Three portable tonometers, the TGDc-01, the ICARE and the Tonopen XL, compared with each other and with Goldmann applanation tonometry*

Clinical evaluation of the Canon TX-10 noncontact tonometer in healthy eyes

PURPOSE

To assess the accuracy and repeatability of intraocular pressure (IOP) measurements obtained with the Canon TX-10 noncontact tonometer (NCT), using the Goldmann applanation tonometer (GAT) as the gold standard.

METHODS

Seventy-three young healthy subjects were enrolled in the study. Central corneal thickness (CCT) was obtained with Orbscan Topography System and then repeated IOP measurements were obtained with both tonometers. Canon TX-10 NCT was performed first, followed by GAT. Another study sample of 32 young healthy subjects was used to test the repeatability with both tonometers. Two sets of data were acquired separated by 1 week. Plotting the difference between the methods against the mean was done to compare the tonometers and the intersession variability. The hypothesis of zero bias was examined by a paired t test. The 95% limits of agreement (LoA) were also calculated.

RESULTS

No statistically significant differences were found when comparing the Canon TX-10 NCT with GAT, displaying close level of agreement with GAT as seen by the 95% LoA (-4.78 mmHg to +4.00 mmHg). CCT ranged from 419 microm to 585 microm and no relationship was found between CCT and IOP measurements. The coefficients of repeatability were 3.70 mmHg and 3.41 mmHg for GAT and TX-10 tonometers, respectively.

CONCLUSIONS

There was a good agreement between Canon TX-10 and GAT in healthy subjects. From the results obtained here, CCT appears to not affect IOP measurements when CCT is thinner than 570 microm.

The iCare rebound tonometer: comparisons with Goldmann tonometry, and influence of central corneal thickness

PURPOSE

To assess agreement between the iCare rebound tonometer and Goldmann tonometry and to assess the influence of central corneal thickness and the value of scleral rebound tonometer readings.

METHODS

Prospective single-centre cross-sectional study comparing iCare rebound tonometer (RT) intraocular pressure (IOP) readings taken from corneal and scleral locations to Goldmann applanation tonometer (GAT) readings in 100 subjects attending ophthalmology clinics.

RESULTS

There was a significant difference between RT and GAT, with RT tending to overestimate IOP. The mean difference between RT and GAT measurements was 3.36 mmHg. The mean difference between the log of RT and the log of GAT measurements was 0.2356, a ratio of 1.27 (P < 0.0001). A formula derived from a linear regression analysis suggested that a 10% increase in CCT increased the RT IOP reading by 9.9%. Scleral RT readings showed no relationship to GAT readings.

CONCLUSIONS

The rebound tonometer cannot replace the Goldmann tonometer in the office setting given the wide limits of agreement between the two devices. Corneal rebound tonometer readings are influenced by CCT whereas scleral rebound tonometer readings are of no value.

The influence of refractive errors on IOP measurement by rebound tonometry (ICare) and Goldmann applanation tonometry

PURPOSE

To evaluate the effect of refractive errors and central corneal thickness (CCT) on the measurement of intraocular pressure (IOP) by ICare rebound tonometer (RT), and its agreement with measurements by Goldmann applanation tonometer (GAT).

PATIENTS AND METHODS

Two observers measured the IOP by using RT and GAT in four groups of healthy volunteers with emmetropic (n = 78), hyperopic (n = 83), myopic (n = 87) and astigmatic (n = 79) eyes. Refraction was assessed by an autorefractometer. CCT was assessed by ultrasound pachymetry.

RESULTS

In all groups, no significant interobserver difference was seen in IOP values detected by both tonometers (Wilcoxon signed-rank test not significant). In all groups, IOP values were higher as measured by RT than by GAT (paired t-test p = 0.000): mean RT-GAT difference was higher in myopic eyes (+1.6 +/- 1.8 mmHg), and it was less than 1 mmHg in the other groups. RT-GAT difference was correlated to the refraction (p < 0.001), and it was greater when an higher IOP was detected by RT (significant correlation between RT-GAT difference and IOP by RT, p < 0.001). Compared with GAT values, the IOP readings by RT were greater than 2 mmHg in respectively 17.9% (emmetropic), 13.3% (hyperopic), 34.5% (myopic) and 7.6% (astigmatic) of the eyes. With both tonometers, in all groups the IOP values were correlated with CCT (p < 0.05), but the discrepancy between RT and GAT values was not related to CCT.

CONCLUSIONS

In all groups of subjects, higher IOP values were detected by RT; the IOP readings exceed the GAT values usually in a range of less than 1 mmHg, except when RT detects IOP >18 mmHg and generally in myopic eyes; RT-GAT discrepancy is related to the refractive error, but not to CCT.

Short-term intraocular pressure changes immediately after intravitreal injections of anti-vascular endothelial growth factor agents

PURPOSE

To assess short-term trends and the need to monitor intraocular pressure (IOP) changes immediately after intravitreal injections of ranibizumab, bevacizumab, pegaptanib, and triamcinolone acetonide.

DESIGN

Retrospective, interventional case series.

METHODS

Charts of 213 consecutive injections to 120 eyes of 112 patients were reviewed. Pressures were measured before injection, immediately after injection (T0), and at five-minute intervals until IOP was less than 30 mm Hg. Optic nerve perfusion was assessed by testing for hand movement vision and by indirect ophthalmoscopic examination. Kaplan-Meier and Chi-square analyses of IOP after injections and correlation of IOP spikes to drug, needle bore size, injection volume, and history of glaucoma were performed.

RESULTS

Mean preinjection IOP was 14 mm Hg (range, 7 to 22 mm Hg). Mean IOP at T0 was 44 mm Hg (range, 4 to 87 mm Hg). All but one eye had at least hand movement vision and a perfused optic nerve at T0. IOP was reduced to less than 30 mm Hg in 96% of injections by 15 minutes and in 100% by 30 minutes. Eyes with a history of glaucoma took longer to normalize the IOP (P = .002). Statistically significant IOP spikes were observed with a smaller needle bore size (P < .0001) and in eyes with a history of glaucoma (P = .001).

CONCLUSIONS

Elevations in IOP immediately after intravitreal injections are common, but are transient. Prolonged monitoring of IOP may not be necessary on the day of injection in most cases if hand movement vision, optic nerve perfusion, and lack of intraocular complications have been verified. However, cautious monitoring should be considered in select cases.

Clinical comparison of the Icare tonometer and Goldmann applanation tonometry

PURPOSE

To compare a new method of intraocular pressure (IOP) measurement, using the Icare tonometer, with Goldmann applanation tonometry (GAT).

PATIENTS AND METHODS

Two observers obtained IOP readings in 292 eyes (143 right and 149 left) of 153 subjects, using the Icare without topical anesthetic. A GAT reading was subsequently obtained by a consultant ophthalmologist, without the knowledge of the Icare readings. Central corneal thickness (CCT) was obtained on all eyes with ultrasound pachymetry. Patient comfort after IOP measurement was assessed in a consecutive subset of patients.

RESULTS

The intraclass correlation coefficient between the 2 modalities of IOP measurement was r=0.95 for the right and r=0.93 for the left eye. The mean difference (Icare-GAT) between the IOP measured by the 2 methods was 0.4 mm Hg in the right eye (SD 3.0, 95% confidence interval -5.5 to 6.3), and 0.8 mm Hg in the left eye (SD 3.0, confidence interval -4.7 to 6.2). GAT measurements did not vary with CCT [correlation coefficient=0.09 (P=0.25) right and 0.14 (P=0.09) left eyes]. However, IOP measured with Icare tonometry increased with increasing CCT [correlation coefficient=0.16 (P=0.05) right and 0.21 (P=0.01) left eyes]. For every 100-microm increase in CCT, the difference (Icare-GAT) increased by 1 mm Hg. Of the 38 consecutive patients surveyed, 28 (73.7%) rated the Icare more comfortable than GAT, with only 2 (5.3%) rating it less comfortable (P<0.001).

CONCLUSIONS

There is good correlation between the 2 methods of IOP measurement, even at extremes of IOP. The Icare instrument was easy to use and recorded rapid and consistent readings with minimal training. It seems to be more comfortable than GAT and obviates the need for topical anesthesia.

Technical note: a comparison of central and peripheral intraocular pressure using rebound tonometry

PURPOSE

To compare central and peripheral intraocular pressure (IOP) readings obtained with rebound tonometry.

METHODS

Intraocular pressure was measured on the right eye of 153 patients (65 males, 88 females), aged from 21 to 85 years (mean +/- S.D., 55.5 +/- 15.2 years) with the ICare rebound tonometer at centre, and 2 mm from the limbus (in the nasal and temporal regions along the 0-180 degrees corneal meridian).

RESULTS

Intraocular pressure values obtained with the ICare were 14.9 +/- 2.8; 14.1 +/- 2.5 and 14.5 +/- 2.7 mmHg at centre, nasal and temporal corneal locations, respectively. On average, nasal and temporal IOP readings were 0.75 and 0.37 mmHg lower than the central reading (p < 0.05 and p > 0.05, respectively). A highly significant correlation was found between central and peripheral measurements in nasal (r(2) = 0.905; p < 0.001) and temporal (r(2) = 0.879; p < 0.001) regions along the horizontal meridian. Almost 80% of patients presented nasal IOP values within +/-1 mmHg of the central value.

CONCLUSIONS

Intraocular pressure values measured with the ICare rebound tonometer on the nasal corneal region is slightly lower on average and highly correlated with IOP values recorded at corneal centre. Both nasal and temporal readings are in good agreement with central IOP, and could be used to obtain a reliable estimate of rebound IOP in corneas where central readings cannot be taken.

Central corneal thickness and Diaton transpalpebral tonometry

BACKGROUND

To examine the effects of central corneal thickness on the measures obtained from transpalpebral tonometry (Diaton), and to identify correlations between intraocular pressure (IOP) measurements with Diaton and the Goldmann applanation tonometer (GAT).

METHODS

In this cross-sectional study, 162 eyes of 81 participants were included. Intraocular pressure measurements were obtained in all patients using Diaton and GAT. Central corneal thickness was determined by ultrasound pachymetry. The participants were stratified by corneal thickness: group I <530 microm (n = 56), group II 530-560 microm (n = 65), and group III >560 microm (n = 41).

RESULTS

There were moderate correlations between IOP readings obtained using the Diaton and corrected GAT (C-GAT) (r = 0.303; P < 0.0001), and between corrected Diaton (C-Diaton), and C-GAT (r = 0.399; P < 0.0001). The mean Diaton tonometer readings were lower than C-GAT measurements (Diaton-corrected GAT mean difference, 0.9 +/- 3.8 mmHg; c-Diaton-corrected GAT mean difference, 0.7 +/- 3.5 mmHg). Differences were detected between the groups of patients for the GAT values [2.4 +/- 3.6 mmHg for those with the thinnest corneas (<530 microm), 0.7 +/- 3.6 mmHg for those with moderate corneas (between 531 microm and 560 microm), and -0.6 +/- 3.6 mmHg for those with the thickest (>560 microm) corneas], whereas a significantly lower difference (0.9 +/- 3.8 mmHg) was noted for the Diaton values of all individuals.

CONCLUSIONS

The Diaton measurements show moderate correlation with those provided by applanation tonometry. The Diaton tonometer seems to be more affected by the corneal thickness, especially in the thinnest corneas.

Comparison of the iCare rebound tonometer and the Goldmann applanation tonometer over a wide IOP range

BACKGROUND

The aim of this study was to compare the intraocular pressure (IOP) results measured by the iCare rebound tonometer with those obtained by the Goldmann applanation tonometer (GAT) over a wide range of IOP values. Furthermore, the comfort level of the iCare measurement was evaluated.

METHOD

The study included 75 eyes of 75 patients. The patients were divided into three groups (7-15 mmHg n = 25, 16-22 mmHg n = 25, 23-60 mmHg n = 25). The measurements were taken by two independent observers in a masked fashion. All patients were asked about discomfort during the iCare measurement. To establish the agreement between the two devices, a Bland-Altman analysis was performed.

RESULTS

Overall, the 95% confidence interval of the differences between the two devices was -8.67 to 10.25 mmHg and in 62.7%, the iCare measurement was within +/-3 mmHg of the GAT measurements. The distribution of the differences in IOP was similar, from 7-22 mmHg. In the higher IOP range (23-60 mmHg), however, the deviation was almost twice as large. The measurement with the iCare tonometer was well tolerated; 100% of the patients denied any discomfort.

CONCLUSIONS

The iCare tonometer is a mobile alternative to GAT in a low to moderate IOP range, but our findings show a greater deviation than previously reported. In high IOP values, measurements with the iCare tonometer do not correlate well with GAT.

The influence of corneal properties on rebound tonometry

PURPOSE

To determine the influence of corneal thickness, corneal hysteresis (CH), and corneal resistance factor (CRF) on intraocular pressure (IOP) measurements obtained using the iCARE rebound tonometer.

DESIGN

Cross-sectional study.

PARTICIPANTS

One hundred twenty-five eyes of 125 normal healthy subjects.

METHODS

Intraocular pressure was determined in all subjects using the iCARE at both central and temporal corneal regions. Corneal thickness at these 2 regions was determined by ultrasonic pachymetry. Corneal hysteresis and corneal resistance factor were measured using an ocular response analyzer. Goldmann applanation tonometry (GAT) was also performed on all eyes.

MAIN OUTCOME MEASURES

Intraocular pressure, corneal thickness, corneal hysteresis, and corneal resistance factor.

RESULTS

Although the peripheral cornea was significantly thicker than the central cornea, IOPs obtained by the iCARE at the 2 regions were similar and significantly higher than GAT measurements. There were an overestimation at higher IOPs and an underestimation at lower IOPs relative to GAT measurements. Multiple regression analysis showed a significant correlation between the iCARE and CH (partial correlation r = -0.67, P<0.01) and CRF (partial correlation r = 0.82, P<0.01). The correlation between the iCARE and central corneal thickness was not significant.

CONCLUSIONS

Rebound tonometry is affected by corneal properties including CH and CRF but not corneal thickness.

Comparison of the rebound tonometer with the Goldmann applanation tonometer in glaucoma patients

PURPOSE

To determine the agreement between the measurement of intraocular pressure (IOP) by the rebound tonometer (RBT) and by the Goldmann applanation tonometer (GAT) and to find out the effect of central corneal thickness (CCT) values on IOP measurements in glaucoma patients.

METHODS

IOP was measured with the RBT and GAT, respectively, in 61 eyes of 61 glaucoma patients. CCT was measured using an ultrasonic pachymeter after all IOP determinations had been made. The mean IOP measurement by the RBT was compared with the measurement by the GAT, by Student's t-test. Bland-Altman analysis was performed to assess the clinical agreement between the two methods. The effect of CCT on measured IOP was explored by linear regression analysis.

RESULTS

The mean patient age was 56.7+/-21.1 years (range: 30-80 years). There were 32 (52.46%) women and 29 (47.54%) men in the study group. The mean IOP readings were 18.70+/-4.76 mmHg using the RBT, and 18.27+/-3.49 mmHg using the GAT. The difference was not statistically significant (mean difference 0.43+/-2.55, P=0.2). A frequency distribution of the differences demonstrated that in more than 80% of cases the IOP readings differed by <2.3 mmHg between the RBT and GAT. There was a strong correlation between the RBT and GAT readings (r=0.852, P<0.0001). The IOP measurements with the two methods were correlated with CCT (r=0.40, P=0.02 for the RBT and r=0.48, P<0.0001 for the GAT). The IOP increased 1.1 mmHg and 8 mmHg for every 100-microm increase in CCT for the GAT and RBT, respectively.

CONCLUSION

The RBT slightly overestimated the IOP value by 0.43 mmHg on average when compared with the GAT. Nevertheless, the RBT readings appeared to be more affected by the various thicknesses of different corneas when compared with those obtained using the GAT.

Rebound Tonometer Compared With Goldmann Tonometer in Normal and Pathologic Corneas

PURPOSE

To compare the intraocular pressure (IOP) measurements obtained with the rebound tonometer (RT) and the Goldmann handheld tonometer (GT) in normal and altered corneas.

METHODS

A total of 208 normal corneas and 50 corneas with pathologies were included in this prospective study. All measurements were randomly obtained by 1 observer. The medians and interquartile range (IR) for both tonometers were compared. The median differences were assessed in IOP groups. Agreement between the tonometers was calculated using the Bland-Altman method.

RESULTS

The median IOP in all eyes was 17 mm Hg (IR, 13-22 mm Hg) with the RT and 16 mm Hg (IR, 13-21 mm Hg) with the GT (P < 0.001). The correlation was excellent between tonometers (r2 = 0.86; P < 0.001). The minimal differences between the two were obtained from 10 to 20 mm Hg (GT). The Bland-Altman scatterplot obtained good agreement between the instruments. In normal corneas, the median difference was < or =2 mm Hg in 77.4% of cases. In the altered corneas, the median difference was < or =2 mm Hg in 73% of cases (P = 0.21 compared with the normal group). In 10% and 2% of cases, the IOP could not be measured using the GT and RT, respectively.

CONCLUSIONS

The results were similar for both tonometers. In the altered corneas, the IOP could be difficult to obtain with the GT because of distorted half-circles. The 1-mm-diameter disposable RT tip facilitated obtaining measurements without anesthetic drops, which avoids infections. The RT could be useful in routine clinical settings when measuring IOP in corneas with pathologies.

Evaluierung der Reboundtonometrie (ICare) im Vergleich zum TonopenXL und dem Goldmann-Applanationstonometer

BACKGROUND

Goldmann applanation tonometry and dynamic contour tonometry (PASCAL) are two well established slit lamp mounted tonometric methods. Intraocular pressure measurement in bedridden patients and children is often only possible using hand held tonometers (TonoPenXL, Perkins tonometer, Draeger tonometer). This study was performed to evaluate the hand held ICare tonometer, which is based on the rebound method.

METHODS

A total of 102 eyes were examined by two highly experienced ophthalmologists for: 1) ophthalmological status, 2) central corneal power (Zeiss IOL-Master), 3) central corneal thickness (Tomey ultrasound pachymetry, five successive measurements, SD<5%), 4) intraocular pressure (IOP) measurement with the Goldmann applantation tonometer (GAT) 1x, 5) TonoPenXL (1x), 6) ICare with three successive measurement series of 6 single measurements.

RESULTS

The mean IOP(GAT) was 13.2+/-3.0 mmHg compared with the mean IOP(TonoPenXL) (13.4+/-3.1 mmHg) and with the IOP(ICare) (mean value of first measurement series: 13.4+/-3.1 mmHg). The series of measurements with the ICare showed a tonography effect (decrease of IOP from 14.6 mmHg at the first measurement and 14.2 mmHg at the second to 14.0 at the third measurement). The ICare-measurements were highly reliable (Cronbach's alpha=0.974) and showed a good correlation between the measurement series (r=0.592-0.642; p<0.001). There was a great intra-individual variability of up to 17 mmHg between the GAT, TonoPenXL and ICare methods.

CONCLUSIONS

The ICare tonometer is easy to handle and high reliability. The data are comparable with those from the Goldmann tonometer. A tonography effect of 0.6 mmHg in the successive measurement series was found.

Reproducibility and Tolerability of the ICare Rebound Tonometer in School Children

PURPOSE

To establish the intraobserver and interobserver reliability of the rebound tonometer (RBT) in healthy schoolchildren and to test patient tolerance in an unanesthetized eye.

SUBJECTS AND METHODS

To examine the reproducibility of the RBT, 2 experienced ophthalmologists undertook 3 consecutive intraocular pressure (IOP) measurements with the RBT without an anesthetic in 304 eyes of 152 healthy schoolchildren. Any pain or discomfort experienced by the children was recorded. Intraobserver and interobserver reliabilities were established by calculating correlation coefficients (r).

RESULTS

Of the 152 patients, 78 (51.3%) were males and 74 (48.7%) were females. The mean patient age was 11.2+/-2.6 years (range: 7 to 15 y). Mean IOP values obtained by examiners 1 and 2 were 16.48+/-2.82 mm Hg and 17.27+/-3.27 mm Hg for the right eyes and 17.15+/-3.36 mm Hg and 17.06+/-3.21 mm Hg for the left eyes. Intraobserver correlation coefficients for examiner 1 were 0.970 for the right eyes and 0.974 for the left eyes. For examiner 2, intraobserver correlation coefficients were 0.963 for the right eyes and 0.970 for the left eyes. The interobserver correlation coefficients were 0.798 for the right eyes and 0.858 for the left eyes (all P<0.0001). With the RBT, 98.6% of the subjects felt no pain and/or discomfort.

CONCLUSIONS

Measurement of IOP with the RBT is a highly reproducible method in schoolchildren showing high intraobserver and interobserver correlation and it seems to be very comfortable when performing IOP measurements in schoolchildren without an anesthetic.

Evaluation of the impedance tonometers TGDc-01 and iCare according to the international ocular tonometer standards ISO 8612

BACKGROUND

Two new tonometers have been introduced that are based on the impedance principle. Both the TGDc-01 (transpalpebral measurement) and the iCare (corneal measurement) do not require corneal anaesthesia. The present work presents an evaluation of both devices.

METHODS

Comparative measurements using one of the new tonometers and applanation tonometry were performed by one investigator according to the international standard for ocular tonometer (ISO 8612). Measurements were performed on 445 eyes without corneal pathology from 243 patients. Six measurements were performed for iCare and 3 for TGDc, immediately followed by 3 applanation tonometry measurements.

RESULTS

The correlation coefficient with respect to applanation tonometry was 0.81 for TGDc and 0.95 for iCare. TGDc-01 measurements showed an average deviation of 3.1 +/- 2.6 mmHg to those of Perkins applanation tonometry. The maximum difference was 28.7 mmHg below and 9.8 mmHg above the results of applanation tonometry. iCare showed an average deviation of 2.5 +/- 1.1 mmHg to Goldmann tonometry. The maximum difference was 14.5 mmHg below and 9.8 mmHg above.

CONCLUSIONS

The results of both new tonometers showed a good correlation with the reference applanation tonometric methods, but the strict requirements of ISO 8612 are not fulfilled by either tonometer at present. Additionally, transpalpebral measurements with the TGDc-01 showed unacceptably high variability.

Comparison of the ICare® rebound tonometer with the Goldmann applanation tonometer by experienced and inexperienced tonometrists

PURPOSE

To assess the agreement between ICare rebound tonometer and Goldmann applanation tonometer in the hands of experienced and inexperienced tonometrists.

PATIENTS AND METHODS

Two tonometrists, experienced with both Goldmann applanation tonometry (GAT) and ICare Tonometry (ICT) measured intraocular pressure (IOP), in a masked fashion, in 100 patients. In another series of 58 patients, ICT was performed by an inexperienced tonometrist and GAT by an experienced tonometrist.

RESULTS

In approximately 80% of patients, the difference in IOP between GAT and ICT was <or=2 mmHg in group 1 and <or=3 mmHg in group 2. The 95% limits of agreement were -4.0-4.4 mmHg in group 1 and -6.0-5.0 mmHg in group 2.

CONCLUSION

ICT compares reasonably with GAT, in both experienced and inexperienced hands. Its ease of use, portability, and sterility make it an attractive tonometer. Its degree of accuracy in inexperienced hands would make it a useful instrument for health care workers with limited ophthalmic experience.

Évaluation clinique du tonomètre dynamique Icare®

PURPOSE

The Icare dynamic tonometer (impact or Rebound tonometry) is a new tonometer based on making a moving object collide with an eye and on monitoring the motion parameters of this object following contact. The purpose of this study was to assess intra- and interobserver variability of IOP measurements with the Icare and their correlations with Goldmann applanation tonometry (GAT) and central corneal thickness (CCT).

MATERIAL AND METHODS

A prospective study including three groups of patients: group 1 (50 normal subjects), group 2 (50 patients with OHT or POAG and GAT IOP>22 mmHg), and group 3 (38 glaucomatous patients with GAT IOP< or =22 mmHg). In group 1, three consecutive IOP measurements were taken by three distinct observers with Icare followed by three GAT measurements by the same clinician. In group 2, the same procedure was followed from patients 1 to 25 and the reverse sequence from patients 25 to 50 after a 10-min break. In group 3, only one clinician took three GAT measurements followed by three Icare measurements after a 10-min break to exclude a tonographic effect in eyes with statistically normal-range IOPs.

RESULTS

: In group 1, intraobserver variability was about 6% for each observer (NS). There was no learning curve effect. The interobserver variation coefficient was 6.4%. Icare overestimated IOP compared to GAT (mean difference, 1.5-2.2 mmHg) (p<0.001). Icare IOP was 23.4 mmHg for observer 1 when GAT was 22 mmHg (95% individual CI, 18-28.9 mmHg). In group 2, intraobserver variation coefficients of the IOP ranged from 5% to 5.4% (NS). Icare overestimated IOP by mean 0.84 mmHg compared with GAT. In group 3, mean IOP was not different between Icare and GAT. Icare IOP of 20.7 mmHg corresponded to a value of 22 mmHg using GAT. In this group, correlations between CCT and IOP measurements were higher for Icare than for GAT (p=0.062).

CONCLUSION

Icare measures IOP in an unanesthetized sitting patient in a very brief time. Patient's minimal cooperation is needed. As long as the device is correctly positioned, the learning curve is short. Icare gives reproducible IOP measurements. Intra- and interobserver variability of IOP measurements are close to those of GAT. Icare overestimates IOP measurements an average 1.5 mmHg compared with GAT. Whatever the IOP level, Icare IOP measurements are well correlated with GAT. To a greater extent than for GAT, the reliability of IOP measurements is influenced by CCT. This tonometer can be used as a screening device for ocular hypertension as long as CCT measurements can be taken.

Corneal structure and biomechanics: impact on the diagnosis and management of glaucoma

PURPOSE OF REVIEW

Highlights recent studies relating to the impact of corneal structure and biomechanical properties on glaucoma evaluation and management.

RECENT FINDINGS

Central corneal thickness has been shown to play a role in the interpretation of intraocular pressure. Central corneal thickness has also been suggested as a glaucoma risk factor. The potential role of other corneal factors, such as stromal makeup, in the accurate measurement of intraocular pressure and the assessment of glaucoma risk remains to be determined.

SUMMARY

Improved understanding of central corneal thickness and corneal biomechanical properties may someday lead to a better understanding of glaucoma risk and its assessment.