Clinical Evaluation Of The Three Kind Of Tonometer In Normal And Primary Glaucomatous Eyes

Objective: Glaucoma is one of the globally leading irreversible eye diseases leading to blindness,and it is a group of eye diseases having characteristic optic nerve injury and visual field defect caused by multiple factors,pathologically increased intraocular pressure is a primary risk factor of it[1].An accurate intraocular pressure measurement is of a great significance to the diagnosis of glaucoma and its follow-up visit.This study is designed to evaluate the relevance,accuracy and clinical agreement of intraocular pressure（IOP）measurement between Goldmann applanation tonometer（GAT）、 Accu Pen（Accu Pen for short in the following）and TOPCON CT-1P Non-contact Tonometry（NCT）among the normal and glaucomatous eyes,and to analyze the effect of central corneal thickness（CCT）,corneal curvature（CC）and axial lengths（AL）on the measurement of intraocular pressure by the three instruments,so as to explore and discuss the advantages and disadvantages and clinical application of each type of tonometer,hoping to provide a guidance for a reasonable clinical selection.Methods: We selected healthy physical examinees and patients with primary glaucoma who had been definitely diagnosed and treated in the department of ophthalmology of the second affiliated Hospital of Dalian Medical University mehospital from Aug,2016 to Jan,2017,merely the right eye of examine had been examined.All the examinees met the inclusion criteria and signed an informed consent in person,they are examined by vision,slit lamp and fundus examination with normal pupils on a regular basis before the measurement of intraocular pressure.All the examinations were performed by the same professionally trained examiner in a special examining room at 13:00 to 15:00 equally,each patient was examined with a normal pupil condition,firstly the NIDEK OPD-Scan III cornea/refraction analyzer was used to measure the corneal curvature（R1,R2）,the measuring sequence for each person was identical,which is NCT（Topcon CT-1P,measuring the intraocular pressure and corneal thickness）-Accu Pen applanation tonometer-GAT,the interval between every two instruments was at least 5 minutes,Finally,the ODM-2100 S ophthalmological A/B supertype diasonograph was used to measure the axial length.This study has adopted stata14.0 software and Medcalc software for statistic analysis.All the measurement data were represented by mean±standard deviation,the intraocular pressure measured by the three different instruments underwent an one-way analysis of variance and a pairwise comparison with the method of LSD.Pearson correlation was applied to the normal group to explore the correlation between the measurement of three tonometers and CCT,CC and AL,the simple linear regression model was used to explore the relationship between three tonometers and CCT,CC and AL,the pairwise consistency between three instruments was investigated by the method of Bland-ALtman.The difference is believed to be statistically significant when P is less than 0.05.Results:1.We collected 203 examinees,among whom,there were 121 normal people and 82 patients with glaucoma（2 patients with glaucoma had been rejected due to a failure to measure the intraocular pressure by Accu Pen applanation tonometer because of an excessively low intraocular pressure）,there is no difference between the age,gender,CCT and CC among the two groups;the AL of the normal group is higher than the glaucoma group.2.There is no difference between the intraocular pressure measured by NCT and the one measured by GAT in the normal group,the intraocular pressure measured by NCT was different from the one measured by Accu Pen,and the intraocular pressure measured by GAT was different from the one measured by Accu Pen,both the intraocular pressure measured by NCT and GAT were higher than that measured by Accu Pen.There is no difference between the intraocular pressure measured by the three instruments in the glaucoma group.In the normal group,the correlation coefficient between GAT and NCT,GAT and Accu Pen and Accu Pen and NCT was respectively r=0.81 、 r=0.74 and r=0.6087,the differences were all statistically significant（P<0.001）.in the glaucoma group,the correlation coefficient between GAT and NCT,GAT and Accu Pen and Accu Pen and NCT was respectively r=0.81、 r=0.79 and r=0.66,the differences were all statistically significant（P<0.001）.3.We can make the linear regression analysis about the intraocular pressure measured by all the three instruments,and the result of linear regression showed:the normal group:IOP_GAT=2.355+0.842*IOP_NCT IOP_GAT=7.575+0.550*IOP_Accupen IOP_Accupen=0.855*IOP_NCT;the glaucoma group: IOP_GAT=3.549+0.830*IOP_NCT;IOP_GAT=8.103+0.646*IOP_Accupen;IOP_Accupen=0.834*IOP_NCT4.Result of Bland-Altman consistency evaluation: the mean value of NCT and GAT of normal group was 0.14±1.74 mm Hg,95% consistency limit was 3.29^-3.56 mm Hg,4.96%（6/121）of the points fell beyond the limit;The mean value of intraocular pressure measured by Accu Pen and GAT was-0.99±2.71 mm Hg,95% consistency limit was-4.32⁶.31 mm Hg,2.48%（3/121）of the points fell beyond the consistency limit of 95%.The mean value of intraocular pressure measured by Accu Pen and NCT was-1.13±2.17 mm Hg,95% consistency limit was-5.39³.13 mm Hg,2.48%（3/121）of the points fell beyond the consistency limit of 95%.The mean value of intraocular pressure measured by GAT and NCT in glaucoma group was-0.15±2.80 mm Hg,95% consistency limit was5.96⁵.34 mm Hg,6.25%（5/80）of the points fell beyond the consistency limit。The mean value of intraocular pressure measured by Accu Pen and GAT was--1.48±3.86 mm Hg,95% consistency limit was-9.06⁶.08 mm Hg,6.25%（5/80）of the points fell beyond the consistency limit of 95%.The mean value of intraocular pressure measured by Accu Pen and NCT in glaucoma group was--1.34±3.05 mm Hg,95% consistency limit was-7.31⁴.46 mm Hg,5%（4/80）of the points fell beyond the consistency limit of 95%.5.In the normal group,CCT was equally correlated with the intraocular pressure measured by NCT,GAT and Accu Pen,the correlation coefficient was respectively r=0.45、 r=0.36、r=0.47,the differences were all statistically significant（P<0.001）.As for the normal group,the measurements of three instruments were all insusceptible to the mean corneal curvature and axial length.In the normal group,the intraocular pressure measured by all the three instruments increased with the central corneal thickness equally,the result of linear regression showed : Iop NCT= 0.04*CCT-5.86,this model was statistically significant,namely,with every 1 mm increased in CCT,the intraocular pressure was increased by 0.04 mm Hg.Iop GAT=0.03*CCT-2.38,this model was statistically significant,namely,with every 1 mm increased in CCT,the intraocular pressure was increased by 0.03 mm Hg.Iop Accu Pen = 0.05*CCT-11.04,this model was statistically significant,namely,with every 1 mm increased in CCT,the intraocular pressure was increased by 0.05 mm Hg.Conclusion: 1.Accu Pen and Topcon CT-1P NCT is accurate and reliable,and they have a good correlation with GAT,so it can be widely applied to clinical measurement.2.Three tonometers in normal group are all correlated with central corneal thickness,,the intraocular pressure measured by three tonometers were all not correlated with the mean corneal curvature and axial length.3.Three tonometer have their advantages and disadvantages,so the doctor should choose the tonometer according their needing.Accu Pen is suitable for various postures of intraocular pressure measurement,and it can be applied to intraocular pressure detection during and after surgery;NCT is suitable for wide census and follow-up;As for the gold standard,GAT can be used for correcting other tonometer.