The diagnosis of RP was according to the typical clinical history of night blindness, characteristically findings of "bone-spicule" change in the fundus, and varying degrees of peripheral visual field constriction. According to the affected loci in the fundus, we defined a typical type of RP as the retinal pathological change was around the banded area outside the main vascular arcs, and a central variant of RP stood for those with bone-spicule change appeared at the macula.[17] The exclusion criteria included eyes with histories of trauma, intraocular laser treatment, intraocular surgery, presence of retinal diseases, high degree of myopia with refraction more minus than -8.0 D or hyperopia with refraction more than +5.0 D. Patients with systemic diseases that may affect retina like diabetes or hypertension were also excluded.