【摘要】 目的：评估大学生群体优势眼和左/右利手间的关系。方法：受试对象为179名大学生志愿者，平均年龄为19.4±1.6岁，其中女110 名（61.5%），男69 名（38.5%）。优势眼由Gündoan和McManus两种方法测得，左或右利手则由Edinburgh Handedness Inventory Oldfield和McManus法确定，t检验评估实验的可信度。结果：Gündoan法测得受试者中110人（61.5%）为右眼优势，69人（38.5%）为左眼优势，无性别差异。McManus法重测相同受试者，则右/左眼优势分别为128人（71.5%）和51人（28.5%）。两法测得的结果相关，一致度κ=0.256（P<0.01）。女性受试者中，Gündoan法测得右/左眼优势分别为62人（56.4%）和48 人（43.6%），McManus法测得的结果为右/左眼优势分别为74人（67.3%）和36人（32.7%）。Fisher检验两法测得的结果相关（P<0.05），一致度κ=0.239 （P<0.01）。男性受试者中，Gündoan法测得右/左眼优势为48 人（69.6%）和21人（30.3%），McManus法检测为54人（78.3%）和15人（21.7%）。Fisher检验两法测得结果相关（P>0.05），一致度κ=0.239（P<0.01）。Oldfield和McManus法分别测得右利手比例为91.6%（n=164）和91.1% （n=163），两者间有较高的一致度κ=0.753（P<0.01）。McManus法检测出的优势眼和左或右利手间的统计学相关性具有显著性意义（Fisher检测P<0.017；一致度评分phi=0.193（P<0.05）。结论：大学生以右利手为主，McManus法检测发现右利手似乎与有眼优势更为相关。左或右利手和优势眼似乎是研究大脑功能不对称性和大脑偏侧型的最可靠的方法。
【关键词】 左/右利手；优势眼；大脑功能不对称性；大脑偏侧型
INTRODUCTION
In humans, two cerebral hemispheres appear to be nearly symmetrical; however each hemisphere has some anatomical, chemical and functional specializations. The right cerebral hemisphere is dominant in visiospatial and nonverbal function such as art, architecture, geometry and mathematics, whereas the left cerebral hemisphere is dominant in recent verbal memory, neural control of writing and speaking and producing language. Interestingly, slight differences in using different brain areas for language processing were recognized between males and females [13]. The specialization of cerebral hemispheres in certain functions of human body is believed to cause some subtle changes in the neural chemical and functional aspects of the different organs and systems. Previous studies to date have concluded that in the righthanded population, righteye dominance was greater than the lefteye dominance and just the opposite in the lefthanded population [46]. Moreover it was suggested that the dominant eye had higher intraocular pressure compared to the nondominant one [7]. Preference for the left eye over rather than the right eye for monocular tasks such as sighting through a tube, was the basis for the conclusion that about one third of the population is left eye dominant [8]. Dominant eye is associated with hand preference which is most conventionally assessed in terms of the hand which is used for writing. Many theorists, particularly in the area of education, have focused on cerebral functional asymmetry called laterality which was diagnosed by hand preference. But various times the educational system has strongly encouraged all children to write with their right hand. Obviously manifested handedness may altered by educational training. On the other hand eye dominance is not changed all through the life by educational training or social influences which means detection of eye dominance is more fundamental measure of underlying cerebral laterality[911]. The aim of this study was to evaluate the relationship between eye dominance and handedness in order to clarify inconsistent results in the literature with detection most reliable method for evaluating functional cerebral laterality due to eye dominance or handedness.
MATERIALS AND METHODS
This study was performed in accordance with the ethical standards of the Declaration of Helsinki 1994 which was approved by the local Ethics Committee of Bakent University (KA06/04). 179 university students aged between 1624 years (mean age, 19.4±1.6 years) were enrolled in the study by giving their informed consent. The majority of the students were female (61.5%). All of the subjects were healthy, without any systemic, chronic or acute illnesses.
Determination of Hand Preference
Oldfield test Hand skill was assessed by performance measurement. All subjects were tested individually in the same laboratory room during 12.0013.00 PA with adequate instruments. Handedness was assessed according to the Edinburgh Inventory Oldfield test[12,13] . Findings were evaluated by the Geshwind [14] and Tan [15] scoring system. Subjects having handedness scores smaller than zero were considered lefthanded; those with scores greater than zero were considered to be righthanded. Mixedhandedness was excluded as Bourassa[9].
McManus test Another evaluation of handedness was assessed by performance measurement according to the McManus[16] test, based on the determination of the throwing hand skill. Subjects were asked to throw, a magnetic arrow at a target on a wall 23m away. The subjects made 10 throws. The well skilled hand for throwing was considered as dominant.
Determination of the Dominant Eye
Gündoan test The dominant eye performance measurement method was described previously[11] which was adapted from the Rosenbach [17] and the Miles[4].
McManus test Another evaluation of the eyedness was assessed by performance measurement according to the McManus [16] and Porac[18] tests in which there was three items for eye sighting, such as: looking down a microscope, looking into a dark bottle, looking through a keyhole [16,8]. Scores were tallied on a point scale (1=always left, 2=either, 3=always right), with the either responses excluded. The dominant eye was accepted to be the left eye if the average score was< 2 and to be the right eye if total score was ≥2.
Statistical Analysis Data were shown as n (%). χ2 and Fisher exact test were used for the analysis of categorical data. The agreement between different methods was analyzed with Kappa statistics. Comparison of proportions was made by two proportions z test. P<0.05 was considered as significant. Statistical analysis was performed using the SPSS 11.5 and MINITAB 13.0 for Windows.
RESULTS
Without gender difference right handedness ratios among students were 91.6% (n=164) and 91.1% (n=163) according to the Oldfield and the McManus tests, respectively.
Table 1Dominant eye results in female of two methods（略）
Table 2Dominant eye results in males of two methods（略）
Table 3 Relationship between eye dominance and handedness tests with the respect to revealed frequencies according to the Gündoan and the Oldfield tests（略）
Table 4 Relationship between eye dominance and handedness result according to the Gündoan and McManus (throwing hand) tests（略）
Table 5 Relationship between eye dominance and handedness results according to the McManus and Oldfield tests（略）
The overall incidence of the left handedness determined by the Oldfield [12] test was 8.4 %, which is very close to the ratio of 8.9 % by the McManus[16] test results (Table 1). The statistical agreement between two test results were also represented with a high score (κ=0.753, P<0.01). Without gender difference right/left eye dominance were found respectively 110 (61.5 %), 69 (38.5%) by Gündoan test. When the same subjects were retested by McManus test method the right/left eye dominance was found respectively 128 (71.5%), 51 (28.5%). The results of these two methods were related significantly (χ2 =12.378, P<0.01; Fisher exact test P<0.01), with an agreement score κ=0.256, (P<0.01, Figure 1).
Table 6 Comparison of eye dominance and hand preference frequencies obtained via different detection tests for the same subjectsn（略）
Figure 1 Without gender difference dominant eye results for two methods（略）
In females the right/left eye dominance were found respectively as 62 (56.4%), 48 (43.6%) by Gündoan test as it was found 74 (67.3%), 36(32.7%) for the same subject when they retest by McManus test According McManus test results 74 subjects were found with right eye dominance and 36 subjects were found with left eye dominance. But only 48 of the 74 subjects were assessed with right eye dominance by the Gündoan test and the rest of 26 were assessed with left eye dominance. In the McManus test 36 subjects were found with left eye dominance, but among those only 22 subjects assessed with left eye dominance according to the Gündoan test. The rest of 14 subjects were assessed with right eye dominance. In the Gündoan test 62 subject were found with right eye dominance, 48 subjects were found with left eye dominance (Table 1). The results of these two tests for females were related significantly by Fisher exact test (P<0.05), with agreement score κ=0.239 (P<0.01).
In males the right/left eye dominance were found respectively as 48 (69.6%), 21 (30.3%) in Gündoan test method as it was found 54 (78.3%), 15 (21.7%) for the same subjects when retested by McManus test. In the males 54 subjects were found with right eye dominance and 15 subjects were found with left eye dominance by McManus test. But only 41 of the 54 subjects were assessed with right eye dominance by the Gündoan test and the rest of 13 were assessed with left eye dominance. According to the McManus method 15 subjects were assessed as they had left eye dominance, but among those only 8 subjects assessed with left eye dominance according to the Gündoan test method. The rest of 7 subjects assessed as they had right eye dominance. According to the Gündoan test 48 subjects were found with right eye dominance, 21 subjects were found with left eye dominance (Table 2).The results of these two tests for male were not related significantly.
There was no significant relationship between eye dominance and handedness when compared Gündoan and Oldfield results for the same subjects (Table 3, χ2=0.456).
There was also no significant relationship between eye dominance and handedness when compared Gündoan and the McManus test results (χ2=0.973, P<0.324,Table 4). Although when the same subjects were retested for evaluating hand/eye dominance by the McManus tests a significant relationship were found between hand/eye dominance P<0.05 (Table 4). Furthermore, there was no significant relation between the McManus and the Oldfield tests for evaluating hand/eye dominance (Table 5).
The relation between handedness and eye dominance were evaluated by four couple different methods. Appropriate left handednessleft eye dominance ratios were as 46.7%; 56.2%; 50.0%; 46.7% and right handednessright eye dominance ratios were found as 62.2%; 74.2%; 62.6%; 73.2%. On the other hand inappropriate left handednessright eye dominance ratios were found 53.3%; 43.8%; 50.0%; 53.3% and right handednessleft eye dominance ratios were found 37.8%; 25.8%; 37.4%; 26.8% by present study for the same subject. The relationship between handedness[12,16] and eye dominance[11,16] is shown in Table 6.
The most righthanded subjects were also found to be right eye dominant in all of the tests applied. If used for both of the hand preference and eye dominance analyses. The McManus test seems to be more sensitive than others for determining the right eye dominance in subjects who were lefthanded for throwing. Similar tendency was also occurred for the determination of right eye dominance in subjects with dominant right hand preference. On the other hand, the Gündoan[11] test for the dominant eye was found to have a similar relationship with the hand preference determined by either writing or throwing tasks.
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