How Eyesight Works
How Eyesight Works
Those with Vision Problems
The estimates of those people in the general population that are in need of corrective visual methods to correct blurred vision ranges from 75%-90%, depending on the source consulted as well as the factors used for the criteria; these factors being age, sex, and the activities that the visual correction is needed for, such as reading or driving. According to the Vision Council of America in 2009, approximately 75% of adults use some sort of vision correction for blurred vision. About 64% of these people wear eyeglasses, and about 11% wear contact lenses, either exclusively, or with glasses. Over half of all women and about 42% of men wear eyeglasses. Regardless of the accuracy of the provided percentages or factors which an individual may not be able to change, the fact that the percentages of men and women requiring vision correction for blurry vision are increasing dramatically over time, is not being disputed.
There are three ways to improve eyesight and correct blurred vision; one, although temporary, is through correction such as eyeglasses or contact lenses, two is surgery, and three is vision therapy. Vision therapy is the safest and most reliable way to improve your eyesight.
Before considering any method or procedure to improve your blurry vision whether it is by correction, surgical, or natural means, it is important to understand how your vision works, as well as the major factors that affect your visual clarity. This will help you to better learn how you can naturally improve eyesight.
How Does Your Eyesight Work?
The Eye is an Organ
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptor cells in conscious vision connect light to movement. In higher organisms the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Problems that occur during this process can result in poor vision.
Light into Sight
Light enters the eye and passes through the cornea where the lens focuses the light onto the retina. The retina contains two types of cells, called rods and cones. The cones handle color vision and detail, and the rods handle vision in low light. When light makes contact with either of these two types of cells, a series of complex chemical reactions takes place. These chemicals result in electrical impulses that when transmitted to the visual system of the brain and are interpreted as the objects you see. These chemicals are derived from vitamin A, which is why a lack of vitamin A causes vision problems.
Parts of the Eye
- The sclera maintains the shape of the eye.
- At the front of the eye, the sclera is clear and is called the cornea. All light must first pass through the cornea when it enters the eye.
- The choroid contains the blood vessels that supply blood to the eye.
- The ciliary muscle is attached to the lens, and contracts and relaxes to control the size of the lens for focusing.
- The iris is the colored part of the eye.
- The iris is an adjustable diaphragm around an opening called the pupil.
- The iris and pupil have a set of muscles that controls the opening of the pupil, allowing more or less light into the eye.
- The retina contains a chemical called rhodopsin that converts light into electrical impulses sent through the optic nerve that the brain interprets as vision.
- The lens is a clear dual convex structure that changes shape based on the contractions of the ciliary muscles. The lens fine tunes vision.
Visual perception is the ability to interpret the surrounding environment by processing information that is contained in visible light. The resulting perception is also known as eyesight, sight, or vision. The various physiological components involved in vision are referred to collectively as the visual system.
The Visual System
The visual system in humans and animals allows individuals to assimilate information from the environment. The act of seeing starts when the lens of the eye focuses an image of its surroundings onto a light-sensitive membrane in the back of the eye, called the retina. The retina is actually part of the brain that is isolated to serve as a transducer for the conversion of patterns of light into neuronal signals. The lens of the eye focuses light on the photoreceptive cells of the retina, which detect the photons of light and respond by producing neural impulses. These signals are processed in a hierarchical fashion by different parts of the brain, from the retina upstream to central ganglia in the brain. The retina sends signals along the optic nerve to the visual cortex of the brain.
Visual acuity is “the ability to distinguish fine detail” and is the function of the cone cells to differentiate one object from another in terms of visual angles.
The eye has multiple angulated surfaces that cause light to bend. When everything is working correctly, the light arrives at the retina in perfect focus for interpretation resulting in clear vision. When the focus is not at the right spot on the retina, the result is blurry vision.
Accommodation is the process by which the eye changes optical power by reshaping the lens to maintain focus or a clear image on an object as its distance varies. Accommodation normally acts as a reflex, but it can also be consciously controlled. We can change the optical power of our eye by changing the shape of the elastic lens by using the ciliary muscle. This is extremely important to the effectiveness of vision therapy.
In order to see objects at a distance the ciliary muscle must relax around the lens to allow it to become thinner. In order to see up close the ciliary muscle must contract around the lens to make it thicker. The ciliary muscle must stay tight and contracted around the lens for long periods when you read or work on computer screens for extended times.