A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.

A cone-shaped appearance of the epiphyses of the fingers of the hand, producing a 'ball-in-a-socket' appearance. The related entity 'angel-shaped' epiphysis refers to a pronounced cone-shaped epiphysis in combination with a pseudoepiphysis at the distal end of a phalanx.

Inability to see well at night or in poor light.

Well-demarcated area(s) of partial or complete depigmentation in the macula, reflecting atrophy of the retinal pigment epithelium with associated retinal photoreceptor loss.

Blindness is the condition of lacking visual perception defined as a profound reduction in visual perception. On the 6m visual acuity scale, blindness is defined as less than 3/60. On the 20ft visual acuity scale, blindness is defined as less than 20/400. On the decimal visual acuity scale, blindness is defined as less than 0.05. Blindness is typically characterized by a visual field of no greater than 10 degrees in radius around central fixation.

Pigment migration into the retina in a bone-spicule configuration (resembling the nucleated cells within the lacuna of bone).

A reduction of previously attained ability to see.