Assessment of intraocular pressure measured by Reichert Ocular Response Analyzer,Goldmann Applanation Tonometry,and Dynamic Contour Tonometry in healthy individuals

AIM:To investigate the accuracy of intraocular pressure (IOP) as measured by a Reichert Ocular Response Analyzer (ORA),as well as the relationship between central corneal thickness (CCT) and IOP as measured by ORA,Goldmann applanation tonometry (GAT),and dynamic contour tonometry (DCT).· METHODS:A total of 158 healthy individuals (296 eyes) were chosen randomly for measurement of IOP.After CCT was measured using A-ultrasound (A-US),IOP was measured by ORA,GAT,and DCT devices in a randomized order.The IOP values acquired using each of the three tonometries were compared,and the relationship between CCT and IOP values were analyzed separately.Two IOP values,Goldmann-correlated IOP value (IOPg) and corneal-compensated intraocular pressure (IOPcc),were got using ORA.Three groups were defined according to CCT:1) thin cornea (CCT<520μm);2) normal-thickness cornea (CCT:520-580μm);and 3) thick cornea (CCT>580μm) groups.· RESULTS:In normal subjects,IOP measurements were 14.95±2.99mmHg with ORA (IOPg),15.21±2.77mmHg with ORA(IOPcc),15.22±2.77mmHg with GAT,and 15.49±2.56mmHg with DCT.Mean differences were 0.01±2.29mmHg between IOPcc and GAT(P >0.05) and 0.28±2.20mmHg between IOPcc and DC(P >0.05).There was a greater correlation between IOPcc and DCT(r =0.946,P =0.000) than that between IOPcc and GAT (r =0.845,P =0.000).DCT had a significant correlation with GAT (r =0.854,P =0.000).GAT was moderately correlated with CCT (r =0.296,P <0.001),while IOPcc showed a weak but significant correlation with CCT (r =0.155,P =0.007).There was a strong negative correlation between CCT and the difference between IOPcc and GAT(r =-0.803,P =0.000),with every 10 increase in CCT resulting in an increase in this difference of 0.35mmHg.The thick cornea group (CCT>580μm) showed the least significant correlation between IOPcc and GAT (r =0.859,P= 0.000);while the thin cornea group (CCT<520μm) had the most significant correlation between IOPcc and GAT (r=0.926,P =0.000).The correlated differences between IOPcc and DCT were not significant in any of the three groups (P >0.05).· CONCLUSION:Measurement of IOP by ORA has high repeatability and is largely consistent with GAT measurements.Moreover,the ORA measurements are affected only to a small extent by CCT,and are likely to be much closer to the real IOP value than GAT.