ABSTRACT
@#AIM: To investigate the central corneal thickness(CCT)distribution of the children with ametropia in the non-contact tonometry(NCT), and the different intraocular pressure(IOP)measurements with Goldmann applanation tonometry(GAT)and the OCULUS Corvis ST(CST)corneal biomechanical analyzer, meanwhile, to evaluate the correlation between IOP and CCT. <p>METHODS: NCT was used to measure 39 children(78 eyes)of non-glaucomatous ametropia with single eye or binocular IOP higher than 21 mmHg. The IOP was measured again with CST and GAT. The two instruments were measured in random order and the CCT was measured by CST and corrected the IOP according to the CCT. The eyes were divided into the normal group and the thicker group according to the CCT. The three IOP values were analyzed by the ANOVA, and the IOP and CCT was analyzed by the Pearson correlation coefficient. <p>RESULTS: In the normal CCT group, the IOP by CST was lower than that the GAT and NCT measurements and the difference was statistically significant(<i>F</i>=5.12, <i>P</i>=0.01). In the thicker group, the comparison of the three intraocular pressure measurement methods was statistically significant(<i>F</i>=15.72, <i>P</i><0.001). IOP by NCT and GAT were significantly correlated with CCT(<i>r</i><sub>NCT</sub>=0.298, <i>P</i><sub>NCT</sub>=0.04; <i>r</i><sub>GAT</sub>=0.408, <i>P</i><sub>GAT</sub>=0.01). There was no significant correlation between CST corrected intraocular pressure and CCT(<i>r</i><sub>CST</sub>=0.062, <i>P</i><sub>CST</sub>=0.593). <p>CONCLUSION: The CCT of ametropia children with high IOP by Topcon tonometry were thicker. The corrected intraocular pressure of CST is lower than NCT and GAT. NCT and GAT were positively correlated with CCT. For children with thicker CCT, CST corrects intraocular pressure was closer to the real intraocular pressure value than NCT and GAT.
ABSTRACT
Background Corvis ST corneal biomechanical analyzer (Corvis ST) can offer corneal biomechanical parameters,intraocular pressure (IOP) and central corneal thickness (CCT),and measured IOP value was corrected based on CCT and biomechanical factors.Corvis ST is applied abroad,but the study on its accuracy is few in China.Objective This diagnostic trial was to evaluate the accuracy of Corvis ST for CCT and IOP measurement in myopic population.Methods Fifty-six eyes from 56 myopic patients were prospective recruited in Visual Science and Optometry Center of Guangxi from November to December in 2012.IOP was measured by using Corvis ST and Goldmann applanation tonometer (GAT),and CCT was measured by Corvis ST and A type ultrasonic pachymetry.The CCT difference between Corvis ST and A type ultrasonic pachymetry as well as IOP between Corvis ST and GAT were compared by using paired-t test,and agreements of measured outcomes were analyzed by Bland-Altman method.This study was approved by the Ethic Committee of People's Hospital of Guangxi and written informed consent was obtained from all subjects.Results The CCT from Corvis ST was (539.82± 19.79) μm,which was significantly higher than (535.34± 19.41) μm from A type ultrasonic pachymetry (t =4.19,P＜0.001).Bland-Altman analysis revealed that the CCT measured by Corvis ST was 4.5 μm higher than that of A type ultrasonic pachymetry,with the 95％ limit of agreement ranged from-11.2 to 20.2 μm,and 7.1％ (4/56) of points were located at the outside of the 95％ confidence interval.The IOP measured by Corvis ST and GAT were (15.75±1.60) mmHg and (16.23 ±2.40) mmHg,respectively,showing statistically significant difference between the two methods (t=2.15,P =0.04).Bland-Altman analysis revealed that the IOP measurement of Corvis ST was 0.5 mmHg lower than that of GAT,with the 95％ limit of agreement ranged from-3.8 to 2.8 mmHg,and 3.57％ (2/56) of points were located at the outside of the 95％ confidence interval.Conclusions CCT obtained by Corvis ST is higher than that by A type ultrasonic pachymetry with poor agreement between these two outcomes,and the two methods cannot replace each other clinically in myopic eyes.IOP value from Corvis ST is slightly lower than that from GAT,showing a good agreement between these two outcomes.The IOP value of Corvis ST shows satisfactory accuracy.