What is the definition of Cone Dystrophy?

Cone dystrophy is a general term for a group of rare eye disorders that affect the cone cells of the retina. Cone cells allow a person to see color and fine detail, and they work best in bright light. The cone dystrophies can cause a variety of symptoms such as decreased visual clarity when looking straight ahead, a reduced ability to see colors, and an increased sensitivity to light. There are two main subtypes of cone dystrophy, called stationary cone dystrophy and progressive cone dystrophy. The age when symptoms begin, the type and severity of symptoms, and the progression of symptoms are all very different between individuals, even between people with the same type of cone dystrophy. Mutations in many genes have been found to cause cone dystrophy, and the condition can be inherited in an autosomal dominant, autosomal recessive, or x-linked manner.

How is Cone Dystrophy diagnosed?

The diagnosis of cone dystrophy is made based upon the presence of characteristic symptoms, a detailed family history, a thorough clinical evaluation and a number of supporting tests. While exams that measure visual acuity, perception of color, and field of vision are used to arrive at a proper diagnosis, an electroretinogram (ERG) is used to confirm the diagnosis. During an ERG, eye drops are used to numb the eye before a special contact lens recorder is placed on the eye. Then a series of flashes of light are used to stimulate the retina. Doctors can then measure the electrical response of the rods and cones to the light. The test is performed twice – once in  bright room and again in a dark room. A weak of absent signal of cone cells indicates cone dystrophy. More details about the diagnosis of cone dystrophy can be accessed through the University of Michigan Kellogg Eye Center
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