Effects of axial length and corneal curvature on corneal biomechanics in elderly population

目的:本研究旨在应用可视化角膜生物力学分析仪(Corneal Visualization Scheimpflug Technology,Corvis ST)研究不同眼轴长度(Axial Length,AL)和角膜曲率的老年人角膜生物力学特点.方法:横断面研究.收集拟接受白内障手术的患者220例(426眼),将其中AL在22-24 mm之间、K值在42-44 D范围之间的研究对象按性别进行分组,男性44眼,女性49眼.进而对K值在42-44 D之间的研究对象按AL值的不同进行分组: 22-24 mm,共99眼;24-26 mm,共22眼;大于26 mm,共12眼.对AL在22-24 mm之间的研究对象按K值的不同分组: 42-44 D,共88眼;大于44 D,共102眼.应用可视化角膜生物力学分析仪(Corvis ST)测量角膜生物力学参数,并对不同性别、不同眼轴、不同角膜曲率患者的角膜生物力学参数进行比较性分析,采用单因素方差分析、独立样本t检验等对数据进行统计并分析各组生物力学参数间的相关性.结果:男女之间角膜生物力学参数差异无统计学意义(P>0.05),不同角膜曲率间平均第一压平长度、平均第二压平长度,差异具有统计学意义(P<0.05).不同眼轴长间:AL为22-24 mm和AL为24-26 mm两组间只有第二压平长度、角膜中央厚度差异具有统计学意义(P<0.05),AL为22-24 mm和AL大于26 mm两组间第二压平长度、最大形变幅度、中央角膜厚度、第一压平时间、眼压、矫正眼压差异均具有统计学意义(P<0.05),而AL为24-26 mm和AL大于26 mm两组间各参数比较,差异均无统计学意义(P>0.05).患者眼轴长度与最大形变幅度、眼压、矫正眼压值均呈线性正相关(r=0.263,P=0.002;r=0.463,P=0.000;r=0.449,P=0.000),与角膜厚度、第二压平长度均呈线性负相关(r=-0.240,P=0.006;r=-0.344,P=0.000).结论:角膜曲率和眼轴长度可能是影响角膜生物力学特性的一个因素,眼轴长度越长,角膜厚度越薄,角膜越容易发生形变,而且随着眼轴长度的增加眼压也升高.在探讨白内障手术切口的选择是否受到患者自身因素的影响,应该考虑其角膜曲率和眼轴长度的不同.

Effects of axial length and corneal curvature on corneal biomechanics in elderly population

AIM:To explore the corneal biomechanical properties of the elderly with different axial length(AL)and corneal curvature by Corneal Visualization Scheimpflug Technology(Corvis ST).

METHODS: A cross-sectional study. A total of 220 patients(426 eyes)undergoing phacoemulsification were collected in this study. One of them whose the AL was 22-24 mm and the corneal curvature was 42-44 D were divided into male and female groups(44 eyes and 49 eyes, respectively). One of them whose the corneal curvature was 42-44 D were divided into 22-24 mm, 24-26 mm, and more than 26 mm groups according to AL(99 eyes, 22 eyes and 12 eyes, respectively). One of them whose the AL was 22-24 mm were divided into 42-44 D, and more than 44 D according to corneal curvature(88 eyes, 102 eyes, respectively). Corvis ST was used to measure the biomechanical parameters of the cornea. The differences in the parameters between different groups were analyzed using the independent-samples t-test or one-way analysis of variance and correlation analyses were performed using Pearson correlation analysis.

RESULTS: When comparing the corneal biomechanical parameters, no statistically significant differences were found between male and female groups(P>0.05). The first applanation length and second applanation length among different corneal curvatures were statistically significant(P<0.05). There was statistically significant only for the difference of the second applanation length and central cornea thickness between two groups of 22-24 mm and 24-26 mm(P<0.05). There was statistically significant for the difference of the second applanation length, deformation amplitude, central cornea thickness, the first applanation time, intraocular pressure and corrected intraocular pressure between the two groups of 22-24 mm and more than 26 mm(P<0.05). But there was no statistically significant differences of the parameters between groups of 24-26 mm and more than 26 mm(P>0.05). The patient''s AL was positively correlated with deformation amplitude, intraocular pressure and corrected intraocular pressure(r=0.263, P=0.002; r=0.463, P=0.000; r=0.449, P=0.000), and there is negative correlation between the patient''s AL and central cornea thickness, the second applanation length(r=-0.240, P=0.006; r=-0.344, P=0.000).

CONCLUSION: The corneal curvature and ocular AL may be the factor affecting the corneal biomechanical properties. The longer AL, the thinner corneal thickness, the more easily the corneal is deformed, and with the increase of the AL, intraocular pressure also increases. When discussing whether the preparation of the cataract incision is affected by the patient''s own factors, the different corneal curvatures and AL shall be considered.