Presbyopia
How Presbyopia Affects Vision and Perception
Normal Vision
The eye and the structures within allow us to view the world and everything in it. As light is reflected off an object and into a persons eye, the cornea and lens work to focus the object (Goldstein, 2014). The clear, sharper image of the object is formed by the retina, a network of nerve cells covering the back of the eye (Goldstein, 2014).
Vision with Presbyopia
The lens starts out as a soft and flexible structure that changes shape in order to focus (www.essilorusa.com...). As we age, the lens hardens and becomes less flexible making it impossible for light to properly focus on the retina (Krucik, 2013). This disorder is inevitable with the natural aging process (Krucik, 2013).
Normal Vision vs. Presbyoipa
Portions of the Brain Used in Visual Perception
Vision is processed through a series of steps that form our perception. The first obvious starting point is that the person needs an object to look at. This can be an object in our environment such as a car or even words in a book. The light first reflects from the object to the persons eye. The cornea and lens then work to focus the light rays from the stimulus and create a clear image on the retina (Goldstein, 2014). The retina is a network of nerve cells covering the back of the eye (Goldstein, 2014). The next step is transduction or the change from light energy to electrical energy (Goldstein, 2014). The visual receptors allow the image to change from light to electrical energy. These signals are sent through the network of neurons of the retina to the cerebral cortex which is the primary processing center as well as the occipital lobe and frontal lobe. The frontal lobe processes information from all of the senses and allows for perception that requires more than one of our senses (Goldstein, 2014).
Percieving objects and scenes
How we perceive objects and scenes can be described in a number of ways. Our knowledge, memory and expectations or cognitive influences on perception, help us to form perception through top down processing (Goldstein, 2014). Another approach to perception is the psychological approach that consists of measuring the relationship between stimuli and physiological responses as well as the relationship between behavioral and physiological responses (Goldstein, 2014). The Gestalt Principles also contribute to the explanation of how we perceive objects. The principle of good continuation explains why we perceive things in a continuous manner or belonging together (Goldstein, 2014). The principle of pragnanz or simplicity describes that our brain views stimulus in its simplest form. The next Gestalt Principle of similarity explains how the human brain combines similar stimulus by color, shape, size or orientation (Goldstein, 2014). The principle of proximity is the tendency to group objects that are close to each other and common fate explains how objects going in the same direction are also grouped together (Goldstein, 2014). In the event that a stimulus is grouped together the proximity principle is over turned. This is known as the principle of common region. The last Gestalt principle is uniform connectedness, This principle also over turns proximity stating that connectedness overpowers proximity (Goldstein, 2014). Our brain is a very complex organ that is capable of organizing all of the information obtained through our vision. Our brain helps to create our perception but good vision creates a clear image for the brain to process.
How Presbyopia Affects Vision
Although the color of objects may not be affected by Presbyopia, the ability to see objects and or words up closely is. Things that are close are harder to focus due to the hardening of the lens as well as the ciliary muscles becoming weaker due to age (Goldstein, 2014). This disorder only affects near vision. In normal vision the lens is capable of flexing and bending to accommodate the close proximity of stimulus.
Treatment for Presbyopia
Treatment or correction of Presbyopia depends on the individual and their preference. Some may opt to hold objects and reading material at an arms length for better focus. Others may be happy with a pair of reading glasses that can be purchased at most stores. If these options do not fit, one may wish to visit their eye doctor for reading glasses that are customized for their eyes. Multifocal Contact lenses are also an option for those who need multiple levels of correction (Boyd,2013). Presbyopia can also be corrected with monovision contact lenses that train one eye for long distance vision and the other eye for near vision (Boyd, 2013). This can also be achieved through Lasik eye surgery. Another surgical option is called CK or conductive keratoplasty. Although this correction is temporary, radio waves curve the cornea improving the individuals near vision (Boyd, 2013).
Resferences
Boyd,K.(2013). Presbyopia Treatment. retrieved from www.geteyesmart.org/eyesmart/diseases/presbyopia/treatment.cfm
Goldstein,B.E.(2014). Sensation & Perception. (9th ed.). Belmont,CA. Cengage Learning.
Krucik,G.MD.(2013). Presbyopia. retrieved from www.healthline.com/health/eye-health
n.a.(n.d.). Getting Focused. retrieved from www.essilorusa.com/EN/AboutVision/AboutYourEyes/HowEyeWorks/Pages/GettingFocused.aspx
Goldstein,B.E.(2014). Sensation & Perception. (9th ed.). Belmont,CA. Cengage Learning.
Krucik,G.MD.(2013). Presbyopia. retrieved from www.healthline.com/health/eye-health
n.a.(n.d.). Getting Focused. retrieved from www.essilorusa.com/EN/AboutVision/AboutYourEyes/HowEyeWorks/Pages/GettingFocused.aspx