About the diseases
Hope for Vision is dedicated to funding the development of treatments and cures for blinding diseases, particularly retinal degenerative diseases. These diseases can affect anyone - all age groups, genders, and ethnicities. Although many of them progress at different rates and at different times in life, they all cause the degeneration or deterioration of the retina - the light-sensitive tissue lining the back of the eye that converts light to electrical impulses. These electrical impulses are sent to the brain through the optic nerve allowing us to see. The degeneration of the retina disrupts this process and causes progressive vision loss, ultimately leading to blindness.
Below is a list of the most common forms of these diseases.
Retinitis Pigmentosa and other Retina-wide Degenerations
Retinitis Pigmentosa (RP) is the name given to a group of inherited eye diseases that cause the degeneration of photoreceptor cells of the retina, also called rods and cones. These are the cells which capture and process light helping us to see: the rods are associated with peripheral vision and night vision; the cones with clear central vision and color vision. RP mutates the function of the rod and cone cells and they slowly stop working.
Most forms of RP first cause the degeneration of rod cells, leading to night-blindness. As the disease progresses and more rod cells degenerate, loss of peripheral vision is experienced too. Many people with RP often experience a ring of vision loss in their mid-periphery with small islands of vision in their very far periphery. Others report the sensation of tunnel vision, as though they see the world through a straw. Many retain a small degree of central vision throughout their life.
Other forms of retinal degeneration first affect cone cells and central vision. Such conditions tend to be named cone-rod dystrophies (CRD). People with CRD first experience a loss of central vision that cannot be corrected with glasses or contact lenses. With the loss of cone cells also come disturbances in color perception. As the disease progresses, rod cells degenerate, causing night blindness and low peripheral vision.
Symptoms of retinitis pigmentosa and CRD are most often recognized in children, adolescents and young adults, with progression of the disease continuing throughout the individual’s life. The pattern, degree and rate of visual loss are variable. These diseases are genetic, meaning that parents can pass the disease down as unaffected carriers or actually show the eye problems themselves. There are recessive, dominant and X-linked forms of the diseases.
Usher Syndrome
Usher syndrome is a genetic recessive disorder that causes the combination of progressive hearing loss leading to deafness and retinitis pigmentosa leading to blindness.
Researchers have identified three major types of Usher syndrome, designated as types I, II, and III, which are then further divided into distinct subtypes. These types are distinguished by their severity and the age when signs and symptoms appear.
- Type I: Individuals with Usher syndrome type I are typically born completely deaf or lose most of their hearing within the first year of life. Progressive vision loss caused by retinitis pigmentosa becomes apparent in childhood.
- Type II: Usher syndrome type II is characterized by hearing loss from birth and progressive vision loss from retinitis pigmentosa that begins in adolescence or adulthood. The hearing loss associated with this form of Usher syndrome ranges from mild to severe.
- Type III: People with Usher syndrome type III experience progressive hearing loss and vision loss due to retinitis pigmentosa beginning in the first few decades of life. Unlike the other forms of Usher syndrome, infants with Usher syndrome type III are usually born with normal hearing. Hearing loss typically begins during the first two decades of life, and by middle age, most affected individuals are profoundly deaf. Vision loss caused by retinitis pigmentosa develops in late childhood or adolescence.
Click here to learn more about Hope for Vision's Usher III Initiative - a special program dedicated to finding treatments and cures for Usher Syndrome Type III.
Age Related Macular Degeneration and Juvenile Macular Degeneration
Age-related macular degeneration (AMD) is the leading cause of vision loss in Americans 60 years of age and older. It is a progressive disease of the retina wherein the light-sensing cells in the central area of vision (the macula) stop working and eventually die. The disease is thought to be caused by a combination of genetic and environmental factors. An estimated fifteen million people in the United States have it, and approximately two million new cases are diagnosed annually.
AMD occurs in two forms: wet and dry. Wet AMD occurs when abnormal blood vessels behind the retina leak blood and fluid, rapidly causing photoreceptor cells in the macula to stop functioning and deteriorate. Dry AMD occurs when deposits of debris, called drusen (which are normally carried away by blood vessels in the eye,) build up and cause photoreceptor cells in the macula to stop functioning.
Other less common types of macular degeneration, which are hereditary and can affect younger people, are Best's disease, Stargardt's disease, and Sorsby's disease. Collectively, these types are called juvenile macular degeneration.