DCT和GAT对LASIK手术前后眼压的比较性研究

目的 评价动态轮廓眼压计(DCT)和Goldmann压平眼压计(GAT)对在准分子激光原位角膜磨镶术(LASIK)手术前后眼压测量值的变化.方法 取71例141只眼近视患者在LASIK术前和术后一周分别进行角膜厚度(CCT)、GAT、DCT测量.结果 ①LASIK手术前后DCT测得值尤显著性差异(P=0.062),GAT测得值有显著性差异(P＜0.001),CCT测得值有显著性差异(P＜0001).②Bland-Altman分析示LASIK手术前后DCT与GAT两种测量方法均呈现高度一致性.术前DCT测量值高于GAT测量值1.1mmHg,95%可信区间为(-0.6,2.8)mmHg;术后DCT测量值高于GAT测量值8.2mmHg,95%可信区间为(5.3,11.1)mmhg.③△GAT与△CCT呈正相关,△DCT与△CCT无统计相关性.结论 DCT测量值不受LASIK手术切削的影响,更适合于LASIK手术前后眼压的测量.     

Dynamic contour tonometry: a new way to assess intraocular pressure in ectatic corneas

PURPOSE: To compare intraocular pressure (IOP) measurements in patients with keratoconus (KC), pellucid marginal degeneration (PMD), and unilateral penetrating keratoplasty (PK) for KC by Goldmann applanation tonometry (GAT), Tono-Pen tonometry (TP), and Pascal dynamic contour tonometry (DCT). METHODS: Patients with KC, PMD, or PK were included in a prospective study. IOPs were measured by GAT, TP, and DCT. Severity of ectasia was determined by the steep curvature by corneal topography and central thinning by contact ultrasound pachymetry. IOP measurements were compared and correlated with disease severity. RESULTS: Fifty-three eyes of 36 patients were enrolled. Mean age was 45.3 +/- 12.5 years (range: 28-72 years). Twenty-nine eyes had KC, 21 eyes had a PK for KC, and 3 eyes had PMD. Mean DCT, GAT, and TP readings were 16.1 +/- 2.9, 14.3 +/- 4.1, and 13.8 +/- 4.1 mm Hg, respectively. The differences of mean IOP between GAT and DCT and TP and DCT were statistically significant, whereas the difference between GAT and TP was not. Both GAT and TP readings were significantly higher in the PK eyes than the KC and PMD eyes, whereas DCT readings were not. DCT measurements were not significantly different in PK versus non-PK eyes. CONCLUSION: DCT is a newly Food and Drug Administration (FDA)-approved device that is designed to measure IOP, independent of corneal thickness, corneal curvature, and ocular rigidity. DCT gave significantly higher IOP readings than GAT and TP in this study. DCT readings were not affected by corneal thickness. DCT may be more accurate in IOP measurement in eyes with KC and PMD.     

Intraocular pressure measurements following Descemet stripping endothelial keratoplasty

PURPOSE: The effect of increased corneal thickness after Descemet stripping endothelial keratoplasty (DSEK) on intraocular pressure (IOP) measurement has not been previously studied. It is uncertain if this increase in corneal thickness would artificially elevate IOP reading by Goldmann tonometry [GAT] (Haag-Streit, Konig, Switzerland). Therefore the effect of DSEK-related thick cornea on IOP measurement was investigated using three different techniques. DESIGN: Prospective cross-sectional study. METHODS: Participants were recruited from a single tertiary referral center. Fifty eyes of 38 patients with successful DSEK at least three months prior to testing were evaluated. At the time of the study, none of the participants had clinically detectable corneal edema. IOP was measured with GAT, pneumatonometry, and dynamic contour tonometry (DCT) in an unmasked randomized sequence. Central corneal thickness (CCT) was measured by ultrasonic pachymetry. RESULTS: Mean CCT was 701 +/- 68 microm. The mean IOP +/- standard deviation (SD) was 15.9 +/- 4.9 mm Hg for GAT, 20.3 +/- 4.5 mm Hg for pneumatonometry, and 19.8 +/- 4.4 mm Hg for DCT. Pneumatonometry and DCT IOP measurements were significant higher than GAT (P < .01). In contrast, the difference between pneumatonometry and DCT readings was not statistically significant (P = .28). The correlations between IOP and corneal thickness were not significant in this cohort (P > .05). CONCLUSIONS: Falsely elevated GAT, as expected in thick corneas, was not demonstrated after DSEK. High IOP reading by GAT therefore should raise suspicion of elevated IOP in DSEK eyes.     

Pneumotonometry versus Goldmann tonometry after laser in situ keratomileusis for myopia.

PURPOSE: To assess the reliability of intraocular pressure (IOP) measurement by Goldmann applanation tonometry (GAT) versus pneumotonometry in patients after laser in situ keratomileusis (LASIK) for myopia. SETTING: Shiley Eye Center, University of California San Diego, La Jolla, California, USA. METHODS: In this prospective study, 31 eyes of 17 patients were evaluated before and 1 month after having LASIK for myopia. A masked observer measured preoperative and postoperative IOP by GAT centrally and by pneumotonometry at the center and the periphery of the cornea. Central corneal thickness and curvature were evaluated. RESULTS: Preoperative IOP showed a good correlation between GAT and pneumotonometry values (r = 0.82). Mean postoperative IOP by GAT was lower by 3.8 mm Hg +/- 2.2 (SD) (26.3% +/- 15.2%) than by pneumotonometry: 2.3 +/- 2.8 mm Hg (15.4% +/- 10.7%) (P = .01). There were no statistically significant differences in central IOP versus peripheral IOP measured by pneumotonometry (P = .4). Regression analysis showed no statistically significant differences in IOP as a function of change in corneal thickness or change in corneal curvature with either device. CONCLUSION: Postoperatively, there was a decrease in IOP measured by central GAT that was statstically significant. Differences in pneumotonometry were less substantial, with greater reliability of pneumotonometry than GAT after LASIK.     

Comparison of dynamic contour tonometry with goldmann applanation tonometry

PURPOSE: The dynamic contour tonometer (DCT; Pascal tonometer) is a novel tonometer designed to measure intraocular pressure (IOP) independent of corneal properties. The purpose of this study was a comparison of the DCT with the Goldmann applanation tonometer (GAT) with respect to mean of IOP readings, the influence of ocular structural factors on IOP readings, and both intra- and interobserver variability, in a large group of healthy subjects. METHODS: In a prospective study of 228 eyes, IOP measurements by GAT and DCT were compared, and the effects of central corneal thickness (CCT), corneal curvature, axial length, and anterior chamber depth were analyzed. To evaluate intra- and interobserver variability, IOP was measured in eight eyes by four observers. RESULTS: There was a high concordance between the IOP readings obtained by DCT and GAT. However, IOP readings were consistently higher with DCT than with GAT (median difference: +1.7 mm Hg, interquartile range [25th-75th percentile] = 0.8-2.7 mm Hg). In contrast to GAT, multivariable regression analysis showed no significant effect of corneal thickness, corneal curvature, astigmatism, anterior chamber depth, and axial length on DCT readings. For repeated measurements the intraobserver variability was 0.65 mm Hg for the DCT and 1.1 mm Hg for the GAT (P = 0.008). Interobserver variability was 0.44 mm Hg for the DCT and 1.28 mm Hg for the GAT (P = 0.017). CONCLUSIONS: IOP measurements by DCT are highly concordant with IOP readings obtained from GAT but do not vary in CCT and have a lower intra- and interobserver variability. DCT seems to be an appropriate method of tonometry for routine clinical use.     

Assessment of the Pascal dynamic contour tonometer in monitoring intraocular pressure in unoperated eyes and eyes after LASIK

PURPOSE: To assess the performance of the Pascal dynamic contour tonometer (PDCT) (Swiss Microtechnology AG) by comparing it to Goldmann applanation tonometry (GAT) and noncontact air tonometry (NCT) before and after laser in situ keratomileusis (LASIK). SETTING: Vlemma Eye Institute, Athens, Greece. METHODS: Intraocular pressure was measured in 118 eyes before and 1 and 4 weeks after LASIK using GAT, NCT, and the PDCT, which allows direct, digital, transcorneal measurement of intraocular pressure. RESULTS: Preoperatively, central corneal thickness (CCT) correlated with GAT and NCT measurements but not with PDCT measurements. After LASIK, the mean reduction in CCT ranged from -3.0 to -171.0 microm (median 78 microm). The mean GAT measurement dropped by -4.9 mm Hg +/- 2.7 (SD) at 1 week and was -5.4 +/- 3.0 mm Hg at 4 weeks. Similar drops were observed in NCT measurements. The observed post-LASIK changes in GAT and NCT IOP measurements were not directly proportional to the change in CCT, refractive error, or mean keratometric readings. The preoperative and postoperative PDCT measurements did not differ significantly. CONCLUSIONS: The structural corneal changes induced by LASIK appeared to influence GAT and NCT measurements but not PDCT measurements. Therefore, PDCT may be better suited for monitoring IOP in unoperated eyes and in eyes that have had LASIK.     

Intraocular pressure measurement after hyperopic LASIK.

PURPOSE: Previous studies have shown that Goldmann applanation tonometry (GAT) underestimates intraocular pressure (IOP) following photorefractive keratometry (PRK) and myopic laser in situ keratomileusis (LASIK). The purpose of this study was to evaluate the reliability of intraocular pressure (IOP) measurements by Goldmann applanation tonometry and pneumotonometry (PT) after hyperopic LASIK. METHODS: The IOPs of 20 eyes of 15 patients who underwent hyperopia LASIK were prospectively evaluated. Central and peripheral IOP were measured with GAT and PT, and central and peripheral corneal thicknesses were measured with ultrasonographic pachymetry. Patients were evaluated preoperatively and at 12 months postoperatively. RESULTS: Postoperative GAT measurements of IOP made from the central (13.1+/-2.7 mm Hg) and peripheral (13.9+/-3.3 mm Hg) corneal areas were significantly lower (P <0.001) than central IOP measured preoperatively (17.0+/-2.5 mm Hg). Postoperative PT measurements from the central (17.4+/-3.2 mm Hg) and peripheral (17.6+/-2.9 mm Hg) corneal areas were slightly lower than preoperative central IOP (18.4+/-2.4 mm Hg), but not statistically significant. There were no significant differences between central and peripheral IOP measurements using either method. CONCLUSION: The data demonstrate that GAT may underestimate IOP measurement, following hyperopic LASIK.     

Comparison of dynamic contour tonometry and goldmann applanation tonometry in deep lamellar and penetrating keratoplasties

PURPOSE: To compare the measurements of intraocular pressure (IOP) with dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in eyes with corneal graft and to evaluate the influence of corneal thickness (CCT), corneal curvature (CC), and astigmatism on these methods. DESIGN: Prospective, observational cross-sectional study. METHODS: Eighteen eyes of 18 patients after penetrating keratoplasty (PKP) and 14 eyes of 14 patients after deep lamellar keratoplasty (DLKP) underwent IOP evaluation with DCT and GAT, and measurements of CCT, CC, and astigmatism. Bland-Altman plots were used to evaluate the agreement between tonometers. Multivariate regression analysis was used to evaluate the influence of ocular structural factors and running suture on IOP measurements obtained with both tonometers. RESULTS: IOP values obtained by DCT and GAT were strongly correlated in all eyes (r = .91; P < .001). DCT values measured 2.5 +/- 1.7 mm Hg higher than GAT readings (P < .001). A reduction of the mean IOP difference between DCT and GAT with an increase in IOP values (P < .001) was found. Regression analysis showed no effect of CCT, CC, astigmatism, and running suture on both DCT and GAT readings, either in DLKP or in PKP eyes. CONCLUSIONS: We found a good overall correlation between both tonometers but the agreement between instruments differs in high or low IOP ranges. The wide and varying 95% limits of agreement between DCT and GAT indicates that DCT provides IOP measurements on deep lamellar and penetrating keratoplasties which can be used in the clinical practice.     

Dynamic contour tonometry for post-LASIK intraocular pressure measurements

BACKGROUND: Standard applanation tonometers are subject to systematic errors when applied to corneas with non-standard properties. Dynamic contour tonometry has been proposed as an alternative method for obtaining correct IOP data from such corneas. We have examined its applicability for patients who have undergone LASIK surgery. PATIENTS AND METHODS: 20 healthy individuals scheduled for bilateral myopic LASIK were selected. Pre- and postoperative examination (3 months) included applanation tonometry (Goldmann), contour tonometry, pachymetry, keratometry, and refraction. LASIK was performed with an MEL-70 Excimer Laser and a Hansatome Microkeratome. A tobramycin/dexamethasone preparation (Tobradex eye drops) was prescribed during one week after surgery. RESULTS: Applanation tonometry and contour tonometry furnished comparable IOP results prior to surgery (GAT: 15.1 +/- 2.2 mm Hg [mean +/- SD] DCT: 17.0 +/- 2.2 mm Hg), with corneal thickness ranging from 473 - 601 micro m (mean: 555 micro m). 3 months postoperatively, mean corneal thickness was reduced by - 85 micro m. Contour tonometer readings were not significantly different from preoperative results (16.0 +/- 2.4 mm Hg); whereas the Goldmann tonometer furnished significantly lower values at 11.8 +/- 1.3 mm Hg. CONCLUSIONS: Preoperative IOP measurements with the two types of tonometer were in good agreement. Post-operative results with the contour tonometer agree well with preoperative figures. However, the Goldmann tonometer furnishes values 3.3 mm Hg lower on average. This result is indicative of a significant measurement error of this device on post-LASIK eyes, which persists even 3 months postoperatively. The Dynamic contour tonometer appears to be suitable, reliable, and easy to use for IOP measurements after LASIK surgery.     

Dynamic contour tonometry in keratoconus and postkeratoplasty eyes

PURPOSE: To compare the performance of dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in measuring intraocular pressure in eyes with irregular corneas. METHODS: GAT and DCT measures were taken in 30 keratoconus and 29 postkeratoplasty eyes of 35 patients after pachymetry and corneal topography. Regression and correlation analyses were performed between both tonometry methods and between tonometry methods and corneal parameters. Bland-Altman plots were constructed. RESULTS: DCT values were significantly higher than GAT values in both study groups: +4.1 +/- 2.3 mm Hg (mean +/- SD) in keratoconus and +3.1 +/- 2.5 mm Hg after keratoplasty. In contrast to DCT, GAT values were significantly higher in postkeratoplasty eyes than in keratoconus. The correlation between the 2 tonometry methods was moderate in keratoconus (Kendall correlation coefficient, tau = 0.34) as well in postkeratoplasty eyes (tau = 0.66). The +/-1.96 SD span of the DCT-GAT differences showed a considerable range: -0.42 to +8.70 mm Hg in keratoconus and -1.87 to +7.98 mm Hg in postkeratoplasty eyes. In the keratoconus group, neither DCT nor GAT correlated significantly with any of the corneal parameters. In the postkeratoplasty group, both DCT and GAT measures showed a moderate positive correlation with corneal steepness, but only DCT had a significant negative correlation with the central corneal thickness (tau = -0.33). CONCLUSIONS: DCT measured significantly higher intraocular pressures than GAT in keratoconus and postkeratoplasty eyes. DCT and GAT measures varied considerably, and DCT was not less dependent on biomechanical properties of irregular corneas than GAT.     

Changes in corneal biomechanics and intraocular pressure following LASIK using static, dynamic, and noncontact tonometry

PURPOSE: To compare the preoperative and postoperative measurement of corneal biomechanical properties and intraocular pressure (IOP) using Goldmann applanation tonometry (GAT), the ocular response analyzer (ORA), and the Pascal dynamic contour tonometer (PDCT) in eyes undergoing myopic laser in situ keratomileusis (LASIK). DESIGN: Prospective, nonrandomized clinical trial. METHODS: IOP was measured in 66 myopic eyes before and after LASIK by GAT, ORA, and PDCT in a randomized sequence. Metrics of corneal biomechanical properties (corneal hysteresis [CH], corneal resistance factor [CRF], and ocular pulse amplitude [OPA]) were recorded. RESULTS: After LASIK, there was a reduction in mean corneal pachymetry of 90.2 mum and in IOP measurements with GAT (Delta = -1.8 +/- 2.8 mm Hg; P < .01), ORA-Goldmann (Delta = -4.6 +/- 2.8 mm Hg, P < .01), and ORA-corneal compensated (Delta - 2.1 +/- 2.6 mm Hg; P < .05). However, there was no statistically significant difference between preoperative and postoperative IOP measurements taken by PDCT (Delta = -0.5 +/- 2.6 mm Hg). Postoperatively, CRF decreased by 28.6% (P < .01), CH by 16.2% (P < .01), and OPA by 1.8% (P = .32). CONCLUSIONS: Measurement of IOP with PDCT appears to be relatively immune to changes in corneal biomechanics and pachymetry after LASIK, in comparison to GAT and ORA measures of IOP. PDCT and ORA both showed statistically lower variation in measurement than GAT. LASIK produced a marked decline in CH and CRF, which may reflect respective changes in the viscous and elastic qualities of the post-LASIK cornea. In contrast, there was no statistical change in OPA.     

Comparison of Goldmann applanation tonometry, rebound tonometry and dynamic contour tonometry in normal and glaucomatous eyes

AIM: To compare the intraocular pressure (IOP) measurements obtained with the rebound tonometry (RT), dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in normal and glaucomatous eyes and investigate the effects of central corneal thickness (CCT) and corneal curvature (CC) on IOP measurements. METHODS: One hundred and twenty-four eyes of 124 subjects were enrolled in this cross-sectional study. Fifty-six of participants were healthy individuals and 68 of them were glaucomatous patients. IOP was measured on each subject always in the same order, ICare RT-Pascal DCT-GAT, after a minimum interval of 10min between measurements. CCT and CC were measured using a rotating Scheimpflug camera before the IOP measurements in all subjects. One way repeated measures ANOVA, Pearson correlation coefficient and regression analysis, and Bland-Altman analysis was used for the statistical assessment. RESULTS: Mean IOP for all enrolled eyes was 16.00±3.80 mm Hg for GAT, 16.99±4.91 mm Hg for RT, and 20.40±4.44 mm Hg for DCT. Mean differences between GAT and RT was -1.75±3.41 mm Hg in normal (P<0.001) and -0.37±3.00 mm Hg in glaucomatous eyes (P=0.563). Mean differences between GAT and DCT was -4.06±3.42 mm Hg in normal (P<0.001) and -4.67±3.12 mm Hg in glaucomatous eyes (P<0.001). GAT and RT were significantly positive correlated with CCT in normal (r=0.317, P=0.017 and r=0.576, P<0.001, respectively) and glaucomatous eyes (r=0.290, P=0.016 and r=0.351, P=0.003, respectively). DCT was also significantly positive correlated with CCT in normal eyes (r=0.424, P=0.001) but not in glaucomatous eyes (r=0.170, P=0.165). All tonometers were unaffected by CC. CONCLUSION: IOP measurements by RT and DCT were significantly higher than GAT. DCT has highest IOP measurements among these tonometers. RT was most influenced tonometer from CCT although all tonometers were significantly positive correlated with CCT except DCT in glaucomatous eyes. CC did not influence IOP measurements.     

The effect of corneal edema on dynamic contour and goldmann tonometry

PURPOSE: To determine the effect of contact lens-induced corneal edema on measurements of intraocular pressure (IOP) using the Pascal dynamic contour tonometer (DCT), compared with the Goldmann tonometer. METHODS: Thirty young healthy subjects (23.0 +/- 3.0 years) were recruited from the student population at the University of New South Wales. Thick hydroxyethyl methacrylate contact lenses were worn monocularly for 2 hours under closed-eye conditions to induce corneal edema via hypoxia. IOP (Goldmann and Pascal DCT), ocular pulse amplitude (OPA), and central corneal thickness (CCT) were measured in both eyes before and after lens wear. Paired t-tests, Pearson correlation, and Bland-Altman plots were used to identify changes in, and relationships between, these parameters resulting from corneal edema. RESULTS: Lens wear resulted in statistically significant changes in CCT (+48.3 +/- 14.4 microm, p < 0.001), Goldmann IOP (+1.5 +/- 2.8 mm Hg, p = 0.007), and Pascal DCT IOP (-0.7 +/- 1.1 mm Hg, p = 0.001) but not OPA (0.0 +/- 0.3 mm Hg, p = 0.721, two-tailed paired t-test). The Pascal DCT provided IOP readings that were 1.3 +/- 2.0 mm Hg higher than the Goldmann IOP readings when hydration was normal, but the Goldmann tonometer provided readings that were 0.8 +/- 2.5 mm Hg higher than the Pascal DCT readings when the cornea was edematous. The variation between the two instruments was weakly correlated to the change in CCT (r = -0.261, p = 0.044). CONCLUSIONS: Contact lens-induced corneal edema caused a small underestimation error in IOP measurements by the Pascal DCT, and an overestimation error in Goldmann tonometry measurements. The OPA measurement provided by the Pascal DCT is insensitive to corneal edema-induced changes in corneal properties.     

Comparison of dynamic contour tonometry with goldman applanation tonometry over a wide range of central corneal thickness

PURPOSE: To compare dynamic contour tonometry with Goldmann applanation tonometry in structurally normal corneas over a wide range of central corneal thickness (CCT). PATIENTS AND METHODS: Twenty-five patients each with normal CCT (group A), thin corneas (group B), and thick corneas (group C) had IOP measured with the Goldmann (GAT) and dynamic contour tonometer (DCT). RESULTS: In group A (mean CCT = 552 +/- 16 microm) the mean GAT was 15.9 +/- 3.1 mm Hg and mean DCT was 16 +/- 3.3 mm Hg (P = 0.91). In group B (mean CCT = 491 +/- 19 microm) the mean GAT was 13.2 +/- 3.5 mm Hg and the mean DCT was 15.9 +/- 3.5 mm Hg (P = 0.009). For group C (mean CCT = 615 +/- 22 microm), the mean GAT was 17.4 +/- 3.8 mm Hg and the mean DCT was 17.4 +/- 3.5 mm Hg (P = 0.95). The 95% agreement limits for DCT were -3.1 mm Hg to 2.9 mm Hg. The mean GAT-DCT difference was -2.6 mm Hg in thin corneas and -0.06 mm Hg in thick corneas. Below 520 microm reduction of 10 microm in CCT appears to result in a significant underestimation of the GAT IOP by 0.7 mm Hg (P < .001) and above 580 microm a non-significant overestimation of 0.2 mm Hg per 10 microm increase in CCT (P = 0.27). CONCLUSION: Dynamic contour tonometer agrees well on average with GAT but the agreement limits are wide. In structurally normal thin corneas DCT may give a more accurate assessment of the true IOP but it does not appear to have any benefit over GAT in thick corneas.     

Correlation between intraocular pressure and corneal stromal thickness after laser in situ keratomileusis

PURPOSE: To assess the relationship between intraocular pressure (IOP) and corneal stromal thickness following laser in situ keratomileusis (LASIK) for myopia or myopic astigmatism. SETTING: Private clinic in Turkey. METHODS: The database of patients who had LASIK was retrospectively reviewed. Preoperative and postoperative IOP and corneal thickness were measured in both eyes of 353 patients by noncontact tonometry and ultrasonic pachymetry, respectively. The correlation between changes in IOP and corneal thickness was evaluated by regression analysis. RESULTS: Laser in situ keratomileusis was associated with a mean decrease in pachymetry of 46.7 microm +/- 28.9 (SD) and a mean decrease in IOP of 2.8 +/- 2.1 mm Hg. There was a significant correlation between the decreases in IOP and pachymetry (P <.001). CONCLUSION: The decrease in IOP after LASIK was related to the decrease in corneal stromal thickness, although there may be other contributing factors.     

Reproducibility of dynamic contour tonometry. Comparison with TonoPenXL and Goldmann applanation tonometry - a clinical study on 323 normal eyes

BACKGROUND: The PASCAL Dynamic Contour Tonometer (DCT) is a new diagnostic approach for the digital measurement of intraocular pressure (IOP) in eyes with glaucoma. The aim of this study was to evaluate the reproducibility of DCT in normal eyes and to compare DCT with Goldmann applanation tonometry (GAT) and TonoPenXL. PATIENTS AND METHODS: A prospective cross-sectional study on 323 normal, consecutive eyes was performed. Eyes with an IOP of more than 23 mmHg (GAT) were excluded. Central corneal power (Zeiss Ophthalmometer) and central corneal thickness (ultrasound pachymetry: Tomey AL-1000) were taken. The IOP readings were obtained as follows: 3 x DCT [quality of measurement, IOP and ocular pulse amplitude (OPA) were taken], 1 x TonoPenXL, GAT, finally: once again DCT to evaluate the tonography effect. RESULTS: The quality of 3 following IOP (DCT) readings was good (quality Q1 = 43.4 %, Q2 = 32.5 %, Q3 = 22.7 %). The reproducibility of the IOP (DCT) measurements was excellent (first measurement IOP (DCT) = 18.1 +/- 3.4 mmHg, second measurement IOP (DCT) = 18.1 +/- 3.4 mmHg, third measurement IOP (DCT) = 17.8 +/- 3.4 mmHg, Cronbach's alpha = 0.976). First and second IOP (DCT) values showed a strong correlation (r = 0.93). A significant tonography effect was observed between first and third IOP (DCT) measurements (0.4 mmHg; p = 0.004). Mean OPA (DCT) was 3.0 mmHg during the first three measurements (Cronbach's alpha = 0.964). IOP (DCT) and OPA (DCT) reproducibility showed no laterality. IOP (DCT) (17.7 +/- 3.4 mmHg) was significantly higher than IOP (TonoPenXL) (16.0 +/- 3.2 mmHg, n = 275; p < 0.001) and higher than IOP (GAT) (14.5 +/- 3.1 mmHg, n = 275; p < 0.001). The effect of tonography between the third and last IOP (DCT) measurement was zero (p = 0.6). IOP (DCT) and IOP (GAT) values were only weak correlated with central corneal thickness. CONCLUSIONS: IOP and OPA values measured with the DCT are extraordinary reproducible in normal eyes. Frequently, DCT detects higher IOP values than those obtained with TonoPenXL and GAT. A reproducible measurement of IOP and OPA may open new diagnostic fields, e. g., in glaucoma detection or ocular vascular diseases.     

LASIK前后眼压测量方法选择

目的 比较四种常用眼压计在近视准分子激光原位角膜磨镶术(Laserin situ eratomileusis,LASIK)前后的应用,探讨LASIK手术前后眼压测量方式的选择,以做到术前高眼压患者筛查及术后患者青光眼的早期发现.方法 对71例接受LASIK手术近视眼患者按等效球镜分为三组,分别在术前和术后1个月和3个月采用Schiotz眼压计(Schiotztonometer,ST)、Goldmann眼压计(Goldmann applanationtonometry,GAT)、非接触眼压计(non-contacttonometer,NCT)和Tono-Pen眼压计(TP)测量眼压,同时记录手术前后角膜中央厚度.结果 各屈光度组间同时间点相同眼压计测量值差异无统计学意义,术前除GAT、TP外其他眼压计差异有统计学意义,术后各眼压计测量值均降低,TP受角膜变化影响较小,GAT及NCT受影响明显,三者均与术前GAT值相关.ST不受角膜变化影响但其测量值明显偏高且术后与术前GAT无相关关系.结论 术前采用TP或GAT均可,术后应用TP,而NCT可作为术前筛查辅助手段.ST的应用仍有待探讨.     

Changes in corneal biomechanics and intraocular pressure following Femto-LASIK using Goldman applanation tonometry and ocular response analyzer

AIM:To compare intraocular pressure(IOP)measurements before and after laser in situ keratomileusis(LASIK)with a femtosecond laser for flap creation using ocular response analyzer(ORA)and Goldmann applanation tonometry,and to identify factors that may influence the preoperative and postoperative IOP.METHODS:A prospective study conducted on myopic patients who underwent LASIK using a femtosecond laser for flap fashioning.Enrolled patients were evaluated preoperatively,6 wk and 3 mo postoperatively for manifest refraction(MR),keratometric(K)readings and central corneal thickness(CCT)using a scheimpflug-based topography.Corneal resistance factor(CRF),corneal hysteresis(CH),Goldmann correlated IOP(IOPg)and corneal compensated IOP(IOPcc)were measured using ORA besides IOP assessment by Goldman applanation tonometry(GAT).RESULTS:There was a statistically significant decrease in measures of IOPg by 3.35±0.83 mm Hg,followed by GAT which decreased by 2.2±0.44 mm Hg,and the least affected by operation was IOPcc which decreased only by 0.87±0.1 mm Hg after 6 wk.After 3 mo follow up there was a statistically significant decrease in IOPcc which decreased only by 0.76±0.4 mm Hg,followed by IOP GAT by 1.6±0.5 mm Hg,and the most affected by operation was IOPg which decreased by 2.3±0.3 mm Hg.Correspondingly,there was a statistically significant decrease in CH and CRF after 6 wk and 3 mo.At 3 mo,the preoperative MR and preoperative GAT were prominent significant predictors of the postoperative GAT changes.The prediction equation was subsumed.CONCLUSION:IOP measurements and corneal biomechanical factors reduce significantly after LASIK with a femtosecond laser for flap creation.The IOPcc values are less influenced by changes in corneal properties than IOPg and GAT,indicating that IOPcc may provide the most reliable measurement of IOP after this procedure.     

Comparisons between Pascal dynamic contour tonometry, the TonoPen, and Goldmann applanation tonometry in patients with glaucoma

PURPOSE: To compare intraocular pressure (IOP) measurements taken with Pascal dynamic contour tonometry (DCT), the TonoPen and the Goldmann applanation tonometry (GAT). The influence of central corneal thickness (CCT) on IOP measurements taken with Pascal DCT and the TonoPen was evaluated. METHODS: One eye in each of 101 consecutive patients with primary open-angle glaucoma (POAG) underwent ultrasonic CCT measurement and IOP evaluation with GAT, Pascal DCT and the TonoPen in random order. The agreement between results from Pascal DCT and the TonoPen and those of GAT was assessed using the Bland-Altman method. The deviation of Pascal DCT and TonoPen readings from GAT values, corrected for CCT, was calculated and correlated to CCT using a linear regression model. RESULTS: The mean of the differences in IOP measurements was 3.2 +/- 2.4 mmHg for Pascal DCT minus GAT readings and 0.5 +/- 4.5 mmHg for TonoPen minus GAT readings. The 95% confidence interval of differences in IOP measurements was higher between TonoPen and GAT readings (- 6 to 7 mmHg) than between Pascal and GAT readings (0.1-6.8 mmHg). Pascal DCT significantly overestimated IOP compared with GAT, especially for higher IOP readings. Bland-Altman scatterplots showed reasonable inter-method agreement between Pascal DCT and GAT measurements, and poor agreement between TonoPen and GAT measurements. The deviations of Pascal DCT and TonoPen readings from the corrected GAT values were both highly correlated with CCT values (linear regression analysis, p < 0.0001). The mean change in measured IOP for a 10-microm increase in CCT was 0.48 mmHg for Pascal DCT and 0.74 mmHg for the TonoPen. CONCLUSIONS: Agreement with GAT measurements was higher for Pascal DCT than for TonoPen readings; however, Pascal DCT significantly overestimated IOP values compared with GAT. Measurements of IOP obtained with both Pascal DCT and the TonoPen appeared to be influenced by CCT, and this influence appeared to be greater for the latter.     

Changes in intraocular pressure after laser in situ keratomileusis

PURPOSE: To evaluate changes in intraocular pressure (IOP) measurements by Goldmann applanation tonometry after laser in situ keratomileusis (LASIK) for myopia and myopic astigmatism, and to assess the accuracy of Goldmann applanation tonometry measurements after LASIK in these eyes. METHODS: LASIK was performed on 166 eyes of 93 patients for correction of myopia and myopic astigmatism. Intraocular pressure was measured by Goldmann applanation tonometry at the central and temporal parts of the cornea before and at 1, 3, 6, and 12 months after LASIK. The amount of change in IOP was computed and its relation to different variables was evaluated by regression analysis. RESULTS: Intraocular pressure measured at the center of the cornea was reduced by a mean of 3.69 +/- 1.63 mmHg after LASIK. Multiple regression analysis showed that the decrease in IOP was related to the preoperative IOP and the change in central corneal thickness after LASIK. Measurements of IOP at the temporal part of the cornea were also reduced by a mean of 2.39 +/- 1.71 mmHg. There was wide variability in the amount of difference between the temporal and central measurements after LASIK (temporal measurements were higher than central by 0 to +4 mmHg). CONCLUSION: LASIK for myopia produced underestimation of IOP measured by Goldmann applanation tonometry at the central part of the cornea by a mean of 3.69 +/- 1.63 mmHg. The decrease of IOP was related to preoperative IOP and the change in central corneal thickness after LASIK. Temporal Goldmann applanation tonometry measurements, although decreased after LASIK, were less reliable.