先证者为8岁男性患儿，双眼视力进行性下降3年，视网膜电图表现为独特的闪光视网膜电图波形，视杆和视锥系统反应下降；但暗适应状态高刺激强度时，视锥和视杆系统混合反应振幅“超正常”。基于靶向捕获（panel）的二代测序检测显示患儿KCNV2基因发生纯合非移码缺失变异c.1002-1004del（p.L335del），患儿父亲携带该杂合变异。经生物信息分析，该变异具有致病性，诊断为视锥细胞营养不良3B型，即视锥细胞营养不良伴超正常视杆系统反应。“,”The proband was an 8-year-old boy, complaining of progressively decreased vision in both eyes for 3 years. The electroretinogram was characterized by supernormal rod response. While the responses of the rod and cone system were reduced, the amplitudes of dark-adapted electroretinogram responses at a high intensity were supernormal. A homozygous non-frameshift deletion variant c.1002-1004del (p. L335del) in KCNV2 was found by the Next Generation Sequencing using a custom designed panel. His father was a heterozygous carrier of this variant. In silico analysis indicated the variant was harmful. The proband was diagnosed as cone dystrophy type 3B which also known as cone dystrophy with supernormal rod response.