Zhixiang Hua,1– 5,* Qiulin Zeng,6,* Limei Zhang,7 Jiying Shen,7,* Jin Yang1– 5,* 

1Department of Ophthalmology and the Eye Institute, Eye and Ear, Nose, and Throat Hospital, Fudan University, Shanghai, People’s Republic of China; 2The Key Laboratory of Myopia, Ministry of Health, Shanghai, People’s Republic of China; 3Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, People’s Republic of China; 4Key National Health Committee of the Key Laboratory of Myopia, Fudan University, Shanghai, People’s Republic of China; 5The Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, People’s Republic of China; 6Department of Ophthalmology, Shanghai Xinshijie Dongqu Eye Hospital, Shanghai, People’s Republic of China; 7Department of Ophthalmology, Shanghai Heping Eye Hospital, Shanghai, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Jin Yang, Department of Ophthalmology, Eye, Ear, Nose, and Throat Hospital of Fudan University, Shanghai, People’s Republic of China, Tel +008613671632525, Email jin_er76@hotmail.com Jiying Shen, Department of Ophthalmology, Shanghai Heping Eye Hospital, Shanghai, People’s Republic of China, Tel +008613817505149, Email susu22yoyo@163.com

Purpose: To describe the distribution of angle alpha orientation and magnitude in a large population and to analyze the impact of eye laterality, gender, and age on angle alpha.
Setting: EENT Hospital of Fudan University and Shanghai Heping Eye Hospital, 2017– 2023.
Design: A retrospective analysis utilizing the iTrace system to examine preoperative angle alpha in patients undergoing cataract surgery.
Methods: Angle alpha orientation and magnitude were collected from 30,705 individuals. The distribution of angle alpha direction and the value of its magnitude were analyzed. In addition, the influence of eye laterality, gender, and age on angle alpha was analyzed in different subgroups.
Results: The analysis revealed that the binocular angle alpha orientation was predominantly located in the temporal region, followed by the nasal region, while the upper and lower regions had a smaller proportion. The average magnitude of angle alpha in the right eye was 0.32 ± 0.19 mm, larger than that of the left eye, and this result was consistent in all subsequent subgroup studies. In a subgroup analysis categorized by gender, females exhibited significantly larger angle alpha than males. Furthermore, in an age-grouped subgroup analysis, a clear tendency was observed that the angle alpha value was increasing with age.
Conclusion: This study analyzed the distribution of angle alpha in a large population and is the first to report the effects of eye laterality, gender, and age on angle alpha. These findings enhance ophthalmologists’ understanding of angle alpha and provide a deeper perspective for cataract surgical planning.

Keywords: angle alpha, iTrace, cataract