Nine percent of patients have been identified as X chromosome linked, sixteen percent are autosomal recessive, and twenty-two percent are autosomal dominant. There are also several other less common types. (Anthony de Bues, MD, PhD.). Contrary to Retinitis Pigmentosa, Macular Degeneration is usually not inherited in any foreseeable manner. Studies are in the process of identifying the role of heredity in Juvenile Macular Degeneration, which is not age related. AMD is difficult to prove whether it is genetic since the onset of AMD is so late in life.
The onset of Retinitis Pigmentosa varies from infancy to the thirties and forties, although patients are mostly diagnosed in young adulthood. On the other hand, Age-related Macular Degeneration usually affects people over the age of 60. There are less frequent reports of patients as young as 40 years old who have developed AMD. While there are no external or environmental teratogens that influence the occurrence of RP, AMD can be stimulated by factors such as smoking, obesity, gender (women are more likely to fall subject to AMD than men), and race (Caucasians are at a greater risk than African Americans). There is no sexual predilection for Retinitis Pigmentosa; men and women are equally affected. .
While both RP and AMD attack the cells in the retina, the two diseases are quite different in their retinal deterioration. Retinitis Pigmentosa attacks the delicate layer of rod cells affecting the peripheral vision, while Age-related Macular Degeneration affects the cone cells, damaging central vision. The retina in the eye is made up of these rod cells and cone cells. Rod cells are responsible for seeing movement out of the corner of the visual field, as well as sending signals to the brain about images picked up in low light or at night. Rod cells are located in each eye, but they are more numerously concentrated towards the outer part of the retina.
