Vision and Perception - Visual Pathology
There are several vision disorders that are more common as one ages. These pathological changes alter the structure and function of the eye and can severely limit vision if not treated. The most common disorder is cataracts. A cataract is a pathological increase in lens opacity that severely limits visual acuity. While there is a reduction in lens clarity for nearly all elderly individuals, cataracts affect only one in twenty persons over the age of sixty-five. It is the leading cause of functional blindness in older adults but it can be successfully treated by simply removing the affected lens and replacing it with a prosthetic lens.
Glaucoma. is the second leading cause of blindness in the United States. Although the pressure within the eye remains essentially constant until the later decades of life, a pathological increase sometimes occurs. Glaucoma is characterized by both increased intraocular pressure and the resulting atrophy of the nerve fibers at the optic disk. The behavioral symptom of the disorder is a reduction in the perceiver’s visual field. That is, a person loses sensitivity in the periphery of his vision. Unfortunately, this alteration in vision often goes unnoticed until the damage is quite advanced. Regular screening for glaucoma by measuring intraocular pressure would permit the detection of the disease at a point when medical intervention could be effective in limiting damage to vision.
Macular degeneration is a deterioration of the retina in the area of central vision that is critical for the perception of fine detail and color. The afflicted person has difficulty with all visual tasks that are ordinarily dependent on central vision, such as reading, face identification, and television viewing. Strong magnification can be used to improve reading ability. Since the peripheral fields are not affected, the person does not have difficulty in walking and moving through his environment.