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论文题目：

The "Finger-and-Fist" teaching model in functional anatomy of the extraocular muscles

论文作者：

Hongxi Wang, Gehan Ai, Xin Tan, Binyao Chen

王泓熹，艾戈晗，谭欣，陈镔瑶

论文摘要：

Dear Editor,

The intricate functional anatomy of the extraocular muscles (EOMs) has long been a challenge for medical students. Previously, the "Hand as Foot" teaching method been designed to illustrate the spatial arrangement of the EOMs.^1,2 Besides, other researchers have employed the limb teaching method to show the coordinated actions of yoke muscles at six cardinal positions of gaze.³ However, these methods only offered superficial analogies for memorization, with limited insight into the interplay between structure, function, and clinical relevance.

Recently, building on the "Hand as Foot" analogy, we have introduced a "finger-and-fist" model to comprehensively elucidate the EOMs' anatomy, actions, and cardinal positions of gaze. In this model, the extended index finger of one hand symbolizes one specific EOM, while the clenched fist of the other hand represents the ipsilateral eyeball, with palm facing down. The various eye movements—elevation, depression, adduction, abduction, intorsion, and extorsion—are mimicked by dorsiflexion, flexion, adduction, and abduction of the wrist, as well as pronation and supination of the forearm, respectively. The distal transverse arch passing through the metacarpophalangeal joints symbolizes the eyeball's equator. 

In teaching practice, we use the index finger to trace the EOMs, intuitively demonstrating the vector orthogonal decomposition of muscular action. For instance, the superior rectus (SR) extends forward, inserting into the sclera anterior to the equator at an angle of 23° to the visual axis in the primary position (Figure 1A). The SR's primary action (elevation) is determined by its major vector component along the visual axis (cos 23°), which pulls the anterior segment upwards. The minor component, perpendicular to the visual axis (sin 23°), rotates the upper part of the eyeball medially and pulls the anterior segment inwards, inducing intorsion and adduction. Similarly, the inferior oblique (IO) originates from the nasal orbital floor, courses posterolaterally, and inserts into the posterior sclera at an angle of 51° to the visual axis (Figure 1B). The major component, perpendicular to the visual axis (sin 51°), rotates the lower part of the eyeball medially and pulls the posterior segment inwards, inducing extorsion and abduction, while the minor component (cos 51°) pulls the posterior segment downwards, facilitating the elevation of the eyeball. 

The "finger-and-fist" model also effectively illustrates the cardinal positions of gaze by manipulating the fist into adducted or abducted positions. In adduction, the visual axis aligns almost parallel to the IO but perpendicular to the SR (Figure 1C), allowing the IO to function as a pure and independent elevator. Thus, underelevation in adduction indicates an IO palsy. Conversely, in abduction, the visual axis aligns almost parallel to the SR but perpendicular to the IO, enabling the SR to act as a pure elevator with the IO exerting minimal vertical action (Figure 1D). Consequently, underelevation in abduction suggests an SR palsy.

This simple teaching method aims to provide a vivid representation of the complex and abstract functional anatomy of the EOMs. Future studies will assess the pedagogical efficacy of this model in medical education.

基金项目：

广东省临床教学基地教学改革研究项目，2023JD131

广东省临床教学基地教学改革研究项目，2023JD132

第一作者简介：

王泓熹，眼科学博士，主治医师，硕士研究生导师。

2019年毕业于中山大学，获博士学位，后于汕头大学医学院从事博士后研究工作。现为汕头国际眼科中心白内障科主治医师，主要从事白内障、青光眼、屈光不正等常见眼病的临床诊疗和研究工作。

教学方面，现为汕头大学医学院教师成长中心培训师、眼视光医学专业教学秘书，教授《眼科光学》等基础课程和《眼科学》等临床课程。主持省级课题3项（研究生教育创新计划项目1项、临床教学基地教学改革研究项目1项），发表论文19篇（第一作者8篇；教学论文5篇），研发教具获专利授权2项。

曾获得广东省第三届高校教师教学创新大赛二等奖、广东省第六届青年教师教学大赛三等奖、南粤青年好医生、汕头大学年度嘉奖等荣誉。

通讯作者简介：同第一作者