The changes of ocular optic axis observed by MRI while on accommodation

• Main Authors: Yu Fong Lin, 林鈺峰
• Other Authors: Yin Chang
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/19686969791962355455

碩士 === 國立陽明大學 === 醫學工程研究所 === 90 === The main aim of the study is to observe the role of the lens to the state of lens accommodation，whether to cause visual axial moving on account of physiological reaction，and to make a objective explanation of the lens rotated while on accommodation of two kinds psychophysical methods of Stiles-Crawford Effect and Retinal Eccentric Sensitivity. When we fixed a target which moved from far point to near point，the lens products a phenomenon “accommodation”. Lens is controlled by zonule fiber and ciliary muscle that are suspended in the posterior chamber. Therefore, rotation and displacement of lens may occur owing to the stretch of lens accommodation and the inequality of coefficient of elasticity. The study obtained three different degree accommodation by means of MRI, and the distance are : far point(60 centimeter); middle point(40 centimeter); near point(20 centimeter), and in term of far point to near point, and used the images which imaged by means of MRI to structure three dimension images. The result of six subjects (six eyes) among three subjects maked repeated experiment away from one month, and these two experiments named test-retest, but we only use first result which sum up total result. We found the lens thick and the pole of the anterior surface of lens moved toward cornea among accommodation, and average movement 0.27 0.16mm, and the ratio 4/6 of subjects, the pole of posterior surface of the lens moved toward retina and average movement 0.10 0.03mm, and the ratio 1/6 of subjects no change, the ratio 1/6 of subjects moved toward cornea and movement 0.03mm.Besides the lens tilted and displaced while on accommodation, from far point to middle point, the ratio 3/6 tilted nasal side and chin side, average angle 1.94 0.76 degree, and movement 0.23 0.07mm, the ratio 2/6 titled temple side and chin side, average angle 1.11 0.42 degree, movement 0.19 0.18mm, the ratio 1/6 almost not tilt, and movement 0.29mm. From middle point to near point, the ratio 3/6 tilted nasal side and chin side, average angle 2.71 0.87 degree, movement 0.28 0.11mm, the ratio 2/6 titled temple side and chin side, average angle 3.43 1.22 degree, movement 0.32 0.01mm, the ratio 1/6 titled temple side and forehead side, angle 6.93 degree, and movement 0.19mm. During accommodation, the lens thick to comply with the target to be near to the eyes, more than tilted and rotated. By means of MRI to observe the change of the lens do not have to be related to reports about this, and the reports by means of others methods to measure are not many, therefore the study will have a contribution in an academic research.