兔眼中央角膜厚度与Perkins压平眼压关系的研究

目的探讨中央角膜厚度(CCT)与Perkins压平眼压的关系,建立CCT、真实眼压与Perkins压平眼压三者关系的数学模型和CCT对Perkins压平眼压的校正公式。方法健康新西兰大耳白兔32只,双眼中1只眼行准分子激光屈光性角膜切削术(PRK),另1只眼测得的数据对行PRK眼得出的数据进行验证。采用随机数字表法随机取1只眼,采用PRK,人为改变兔眼的CCT,建立不同CCT的活体眼模型,分别采用Perkins压平眼压计、A型超声角膜测厚仪、角膜曲率计测量术前、术后Perkins压平眼压、CCT、角膜曲率以及应用电子直接眼压计测量真实眼压,分别对术前和术后测量值做相关分析和多元线性回归分析,并对另1组未行PRK眼测得的真实眼压、Perkins压平眼压、CCT对实验组得出的公式进行验证。结果兔眼双眼Perkins压平眼压、CCT、角膜曲率无统计学差别,无论是术前还是术后Perkins压平眼压与CCT均显著相关(r=0.761P<0.01;r=0.829,P<0.01),与角膜曲率无关(r=0.098,P>0.05;r=0.260P>0.05)。对术前、术后Perkins压平眼压与CCT建立回归公式,曲线的斜率分别为0.066、0.053,Perkins压平眼压的改变与CCT的改变有关。对真实眼压Y与Perkins压平眼压、CCT三者的关系建立回归公式为Y=12.107+1.254X1-0.033X2(X1=Perkins压平眼压,X2=CCT)。结论CCT的改变影响Perkins压平眼压的测量值,临床上应根据CCT来校正Perkins压平眼压的测量值。

The relationship between central corneal thickness and Perkins applanation tonometry in rabbits

Objective To investigate the relationship between central corneal thickness(CCT) and Perkins applanation tonometry and establish a mathematic model of correlation between true intraocular pressure(IOP),CCT and Perkins applanation tonometry.Methods The study included thirty-two new Zealand rabbits .One eye received excimer laser photorefractive keratectomy (PRK),the other eye was used as control. The eye selected randomly according to stochastic digital chart received PRK to thin the central cornea and to generate different central corneal thickness. The Perkins applanation tonometry,CCT, corneal curvature(CC) were measured by Perkins applanation tonometer, ultrasonic pachymetry and keratometer pre-and post-PRK. Direct intracameral IOP readings was measured by IOP transducer. Statistical analyses were performed with the Pearson correlation coefficient and stepwise regression analysis.Results There is no difference in the measurement of Perkins applanation tonometry,CCT and CC between experimental and controls. A significant correlation was found between IOP and CCT pre-and post-PRK(r= 0.761, P< 0.05;r=0.829 P<0.05). There is correlation between IOP and CC,(r= 0.098,P> 0.05; r=0.260, P> 0.05 ).The slope of CCT was 0.066 mm Hg/micron pre-PRK and 0.053 mm Hg/micron post-PRK . However, the change of IOP correlated with CCT. Regression equation for direct intracameral IOP Y=12.107+1.254X_1-0.033X_2 (X_1= Perkins applanation tonometry, X_2=CCT). Conclusions CCT is an important variable in the evaluation of applanation IOP and should be considered when the Perkins applanation tonometry was taken.