly."
See also
- blindsight - when a blind person can perceive visual stimuli unconsciously.
- Hand-eye coordination
- Mike May who recovered his vision late in life after losing it at the age of 3.
Notes
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- Cohen, L. G. et al. (1997). Functional relevance of cross-modal plasticity in blind humans. Nature, 389, 180-183.
- Hannan, C. K. (2006). Review of Research: Neuroscience and the Impact of Brain Plasticity on Braille Reading. Journal of Visual Impairment & Blindness, 7, 397-412.
- ^ Hothersall, David. History of Psychology. McGraw Hill, 2004.
- Siu, T.L., & Morley, J.W. (2008). Suppression of visual cortical evoked responses following deprivation of pattern vision in adult mice. European Journal of Neuroscience, 28, 484-490. doi: 10.1111/j.1460-9568.2008.06342.x
- Thinus-Blanc, C., & Gaunet, F. (1997). Representation of Space in Blind Persons: Vision as a Spatial Sense? Psychological Bulletin, 121, 20-39.
External links
- "Giving Sight to the Blind" lecture by Brian Wandell at Stanford University
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The seventeenth-century philosopher William Molyneux, whose wife was blind, posed the following question to his friend John Locke: “Suppose a man born blind, and now adult, and taught by his touch to distinguish between a cube and a sphere [be] made to see: [could he now] by his sight, before he touched them . . . distinguish and tell which was the globe and which the cube?”
