Évaluation clinique du tonomètre dynamique de contour Pascal®

Intraocular Pressure Measurement after Penetrating Keratoplasty

Assessing the intraocular pressure is a difficult but crucial task in the follow-up of patients that have undergone penetrating keratoplasty. Early recognition of elevated intraocular pressure and/or glaucoma and establishment of the appropriate treatment is essential to ensure the best possible visual outcome for patients dealing with this feared complication. Although Goldmann applanation tonometry is still the gold standard for measuring the intraocular pressure, its limitations in postkeratoplasty eyes, due to postoperative modified corneal morphology, have led to the search for more suitable alternatives. This review is the result of a comprehensive literature search in the MEDLINE database that aims to present glaucoma in the context of perforating keratoplasty, the corneal properties with impact on ocular pressure measurement, and the results achieved with the most important tonometers that have been studied in this pathology. Goldmann applanation tonometry remains the reference for intraocular pressure assessment even in corneas after penetrating keratoplasty. However, some promising alternatives have emerged, the most important of which are the Pascal dynamic contour tonometry, the Tono-Pen XL, the ocular response analyzer, and the iCare. All have advantages and disadvantages but have proved to be appropriate alternatives, especially in cases in which Goldmann applanation tonometry cannot be used.

Effect of Recipient Corneal Pathology on Pascal Tonometer and Goldmann Tonometer Readings in Eyes after Penetrating Keratoplasty

Purpose

To assess the influence of recipient corneal pathology on the performance of the Pascal dynamic contour tonometer (PDCT) (Swiss Microtechnology AG) by comparing it to Goldmann applanation tonometry (GAT) in post-penetrating keratoplasty (PKP) eyes.

Methods

Intraocular pressure (IOP) was measured in 40 post-PKP eyes of 40 patients using PDCT and GAT. The study patients were divided into two groups. Group A included patients who had undergone PKP for ectatic corneal disorders (keratoconus, n=20) and group B included patients who had undergone PKP for other non-ectatic corneal disorders (Fuchs, post-corneal ulcer, post-chemical burn, post-trauma, n=20). Keratometric measurements were obtained in all eyes using Orbscan II (Bausch & Lomb) and central corneal thickness (CCT) was measured using Corneo-Gaze Plus (Sonogaze).

Results

In group B, a correlation between PDCT and GAT IOP measurements was observed. In group A, GAT IOP measurements were significantly lower than PDCT measurements (3.7±1.8 mmHg, p<0.001). Additionally, CCT affected GAT IOP measurements much more than PDCT measurements, while corneal curvature did not significantly affect IOP measurements of any instrument in either group.

Conclusions

In post-PKP eyes, PDCT appears to be less influenced than GAT by CCT and pre-existing recipient corneal pathology. Therefore, PDCT may be better suited for monitoring IOP in post-PKP eyes.

Can dynamic contour tonometry and ocular pulse amplitude help to detect severe cardiovascular pathologies?

We demonstrate the close relationship between a conspicuous ocular pulse amplitude and severe underlying cardiovascular disease. Two otherwise symptom-free glaucoma patients without any previously diagnosed underlying cardiovascular pathology but with a conspicuous ocular pulse amplitude and who underwent routine examinations in our glaucoma department were referred to the appropriate specialty for further diagnostic procedures. In both patients, the diagnosis of a tachyarrhythmia was made as suspected on dynamic contour tonometry measurements. In addition to medical treatment, one patient underwent electric cardioversion and the second patient was scheduled for pacemaker implantation. A third patient with an unexpected high ocular pulse amplitude despite severe cardiovascular pathology underwent major surgery due to an aortic aneurysm. Carotid stenosis was diagnosed due to side differences in ocular pulse amplitude as well. Ocular pulse amplitude might be a noninvasive and affordable screening tool and could be used to detect severe cardiovascular disease. A prospective study including a larger number of patients is needed to prove this hypothesis.

Correlation between ocular perfusion pressure and ocular pulse amplitude in glaucoma, ocular hypertension, and normal eyes

Background

The purpose of this study was to investigate the correlation between ocular perfusion pressure and ocular pulse amplitude in glaucoma, ocular hypertension, and normal eyes.

Methods

Ninety eyes from 90 patients were included. Thirty patients had been recently diagnosed with glaucoma and had no previous history of treatment for ocular hypotension, 30 had elevated intraocular pressure (IOP) without evidence of glaucoma, and 30 had normal IOP (<21 mmHg) with no detectable glaucomatous damage. Goldmann applanation tonometry (GAT), dynamic contour tonometry (DCT), blood pressure measurement, pachymetry, Humphrey visual field, and routine ophthalmic examination was performed in each patient. Ocular perfusion pressure was calculated as the difference between mean arterial pressure and IOP. The ocular pulse amplitude was given by DCT. The Pearson correlation coefficient was used to compare the glaucomatous and ocular hypertensive groups, and comparisons with the normal IOP group were done using the Spearman’s rank correlation coefficient.

Results

Mean IOP by DCT was 22.7 ± 4.3 mmHg in the glaucoma group, 22.3 ± 2.8 mmHg in the ocular hypertension group, and 14.3 ± 1.6 mmHg in the control group. Mean IOP by GAT was 19.0 ± 5.1 mmHg for glaucoma, 22.4 ± 2.1 mmHg for ocular hypertension, and 12.9 ± 2.2 mmHg for controls. Mean ocular pulse amplitude was 3.4 ± 1.2 mmHg in the glaucoma group, 3.5 ± 1.2 mmHg in the ocular hypertension group, and 2.6 ± 0.9 mmHg in the control group. Mean ocular perfusion pressure was 46.3 ± 7.9 mmHg in the glaucoma group, 46.3 ± 7.9 mmHg in the ocular hypertension group, and 50.2 ± 7.0 mmHg in controls. No significant correlation between ocular perfusion pressure and ocular pulse amplitude was found in any of the groups (P = 0.865 and r = −0.032, P = 0.403 and r = −0.156, P = 0.082 and ρ = −0.307 for glaucoma, ocular hypertension, and normal eyes, respectively).

Conclusion

There is no significant correlation between ocular perfusion pressure and ocular pulse amplitude values in glaucoma, ocular hypertension, or normal eyes. IOP values measured by GAT correlate with those measured by DCT.

Dynamic contour tonometry in primary open angle glaucoma and pseudoexfoliation glaucoma: factors associated with intraocular pressure and ocular pulse amplitude

Purpose:

To compare the intraocular pressures (IOP) and ocular pulse amplitudes (OPAs) in patients with primary open-angle glaucoma (POAG) and pseudoexfoliation glaucoma (PXG), and to evaluate ocular and systemic factors associated with the OPA.

Materials and Methods:

In this prospective study, on 28 POAG and 30 PXG patients, IOP was measured with the Goldmann applanation tonometry (GAT) and the Pascal dynamic contour tonometry (DCT). Other measurements included central corneal thickness (CCT), vertical cup-to-disc ratio (CDR), and systolic and diastolic blood pressure. Statistical significance was defined as P < 0.05.

Results:

In each of the POAG and PXG groups, GAT IOP was correlated with CCT (r = 0.40, P = 0.03 and r = 0.35, P = 0.05, respectively), whereas DCT IOP and CCT were not correlated. In all patients and in the POAG group, OPA was positively correlated with DCT IOP (r = 0.39, P = 0.002). OPA was not correlated with CCT in the POAG (P = 0.80), nor in the PXG (P = 0.20) group, after adjusting for DCT IOP. When corrected for DCT IOP and CCT, there was a significant negative correlation between OPA and vertical CDR in all patients (r = −0.41, P = 0.002). There was no significant difference in OPA between groups (P = 0.55), even when OPA was adjusted for IOP and systolic and diastolic pressure (P = 0.40), in a linear regression model.

Conclusion:

DCT IOP and OPA are not correlated with CCT. There is no significant difference between the OPA of PXG and POAG eyes. OPA is correlated with DCT IOP, and is lower in eyes with more advanced glaucomatous cupping.

Ocular pulse amplitude and retrobulbar blood flow change in dipper and non-dipper individuals

PURPOSE

To evaluate ocular pulse amplitude (OPA), IOP values, and hemodynamic changes in the ophthalmic artery, central retinal artery, and short posterior ciliary artery in dipper and non-dipper patients.

METHODS

A total of 59 right eye measurements of healthy subjects with normotensive were included to the study. Ambulatory blood pressure (BP) monitoring measurement (ABPM), Doppler imaging, and OPA measurements were performed in the same day. The patients in which systolic BP decreased during the nocturnal time by 10% of the diurnal BP or more were called dippers. A patient whose nocturnal systolic BP fell by <10% or even rose was defined as non-dipper. Color Doppler imaging was used for blood flow velocity assessment of ophthalmic, central retinal, and posterior ciliary arteries. For each artery, peak systolic and end-diastolic velocities (PSV and EDV, respectively), resistive index (RI), and pulsalite index (PI) were automatically calculated by the machine. Mean IOP and OPA values were calculated after three consecutive measurements.

RESULTS

The mean OPA in non-dipper patients was significantly lower compared with that of dipper patients (P=0.011). There was no significant difference in IOP levels between groups. There was no significant difference in the PSV, EDV, RI, and PI in the ophthalmic, posterior ciliary, and central retinal arteries between the groups.

CONCLUSION

Our study demonstrated that OPA level in non-dippers is lower than dippers. This may give additional information about the effect of BP changes on OPA values.

Relationship between ocular pulse amplitude and systemic blood pressure measurements

PURPOSE

This study aimed to determine whether ocular pulse amplitude (OPA) measured with dynamic contour tonometry (DCT) is related to systemic blood pressure (BP) parameters.

METHODS

Blood pressure was measured continuously and simultaneously with OPA in one randomly selected eye in 29 healthy subjects. Systemic parameters of interest were: systolic and diastolic BPs and their difference (BP amplitude), and left ventricle ejection time (LVET; defined as the time between the diastolic trough and the incisural notch in the BP curve). In addition, the axial length (AL) of the eye was measured. Associations between OPA, AL and systemic cardiovascular parameters were analysed in a multivariate regression model.

RESULTS

Measurements of OPA ranged from 1.0 mmHg to 4.9 mmHg (mean 2.3 +/- 0.9 mmHg, median 1.9 mmHg). In a univariate analysis with one predictor at a time, means of intraocular pressure (IOP) (p = 0.008), AL (p = 0.046) and LVET (p = 0.037) were significantly correlated with OPA, whereas systolic and diastolic BPs and their amplitude were not. A multiple linear regression analysis showed that mean IOP (p < 0.005), AL (p = 0.01) and LVET (p = 0.002) all independently contributed to OPA.

CONCLUSIONS

The OPA readings measured with DCT in healthy subjects were not related to BP levels and amplitude. It seems that the OPA strongly depends on the time-course of the cardiac contraction. Regulating mechanisms in the carotid system as well as scleral rigidity may be responsible for dampening the direct effect of BP variations.

Poor agreement between Goldmann and Pascal tonometry in eyes with extreme pachymetry

AIM

To compare the intraocular pressure (IOP) measurements obtained using the Pascal dynamic contour tonometer (PDCT) with the standard Goldmann applanation tonometry (GAT) and to correlate them with the central corneal thickness (CCT) in a non-glaucomatous population.

METHODS

We prospectively measured IOP using PDCT and GAT in random order in 100 normal eyes. CCT was analysed with an ultrasonic pachymeter in each case. Statistical analysis of baseline and stratified data included intraclass correlation coefficient (ICC), Lin correlation, and Bland-Altman analysis to evaluate the agreement between both techniques.ResultsGAT was used first in 51 eyes and PDCT in 48 cases. Mean IOP was 14.8 mm Hg with GAT and 20.3 mm Hg with PDCT. Mean pachymetry was 553.23 micrometres (microm) (SD: 4.7 microm). Global agreement of IOP between GAT and PDCT was 0.09 by ICC and 0.170 by Lin correlation. When CCT values ranged between 540 and 545 microm, the agreement between both tonometers was optimal (ICC 0.54 and Lin 0.61). Outside these pachymetry values, agreement between both tonometers diminished dramatically.

CONCLUSION

Statistically significant agreement between both devices was reached only at intermediate pachymetry readings in contrast with other studies that show excellent global agreement between GAT and PDCT.