Distribution of refractive errors by key socio-demographic factors.

* No qualifications, State school examinations at 16 years of age (‘O’ levels), at 18 years (‘A’ levels) or University/other professional qualification
Missing data: educational qualification: 1,466 (1.4%), accommodation tenure: 2,102 (2.0%), ethnicity: 779 (0.7%)
Distribution of refractive errors by key socio-demographic factors.

* 无学历资质，或持有16岁时参加的英国普通中等教育证书考试（‘O’水准考试，‘O’ levels）、18岁时参加的英国高级程度会考（‘A’水准考试，‘A’ levels）成绩，亦或是大学学历或其他职业资格。
缺失数据统计：学历资格字段共1466条记录缺失，占比1.4%；住房保有期限（accommodation tenure）字段共2102条记录缺失，占比2.0%；种族背景字段共779条记录缺失，占比0.7%。
基于关键社会人口学因素的屈光不正分布情况。