Human Vision Disorders

Vision is perhaps the most critical sense available to humans. Those suffering from vision disorders are often subject to significant inconvenience. While many are familiar with common diseases of the eye, many are unaware of several of the more debilitating disorders.

While there are a wide variety of disorders associated with the eyes and vision, two of the most common, most diagnosed, and most treatable, are myopia and hyperopia. Myopia, typically called "nearsightedness" is a condition in which the patient has difficulty focusing on distant targets, yet nearby targets can be focused upon with ease. Conversely, hyperopia is a condition in which distant objects can be easily brought into focus while much more immediate stimuli appear blurred and out of focus. This disorder is often referred to as farsightedness. While each of these disorders provides difficulty in focusing on objects, the difference lies primarily in the distance at which an object is unclear. Each of these disorders is thought to be the result of a shape abnormality in the eye, an inability of the lens to properly expand, contract, flatten, or round itself. Both of these disorders can be contracted at any point in the life span; however increased vision problems are associated with increased age. Both disorders can be corrected with surgery, or accommodated for with corrective lenses such as glasses or contact lenses. Neither of these pathologies should be confused with astigmatism, as that is caused by an abnormality in the shape of the cornea. Astigmatism causes difficulty recognizing fine detail, especially at a distance. Frequently, patients report vertical lines and objects such as walls appear slanted or leaning. Color blindness or color deficiency is the inability to perceive or recognize differences between certain colors. Typically, color blindness is hereditary, but may also be caused through injury or chemical exposure. Glaucoma is a group of diseases of the optic nerve involving loss of retinal cells. Glaucoma is typically associated with inner eye pressure and clouded vision. While treatment option range from surgical procedures, to medicinal marijuana, to oral medication, there is no cure. Between three and five percent of the population suffers from Amblyopia, or lazy eye. Primarily associated with non-aligned eyes, Amblyopia is also associated with poor depth perception, poor spacial acuity, and reduced sensitivity to motion. Nyctalopia or night blindness is a disorder impairing vision in low light. Nyctalopia may be hereditary, or be caused by injury or malnutrition.