The diagnosis of CRD II is based on a positive family history in association with the clinical findings (visual field defects and abnormal
electroretinography). The clinical signs are limited to the eyes with initial loss of color vision (cone-mediated; most often red-green or blue-yellow defects) and
visual acuity, then followed by nyctalopia (night blindness; rod-mediated) and peripheral visual field loss and early blindness. Severe photophobia and a fine
nystagmus are common and chorioretinal atrophy may occur in severe cases. Examination shows cone-rod retinal dystrophy, “Bull's eye" macular lesions, widespread
retinal pigmentation, and chorioretinal atrophy. The onset of decreased central vision with progredient shrinkage of the peripheral visual field and loss of visual
acuity usually manifests before the age of 10 years. Onset of nyctalopia occurrs in the third decade of life, and after the fifth decade of life, visual function
is severely reduced. Unfortunately, progression to complete lack of light perception in CRD is inexorable. CRD II is not associated with extraocular findings.