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The Fantasy Realm of Vision: How Much of the World Can the Human Eye See?
In our daily lives, we often overlook the complexity of vision. It is not only a sense, but also the entrance to a whole world. How is the range of human vision defined? What causes the reduction in vision? These questions not only involve physiology and psychology, but are also closely related to how we understand and perceive our surrounding environment.
Visual range is "the part of space where an object is visible at the same time while gazing steadily in one direction."
Vision is widely studied in medicine, especially in the fields of ophthalmology and neuroscience. The structure of the visual field is often of concern, and visual field testing is often performed to determine whether the visual field is affected by the disease. These tests can reveal localized vision loss or more widespread vision loss caused by the disease.
Normal visual field range
Under normal circumstances, the range of human monocular vision is about 60 degrees, looking toward the nose and up to 107 degrees toward the outside. In addition, the upward and downward visual ranges are 70 degrees and 80 degrees respectively. When the fields of view of the two eyes overlap, a binocular field of vision is formed, which further improves our visual ability.
It is said that the central 17-degree diameter visual field of the eye corresponds to the macula, and the central 5.2-degree diameter is called the fovea, where the precision of vision reaches its highest level.
Measuring method of visual field
The measurement of visual field is usually carried out through a method called "visual field test", including dynamic and static methods. In the dynamic test, a light spot will move slowly within the white interior of the hemisphere, while in the static test, the light spot will flash at a fixed position with different intensities until it is noticed by the observer. Commonly used visual field testing instruments include automated Humphry visual field analyzers, Optopol visual field meters, etc.
The results of a visual field test are often shown as "full field of view to finger count," which means the observer has a correct idea of the extent of the visual field.
Causes of loss of visual field
Loss of visual field is caused by various diseases of the eye, optic nerve, or brain. For example, glaucoma causes loss of peripheral vision, while conditions such as macular degeneration affect central vision. Lesions in the optic nerve path can also cause specific visual impairments, such as hemianopia, quadrantopia, etc.
The mainstream classification of visual field defects includes: retinal lesions, optic nerve lesions, and optic chiasm lesions.
Visual field defects in glaucoma
A common visual field defect in glaucoma patients comes from damage to the retinal nerve fiber layer. Many early glaucoma changes will appear primarily in the central visual field, especially in the Bjerrum area, which is an important reference for identifying glaucoma during visual field testing.
Small parapterygoid central scotoma is a clinically important visual field defect in early glaucoma.
Other visual field defects
In addition to glaucoma, macular degeneration (AMD) and visual pathway lesions can also cause visual field defects. Lesions in the macular area can cause loss of central visual field; lesions in the visual pathway may lead to changes in various visual patterns, thereby affecting people's quality of life.
The type of damage to the visual pathway can help locate the location of the lesion, including lesions in the eyeball, optic nerve and its cross, and visual radiation.
The secrets of vision are closely related to our sensory experience. When we realize the limited scope of vision, we can't help but think about all this: How much real reality can we see in the many unobserved worlds?
