hind the lower eyelid and around
             the eye. When light is shone in the eye, the ERG records any electrical
             changes in the retina. This provides valuable information on the
             The patient's retina is also examined using an indirect
             opthalmoscope. This instrument enables the doctor to examine different
             parts of the eye through a dilated pupil. In this exam, a healthy retina
             has an orange-red coloration. An eye afflicted with RP has the orange area
             broken up by black or dark brown spots. These spots, also known as bone
             spicules, are caused by the breakdown of pigment epithelial cells. Other
             findings common in a case of RP are a pale optic nerve and narrowed retinal
             The patient's visual acuity is tested using a standard eye chart
             (black letters on a white background). The refraction test is also used to
             test visual acuity and determines the proper prescription for eyeglasses or
             contact lenses. While corrective lenses do not help RP, they may help with
             accompanying eye disorders such as nearsightedness.
             A series of simple screening tests is used to measure the patient's
             color vision. The Hardy-Rand-Rittler (HRR) test and the Ishihara test
             evaluate the type and degree of color blindness. The Holmgren Yarn-
             matching test and the Farnsworth-Munsell 100 Hue disk-matching test
             evaluate the patient's ability to match up colors.
             Eye exams are given yearly to track the progress of the disease.
             Retinitis Pigmentosa is caused by a genetic defect composed of three
             distinct patterns.[iv] Two of the forms are autosomal, and can afflict men
             and women. The third is specific to men. In the non-sex-linked
             (autosomal) form, it can either be a dominant or recessive trait. These
             are labeled autosomal dominant inheritance and autosomal recessive
             inheritance, respectively. In a sex-linked form, called X-linked
             recessive, it is a recessive trait. This X-linked form is mor...