What I would like you to do is to find a topic from the chapter you read for Monday that you were interested in and search the internet for material on that topic. You might, for example, find people who are doing research on the topic, you might find web pages that discuss the topic, you might find youtube clips that demonstrate something related to the topic, etc. What you find and use is pretty much up to you at this point. But use at least 3 sources.
Once
you have completed your search and explorations, I would like you to
say what your topic is, how exactly it fits into the chapter, and why
you are interested in it. Next, I would like you to take the information
you found related to your topic, integrate/synthesize it, and then
write about it. At the end, please include working URLs for the three
websites.
Once you are done with your post make list of the terms and terminology you used in your post.
By integrating/synthesizing I mean to take what your read/experienced from the internet search (and from chapter 1 if you like) organize the information into the main themes, issues, info, examples, etc. about your topic and then write about the topic in your own words using that information. This is hard for some people to do - many students write what we refer to as "serial abstracts." They are tempted to talk about the websites rather than the topic proper. They will talk all about website #1, start a new paragraph and talk all about web site #2, start a new paragraph and talk all about web site #3, and then write some kind of conclusion. Serial means one after the other...This what you DON'T want to do!
At first it is a real challenge to get out of the habit of writing "serial abstracts," but I assure you once you get the hang of it it is much easier to write using the integration method. And besides this is the way researchers and scientists write their technical reports and findings - many of you will have to be able to do this for other classes and for jobs that you may eventually be hired for so now is a good time to learn this skill. At this point don't worry about a grade, worry about doing your best to have fun with the topic and then integrate it into your own words to share what you found and now know. We will work on citing the sources later....
Let me know if you have any questions.
Selective adaptation is used as a rare and frequent stimuli to when both stimuli are presented, the neurons are more responsive to the more frequent input. It takes a highly demanding foveal task to divert attention away from stimuli. In a study that a few people did, they found orientation-selective response adaption is to both first and second order patterns in multiple visual areas. The second order patterns were focused on more strongly than the first order pattern. This implies that the proportion of neurons is bigger in the second order than in the first order. Different people adapt to selective adaptation also within different cultures. Many of the selective adaptation is unconscious and sublinial. Examining perceptions of multiple different people, has given a way to process the examination of selective adaptation.
Terms: selective adaptation, stimuli, neurons
Links:
http://www.ncbi.nlm.nih.gov/pubmed/14561862
http://jn.physiology.org/content/95/2/862.full
http://www.youtube.com/watch?v=16f4jQSMAQc
Try to give your opinion of the information you found from your research on the topic.
One thing I found especially interesting from chapter three was how optometrists and vision scientists measure visual acuity. I enjoyed reading about this because I never fully understood what the optometrist was talking about, or how they got the measurements, for my vision strength. Acuity is the smallest spatial detail that can be resolved. Optometrists refer to this acuity in terms like 20/20. Visual scientists use different terminology; they talk about the smallest visual angle of a cycle of the grating that a person can perceive. In regards to a grating, a cycle is a pair consisting of one dark bar and one bright bar. It’s a repetition of a black and a white stripe. A visual angle is formed by lines going from the top and bottom, or left and right, of a cycle through the center of your lens, and then to the retina.
A standard eye chart is needed to make comparisons and record people’s visual acuity. When you visit the optometrist, you read a series of letters decreasing in size until you start making several mistakes in identifying the letters. The most common eye chart used is the Snellen eye chart, developed by Hermann Snellen in 1862. He determined that there was a relationship between the sizes of certain letters viewed at certain distances. Your doctor will tell you your vision acuity is 20/30 if you need glasses, 20/20 if your vision was good or 20/10 if you could read all the letters on the chart. The Snellen fractions, 20/20, 20/30, etc., are measures of sharpness of sight. They relate to the ability to identify small letters with high contrast at a specified distance. They give no information about seeing larger objects and objects with poor contrast, though. Later on, the test was changed to set the patient at a constant distance of 20 feet, and the letter size was altered instead of the patient’s position. Thus, normal vision was defined as 20/20, but most healthy young people have a 20/15 acuity level. Dr. Mark Wilkinson, of the University of Iowa Hospitals, wants people to know that standard projection acuity charts have no acuity levels between 20/100 and 20/200 and 20/200 and 20/400. There is only one 200 and one 400 letter available on these charts. Therefore, standard Snellen charts are only useful if the visual acuity is 20/100 or better.
A newborn’s visual acuity is 20/400, reaching 20/20 after age six. Measuring visual acuity in infants, children, and handicapped persons is not always possible using letter charts. For these individuals, one must check whether visual stimuli can be fixed, centered and followed. One formal testing technique is called the Teller Acuity cards. A technician presents the cards from behind a window in the wall, while the child sits in an adult’s lap. The technician checks whether the child is more visually attentive to a random presentation of vertical or horizontal bars on one side compared with a blank page on the other side. The bars become progressively closer together, and the endpoint is noted when the child equally prefers the two sides.
Basically, visual acuity measures only the smallest detail we can see; it does not represent the quality of vision in general, and the measurement tests used in adults cannot be used in children younger than six, or some handicapped populations so other forms of measurement must be used.
http://www.mdsupport.org/library/acuity.html
http://www.nmsbvi.k12.nm.us/LowVisionClinic/Articles_LVC/Visual%20Acuity%20Testing%20Measurement%20Making%20Sense%20of%20the%20Numbers.pdf
http://en.wikipedia.org/wiki/Visual_acuity
Terms: visual acuity, visual angle, cycle, grating, lens, retina, Snellen eye chart, Teller acuity cards, spatial detail
Good points. I like how you started with what interested you about the topic and expanded upon it from there with information you found from your research.
One section of the chapter that really grabbed my interest was ocular dominance. Ocular dominance is the property of the receptive fields of the primary visual cortical neurons to demonstrate a preference to one eye over the other. This can be compared much to handedness (left-handed/right-handed); however, there is no relationship between handedness and ocular dominance. This preference is made in the primary visual cortex, because information from the two eyes are kept separate until then.
Two-thirds of the population is right-eyed dominant (including myself) and one-third is left-eyed. There is also a small percentage of individuals who have no dominant eye. One way to check your dominant eye is going through the Miles test. This is done by extending your arms out and creating a small hole with your fingers and thumbs (much like the same hand motions in creating a "camera"). In this hole, look at some object 15-20 feet away. While looking at this object, close one of your eyes, and see if the object is still in the hole. Repeat with your other eye. The eye in which the object moved less when it the eye remained open is your dominant eye.
The development of ocular dominance is still debated throughout scientific circles today. However, there are two leading theories. The first is called Hebbian learning, and this is triggered by spontaneous activity coming from the retina in the fetus. Hebbian learning, or Hebbian theory, is a basic mechanism for synaptic plasticity. It is where the increased ability for an effect is made by repeated and persistent stimulation of the post-synaptic neuron by the pre-synapstic neuron. Or, to put more simply, the repeated stimulation in a synapse strengthens the relationship between the two neurons. The second theory is where axonal guidance cues, or specific chemicals guiding the path of the axon, may help create this ocular dominance. However, with most answers, it probably is a combination of the two.
https://en.wikipedia.org/wiki/Ocular_dominance
https://en.wikipedia.org/wiki/Ocular_dominance_column
http://www.topendsports.com/testing/tests/eye-dominance.htm
https://en.wikipedia.org/wiki/Hebbian_learning
Terms: ocular dominance, receptive fields, primary visual cortical neurons, Miles test, Hebbian learning, synaptic plasticity, pre/post- synaptic neuron, axonal guidance cues.
Good deal. I like how you took information you found in the book and expanded on it based on your interests in the topic.
I chose to do Amblyopia for my topical blog. This was mentioned towards the end of Chapter 3 in the section about normal and abnormal visual development.
Amblyopia is a disorder of the visual system, also often called “lazy eye”. This disorder is characterized by visual deficiency in an eye that is otherwise physically normal. It is estimated that this disorder affects about 1-5% of the population.
Basically, amblyopia means that the visual stimulation that normally happens, does not occur, or is poorly transmitted through the optic nerve to the brain for a long period of time. This can also occur when the brain discontinues the visual processing of one eye, to in turn prevent double vision or crossed eyes. This issue is often found in early childhood, which will result in poor or blurry vision. Normally this disorder only affects one eye, but there have been extreme cases where it can affect both eyes. If amblyopia is detected in early childhood than it is possible to treat effectively, especially before age five. If detected it can be corrected with glasses and/or surgery.
Interestingly enough, amblyopia is a developmental problem that occurs in the brain. This disorder does not affect the physical eye at all. The part of the brain that is supposed to be receiving images and messages from the affected eye is not stimulated properly which then results in poor vision or not fully developed to its potential. Those affected by amblyopia may not even know they have it if it is just a mild case until they reach an older age. However, those with severe amblyopia, experience very poor depth perception. Amblyopes may also suffer from poor spatial acuity, low sensitivity to contrast and some sensitivity to motion. Furthermore, they may also experience problems with their binocular vision such as limited vision when it comes to three-dimensional images.
There are three different types of amblyopia. Strabismic amblyopia is a condition in which the eyes are misaligned. Refractive or anisometropic amblyopia is a difference in refractivity between the two eyes. Finally, form-deprivation and occlusion amblyopia is when the ocular media become opaque. This is also the case with cataracts or corneal scarring from forcep injuries during birth. If any of these issues is caught before age five, they can be corrected with wearing a patch on the patient’s good eye to try and correct the bad eye, surgery, or instilling a solution called topical atropine to the eye to help with better vision.
TERMS: amblyopia, optic nerve, spatial acuity, binocular vision, Strabismic amblyopia, corneal scarring, form-deprivation and occlusion amblyopia, opaque, ocular media, cataracts, Refractive or anisometropic amblyopia
http://en.wikipedia.org/wiki/Amblyopia
http://www.aoa.org/x4699.xml
http://www.nlm.nih.gov/medlineplus/ency/article/001014.htm
Definitely an interesting visual deficit that affects alot of people. Good topic to follow your interests and learn something new.
I chose to do my blog on strabismus, which is a condition where the two eyes are not properly aligned with each other. This fits into the chapter because it is a condition where spatial recognition is compromised. There are six different muscles in the eye that affect this. These muscles are called the extraocular muscles. The muscles do not work as a team and as a result they do not come to the same point at the same time, which cases problems with seeing clearly and also with depth perception and double vision. One eye will be focused on one object and the other eye will be focused on a different object causing two different images to be sent to the brain. This would be like looking through two telescopes pointed in different directions. It would be hard to process both images.
This usually is noticeable at birth because the child will either be cross-eyed or have a lazy eye, otherwise known as amblyopia. It is not true that children will grow out of this condition in time without some form of treatment. However sometimes the brain will actually only process the image from the stronger eye and discard the image from the weaker eye. In some cases the eye doctor may actually try to get the brain to do that by recommending wearing an eye patch over the weaker eye. This trains the stronger eye to work harder. In many cases glasses are needed to be able to see more clearly. Sometimes surgery is required on the eye muscles to attempt to make the muscles in the eye stronger or weaker. Strabismus can usually be corrected or controlled for through treatment.
Terms- strabismus, extraocular, amblyopia,
http://en.wikipedia.org/wiki/Strabismus
http://www.nlm.nih.gov/medlineplus/ency/article/001004.htm
http://strabismus.com/causes.html
We are definitely drawn to the abnormal properties of vision, because it seems odd to not perceive the world in the way we do.
Topical blog Ocular dominance:I first did an eye dominance test, which I quickly realized we used to do in P.E. every year when we began our archery unit. I learned/relearned that I am left eye dominant or haved "left eyedness." I learned some other important "real world" information from this page, that athletes who are cross dominant meaning that you are oppositly handed in comparison to eyedness is an advantage which is pretty neat. This test also helps athletes in target sports because the knowledge of eyedness helps determine stance, etc. While ocular dominance may be imporant to athletes it turns out that mice, cats, and monkeys also need it. In a study done on mice related to ocular dominance researchers deprived the mice of their dominant eye for a various number of days, what they found was quite interesting! It turns out that your eyedness(well at least if your a mouse)can change if you are very young in just seven days. This left me with an important question, why does the brain allow the eyedness to have a certain plasticity related to age? My best guess would be something related to the fact that many babies, in the early human times, would loose one eye or eye sight in one eye but this doesn't really make a lot of sense so kept looking and found another experiment. This one assessed people with neglect-which we learned in the video from class that this is a problem for mainly people who have strokes. This causes their brain, for some strange reason, not to detect the information coming in from half of their world. The experiment found that if the researchers covered the left eye the participants made less errors. Which left me with yet another question, why are people like me, who are left eye dominant less likely to make errors and for selfish reasons are we better at other things in life than right eye dominant people. hahaha.
http://www.topendsports.com/testing/tests/eye-dominance.htm
http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0003120
http://brain.oxfordjournals.org/content/125/9/2023.full
Terms:ocular dominance, eyedness, dominant, plasticity, and neglect.
It's pretty cool when you apply the stuff you learn to your own life and figure out that you are left or right eyed or express a certain gene type, etc. I think that is the most fascinating part for me is how my experience is altered by knowledge of how I have come to gain these experiences.
I chose to research vision therapy. I am very interested in the treatment of things, as well as the prevention. I learned from researching about amblyopia, that it doesn't always occur from birth. It can actually come to people in an older age. Strabismus is also a condition that can come up suddenly with age. I came across vision therapy as an alternative to surgery to the eye. This topic relates to the chapter very well. In the end of the chapter we learned about a girl named Jane who had had cataracts from when she was a little girl and resulted in amblyopia.
Vision therapy is an alternative to surgery to the eye that is not always supported by optometrists. It seems as though they do not always support vision therapy because they either do not know a lot about it, or it is a matter of politics. The health care providers know that it costs more to do surgery, thus making them more money. Therefore economically it makes more sense for them to press surgery upon people, rather than having them try vision therapy first.
Vision therapy is basically teaching the eyes how to see correctly. The first three to eight years of life are a critical time to develop our vision. If cataracts go untreated during this time, it is said that we as humans cannot get over the symptoms of amblyopia, strabismus or anisometropia. I have learned from my research that this is not always true. I read different tutorials about grown-ups or people who have gone through the first quarter or so of their lives with blurry/fuzzy/not clear vision, who have a hard time with driving because they can't focus on far away objects, or have little reading abilities and do poorly in school because of vision problems. In the tutorials they all had gone to their optometrist's and they told them to wear glasses, it wont get worse, and there is nothing to worry about. They got second opinions from vision therapists, and with continuous therapy, they taught themselves how to see clearer.
Vision therapy should be more prevalent in schools. Schools have two options. 1) have someone on staff to help (usually an occupational therapist) or 2) deny that the therapy has anything to do with their learning problems. Vision is a huge contender when dealing with kids who have learning problems. Educators usually have an occupational therapist on staff (which gives the school more money), but occupational therapists do not know anything about vision therapy, thus they are beating around the bush, when all they need is a vision therapy session.
http://www.psychologytoday.com/blog/eyes-the-brain/201110/teaching-cross-eyed-people-see-in-3d
http://www.visiontherapy.org/vision-therapy/faqs/vision-therapy-FAQs.html#Q:5
http://www.thevisiontherapycenter.com/what-is-vision-therapy/definition/
Terms: amblyopia, strabismus, anisometropia.
It is interesting how people go about treatment. Some people might notice a problem but not report it until it gets bad enough to affect them in some significant way. It seems our interests lie in the things that can go wrong and if they do go wrong, how to fix them. Interesting post on treatment options.
After reading chapter 3 and some of the other blog posts, I decided to do my topical blog on strabismus. Strabismus is a condition in which the eyes are not properly aligned with one another. Abnormalities have a lot to do with anytime of biological finds that scientists have. It’s one thing to know how the eye works, but it’s also very intriguing to see how something can go wrong with an eye. My main interest in this topic is simply that I find abnormalities interesting. I think for many people, knowing what can go wrong with a particular topic is far more exciting than the topic itself.
When doing some reading on this strabismus, I searched mainly to just learn more about it. Again, strabismus occurs when both eyes do not look at the same point at the same time. Other names for strabismus are crossed eyes, walleye, squint, cock eye. Having strabismus prevents the eyes from having proper binocular vision, which can affect a person’s depth perception. There is no known cause for strabismus but it does run in families.
Strabismus occurs when the eye muscles that normally move both eyes in the same direction are not working correctly. There are six different muscles that surround the eye so that they can move the eye to focus on one object. Someone with strabismus usually has one eye that focuses on the object while the other eye turns the opposite direction and focuses on something else. This can confuse the brain, and may lead to the image from the weaker eye to be ignored.
Strabismus can occur in many different ways. Children develop it after birth but the cause is still unknown. Adults can acquire it from the eyes compensating for farsightedness. Other ways to develop it may be from blood vessel damage, brain damage, stroke, muscle and nerve damage.
Diagnosis is usually done by orthoptists, ophthalmologists and optometrists. The test for strabismus happens by placing a cover over the good eye and then watching the strabismic eye fixate on an object in front of it. The strabismic eye will then move to focus on it. After that, the doctor will remove the cover and will have the patient try to focus both eyes on the object. The strabismic eye will not move in this case because the good eye is already focused on the object.
Treatment for strabismus includes glasses, a patch over the lazy eye, medicines, and surgery. Wearing glasses is the most common form of treatment and usually corrects slightly misaligned eyes. An eye patch and medicines can help by using both eyes equally to focus on objects. For severe cases, surgery is required. Doctors will change the length or position of the muscles attached to the eye to help it align better.
After treatment, the eyes may look straight but there can still be some vision problems. Reading problems may occur and driving may become difficult. But, with early diagnosis and treatment, most people have their vision corrected. If not caught early, strabismus can lead to amblyopia.
Terms: Strabismus, amblyopia, depth perception, binocular vision, nerve, farsightedness.
http://children.webmd.com/tc/strabismus-topic-overview?page=2
http://www.nlm.nih.gov/medlineplus/ency/article/001004.htm
http://en.wikipedia.org/wiki/Strabismus
People are loving the visual deficits. It is interesting stuff. Hope you learned more after doing some research.
The section in the chapter concerning visual acuity sparked my attention. Acuity is the smallest amount of detail that the visual system can detect. Visual angle is similar to acuity, though it focuses on the angle that is subtended at the retina. An important factor that affects acuity is contrast. The higher the contrast is between objects, the more detail that can be detected. This is because in order for contrast to occur, the cycle must be taken into perspective. An example would be black symbols against a white background. This one reason why the eye doctor uses charts that have black letters against a white backdrop, it improves acuity.
Distance is also a factor that influences acuity. According to Wikipedia, 26 feet is essentially infinity because the eye treats 26 feet in distance similar to objects that are a longer distance away. This is another construct that eye doctors examine. Testing how far away one can see can affect accuracy of acuity.
An interesting aspect that I found what how visual acuity develops. Infants are typically born with an acuity of 20/400. When you note that a healthy functioning eye is measured at 20/20, this can become quite a shock. It appears that infants are essentially blind at first, because their eye continues to develop long after they are born. In fact, visual acuity typically develops in children around the age of 5. Another study found that contrast sensitivity matures between the ages of 8 and 19.
Acuity is important to sensation and perception because without it, we would feel quite helpless. It explains how people do everyday functions such as read the words on a screen or type out font on a computer. Without visual acuity, we would struggle to read and to determine fine details. It helps us understand that eyeglasses aren’t necessarily fixing the entire eye, but rather they are fixing ones acuity in the retina.
Terms: acuity, contrast, visual system, retina, visual angle, cycle.
http://en.wikipedia.org/wiki/Visual_acuity
http://www.journalofoptometry.org/en/revistas/journal-of-optometry-310/development-of-visual-acuity-and-contrast-sensitivity-13188760-reviews-2009
http://www.allaboutvision.com/eye-test/
Good stuff. It probably allowed you to learn more about things that are common "fixes" in our society that we sometimes don't know much about (e.g., eyeglasses, etc).
For this chapter the topic I found interesting was amblyopia. This topic was interesting to me because it was something abnormal, and I also wanted to know more information about why it develops. Amblyopia fits into our chapter because it deals with the development in our visual system.
I found it to be interesting that amblyopia usually only develops in one eye and it’s not only an abnormality in the visual system, but it is also an abnormality in the brain. The eye that has the amblyopia is a healthy eye, but the visual system for some reason does not communicate at all or correctly with the optic nerve in the brain. This causes the person to have blurry vision or double vision. Amblyopia can also cause depth perception because one eye is seeing normal and the other is not. Amblyopia can be caused by cataracts, strabismus (the eye is receiving an abnormal view), or refractive error (nearsightedness or farsightedness).
Often times amblyopia is referred to as “the lazy eye,” The wiring in one eye does not develop the same as the other eye which causes one eye to be stronger than the other. For the bad eye the wiring to the occipital cortex is incorrect. Amblyopia develops in children usually at a young age because their eyes and brains are still developing. It happens in 2- 3 percent of children
When this happens it is important that it is caught and corrected because if it continues the brain ignores the eye with the amblyopia. Also if waited too long (around the age of 9) the problem can never be corrected because the development of the visual system has already finished. The best way to correct amblyopia is to find it as soon as possible and to patch the good eye. Patching the good eye makes the eye with amblyopia develop and wire correctly and more strongly.
In some cases children do not even realize they have amblyopia, which is why it’s important to see an eye doctor as soon as possible. Someone may have a small case of amblyopia, in which it is never found. But in other cases it can be found as early as infancy. The earlier it is detected the better chance someone has of getting it corrected.
Terms: amblyopia, visual system, optic nerve, cataracts, strabismus, refractive error, occipital cortex
http://www.youtube.com/watch?v=0kHCHvFhzWc
http://www.youtube.com/watch?v=hc1uLN6OiTI
http://en.wikipedia.org/wiki/Amblyopia
Definitely helps you put normal visual deficiencies in perspective of what actually is going wrong with these types of impairment. Hope it was interesting to learn more.
As a kid I remember going to daycare, and seeing all sorts of different kids. A few times I encountered kids wearing eye patches, and this weeks research yielded a possible reason for that. I ended up deciding to look further into Amblyopia.
A person who has Amblyopia is commonly referred to as having a lazy eye, even though in actuality it is more complicated than that. This disorder often occurs with Strabismus, as it is the most common cause of Amblyopia, but neither have to exist for the other to. Strabismus is often a hereditary disorder. There are other problems that cause Amblyopia such as: Childhood Cataracts, Astigmatisms, Nearsightedness, and Farsightedness. Amblyopia can cause problems in depth perception, and can cause poor vision in one eye. It can also cause strange eye movements.
Amblyopia most often develops before age 6, so The American Optometric Associations suggests conducting eye examinations at 6 months and 3 years of age. The longer it takes to diagnose Amblyopia the harder it is to correct. Lazy eye does not dissipate over time, and in order to have decent treatment effectiveness it must be treated before the pre-teen years. Treatment can be started after the pre-teen years, but it has been shown to be decidedly less effective. There is very little research on treatment effectiveness with adults at the moment.
There are two fairly common treatment methods for children. The first is called Atropine. This method involves placing a drop of the drug Atropine in the stronger eye, daily. This blurs the vision of the stronger eye temporarily which requires the child to use the weaker eye. This is in turns stimulates the weaker eye causing the part of the brain where the visual system is seated to develop more fully. This seems like it would be rather crappy to experience. I have major allergies, so I grew up with eye drops. I hated those, so I can't imagine having eye drops that blurred your vision. The second treatment is called Patching. It involves putting a patch on the stronger eye obstruction the vision in that eye. This again causes the weak eye to be used. This also causes the visual system to develop more fully having the same affect as the first treatment type. These are being shown by current research to be effective on those age 7 to 17, even though these treatment methods were not thought to have much affect in that age group.
Key Terms: Amblyopia, Lazy Eye, Strabismus, Disorder, Hereditary, Cataracts, Astigmatism, Nearsightedness, Farsightedness, Depth Perceptions, Eye Examinations, Treatment Effectiveness, Pre-Teen, Atropine, Patching
Interesting how just blocking input and making you rely on your weaker eye can help people out. My friend is doing some cutting edge research on amblyopia with psychophysics if you are interested in learning more about it.
Sorry forgot to add my websites to the bottom of my post.
Here they are:
http://www.nlm.nih.gov/medlineplus/ency/article/001014.htm
http://www.aoa.org/x4699.xml
http://www.nei.nih.gov/health/amblyopia/amblyopia_guide.asp
I decided to devote this week's topical blog to the subject of contrast sensitivity. The book covers our ability to detect differences between bands of light and dark quite well. Our ability to distinguish between lower frequencies (black) and higher frequencies (white) is largely a product of the human contrast sensitivity function. This ability is measured by use of cycles, or repeated alternating series of light and dark bars. The smaller amount of contrast needed to pick out a sine wave grating, the greater a person's sensitivity.
As with most functions of the visual system, contrast sensitivity in humans has long been thought to peak at a young age and gradually decline with age. Poor contrast sensitivity is common in many visual disorders including cataract, diabetic retinopathy and many retinal disorders. Until recently, the only methods known to combat this slow degradation were corrective glasses, contact lenses, or eye surgery. For those patients with disorders that cannot be overcome through these methods contrast sensitivity can also be aided by the use of higher-contrast materials or better lighting.
As our visual systems deteriorate throughout our lives, a large premium has been placed upon acuity at the expense of contrast sensitivity. Sure, it does become more difficult to sharply detect smaller objects as we get older, but this may not simply be due to the size of the object. Often, the visibility of objects is decreased more by reduced contrast than by their size alone. In fact, the link between declines in a person's functional performance is oftentimes more strongly correlated with reductions in contrast sensitivity than losses in visual acuity!
With all this in mind, it is encouraging to note that researchers may have found an alternate way to fight contrast sensitivity loss that is independent of any optometric
aids or surgeries. Scientists at the University of Rochester recently discovered a possible link between action video games and improved contrast sensitivity. "Action" video games are categorized as first-person shooters with multiple unpredictable targets. Regularly playing these action video games is thought to train the brain to process the existing visual information more efficiently. The resulting improvements in contrast sensitivity even lasted for months after the study had ended! This sort of study just goes to show how the plasticity of the human brain should never be underestimated.
http://vision.psy.mq.edu.au/~peterw/csf.html
http://www.scientificamerican.com/blog/post.cfm?id=what-are-video-games-good-for-possi-2009-03-29
http://www.eyes.uab.edu/ohc00090.pdf
Good points. Interesting find on the video games increasing visual abilities. People with video game expertise also are pretty efficient at visual search and attention based find the target tasks. Probably is well related to the contrast sensitivity functions that they exhibit as well. Nice post.
A subject that stuck out to me was strabismus. The reason why I found this subject so interesting is because my sister actually has this condition. This condition is intertwined with this chapter by being mentioned in the book. Strabismus is a condition in which the eyes are not aligned properly. It appears as if they are what our society considers as “cross-eyed”. It is also commonly called esotropia or exotropia which means misalignment of the eyes. It typically looks as if one eye is in place and the other looks unaligned. Fortunately this condition cannot be correct by either glasses or contact lenses. Another treatment option for this condition is a patch that covers the weaker eye that forces the child to use the weaker of the two eyes. My sister had to wear an eye patch for 1 year while in grade school. Though she now has corrected this condition, sometimes her “lazy” eye does make an appearance if she gets too sleepy. It is reported that around %5 of children experience some form of strabismus during their life. If either glasses or an eye patch does not work, surgery can be a last resort. After the surgery is completed, the eyes may look as if they are straight however the vision problems may still be there. An individual who does have strabismus may view the world with an abnormal angle. Once an individual gets strabismus, it is very common for this condition to reoccur, so they must get routine checkups. The reason of this condition may be caused by the cranial nerves having a lesion. If the strabismus goes untreated, that is when is can result is an amblyopia. An Amblyopia is a disorder that reduces spatial vision in the healthy eye. Amblyopia is commonly referred to as a “lazy eye”.
http://en.wikipedia.org/wiki/Strabismus
http://www.strabismus.org/
http://www.nlm.nih.gov/medlineplus/ency/article/001004.htm
Terms: Strabusmus, cranial nerves, lesion, amblyopia, esotropia, exotrobia.
Definitely an interesting disorder.
I somewhat struggled to find something that I was interested in doing further research on. I found this chapter to be a little tougher read than the first two. What did strike my attention was the final section about the girl who almost couldn’t see stripes. In that section monocular deprivation is discussed. This stuck out to me because I was interested in learning how others who may have been in positions like Jane faired.
Another name fore amblyopia is “lazy eye” and it occurs when both eyes do not develop normal vision in early childhood. This condition affects 4% of children. 20/20 vision is not something that humans are born with but it is developed over time as images fall onto the retina.
There are three different causes of amblyopia they are deprivation, anisometropia, and strabismus. Deprivation is said to be the cause of the most severe forms of amblyopia. This is when there is a cloudiness or obstruction in the eye tissue that prevents the eye from forming clear images. In anisometropia, or unequal refractive error means that both eyes can not be in focus at the same time. Over time the brain will eventually disregard the image the unfocused eye captures. The unfocused eye will then never have normal vision. The last cause is misaligned eyes or strabismus. This is the most common cause. Strabismus happens because both eyes are not focused in the same direction. Although in most cases only one eye is affect in these situations it could affect both.
As far as treatment for amblyopia goes the earlier the better. The best outcome is predicted if corrective measures are taken before the age of 8. One way to try and improve the eyes that is lacking is by patching the good eye. Another way would be by prescribing glasses or even doing surgery in order to improve the issue. There are some cases where older children or adults can be improved through treatment. For adults perceptual learning is used to help improve vision. Researchers at McGill University have also found a way to temporarily improve visions in the bad eye for adults by using repetitive transcranial magnetic stimulation. This is done by rapidly changing magnetic fields to the head. This technique has also been used to treat Parkinson’s disease, migraines, and depression. Although the effects are short live it is a step in the right direction. I have known a few people with amblyopia or a “lazy eye”. Doing this research was pretty interesting and it makes me want to ask them what theirs was caused by.
Key terms: Amblyopia, strabismus, retina
http://www.drpatch.ca/adult-amblyopia-cure.html
http://en.wikipedia.org/wiki/Amblyopia#Clinical_trials_and_experiments
http://www.kellogg.umich.edu/patientcare/conditions/amblyopia.html
http://www.cybersight.org/bins/volume_page.asp?cid=1-3-5-68
The rTMS stuff is pretty hot right now. They've used it for cognitive experiments and also rehabilitating stroke patients and as you mentioned parkinson's. Sometimes the idea is to silence the intact hemisphere so that it isn't doing too much work, and letting the damaged hemisphere catch up. We have tDCS in my lab, which is a bit different, but they have used both of these neurostimulation techniques as rehabilitative tools as well as devices for conducting research about what happens to certain cognitive functions based on different types of stimulation to various sites on the scalp corresponding to various brain regions.
The topic I chose was lateral geniculate nucleus (LGN). This structure takes the input collected from the retinal cells and sends it to the cortex in the brain. Information from the left vision field goes to the right LGN while information taken in from the right vision field goes to the left LGN. This relates to the third sensation and perception because it is what happens after the cells in the eye have taken in information and before it gets to the back of the brain where it is processed into sight.
This chapter was not as easy to do as the first two, I actually changed my subject that I wanted to research. I started with cortical topography and that didn’t bring up any new or worth sharing information. So I changed to lateral geniculate nucleus (LGN) which leads me to blindsight. I was not only able to find a better definition, but also an experiment to test one’s blindsight. Blindsight is when someone claims they didn’t see anything (like a dot appearing on a screen) but later were able to point out where it was like they had seen. I try to stay away from .com sites due to the fact that I had a teacher at one point that would not let us use them for a project, but I think that msnbc.com is an exception to that rule. Although the only thing I really found interesting was this hand-held device that sends out a wave. If targeted at the back of a person’s head, that person will go temporarily blind because the wave disrupts the brain’s ability to process vision. (If this thing was released to the public, no one would have to say ‘close your eyes, it’s a surprise!’ ever again.) I also found studies that had taken place focusing on blindsight, but none that were less than ten pages. I was able to find one that contained a video of a blind sighted patient who was able to show that he could walk down a hallway and avoid objects in his path. It is pretty cool to watch.
http://serendip.brynmawr.edu/bb/blindsight.html
http://www.msnbc.msn.com/id/9879390/ns/health-health_care/t/study-suggests-brain-may-have-blindsight/
http://www.labspaces.net/blog/1550/Blindsight_and_Consciousness__what_can_we_learn_from_the_blindsighted_
Terms: lateral geniculate nucleus (LGN), retinal cells, cortex, vision field, cortical topography, blindsight, and blind.
The blindsight stuff is cool. The projections from the LGN also run to the superior colliculus which is our more primitive vision for action type pathway that allows us to avoid obstacles in our environment despite a lack of conscious awareness of doing so. So you don't have awareness that you just walked around an open deep pit, but you do it because your superior collicular pathway is still intact despite some damage to V1. Interesting stuff.
One of the most interesting concepts from chapter three that I took interest in was the disorder of amblyopia. From our chapter assignment I mentioned this concept and thought it would be a great way to learn more about the topic other than the very minimal information the book places on it. Amblyopia is a developmental disorder. To sum up this word, it is defined as an early occurrence of visual experience that causes an abnormal phenomenon in reduced pictorial perception in one eye. By this basic definition and the word alone, it may not seem like a familiar concept to the layperson. Simply put, it is most commonly known as “lazy eye”. The result of this uncharacteristic abnormality is often caused by lack of treatment left for a long and critical period where cortical connections are impossible. Strabismus is often the underlying factor that effects the alignment of the eyes where one object is shown as on image on the fovea for one eye, while the other eye is on a nonfoveal area. It is important to note that there is a definite difference and that amblyopia and strabismus are not the same condition, but that strabismus may lead to the disorder of amblyopia. Amblyopia may also be caused from astigmatism. Astigmatism causes a defect in the refractive exteriors in the eye, most commonly in the cornea. Another type may also come from the obstructed vision caused by cataracts due to unevenness of the crystallins. There appears to be many different associating factors that may ultimately lead to a lazy eye, however, roughly only one to five percent of individuals are actually affected by this disorder. Symptoms do not appear to always be very obvious and is not related to any health problems. The age of development from amblyopia is usually before the age of six, because of this it is recommended that optometric exams early in childhood are the best preventative care. Without preventative care and proper examination by a professional it is highly likely that both the child and parents or peers will not recognize it. Previously it was thought that this disorder was impossible to fix after around the age of seven. New research has disproven this idea and clinicians have proven progress in the treatment of amblyopia during adolescence. One key contribution to this progressive effort includes eye therapy.
http://en.wikipedia.org/wiki/Amblyopia
http://www.aoa.org/x4699.xml
http://www.strabismus.org/amblyopia_lazy_eye.html
Terms: amblyopia, strabismus, astigmatism, cataracts.
Definitely interesting stuff. Try to grab some articles from people doing the research on amblyopia to see what the current research endeavors are.
One topic I found interesting from the text was the information on amblyopia. Amblyopia is also known as a lazy eye, which is actually the proper term refering to strabismus. Amblyopia is a visual defeceincy in which the optic nerve doesn't properly transmit the visual stimulant. It is caused by anything that affects the clear vision of a persons eye before the age of six. An example of this is when a child is near or far sighted in one eye. This will cause the child to have a blurry picture in one eye which the brain will ignore. The brain ignoring the bad eyes signals will cause their vision in the bad eye to deteriorate. Amblyopia effects 1-5% of the population an can affect both eyes (which is rare.) It was discovered by David Hubel and Torsten Wiesel in 1891 when they showed the affects on cats. It can often go unnoticed until adulthood because the other eye makes up for the other one. In patients with severe cases patients suffer from poor spatial ability, poor contrast ability, and poor sensitivity to motion. Treatment can be patching the eye. Patching the eye involves covering of the good eye, which will force the bad eye to correct. If amblyopia is caught early enough, patching the eye can sometimes restore a persons vision to 20/20. No research has been done on amblyopia sufferers after the age of 17, but patching has been shown to work up until that point. It works best when corrected before the age of seven. Because of this, it is important that parents make sure their children get regular eye exams. Amblyopia causes more visual problems for people age 40 and under than all other diseases and injuries combined. I thought this was interesting because I had never heard of it before. I also thought it was important to know because I plan on having kids someday. If I had not known about this condition I may have let it go untreated and ultimately left my child with only one good eye as an adult.
Terms:amblyopia, optic nerve, strabismus,
http://www.webmd.com/eye-health/amblyopia-child-eyes?page=2
http://en.wikipedia.org/wiki/Amblyopia
http://www.strabismus.org/amblyopia_lazy_eye.html
I chose to write about spatial vision and contrast threshold developments as I observed my two nieces progress from infancy to the toddler stages, I find this of great interest to learn more about their visual development and growth. As they mature, they are more aware of physical things around them and their response to contrast and color has continually increased as they develop, along with their attention to detail and their responses to activity at a distance has increased significantly with age and their visual sensations, perceptions and development.
Spatial Vision is referred to the ability to see and visually define features. Two of the primary measurements of spatial vision are acuity and contrast sensitivity. The ability to visualize and define high contrast targets is static visual acuity. High contrast targets are usually black symbols, designs or letters against a white background to stimulate the visual attention or contrast and is a test in improving acuity.
According to the text, William James (1890) described spatial vision as the infant’s world as a blooming, buzzing confusion. Studies have shown that infants have a more developed visual system than originally thought. It has been hard to study, since you can’t ask an infant what they can or cannot see. But is has been observed that an infant is more drawn to a more complex view, (black and white view that is busy with varying figures, lines or shapes) over the non-stimulating or plain view, (dull or grayed view with no shapes, lines or other colors).
Studies have found that infant acuity improves rapidly over the first six months of life. An infant is usually born with an acuity range from about 20/400, (which indicates almost complete blindness), that improves to about 20/25 at six months of age. The reason infants do not have clear vision at birth is due to the lack of cone development. Visual acuity development begins as the cones elongate and migrate closer together, and may be fully developed by the age of seven.
Acuity measures detail, where contrast sensitivity measures different sized objects. Contrast sensitivity provides a more complete test of spatial vision. The text indicated that sensitivity to low spatial frequencies develops more rapidly than sensitivity to high spatial frequencies. Contrast sensitivity in infants may reach adult levels as early as nine weeks old. As the foveal cones develop, improvements in acuity and contrast sensitivity occur, along with development of the visual cortex. Sensitivity to fine and high special frequency and acuity improves steadily with age, contrast sensitivity development occurs between the ages of eight and nineteen.
I have observed the obvious differences in the acuity and contrast sensitivity between the two girls. The three year old is much more sensitive to detail at a distance, and also has a greater attention to color. While the one year old is more focused on objects that are presented to her and are in her reach. It has been helpful in being able to observe the girls as we study spatial vision and contrast threshold.
Terms: acuity, contrast sensitivity, spatial vision, contrast threshold, visual cortex
http://www.psych.ucalgary.ca/pace/va-lab/Marcela/Pages/page35a.html
http://www.ics.uci.edu/~majumder/vispercep/spatialvision.pdf
http://medical-dictionary.thefreedictionary.com/Contrast+threshold+function
Topical Blog #4
After reading the chapter on vision, I wanted to research more on how the eye adjusts to darkness.
-I found an old school video from 1941, showing how the eye functions. This visual ad was used in schools. How the light comes into the eye it first goes through the cornea then the aqueous humor, the pupil, crystalline lens, and finally reaches the retina. This visual shows that the light goes through many steps before being processed and sent signals to the brain for perception. When you are in the dark, there is no light, so the eye has to adjust to the dark and finally see the little light that is being absorb from the room. Light radiates from objects, and when we adjust to the dark, it accommodates to the room and focuses on the image.
http://www.youtube.com/watch?v=Lg73u1B61rM
-The second research I found tells step by step how the eye adjust to the dark. The eyes are compared to a camera, and it has range and can see in the light and the dark. The pupils gets smaller or bigger due to the amount of light that is around the person. The eyes can sense the light and has a rhodopsion chemical that acts as night vision. The rods and cones are used to see color and motion.The chemical absorbs and perceives the light, which is why it takes a couple minutes to adjust to the light again.
http://health.howstuffworks.com/human-body/systems/eye/eyes-adjust-darkness.htm
-The third article I found was in the New York Times, about aging and seeing in the dark. The theory in this article states that the older a person gets they lose more rods and cones in their eye, which does not allow them to focus well in the dark. The pupil in the eye gets very large when the lights are shut off to let in as much light as possible to see. The pupil, rods, and cones need to adjust, but when you do not have as many rods and cones as when you were younger, it is more difficult to see in the dark. The rods in the eye are the factor that is light-sensitive and goes slower in older eyes. When an older person can not adjust to the dark it is called dark adaptation. The eyes need all the rods and cones to be able to see in the light or the dark, it is very important part of the eye for visual perception. The only way to help older adults with their difficulties in vision in the dark, is to put up night lights around the house and go to the eye-doctor frequently to make sure things are not getting worse.
http://www.nytimes.com/2007/03/13/health/13brody.html?pagewanted=all&_r=0
vocab- accomadation, dark adaptation, rods, cones, retina, rhodospin, pupil,crystalline lens, aqueous humor, cornea
I liked learning about the disorder called Strabismus in the book, so I decided to focus on this in my topical blog for this week! I don't really fully understand how this disorder works, so I am hoping to find that out through this research!
I decided to go to the American Optometric Association website again to learn more information about this disorder and I was surprised to find that this is what they call cross eyed! I never knew that being crossed eyed had a technical term and I didn't get that this is what it meant in the book. Basically, the website elaborated on the fact that both eyes don't look in the same way at the same time. I also liked learning that this can be caused in several other ways than being born with it. Accidents and medical conditions can also make this disorder appear in a patient.
http://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/strabismus?sso=y
I went to the medical encyclopedia for my second point and found some more interesting points about this disorder. I learned here that there are 6 different eye muscles around the eye to make them look at an object and in strabismus, the muscles don't work together and can't focus on one specific object. This is due to muscle control, not muscle strength. This is a cool concept to me because I thought this had to do with something in the back of the eye, not the surrounding muscles. This website also was cool to look at because it shows several reasons as to what can cause strabismus in both children and adults.
http://www.nlm.nih.gov/medlineplus/ency/article/001004.htm
Strabismus has it's own website! I didn't know that so I had to make sure to look at it for my blog. Through this website, I learned that the eye with the disorder actually moves all the time. Some have a constant motion and others have a less constant or frequent motion. This was interesting to me because I thought the eye was stable in another position, not constantly moving. I also learned that this disorder can be treated, but usually you have to wait until adulthood.
http://www.strabismus.org/