Correcting Peripheral Vision Disorders - Improve Vision
Loss of peripheral vision is one of the many vision disorders that can affect the human eye. Eyesight that occurs outside the center of your vision is known as peripheral vision. When you look at any object, your center vision focuses mainly on that object. However, you can also see other things that are outside the scope of your center vision, without actually moving your eyes or your head. This field of vision is known as peripheral vision or inside vision. In simpler terms, peripheral vision means being able to see ¡®out of the corner of your eye.
Types of Peripheral Vision Disorders
Peripheral vision can be classified into 3 different types, namely:
- Far peripheral vision: Eyesight that exists at the very edges of your field of view.
- Mid-peripheral vision: This exists in the middle of your vision field
- Near-peripheral vision: This sight exists immediately adjacent to your center vision. It is also known as Paracentral Vision.
When a person's visual field becomes lower than normal, they are said to be suffering from loss of peripheral vision. Normal ranges in this regard are about 140 to 180 degrees for the horizontal visual field, and about60 degrees above and approximately 75 degrees below the horizontal axis of vision, for vertical field of vision.
Here are the various types of peripheral vision disorders:
- Reduced Peripheral Disorders:This indicates a loss of only a small portion of the visual field.Horizontal field of vision in this case is usually more than 90 degrees.
- Tunnel Vision Disorders:Here, the horizontal visual field is typically less than 90 degrees.The vision that remains is like looking through a tunnel, thus the name.
- Vision Mobility Impaired:In this type of peripheral vision disorder, the visual field is less than 30 degrees. Such people are not even safe when walking on the street, unless they use vision improvement devices.
Causes of Peripheral Vision Disorders
These vision disorders can be caused due to a number of reasons, such as:
- Glaucoma: A progressive eye disease, glaucoma is the most common cause for tunnel vision.
- Branch retinal vein occlusion: Formation of a localized clot in a branch retinal vein, leading to loss of peripheral vision.
- Branch retinal artery occlusion:This condition is generally the result of a clot from a carotid artery,either in the neck or heart. This causes interruption of blood flow to the macula, thereby lowering side vision.
- Migraine: A neurological disease that causes severe, unbearable headaches.
- Ischemic optic neuropathy:A portion of the optic nerve loses its function due to interrupted blood flow to the nerve, thus causing loss of peripheral vision.
These are the more common causes of peripheral vision disorders, whereas some of the rare causes include:
- Retinitis pigmentosa: A hereditary disorder that results in the development of pigmentary deposits on the peripheral retina, which in turn causes peripheral vision to become lower and lower.
- Stroke: If a stroke attacks any side of the visual center in the brain, peripheral vision can be affected
Other rare causes of peripheral vision disorders include gyrate atrophy,tilted optic disc, tumors in the pituitary gland, brain tumors, and retinal degenerative diseases such as choroideremia.
Vision Improvement Technologies For Improving Peripheral Eyesight
Vision improvement technologies have made available a device known as Field-expanding eyeglasses that help to improve side vision. These field-expanding devices do not actually increase the usable visual field. Instead, they help to displace images towards the remaining vision field of the patient, so that awareness is created in the areas where vision field is lost. A person can thus see images at the side,above, and below their center of sight without moving their eyes, or turning their heads.
Optical field-expanding devices make use of many aids such as:
- Spectacle-mounted mirrors
- Amorphic lens10
- Reverse telescopes
- Cemented prisms
- Fresnel press-on prisms
- Magnification and illumination devices
Many adaptive vision improvement technologies can also be used to enhance field of vision. These are:
- Scanning therapy
- Orientation and mobility training
- Eccentric viewing
- Various cane techniques
- Occupational therapy
- Using guide dogs
To be able to use these adaptive technologies proficiently, extensive training and adjustment is required. However, if a person can adapt to these vision improvement technologies, then it is possible to correct peripheral vision disorders considerably.