Blind Spots
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Blind Spots
Abstract
Everyone has a blind spot in the visual field caused by an absence of nerves on the retinal wall where the nerve ganglia enter. Our brains “correct” this blind spot by filling-in the missing information so that we do not notice the blind spot in normal, daily activity. There have been a few studies conducted to determine how the brain compensates for the phenomenon.
Recent studies indicate that in certain people seeking chiropractic treatment, unequal blind spots result from muscoloskeletal misalignments. This research has been controversial; however, it brings up several interesting questions. There are conditions that can damage the retina, causing blind spots in the visual field. It is generally assumed that athletes maintain a better level of general health, via exercise and a healthier diet, than those who do not engage in athletic pursuits.
This study used blind spot mapping techniques of the chiropractic industry to map the blind spots of 10 athletes and 10 non-athletes. The blind spots of athletes and non-athletes showed a statistically significant difference.
Introduction
Every eye has a blind spot .The blind spot is the hole in the retinal wall where the nerve ganglia pass though. This area of the retina contains no photoreceptors and therefore creates a black spot in every persons vision. The gap created by the blind spot is approximately 6 degrees of the total visual field, which is a large area, relatively speaking. We do not see this area in our normal functioning because our brain has a mechanism for “filling in” the missing information. The information that would normally be received by the blind spot is projected onto the other eye and the brain essentially “averages” the image (Lou and Chen, 2003).
The blind spot in physical structure and given the normal variances in human physiology, it would be expected that there would be little variation in the blind spot from person to person. However, there are certain conditions that could cause damage to the retinal wall, thus causing nerve damage to he photoreceptors, thus causing a blind spot. This damage may cause an additional blind spot in the visual field; of if damage occurs to the retina surrounding the natural blind spot, the natural blind spot could essentially be enlarged. (Windsor and Windsor, 2003; Hall, 2003; and Seddon and Kuijk, 1998).
There are several factors that can effect eye health, such as nutrition and general health. It is generally assumed that athletes have an overall healthier lifestyle that n the general public. They are assumed to engage in habits that promote good health such as eating more nutritiously, exercising and maintaining a generally higher level of health than the general public. It is therefore the premise of this study that athletes would be expected to have fewer eye-related health problems and that these problems would result in fewer visual blind spots or smaller naturally occurring blind spots than in non-athletes.
This study will use methods for mapping blind spots in the chiropractic field to measure the blind spots of a group of athletes and a group of nonathletes. This research will support the hypothesis that the group of nonathletes will be found to have larger blind spots due to decreased general health.
Literature Review
The existence of a blind spot in each eye is a naturally occurring anatomical trait and therefore has received very little academic attention in itself. There has been limited attention to the study of how our brain “compensates” for this phenomenon, however, once explained, it received very little attention. The blind spot can be located if a person trains their attention to it. There is a simple visual test; contained in APPENDIX I that can help a person “see” the blind spot in their right eye.
There have been a group of chiropractors that claim that in persons with certain musculoskeletal misalignments, the blind spot in each eye is unequal. They also claim that adjusting the spine can alleviate this condition. This research will not attempt to confirm or deny these claims, but will rely on techniques derived from the practice of “blind spot mapping” or develop a method for testing the blind spots of a group of athletes and a group of nonathletes. No similar studies could be found, save for one study conducted by an ophthalmologist, using opthamological equipment to assess general retinal scarring in certain persons diagnosed with opthamological disease (Cai and Cavanagh, 2002).
Chiropractors have developed a technique, primarily to be used as a diagnostic technique to detect what they claim is an “unequal blind spot” in the eyes. The claim that an enlarged blind spot can diagnose a malfunction in the brain. These studies have come under heavy criticism as there are several illogical arguments posed by them (Hall, 2003). Hall finds several areas of contention in the design of these experiments. In addition, several chiropractors claim to “cure clumsiness” by increasing the peripheral vision of patients. These claims are completely unfounded, as the blind spot is located in the primary visual field, not the peripheral vision. These doctors are causing confusion with the blind spot when driving that is caused by mirrors, not the eyes (Hall, 2003). These studies have very little academic credibility, however, do provide a useful tool for mapping the blind spot of the groups being studied in this research.
It has been a long held concept that eating certain vegetables can improve eyesight. Recently, physicians have been prescribing leafy green vegetables to prevent a condition called macular degeneration. Other food have also been recently cited as having health benefits for the eyes such as egg yolks, orange juice, and corn (Seddon, and Kuijk, 1998). Macular degeneration causes blindness by the development of “macular hole,” which consists of patches of dead nerves on the retinal well, thus creating blind spots.
It is generally held that athletes tend to follow a more nutritious diet than the non-athletic population. The typical athletic diet is high in carbohydrates, proteins and a balance of the necessary vegetables to maintain overall health. This improved diet has been shown to have a number of health benefits. Athletes are expected to have an improved diet and improved general health as compared to the average population. Therefore, it could be expected that there would be fewer eye problems than in the general population. One effect of this improved eye