There are many viral skin infections. They range from the common to the rare, from the mild to the severe and from those causing just skin infection to those with associated systemic disease. The following is a brief account of a selection of the important viral skin infections. Many of the diseases mentioned here are covered in greater detail elsewhere and the reader is referred to appropriate links. Nonspecific viral rash. This is a widespread erythematous rash sometimes seen in viral infections. It is accompanied by the common symptoms of a viral infection, such as fever, headache and malaise. The rash usually develops rapidly. The appearance varies but commonly takes the form of an erythematous blotchy eruption. Local viral infections
The retina is the array of light receptor cells that lines the back of the eye. It contains two types of receptor cells, named after their shape; rod and cone cells, and interconnecting ganglion cells, of which there are two types with differing properties, X and Y cells.
Rod cell. Rod cells, or rods, are photoreceptor cells in the retina of the eye that can function in less intense light than the other type of visual photoreceptor, cone cells. Rods are concentrated at the outer edges of the retina and are used in peripheral vision. On average, there are approximately 90 million rod cells in the human retina. More sensitive than cone cells, rod cells are almost entirely responsible for night vision.