不同屈光状态儿童角膜前表面非球面特性分析及建模

doi:10.3760/cma.j.issn.1674-845X.2013.07.002

摘要
图/表
参考文献(22)
相关文章 (15)

全文: PDF 828KB HTML (1 KB)
输出: BibTeX | EndNote (RIS)

摘要

目的运用正切曲率半径推算儿童角膜前表面Q值并分析水平区间Q值规律及不同屈光状态与Q值的关系。通过拟合计算垂直方向Q值，得出360条半子午线范围的Q值，完成全角膜前表面数学模型的建立。方法横断面研究。通过Orbscan Ⅱ角膜地形图仪得到84例儿童右眼（12例近视、45例正视、27例远视）360条半子午线Ft值，运用线性回归方程计算各半子午线Q值，分析角膜鼻、颞侧区间Q值分布规律（配对t检验）及屈光状态对Q值的影响（单因素方差分析）。运用Matlab R2009b（矩阵实验室Matrix Laboratory）系统拟合计算其中62例儿童右眼数据（10例近视、25例正视、27例远视）得到360条半子午线Q值，并分析角膜360条半子午线Q值分布规律（配对t检验）。结果 ①进行计算的所有半子午线所得到的决定系数R2均大于或等于0.5。84眼鼻侧、颞侧区间Q值均在-1与0之间，平均值分别为：-0.42±0.16，-0.23±0.08，二者差异有统计学意义（t=-9.527，P<0.05）。鼻侧、颞侧r0平均值分别为：7.85±0.24，7.83±0.24，二者差异有统计学意义（t=3.213，P<0.05）。鼻侧和颞侧半子午线Q值与r0不存在相关性（鼻侧r=-0.077，P=0.487；颞侧r=0.001，P=0.992）。②近视组和正视组、近视组和远视组鼻侧Q平均值差异有统计学意义（F=3.907，P<0.05），颞侧各组之间均无统计学意义（F=0.204，P＞0.05）。③经过MATLAB系统进行拟合计算得到的曲线决定系数R2均大于0.9。④对48只眼进行垂直方向Q值拟合计算。拟合前后水平鼻侧方向半子午线Q值平均值分别为-0.45±0.16，-0.45±0.16，颞侧分别为-0.21±0.08，-0.20±0.10，拟合前后水平鼻、颞侧区间平均Q值t检验差异无统计学意义（鼻侧t=2.009，P>0.05；颞侧t=2.009，P>0.05）。拟合后垂直方向上方、下方半子午线Q值平均值为-0.24±0.10、-0.17±0.08。结论 ①采用线性回归以正切曲率半径推算Q值的方法结果稳定可靠。研究对象角膜前表面趋向长椭圆形（prolate），鼻侧较颞侧区间显著，水平较垂直区间显著。屈光不正对Q值影响较小。②将360条半子午线Q值通过拟合曲线计算，Q值呈双峰状分布，峰顶分别为上方及下方垂直半子午线。③拟合计算后水平方向半子午线的非球面性均较垂直方向显著，垂直方向Q值向0靠拢。④采用MATLAB系统的曲线拟合计算全角膜Q值的方法证明是稳定可靠的。解决了垂直方向半子午线Q值的计算问题，使建立全角膜前表面数字模型成为现实。

	服务

	把本文推荐给朋友
	加入我的书架
	加入引用管理器
	E-mail Alert
	RSS
	作者相关文章
	林成敏
	王波
	施明光

关键词 ：近视, 远视, 正视, Orbscan Ⅱ角膜地形图, 正切曲率半径, Q值, 曲线拟合计算

Abstract：

Objective To calculate the Q-value of the anterior corneal surface of children by using the tangential radius of curvature； to analyze the distribution of horizontal Q-values and the relationship between Q-value and different refractions. The vertical Q-values were calculated by curve fitting， and the Q-values of the 360° semi-meridians were then obtained， to complete the mathematical model of the anterior corneal surface. Methods The Ft-values of the 360 semi-meridians from the 84 right eyes of the children （12 cases of myopia， 45 cases of hyperopia， and 27 cases of emmetropia） were calculated by Orbscan Ⅱ topography using a linear regression equation to calculate the Q-values of the semi-meridians and analyze the nasal and temporal distribution of the Q-values and the effect of refractive state. MATLAB R2009b （Matrix Laboratory） was used for curve fitting calculations of the right eye data from 62 children （10 myopes， 25 hyperopes and 27 emmetropes） to obtain Q-values of 360 semi-meridians and to analyze the distribution of the Q-values. Results ①All of the coefficients of determination （R2） were greater than or equal to 0.5. The Q-values of the nasal and temporal distributions were between 1 and 0. The mean Q-values of the nasal distribution of 84 right eyes was -0.42±0.16， and the temporal distribution was -0.23±0.08. The difference was statistically significant （t=-9.527， P<0.05）. The mean r0 of the nasal distribution of 84 right eyes was 7.85±0.24 and the temporal distribution was 7.83±0.24. The difference was statistically significant （t=3.213， P<0.05）. No statistical correlation was found between Q-values and r0 in this study （nasal distribution r=-0.077， P=0.487， temporal distribution r=0.001， P=0.992）. ②The Q values of a one-way ANOVA analysis of emmetropes， myopes and hyperopes showed that the differences between the nasal corneas of myopes and emmetropes and of myopes and hyperopes were statistically significant （P<0.05）. No significant difference was found between the emmetropes and hyperopes （P>0.05）. The differences between the temporal distributions were not statistically significant （P>0.05）. ③The coefficient of determination （R2） of the curve fitting by MATLAB was greater than 0.9.④Fitting the vertical Q-values of the 48 eyes： the mean Q-values of the nasal distribution of the semi-meridian before and after curve fitting were -0.45±0.16 and -0.45±0.16 and the temporal distributions were -0.21±0.08 and -0.20±0.10. There were no significant differences before and after curve fittings （nasal distribution， t=2.009， P>0.05， temporal distribution， t=2.009， P>0.05）. The mean vertical Q-values of the superior and inferior distributions after curve fitting were -0.24±0.10 and -0.17±0.08. Conclusion ①The method of using linear regression to calculate the Q-value of the anterior corneal surface by the tangent radius of curvature proved to be stable and reliable. Corneal asphericity was represented by a prolate ellipse and a trend toward a more prolate Q-value was found in the nasal and horizontal distributions. The Q-value had a weak correlation to ametropia. ?②The distribution of 360 semi-meridians of the Q-value calculated from the curve fits were in the form of a double hump and the two peaks were above and below the vertical semi-meridinans. ③After curve fitting calculations， the horizontal semi-meridians had more asphericity than the vertical meridians， which were more round.④The method using the Curve Fitting Toolbox of the MATLAB System to fit the Q-values proved to be stable and reliable. It solves the problem of calculating Q-values， and enables the creation of a digital model of the corneal anterior surface to become a reality

Key words： Myopia Hyperopia Emmetropia Orbscan Ⅱ Topography Tangential radius of curvature Q-value Curve fitting calculation

收稿日期: 2012-06-05

基金资助:

国家自然科学基金（30872816）

通讯作者: 施明光

引用本文:

林成敏,王波,施明光. 不同屈光状态儿童角膜前表面非球面特性分析及建模[J]. 中华眼视光学与视觉科学杂志, 2013, 15(3): 131-136. LIN Cheng-min,WANG Bo,SHI Ming-guang. An analysis of corneal asphericity and modeling of the anterior corneal surface in children with different refractive states. Chinese Journal of Optometry Ophthalmology and Visual Science, 2013, 15(3): 131-136. DOI: 10.3760/cma.j.issn.1674-845X.2013.07.002

链接本文:

https://www.cjoovs.com/CN/10.3760/cma.j.issn.1674-845X.2013.07.002 或 https://www.cjoovs.com/CN/Y2013/V15/I3/131

[1]	Douthwaite WA， Hough T， Edwards K， et al. The EyeSys videokeratoscopic assessment of apical radius and p-value in the normal human cornea. Ophthalmic Physiol Opt，1999，19：467-474.
[2]	Scholz K， Messner A， Eppig T， et al． Topography-based assessment of anterior corneal curvature and asphericity as a function of age， sex， and refractive status． J Cataract Refract Surg，2009，35：1046-1054.
[3]	Bottos KM， Leite MT， Aventura-Isidro M， et al． Corneal asphericity and spherical aberration after refractive surgery. J Cataract Refract Surg，2011，37：1741-1742.
[4]	Chan KY， Cheung SW， Cho P. Corneal parameters of six-to 12-year-old Chinese children. Clin Exp Optom，2012，95：160-165.
[5]	Davis WR， Raasch TW， Mitchell GL， et al． Corneal asphericity and apical curvature in children： a cross-sectional and longitudinal evaluation. Invest Ophthalmol Vis Sci，2005，46：1899-1906.
[6]	Carkeet A， Luo HD， Tong L， et al. Refractive error and monochromatic aberrations in Singaporean children. Vision Res，2002，42：1809-1824.
[7]	Baker TY. Ray tracing through non-spherical surface. Proc Phys Soc，1943，55：361-364.
[8]	Bennett AG， Rabbetts RB. What radius does the convential keratometer measure? Ophthal Physiol Opt，1991，11：239-247.
[9]	Mckay T. A clinical guide to the Humphrey corneal topography system. Humphrey system，1998，2：13-15.
[10]	施明光，王波. 正常国人全角膜数字模型的建立. 中华眼科杂志，2007，8：694-697.
[11]	Ying J， Wang B， Shi M. Anterior corneal asphericity calculated by the tangential radius of curvature. J Biomed Opt，2012，17：075005.
[12]	Douthwaite WA. EyeSys corneal topography measurement applied to calibrated ellipsoidal convex surfaces. Br J Ophthalmol，1995，79：797-801.
[13]	Cheung SW， Cho P， Douthwaite W. Corneal shape of HongKong-Chinese. J Ophthalmic Physiol Opt，2000，20：119-125.
[14]	陈如利，王若洁，王波，等. 正切曲率半径对高度近视眼角膜表面Q值计算及特性分析.中华眼视光学与视觉科学杂志，2011， 13：34-38.
[15]	Kiely PM， Smith G， Carney LG. The mean shape of the human cornea. Optica Acta，1982，29：1027-1040.
[16]	Houat M， Gatinel D， Duong MH， et al． Corneal asphericity in myopes． J Fr Ophthalmol，2002，25：488-492.
[17]	Scholz K， Messner A， Eppig T， et al． Topography-based assessment of anterior corneal curvature and asphericity as a function of age， sex， and refractive status． J Cataract Refract Surg，2009，35：1046-1054.
[18]	Koller T， Iseli HP， Hafezi F， et al. Q- factor customized ablation profile for the correction of myopia astigmatism. J Cataract Refract Surg，2006，32：584-589.
[19]	Zhang Z， Wang J， Niu W， et al. Corneal asphericity and its related factors in 1052 Chinese subjects. Optom Vis Sci，2011，88：1232-1239.
[20]	Llorente L， Barbero S， Cano D， et al. Myopic versus hyperopic eyes： axial length， corneal shape and optical aberrations. J Vis，2004，4：288-298.
[21]	Budak K， Khater TT， Friedman NJ， et al. Evaluation of relationships among refractive and topographic parameters. J Cataract Refract Surg，1999，25：814-820.
[22]	Nieto-Bona A， Lorente-Velázquez A， Mòntes-Micó R. Relationship between anterior corneal asphericity and refractive variables. Graefes Arch Clin Exp Ophthalmol，2009，247：815-820.