Agreement of intraocular pressure measurement with Corvis ST,non-contact tonometer,and Goldmann applanation tonometer in children with ocular hypertension and related factors

AIM:To access the agreement of intraocular pressure(IOP)values obtained from biomechanically corrected tonometer[Corvis ST(CST)],non-contact tonometer(NCT),and Goldmann applanation tonometer(GAT)in children with NCT measured-IOP(NCT-IOP)values of 22 mm Hg or more,and related factors.METHODS:A total of 51 eyes with NCT-IOP≥22 mm Hg in children aged 7 to 14y were examined and IOP was measured by CST,NCT,and GAT.Based on GAT measured IOP(GAT-IOP),ocular hypertension(OHT)group(≥22 mm Hg,24 eyes)and the non-OHT group(<22 mm Hg,27 eyes)were defined.We compared the agreement of the three measurements,i.e.,CST measured IOP(CST-IOP),GAT-IOP,and NCT-IOP,and further analyzed the correlation between the differences in tonometry readings,central corneal thickness(CCT),axial length(AL),optic disc rim volume,and age.RESULTS:Compared with the OHT group,thicker CCT,larger rim volume,and higher differences between NCTIOP and GAT-IOP,were found in the non-OHT group.The differences between CST-IOP and GAT-IOP were lower than the differences between NCT-IOP and GAT-IOP in both groups.The mean differences in CST-IOP and GAT-IOP were 1.26 mm Hg(95%limit of agreement ranged from 0.1 to 2.41 mm Hg,OHT group)and 1.20 mm Hg(95%limit of agreement ranged from-0.5 to 3.00 mm Hg,non-OHT group),and the mean differences in NCT and GAT were 3.90 mm Hg(95%limit of agreement ranged from-0.19 to 9.70 mm Hg,OHT group)and 6.00 mm Hg(95%limit of agreement ranged from 1.50 to 10.50 mm Hg,non-OHT group).The differences between CST-IOP and GAT-IOP were not related to CCT,age,and AL in both groups;while the differences between NCT-IOP and GAT-IOP were related to CCT in the OHT group(r=0.93,P<0.001)and to CCT and AL in the non-OHT group(r=0.66,P<0.001,r=-0.81,P<0.001).CONCLUSION:The accuracy of NCT in the diagnosis of pediatric OHT is low.The agreement of CST-IOP and GATIOP was significantly higher in children with and without OHT than in those with NCT-IOP and GAT-IOP.Therefore,CST can be used as a good alternative for IOP measurement in children.The impacts of CCT and AL on NCT measurement need to be fully considered when managing childhood IOP.

Transpalpebral intraocular pressure measurement by Diaton compared to Goldman applanation tonometer in myopic eyes before and after transepithelial photorefractive keratectomy in Saudi Arabia

AIM:To compare intraocular pressure(IOP)measured via the trans palpebral IOP(tp IOP)method using a Diaton or with a Goldman applanation tonometer(GAT)and study the determinants of IOP difference in eyes undergoing transepithelial photorefractive keratectomy(TPRK)for myopia.METHODS:This cross-sectional validation study was held in 2020 in an eye hospital in Saudi Arabia.IOP was measured by Diaton and GAT before treatment,after one week,and one month of TPRK.It is considered if IOP difference by Diaton and GAT was less than±2 mm Hg acceptable.The IOP difference was tested if correlated to spherical equivalent(SE),central corneal thickness(CCT),age,gender,or tp IOP.RESULTS:Totolly 200 myopic eyes of 100 patients were included in the study.The mean difference of IOP measured by two methods before TPRK,1wk,and 1mo after TPRK were 0.790,-0.790,and-0.920 mm Hg,respectively(P<0.001).Diaton could measure IOP effectively 89.5%eyes before TPRK and 82%and 84%at 1wk and 1mo after TPTK,respectively.At week 1,IOP differences were significantly correlated to baseline CCT(P=0.02)and tp IOP at week 1(P<0.001).One month after TPRK,only tp IOP was significantly correlated to the difference in IOP(P<0.001).CONCLUSION:Diaton is a good screening tool for IOP before TPRK.It helps in monitoring IOP after surgery.Although more practical,it is less efficient than GAT.In eyes with high myopia and low tp IOP before surgery,IOP post-TPRK by Diaton and GAT could differ.

Comparison among Ocular Response Analyzer,Corvis ST and Goldmann applanation tonometry in healthy children

AIM: To explore the relationship between different parameters of Ocular Response Analyzer(ORA) and Corvis ST(CST) in a sample of healthy Iranian school-aged children and the relationship between parameters of these 2 instruments against intraocular pressure(IOP), measured by the Goldmann applanation tonometer(GAT-IOP), age and gender, and find possible correlation between ORA and CST with GAT.METHODS: This cross-sectional study included 90 healthy children. A general interview and complete eye examination were performed. Following successful GATIOP measurement, ORA and CST were conducted. The CST parameters were A 1/2 length(A1 L, A2 L), A 1/2 velocity(A1 V, A2 V), highest concavity deformation amplitude(HCDA), radius of curvature(Ro C), peak distance(PD), central corneal thickness(CCT) and IOP. The ORA parameters were corneal hysteresis(CH), corneal resistance factor(CRF), Goldmann-correlated IOP(IOP-G) and corneal compensated IOP(IOP-CC). Extracted data was analyzed using the Statistical Package for Social Science software.RESULTS: Totally 39 males with age of 9.08±1.60(6-12)y and 51 females with age of 8.96±1.55(6-13)y were included. Many CST parameters were significantly correlated with CH, CRF, IOP-G and IOP-CC. Some CST parameters had a significant correlation with GAT-IOP, including IOP-CST in both eyes and HCDA, A2 L, PD, and RoC in the left eye, but none with age, except A2 L in the right eye. The CRF measurement showed a significant correlation with GAT-IOP in both eyes and CH in the right eye, yet, none with age. Among all CST and ORA parameters, CCT-CST in both eyes and A1 L in right eye had a significant correlation with gender, although this was a negligible negative correlation. Comparison of mean IOP values by different devices showed a significantly highest IOP overestimation by CST and lowest by IOP-CC compared with GAT. Also, IOP-G versus IOP-CST significantly had the lowest IOP overestimation among others. Overall, either low positive correlation or negligible correlation was found between IOP measurements by 3 instruments.CONCLUSION: The study finds the highest IOP overestimation by CST and lowest by IOP-CC compared with GAT. Overall, either low positive correlation or negligible correlation is found between IOP measurements by the 3 instruments.

Comparison of ICare and IOPen vs Goldmann applanation tonometry according to international standards 8612 in glaucoma patients

·AIM: To compare IOPen and ICare rebound tonometry to Goldmann applanation tonometry(GAT) according to International Standards Organization(ISO) 8612 criteria.·METHODS: Totally 191 eyes(n =107 individuals) were included. Criteria of ISO 8612 were fulfilled: 3 clusters of IOP, measured by GAT, were formed. The GAT results were given as mean±standard deviation.·RESULTS: GAT(19.7±0.5 mm Hg) showed a significant correlation to ICare(19.8±0.5 mm Hg)(r =0.547, P <0.001)and IOPen(19.5 ±0.5 mm Hg)(r =0.526, P <0.001).According to ISO 8612 criteria in all 3 IOP groups the number of outliers(of the 95% limits of agreement)exceeded 5% for ICare and IOPen vs GAT: No.1(n =68)29.4% and 22.1%, No.2(n =62) 35.5% and 37.1%, No.3(n =61) 26.2% and 42.6%, respectively.·CONCLUSION: The strict requirements of the ISO 8612 are not fulfilled in a glaucoma collective by ICare and IOPen at present. As long as the Goldmann tonometry is applicable it should be used first of all for reproducible IOP readings. ICare and IOPen tonometry should be considered as an alternative tool, if application of Goldmann tonometry is not possible.

Comparison of IOPen rebound tonometer with Goldmann applanation tonometer at different IOP levels

AIM:To compare the accuracy of IOPen rebound tonometer with Goldmann applanation tonometer(GAT) in individuals with low,normal and high intraocular pressure(IOP) and to evaluate the effect of central corneal thickness(CCT) on IOP measurements.METHODS:This cross-sectional study consisted of 159 participants.IOP of one eye of each subject was measured consecutively with IOPen and GAT.Then CCT was measured using an ultrasonic pachymeter.Based on GAT IOP readings,participants were divided into low,normal and high IOP groups.Correlation between tonometers and CCT was calculated by spearman's correlation coefficient.Agreement between tonometers was evaluated using Bland-Altman method.RESULTS:Non-significant underestimation of IOP by IOPen was observed in low IOP group(Mean difference:0.20mmHg;P=0.454) and also in normal IOP group(Mean difference:0.56mmHg;P=0.065).However,IOPen significantly overestimated IOP in high IOP group(Mean difference:1.06mmHg;P=0.038).The 95% limits of agreement(LoA) width between IOPen and GAT IOPs were 7.84,8.57 and 14.27mmHg in low,normal and high IOP groups,respectively.Low IOP group had thinner corneas compared to high IOP group(P=0.034).IOP measurements taken by IOPen were not influenced by CCT(P=0.099) while poor correlation between CCT and GAT was found(R=0.17,P=0.032).Using receiver operating characteristic(ROC) curve,cutoff value of 18.75mmHg was determined for IOPen with sensitivity of 98.1 and specificity of 97.2%.CONCLUSION:Accuracy of IOPen is comparable to GAT in patients with low or normal IOP but IOPen overestimates IOP at high IOP levels.CCT does not affect IOP readings with IOPen.

Comparison of Diaton transpalpebral tonometer with applanation tonometry in keratoconus

AIM:To investigate the added value of using a Diaton transpalpebral tonometer(DT) to measure IOP in keratoconus.Most type of tonometers use corneal applanation or biomechanical resistance to measure intraocular pressure(IOP);however,these factors can be altered by keratoconus.Specifically,we examined whether DT can detect false-negative low Goldmann applanation tonometry(AT) measurements.· METHODS:Patients with keratoconus were recruited from our tertiary academic treatment center.Measurements included AT and DT(in random order)and Scheimpflug imaging.An age- and gender-matched group of control subjects with no history of corneal disease or glaucoma was also recruited.· RESULTS:In total,130 eyes from 66 participants were assessed.In the keratoconus group,mean AT was11.0±2.6,mean DT 11.2±5.5(P =0.729),and the two measures were correlated significantly(P=0.006,R=0.323).However,a Bland-Altman plot revealed a wide distribution and poor agreement between both measurements.Previous corneal crosslinking,corneal pachymetry,and Krumeich classification had no effect on measured IOP.· CONCLUSION:Measurements obtained using a Diaton tonometer are not affected by corneal biomechanics;however,its poor agreement with Goldmann AT values calls into question the added value of using a Diaton tonometer to measure IOP in keratoconus.

Dependence of dynamic contour and Goldmann applanation tonometries on peripheral corneal thickness

AIM:To determine the effects of peripheral corneal thickness(PCT) on dynamic contour tonometry(DCT) and Goldmann applanation tonometry(GAT).METHODS:A cross-sectional study.We created a software which calculates the corneal contour(CC) as a function of the radius from the corneal apex to each pixel of the contour.The software generates a central circumference with a radius of 1 mm and the remainder of the cornea is segmented in 5 rings concentric with corneal apex being its diameter not constant around the corneal circumference as a consequence of the irregular CC but keeping constant the diameter of each ring in each direction of the contour.PCT was determined as the mean thickness of the most eccentric ring.Locally weighted scatterplot smoothing(LOWESS) regression was used to determine the pattern of the relationship between PCT and both DCT and GAT respectively.Thereafter,two multivariable linear regression models were constructed.In each of them,the dependant variable was intraocular pressure(IOP) as determined using GAT and DCT respectively.In both of the models the predictive variable was PCT though LOWESS regression pattern was used to model the relationship between the dependant variables and the predictor one.Age and sex were also introduced control variables along with their first-degree interactions with PCT.Main outcome measures include amount of IOP variation explained through regression models(R2) and regression coefficients(B).RESULTS:Subjects included 109 eyes of 109 healthy individuals.LOWESS regression suggested that a 2 nd-degree polynomial would be suitable to model the relationship between both DCT and GAT with PCT.Hence PCT was introduced in both models as a linear and quadratic term.Neither age nor sex nor interactions were statistically significant in both models.For GAT model,R2 was 17.14%(F=9.02;P=0.0002),PCT linear term B was-1.163(95% CI:-1.163,-0.617).PCT quadratic term B was 0.00081(95% CI:0.00043,0.00118).For DCT model R2 was 14.28%(F=9.29;P=0.0002),PCT linear term B was-0.712(95% CI:-1.052,-0.372),PCT quadratic term was B=0.0005(95% CI:0.0003,0.0007).CONCLUSION:DCT and GAT measurements are conditioned by PCT though this effect,rather than linear,follows a 2^(nd)-degree polynomial pattern.

Rebound Tonometry in Cataract Surgery: Comparison with Goldmann Applanation Tonometry

Purpose: to compare the rebound tonometer ICare? (RT) with the Goldmann applanation tonometer (GAT) in cataract surgery and to assess the influence of central corneal thickness (CCT) on intraocular pressure (IOP) measurements. Design: retrospective, comparative study. Methods: a total of 472 patients underwent IOP measurement using RT (time 0 = RTa). GAT IOP measurement was performed 5 minutes later, followed by a second RT IOP measurement after other 5 minutes (RTa + 10 min = RTb). CCT was obtained by ultrasound pachymetry. In 106 patients IOP was measured by means of RT and GAT before clear corneal cataract surgery (RT1 and GAT1) and at one day postoperatively (RT2 and GAT2). Results: RT IOP values > 5 mmHg were overestimated, while RT IOP values Conclusion: our results showed a good agreement between measurements obtained with RT and GAT in pre and postoperative cataract surgery, although a significant statistically difference was found between RT and GAT measurements performed postoperatively. Moreover, CCT is a parameter to be considered for the IOP measurement, especially for values obtained with RT.

Dynamic Contour Tonometry,Tono-Pen XL^(■),and Goldmann Applanation Tonometry in Comparison to Intracameral Intraocular Pressure(IOP)Measurements in Patients with Corneal Pathologies

Purpose: The accuracy of Goldmann applanation tonometry (GAT) has been shown to depend on several biomechanical properties of the cornea. Newer tonometry devices (e.g., the Dynamic Contour Tonometer PASCAL? [DCT] and the Tono-Pen? XL [TP]) have been designed to accurately measure intraocular pressure (IOP) independent of corneal thickness (CCT) and pathology. This study investigates the influence of corneal pathologies on the accuracy of these IOP measuring devices, and compares this accuracy to that of direct intracameral IOP measurement. Methods: 8 eyes of 8 patients suffering from corneal pathologies scheduled for penetrating keratoplasty, and 10 eyes of 10 patients scheduled for cataract surgery (control group) were examined. Before surgery, the anterior chamber was cannulated at the temporal corneal limbus. In a closed system, the intraocular pressure (IOP) was directly set to 10, 20, and 30 mmHg with a manometric water column. Intraocular pressure measurements taken by GAT, DCT, and TP were compared to intracameral measurements obtained by a precision reference pressure sensor. Results: Control group: All three methods showed good agreement with the intracameral readings (mean deviation of all three devices, -0.9 mmHg). Group with corneal pathologies: The TP yielded the most exact IOP values in the group with corneal pathologies when taking all diagnoses into account. The mean deviations from the intracameral IOP measurements were -0.9 mmHg ± 3.2 mmHg (mean ± SD) for TP, -2.9 mmHg ± 3.3 mmHg for GAT, and -5.0 mmHg ± 7.9 mmHg for DCT. For bullous keratopathy, the most exact IOP readings were obtained by the TP (mean deviation -0.2 mmHg ± 3.5 mmHg). The TP and GAT devices underestimated IOP in the patients with Fuchs’ endothelial dystrophy;all 3 devices underestimated adjusted IOP after keratoplasty. DCT showed the greatest deviations from adjusted IOP in the case of non-herpetic scars. In the control group, none of the devices showed a statistically relevant dependency on CCT. Nevertheless, in the group with corneal pathologies, only TP showed no dependency on CCT. Conclusion: Our results suggest that the Tono-Pen XL? is the most accurate measurement device to determine IOP in patients with corneal pathologies, especially in patients suffering from corneal edema (bullous keratopathy). GAT yielded surprisingly exact IOP values in patients suffering from irregular corneal surface. DCT showed a high degree of deviation from the adjusted IOP, and should not be used to determine IOP in corneas with the disorders listed here.

Evaluation of rebound tonometer iCare IC200 as compared with IcarePRO and Goldmann applanation tonometer in patients with glaucoma

Background:This study investigated the agreement between a new rebound tonometer,IC200,and IcarePRO and Goldmann applanation tonometry(GAT).Methods:This was a prospective cross-sectional study.We measured the intraocular pressure(IOP)in 145 eyes of 145 glaucoma patients in the sitting position using GAT,IcarePRO,and IC200.IcarePRO and IC200 measurements were also obtained in the supine position.IC200 measurement was performed using two modes:single six(IC200-single)and automatic(IC200-continuous)six-measurements mode.Results:All tonometers provided high reproducibility in both positions(all intraclass correlation coefficients>0.90),although it was highest with GAT,followed by IC200-continuous and IC200-single and then IcarePRO.In the sitting position,the mean(±SD)IOPs of GAT,IcarePRO,IC200-single,and IC200-continuous were 14.5±2.9 mmHg,13.3±3.2 mmHg,11.6±3.2 mmHg,and 11.5±3.2 mmHg,respectively.IOPs measured with IcarePRO or IC200 were significantly lower than those with GAT,particularly in patients with low IOP.IOPs measured with all tonometers were significantly elevated in the supine position as compared with the sitting position,but this difference was significantly greater with IC200-single and IC200-continuous compared with IcarePRO.IOP elevation was significant in eyes without bleb versus those with bleb,but this finding was not observed when IOP was measured with IcarePRO.The IOPs of the single and continuous modes of IC200 were interchangeable in both positions.Conclusions:GAT,IcarePRO,and IC200 had sufficiently high reproducibility,but measurements with IcarePRO may not be accurate in the supine position.Elevation of IOP in the supine position,especially in eyes with bleb,was more sensitively captured with IC200 than with IcarePRO.

Impact of corneal parameters on intraocular pressure measurements in different tonometry methods

AIM: To evaluate the impact of central corneal thickness(CCT) and corneal curvature on intraocular pressure(IOP) measurements performed by three different tonometers. METHODS: IOP in 132 healthy eyes of 66 participants was measured using three different tonometry techniques: Goldmann applanation tonometer(GAT), Pascal dynamic contour tonometer(DCT), and ICare rebound tonometer(RT). CCT and corneal curvature were assessed. RESULTS: In healthy eyes, DCT presents significantly higher values of IOP than GAT(17.34±3.69 and 15.27±4.06 mm Hg, P<0.0001). RT measurements are significantly lower than GAT(13.56±4.33 mm Hg, P<0.0001). Compared with GAT, DCT presented on average 2.51 mm Hg higher values in eyes with CCT<600 μm and 0.99 mm Hg higher results in eyes with CCT≥600 μm. The RT results were lower on average by 1.61 and 1.95 mm Hg than those obtained by GAT, respectively. Positive correlations between CCT in eyes with CCT<600 μm were detected for all IOP measurement techniques, whereas a similar relationship was not observed in eyes with thicker corneas. A correlation between IOP values and keratometry in the group with CCT<600 μm was not detected with any of the tonometry methods. In thicker corneas, a positive correlation was found for GAT and mean keratometry values(R=0.369, P=0.005). CONCLUSION: The same method should always be chosen for routine IOP control, and measurements obtained by different methods cannot be compared. All analysed tonometry methods are dependent on CCT;thus, CCT should be taken into consideration for both diagnostics and monitoring.

Distribution of central corneal thickness and intraocular pressure in emmetropic eyes of healthy children of Palestine: a representative cross-sectional study

AIM: To determine the distributions of central corneal thickness(CCT) and intraocular pressure(IOP) in emmetropic eyes of healthy children of Palestine.METHODS: This representative cross sectional study included a total of 1156 eyes from 578 healthy school children aged 7-15 y. Inclusion criteria included emmetropia, no previous history of ocular or systemic diseases, no previous history of contact lens use, and the availability of both eyes. CCT and IOP were measured using ultrasound pachymeter and Goldmann applanation tonometer, respectively. The relationship of the results with age and gender was investigated.RESULTS: The mean age of school children was 11.13±2.8 y. Mean CCT was 542.2±37.4 and 544.3±39.2 μm for right and left eyes, respectively. Mean IOP was 12.5±2.2 and 12.3±2.2 mm Hg for right and left eyes, respectively. A positive correlation was observed between CCT and IOP of the right eye(P<0.001, R=0.358) and CCT and IOP of the left eye(P<0.001, R=0.324). No significant differences were observed in CCT and IOP due to age or gender(P>0.05). There were significant differences in mean CCT and IOP between right and left eyes(P=0.004, P=0.001, respectively).CONCLUSION: A population profile of CCT and IOP is established in Palestinian children for the first time. Mean CCT is comparable to some studies but differ from others. Mean IOP is considerably lower than that of majority children of other ethnic groups. Intereye difference of more than 36 μm in CCT, and 5 mm Hg in IOP should prompt evaluation for potential ocular disorders.