先天性下直肌缺如系发育异常所致[1] 。临床报道较少 ,现将我院 1 999年 7月收治 1例报告如下 :临床资料患者刘×× ,男 ,2 0岁 ,自幼左眼上斜视 ,无家族史。视力 :ＯＤ 1 0 ,ＯＳＣＦ/ 30ｃｍ ;眼位 :角膜映光Ｌ/Ｒ 4 0° (图 1 ) ,原在位时左眼角膜下缘距下睑缘5ｍｍ ;眼球 Congenital inferior rectus absent due to dysplasia caused by [1]. Clinical reports are less, now in our hospital in January 1999 1 case admitted as follows: Clinical data Patients Liu × ×, male, 20 years old, his childhood left upper strabismus, no family history. Visual acuity: OD10, OSCF / 30 cm; Eye position: corneal L / R40 ° (Figure 1), the original left corneal margin from the lower eyelid margin 5mm;