Correlation between ocular pulse amplitude measured by dynamic contour tonometer and visual field defects

Ocular pulse amplitude (OPA) in canine ADAMTS10-open-angle glaucoma (ADAMTS10-OAG)

Introduction: The role of ocular rigidity and biomechanics remains incompletely understood in glaucoma, including assessing an individual's sensitivity to intraocular pressure (IOP). In this regard, the clinical assessment of ocular biomechanics represents an important need. The purpose of this study was to determine a possible relationship between the G661R missense mutation in the ADAMTS10 gene and the ocular pulse amplitude (OPA), the difference between diastolic and systolic intraocular pressure (IOP), in a well-established canine model of open-angle glaucoma (OAG). Methods: Animals studied included 39 ADAMTS10-mutant dogs with different stages of OAG and 14 unaffected control male and female dogs between 6 months and 12 years (median: 3.2 years). Dogs were sedated intravenously with butorphanol tartrate and midazolam HCl, and their IOPs were measured with the Icare® Tonovet rebound tonometer. The Reichert Model 30™ Pneumotonometer was used to measure OPA. Central corneal thickness (CCT) was measured via Accutome® PachPen, and A-scan biometry was assessed with DGH Technology Scanmate. All outcome measures of left and right eyes were averaged for each dog. Data analysis was conducted with ANOVA, ANCOVA, and regression models. Results: ADAMTS10-OAG-affected dogs displayed a greater IOP of 23.0 ± 7.0 mmHg (mean ± SD) compared to 15.3 ± 3.6 mmHg in normal dogs (p < 0.0001). Mutant dogs had a significantly lower OPA of 4.1 ± 2.0 mmHg compared to 6.5 ± 2.8 mmHg of normal dogs (p < 0.01). There was no significant age effect, but OPA was correlated with IOP in ADAMTS10-mutant dogs. Conclusion: The lower OPA in ADAMTS10-mutant dogs corresponds to the previously documented weaker and biochemically distinct posterior sclera, but a direct relationship remains to be confirmed. The OPA may be a valuable clinical tool to assess ocular stiffness and an individual's susceptibility to IOP elevation.

Role of excessive weight in intraocular pressure: a systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis aimed to analyse the effect of excess body weight on intraocular pressure (IOP) values.

METHOD AND ANALYSIS

A literature search from PubMed, Medline and ScienceDirect Databases on 18 May 2023 was conducted by three reviewers, then filtered each study based on inclusion and exclusion criteria. For the quality assessment of included studies, the Newcastle-Ottawa Scale was adapted. Meta-analysis was performed using RevMan V.5.4 by entering the IOP values of each group to measure the mean difference.

RESULTS

From 2656 studies, there were 9 studies that matched the criteria and then were included to perform a quantitative meta-analysis. The results showed a mean difference of 0.93 (95% CI: 0.67 to 1.18) of the excessive weight group against the normal weight group. This suggests that there is a significant relationship between excess body weight and increasing values of IOP.

CONCLUSION

It can be concluded that excessive body weight tends to lead to higher IOP, which means that high IOP becomes a major risk factor for glaucoma.

[Tonometry: Review and Perspectives]

Reliable and repeated IOP measurement are essential in the diagnosis and treatment of glaucoma. In this second part, the other contact tonometry and non-contact tonometry are presented. The clinical value of the different methods and the value of multimodality in tonometry will be discussed based on a review of the literature, and the latest innovations with telemetric IOP sensors will be introduced.

Tonometrie: Rückblick und Ausblick (Teil 2)

In 2. Teil des Beitrags werden die sonstigen Kontakttonometer und die Nonkontakttonometrie präsentiert. Es wird anhand einer Revue der Literatur über den klinischen Wert der verschiedenen Methoden und den Wert der Multimodalität in der Tonometrie diskutiert; ferner werden die letzten Innovationen mit den telemetrischen IOD-Sensoren eingeführt.

[Examination of patients with glaucoma during the COVID-19 pandemic]

PURPOSE

To evaluate the efficacy of the optimal examination technique for patients with glaucoma during the COVID-19 pandemic that includes one of the safest methods of tonometry [transpalpebral tonometry (TPT), contour dynamic tonometry (CDT) and Icare rebound tonometry (RBT)] in combination with spectral domain optical coherence tomography (SD-OCT) and optical coherence tomography angiography (OCTA).

MATERIAL AND METHODS

The study included 65 patients with primary open-angle glaucoma (POAG) who sought medical aid at the Ophthalmological Center of FMBA during the COVID-19 pandemic; they were examined using three tonometry methods: RBT, TPT and CDT. All patients underwent central corneal thickness measurement, perimetry, OCT and OCTA with assessment of vessel density (VD) of the superficial plexus in the macula (whole image macula) and peripapillary retina (PPR).

RESULTS

High correlation was found between the results obtained with RBT, TPT and CDT. None of the methods showed a correlation between IOP and corneal thickness. The correlations between IOP and OCTA parameters were obtained: IOP_TPT and VD_PPR in the inferior temporal sector (r= -0.386, p=0.027), IOP_RBT and VD whole image macula (r= -0.69, p=0.019), and in the macula inferior hemisphere (r= -0.75, p=0.008), as well as between the ocular pulse amplitude (OPA) and VD in the macular inferior hemisphere (r=0.380, p=0.039). The OCTA parameters had a moderate, but significant correlation with the perimetric indices.

CONCLUSIONS

Tonometry methods (TPB, CDT and RBT) exhibit high correlation with each other and no correlation with corneal thickness. IOP parameters measured by different methods, especially using the Icare tonometer, correlate with OCTA parameters, and the latter - with perimetric indices. The combination of these tonometry methods with SD-OCT and OCTA is optimal for examining patients during the pandemic.

Using Deep Learning to Automate Goldmann Applanation Tonometry Readings

PURPOSE

To develop an objective and automated method for measuring intraocular pressure using deep learning and fixed-force Goldmann applanation tonometry (GAT) techniques.

DESIGN

Prospective cross-sectional study.

PARTICIPANTS

Patients from an academic glaucoma practice.

METHODS

Intraocular pressure was estimated by analyzing videos recorded using a standard slit-lamp microscope and fixed-force GAT. Video frames were labeled to identify the outline of the reference tonometer and the applanation mires. A deep learning model was trained to localize and segment the tonometer and mires. Intraocular pressure values were calculated from the deep learning-predicted tonometer and mire diameters using the Imbert-Fick formula. A separate test set was collected prospectively in which standard and automated GAT measurements were collected in random order by 2 independent masked observers to assess the deep learning model as well as interobserver variability.

MAIN OUTCOME MEASURES

Intraocular pressure measurements between standard and automated methods were compared.

RESULTS

Two hundred sixty-three eyes of 135 patients were included in the training and validation videos. For the test set, 50 eyes from 25 participants were included. Each eye was measured by 2 observers, resulting in 100 videos. Within the test set, the mean difference between automated and standard GAT results was -0.9 mmHg (95% limits of agreement [LoA], -5.4 to 3.6 mmHg). Mean difference between the 2 observers using standard GAT was 0.09 mmHg (LoA,-3.8 to 4.0 mmHg). Mean difference between the 2 observers using automated GAT videos was -0.3 mmHg (LoA, -4.1 to 3.5 mmHg). The coefficients of repeatability for automated and standard GAT were 3.8 and 3.9 mmHg, respectively. The bias for even-numbered measurements was reduced when using automated GAT.

CONCLUSIONS

Preliminary measurements using deep learning to automate GAT demonstrate results comparable with those of standard GAT. Automated GAT has the potential to improve on our current GAT measurement standards significantly by reducing bias and improving repeatability. In addition, ocular pulse amplitudes could be observed using this technique.

Relationship Between the Parameters of Corneal and Fundus Pulse Signals Acquired With a Combined Ultrasound and Laser Interferometry Technique

Purpose

To estimate the relationship between the characteristics of the corneal pulse (CP) signal and those of the fundus pulse (FP) signal measured with a combined noncontact ultrasonic and laser interferometry technique in healthy subjects.

Methods

Twenty-two healthy subjects participated in experiments that included measurements of intraocular pressure, ocular pulse amplitude, ocular biometry, blood pressure, and heart rate. Additionally, simultaneous recordings of CP and FP signals were acquired with a noncontact ultrasonic device combined with laser interferometry. Subsequently, ocular perfusion pressure (OPP) and the time and spectral parameters of CP and FP signals were computed. A system model was proposed to relate the FP signal to the CP signal.

Results

The system model revealed that the eye globe transfers information between signals of the posterior and anterior eye, relatively amplifying higher spectral harmonics. The amplitude of the second CP harmonic is predicted by FP_RMS and OPP (R² = 0.468, P = 0.002). Partial correlation analysis showed that the CP signal parameters are statistically significantly correlated with those of the FP signal and OPP, after correcting for age and sex.

Conclusions

The eye globe can be viewed as a high pass filter, in which the CP characteristic changes in relation to the fundus pulsation. The FP signal and OPP have an impact on the variations of the CP signal morphology.

Translational Relevance

Investigation of differences between the characteristics of the anterior and posterior tissue movements is a promising method for evaluating the role of circulatory and biomechanical components in the pathophysiology of ocular diseases.

Ocular pulse amplitude in different types of glaucoma using dynamic contour tonometry: Diagnosis and follow-up of glaucoma

The aim of the present study was to compare the ocular pulse amplitude (OPA) in patients with different types of glaucoma using dynamic contour tonometry (DCT), to evaluate ocular and systemic factors associated with the OPA and to verify whether OPA measured by DCT is an independent predictor for glaucoma diagnosis. A total of 217 eyes of 217 participants in the following five groups were included in this cross-sectional study: Chronic angle closure glaucoma (CACG), primary open angle glaucoma, normal tension glaucoma (NTG), suspected open angle glaucoma (SOAG) and normal control (NC). The following tests were simultaneously performed during a single visit: Intra-ocular pressure (IOP), OPA, cup-to-disk (C/D) ratio, mean damage (MD) and loss variance (LV). OPAs were compared in each group. The association between OPA and IOP, age, C/D ratio, MD and LV was detected. OPA analysis prior to and after trabeculectomy was also performed to assess its prognostic value. Among the 217 individuals, the OPA was consistent with the IOP, both measured by DCT, along with the MD and LV. Patients with CACG and SOAG had higher OPA values than those with NTG and normal controls. Compared with patients aged >30 years, the OPA was significantly lower in younger patients, while they may not have been affected by different C/D ratios. After trabeculectomy, the OPA had significantly decreased compared with the values prior to surgery. In conclusion, the present study showed that the OPA is correlated with the IOP determined by DCT. CACG and SOAG patients had higher OPA values than patients with other types of glaucoma. OPA measured by DCT may be a predictor for glaucoma diagnosis and prognosis.

Review on Dynamic Contour Tonometry and Ocular Pulse Amplitude

Intraocular pressure (IOP) measurement is the cornerstone of the management of glaucoma patients. The gold standard for assessing IOP is Goldmann applanation tonometry (GAT). Recently, the dynamic contour tonometer (DCT) has become available. While both devices provide reliable IOP measurements, the results are not interchangeable. DCT has the advantage of measuring an additional parameter: ocular pulse amplitude (OPA). OPA is defined as the difference between systolic and diastolic IOP and represents the pulsatile wave front produced by the varying amount of blood in the eye during the cardiac cycle. It has been shown to vary with ocular structural parameters, such as axial length, corneal thickness, and ocular rigidity, as well as with systemic variables like heart rate, blood pressure, and left ventricular ejection fraction. Although the existence of some of these associations is still controversial, the clinical relevance of OPA has been consistently suggested, especially in glaucoma. Further research on this intriguing parameter could not only provide insight into glaucoma pathophysiology but also help integrate this variable into clinical practice.

Comparison of Ocular Pulse Amplitude Lowering Effects of Preservative-Free Tafluprost and Preservative-Free Dorzolamide-Timolol Fixed Combination Eyedrops

Purpose. To compare the ocular pulse amplitude (OPA) lowering effects of preservative-free tafluprost and dorzolamide-timolol fixed combination (DTFC) using dynamic contour tonometry. Methods. In total, 66 eyes of 66 patients with normal tension glaucoma (NTG) (n = 34) or primary open angle glaucoma (POAG) (n = 32) were included. Patients were divided into two groups: the preservative-free tafluprost-treated group (n = 33) and the preservative-free DTFC-treated group (n = 33). Intraocular pressure (IOP) was measured using Goldmann applanation tonometry (GAT). OPA was measured using dynamic contour tonometry; corrected OPA (cOPA) was calculated at baseline and at 1 week and 1, 3, and 6 months after treatment. Results. After 6 months of treatment, tafluprost significantly reduced IOP (P < 0.001). The OPA lowering effects differed significantly between the two treatment groups (P = 0.003). The cOPA-lowering effect of tafluprost (1.09 mmHg) was significantly greater than that of DTFC (0.36 mmHg) after 6 months of treatment (P = 0.01). Conclusions. Tafluprost and DTFC glaucoma treatments provided marked OPA and IOP lowering effects. Tafluprost had a greater effect than DTFC; thus, this drug is recommended for patients at risk of glaucoma progression, due to the high OPA caused by large fluctuations in IOP.

Comparison of Ocular Pulse Amplitude-Lowering Effects of Tafluprost and Latanoprost by Dynamic Contour Tonometry

PURPOSE

A prospective study was performed to compare the ocular pulse amplitude (OPA)-lowering effects of tafluprost and latanoprost, used in the treatment of glaucoma, using dynamic contour tonometry.

METHODS

The study population consisted of patients with normal-tension glaucoma (NTG) (n = 27) or primary open-angle glaucoma (POAG) (n = 14) treated with tafluprost and latanoprost. All patients were newly diagnosed with NTG and POAG and had undergone no previous treatment. Intraocular pressure (IOP) was measured by Goldmann applanation tonometry (GAT), OPA was measured by dynamic contour tonometry, and corrected OPA (cOPA) was calculated before and after 1 week, 1-3 months of treatment.

RESULTS

Initial IOP and OPA were 17.12 ± 3.75, 2.30 ± 0.56 mmHg and 17.53 ± 2.87, 2.65 ± 0.94 mmHg in the tafluprost and latanoprost groups, respectively. After 3 months of treatment, IOP and OPA were 13.00 ± 2.04 mmHg (24.1%) and 1.51 ± 0.30 mmHg (34.3%), respectively, in the tafluprost group. These values were 15.40 ± 2.32 mmHg (12.2%) and 2.08 ± 0.83 mmHg (21.5%), respectively, in the latanoprost group. Therefore, tafluprost significantly reduced IOP (P = 0.01), but OPA-lowering effects did not differ significantly between the 2 groups (P = 0.17). However, the cOPA-lowering effect of tafluprost (1.27 mmHg, 55.2%) was significantly greater than that of latanoprost (0.84 mmHg, 31.7%) after 3 months of treatment (P < 0.001).

CONCLUSIONS

Tafluprost and latanoprost, used to treat glaucoma, have marked OPA-lowering effects as well as IOP-lowering effects. Moreover, tafluprost has a greater effect than latanoprost. Therefore, it can be used for patients in need of IOP reduction and at risk of glaucoma progression.

Ocular pulse amplitude and Doppler waveform analysis in glaucoma patients

PURPOSE

To determine the correlation between ocular blood flow velocities and ocular pulse amplitude (OPA) in glaucoma patients using colour Doppler imaging (CDI) waveform analysis.

METHOD

A prospective, observer-masked, case-control study was performed. OPA and blood flow variables from central retinal artery and vein (CRA, CRV), nasal and temporal short posterior ciliary arteries (NPCA, TPCA) and ophthalmic artery (OA) were obtained through dynamic contour tonometry and CDI, respectively. Univariate and multiple regression analyses were performed to explore the correlations between OPA and retrobulbar CDI waveform and systemic cardiovascular parameters (blood pressure, blood pressure amplitude, mean ocular perfusion pressure and peripheral pulse).

RESULTS

One hundred and ninety-two patients were included [healthy controls: 55; primary open-angle glaucoma (POAG): 74; normal-tension glaucoma (NTG): 63]. OPA was statistically different between groups (Healthy: 3.17 ± 1.2 mmHg; NTG: 2.58 ± 1.2 mmHg; POAG: 2.60 ± 1.1 mmHg; p < 0.01), but not between the glaucoma groups (p = 0.60). Multiple regression models to explain OPA variance were made for each cohort (healthy: p < 0.001, r = 0.605; NTG: p = 0.003, r = 0.372; POAG: p < 0.001, r = 0.412). OPA was independently associated with retrobulbar CDI parameters in the healthy subjects and POAG patients (healthy CRV resistance index: β = 3.37, CI: 0.16-6.59; healthy NPCA mean systolic/diastolic velocity ratio: β = 1.34, CI: 0.52-2.15; POAG TPCA mean systolic velocity: β = 0.14, CI 0.05-0.23). OPA in the NTG group was associated with diastolic blood pressure and pulse rate (β = -0.04, CI: -0.06 to -0.01; β = -0.04, CI: -0.06 to -0.001, respectively).

CONCLUSIONS

Vascular-related models provide a better explanation to OPA variance in healthy individuals than in glaucoma patients. The variables that influence OPA seem to be different in healthy, POAG and NTG patients.

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.

Relationship between ocular pulse amplitude and glaucomatous central visual field defect in normal-tension glaucoma

PURPOSE

To investigate the relationship between central visual field (VF) defects and ocular pulse amplitude (OPA) in early normal-tension glaucoma (NTG).

PATIENTS AND METHODS

This retrospective study included 100 eyes of 100 subjects: 54 NTG patients whose mean deviations were better than -7.00 dB and 46 normal subjects. OPA was measured by dynamic contour tonometry. NTG patients were divided into 2 subgroups according to VF tests: the central VF-invading and the central VF-sparing groups. Ocular parameters including OPA, intraocular pressure (IOP), and indices of VF tests were analyzed in glaucoma patients and normal subjects.

RESULTS

There was no difference in the OPA between the NTG and normal groups. However, IOP and OPA of the central VF-invading group (14.4 ± 2.87 and 2.9 ± 0.78 mm Hg) were higher than those of the central VF-sparing group (12.7 ± 2.52 and 2.0 ± 0.80 mm Hg; P = 0.025 and P < 0.001, respectively). OPA, but not IOP, showed a positive correlation with the VF test indices that represented central field defects (r = 0.494, P < 0.001).

CONCLUSIONS

Increased OPA was related to more centrally located VF defects in NTG patients with mild VF defects.

Effects of body mass index on intraocular pressure and ocular pulse amplitude

AIM

To investigate the effects of body mass index (BMI) on intraocular pressure (IOP) and ocular pulse amplitude (OPA).

METHODS

Totally 140 healthy individuals without any systemic diseases were included in the study. BMI (kg/m(2)) was calculated for every individual. IOP and OPA were measured with Pascal Dynamic contour tonometer (DCT). Blood pressure was also measured along with the DCT. The patients were divided into three groups according to BMI as: Group1, BMI<25; Group2, 25≤BMI<30; Group3, BMI≥30. Mean values of IOP, OPA, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were used in statistical analysis.

RESULTS

In Group1, the means of IOP, OPA, were 16.8±2.3mmHg, 2.7±0.7mmHg respectively; and SBP, DBP were 120.0±6.1mmHg, and 77.4±5.6mmHg respectively. In group2, the mean IOP, OPA, SBP, and DBP were found to be 16.6±2.1mmHg, 2.4±0.7mmHg, 121.7±5.3mmHg, and 79.5±4.9mmHg respectively. In group3, the mean IOP, OPA, SBP, and DBP were found to be 17.3±1.7mmHg, 2.1±0.7mmHg, 122.4±5.7mmHg, and 79.7±5.2mmHg respectively. There were no statistically significant difference between groups in terms of IOP, SBP and DBP, while OPA values were significantly lower in group3 (P=0.001).

CONCLUSION

Decreased OPA values in individuals with higher BMI may indicate that subjects with higher BMI have lower choroidal perfusion and lower ocular blood flow.

An evaluation of the effects of eyeball structure on ocular pulse amplitude in healthy subjects

To evaluate the effects of eyeball structure on ocular pulse amplitude (OPA) measured using dynamic contour tonometer (DCT). In 86 eyes of 43 healthy subjects, we measured OPA and intraocular pressure (IOP) with DCT (DCT-IOP), IOP with Goldmann applanation tonometry (GAT-IOP), central corneal thickness (CCT), corneal thickness 2 mm (2 mmCT) and 4 mm (4 mmCT) apart from the center, corneal volume within a 3.5-mm radius from the corneal center, corneal curvature, anterior chamber depth, anterior chamber volume, and axial length (AL). OPA had a significant positive correlation with GAT-IOP (Pearson's r = 0.412, p < 0.001), DCT-IOP (r = 0.350, p < 0.001), and 4 mmCT (r = 0.244, p = 0.0231), and had a significant negative correlation with AL (r = -0.268, p = 0.0122). In a multiple linear regression analysis, AL and GAT-IOP were significantly associated with OPA. OPA measured with DCT is significantly influenced by several factors, such as IOP, peripheral corneal thickness (4 mmCT), and AL.

Effects of caffeinated coffee consumption on intraocular pressure, ocular perfusion pressure, and ocular pulse amplitude: a randomized controlled trial

PURPOSE

To examine the effects of caffeinated coffee consumption on intraocular pressure (IOP), ocular perfusion pressure (OPP), and ocular pulse amplitude (OPA) in those with or at risk for primary open-angle glaucoma (POAG).

METHODS

We conducted a prospective, double-masked, crossover, randomized controlled trial with 106 subjects: 22 with high tension POAG, 18 with normal tension POAG, 20 with ocular hypertension, 21 POAG suspects, and 25 healthy participants. Subjects ingested either 237 ml of caffeinated (182 mg caffeine) or decaffeinated (4 mg caffeine) coffee for the first visit and the alternate beverage for the second visit. Blood pressure (BP) and pascal dynamic contour tonometer measurements of IOP, OPA, and heart rate were measured before and at 60 and 90 min after coffee ingestion per visit. OPP was calculated from BP and IOP measurements. Results were analysed using paired t-tests. Multivariable models assessed determinants of IOP, OPP, and OPA changes.

RESULTS

There were no significant differences in baseline IOP, OPP, and OPA between the caffeinated and decaffeinated visits. After caffeinated as compared with decaffeinated coffee ingestion, mean mm Hg changes (± SD) in IOP, OPP, and OPA were as follows: 0.99 (± 1.52, P<0.0001), 1.57 (± 6.40, P=0.0129), and 0.23 (± 0.52, P<0.0001) at 60 min, respectively; and 1.06 (± 1.67, P<0.0001), 1.26 (± 6.23, P=0.0398), and 0.18 (± 0.52, P=0.0006) at 90 min, respectively. Regression analyses revealed sporadic and inconsistent associations with IOP, OPP, and OPA changes.

CONCLUSION

Consuming one cup of caffeinated coffee (182 mg caffeine) statistically increases, but likely does not clinically impact, IOP and OPP in those with or at risk for POAG.

Decreased ocular pulse amplitude associated with functional and structural damage in open-angle glaucoma

PURPOSE

To assess the relationship of ocular pulse amplitude (OPA), as measured by dynamic contour tonometry (DCT), with structural and functional damage in patients with open-angle glaucoma (OAG).

METHODS

In this cross-sectional, observational study, 242 eyes of 139 patients with OAG underwent Goldmann applanation tonometry (GAT), DCT, central corneal thickness (CCT) measurement, visual fields examination (Octopus, Haag Streit), and complete ophthalmologic examination. Linear regression analysis was used to analyze the effect of OPA, DCT, GAT, and CCT to the mean defect (MD) of the visual fields and to the vertical cup to disc ratio (CDR).

RESULTS

Ocular pulse amplitude was the only variable that showed a significant association with MD (slope=-1.1, p=0.012), in contrast to GAT (p=0.98), DCT (p=0.32), and CCT (p=0.42). Ocular pulse amplitude was also negatively associated with CDR (slope=-0.028, p=0.0001). Additional multiple regression analysis revealed that OPA (R2=0.12, r=-0.25, slope=-0.02, p=0.033), GAT (r=-0.27, slope=-0.01, p=0.027), and CCT (r=-0.18, slope=-0.001, p=0.012) were statistically significantly correlated to CDR, while DCT was not (r=-0.20, slope=0.003, p=0.46). Ocular pulse amplitude did not differ statistically significantly (p=0.93) between eyes with (2.79 ± 1.42) and without (2.77 ± 1.21) prior trabeculectomy. No statistically significant difference of OPA was observed between diagnosis groups (p=0.255).

CONCLUSIONS

Decreased OPA seems to be correlated with increased glaucomatous functional and structural damage in OAG. Assessment of OPA by DCT could therefore serve as an important additional parameter in the evaluation of glaucoma patients.

Optic disc area and correlation with central corneal thickness, corneal hysteresis and ocular pulse amplitude in glaucoma patients and controls

BACKGROUND

To examine the relationships between optic disc area and parameters measured at the cornea; central corneal thickness (CCT), corneal hysteresis (CH) and ocular pulse amplitude (OPA) in glaucoma subjects and controls.

METHODS

In this prospective experimental study, patients underwent measurement of CCT, OPA, CH and optic disc imaging with the Heidelberg Retina Tomograph II (HRT-II). Pearson's correlation coefficient was calculated to assess the associations between optic disc area and CCT, OPA and CH.

RESULTS

A total of 100 patients, 38 with glaucoma and 62 controls were examined. In a univariate analysis of this group, CCT and CH were significantly lower in glaucoma patients (P = 0.01). CCT was inversely correlated with optic disc surface area (Pearson's correlation coefficient r = -0.200; P = 0.05). This inverse correlation did not achieve statistical significance when glaucoma patients and controls were analysed separately. There was no statistically significant association between optic disc area and OPA or CH.

CONCLUSIONS

There was an inverse relationship between CCT and optic disc area in this study group. No association was found between optic disc area and OPA or CH.

Ultrasonic in vivo measurement of ocular surface expansion

Our aim was to ascertain whether the ultrasonic measurement of longitudinal corneal apex displacements carried out in a proper headrest is a credible method of ocular pulse (OP) detection. To distinguish between longitudinal movements of the eye globe treated as a rigid body and ocular surface expansion caused by the variations of the eye-globe volume, two ultrasound distance sensors were applied to noninvasively measure displacements of cornea and sclera. The same sensors were used to examine the influence of the anterio-posterior movements of a fixed head on the registration of corneal apex pulsation. In both experiments, ECG signals were synchronically recorded. Time, spectral, and coherence analyses obtained for four healthy subjects showed that the ocular surface expansion due to pulsatile ocular blood flow (POBF) is the main component of longitudinal corneal displacement. Ocular surface pulsation is always affected by the head movement. However, there exist some unique properties of signals, which help to distinguish between head and eye movements. A rigid headrest and a bite bar are required to stabilize the head during OP measurement. Ultrasonic technique enables noninvasive and accurate in vivo measurement of corneal pulsation, which could be of interest for indirectly estimating intraocular pressure propagation and POBF component.

Ocular pulse amplitude and associated glaucomatous risk factors in a healthy Hispanic population

BACKGROUND

With increasing evidence that vascular risk factors play a role in the development of glaucoma, it is critical to be familiar with factors related to intraocular blood flow, such as the ocular pulse amplitude (OPA). This study evaluates OPA and factors related to it in a healthy, Hispanic population.

METHODS

Refractive error, corneal curvature, Goldmann applanation tonometry (GAT), dynamic contour tonometry (DCT), OPA, axial length, and central corneal thickness (CCT) measurements were obtained on 104 Hispanic subjects recruited from the community.

RESULTS

OPA ranged from 0.7 to 4.7 mmHg (mean, 2.1 +/- 0.8 mmHg) and showed a significant correlation with refractive error, axial length, GAT, and DCT (r=0.250, -0.358, 0.460, 0.378; P=0.011, <0.001, <0.001, and <0.001, respectively). Mean intraocular pressure with GAT was 15.6 mmHg. Mean CCT was 541.2 microm. The average refractive error was 0.75 diopters (D) of myopia, with 25% having >1.00 D myopia.

CONCLUSION

Normal OPA values have not been studied in Hispanic populations. OPA is thought to provide information regarding ocular blood flow; however, more studies are needed to determine its significance in glaucoma treatment.

Acetazolamide influences ocular pulse amplitude

PURPOSE

To investigate the effect of systemic acetazolamide on ocular pulse amplitude (OPA) and on intraocular pressure (IOP).

METHODS

We determined OPA, IOP, mean arterial blood pressure and heart rate (HR) in 17 patients suffering from hypertensive primary open-angle glaucoma (htPOAG) and 22 healthy controls. Measurements were taken before and 2 h after oral intake of 500 mg of acetazolamide.

RESULTS

Mean OPA decreased 20.24% (SEM 2.95%) from 2.76 mmHg (SEM 0.16 mmHg) to 2.14 mmHg (SEM 0.13 mmHg) 2 h after oral administration of 500-mg acetazolamide. IOP dropped by 2.98 mmHg (SEM 0.28 mmHg), corresponding to a 17.19% (SEM 1.56%) reduction. The decrease in IOP correlated with the decrease of OPA (r(2) = 0.4, P < 0.0001).

CONCLUSIONS

Ocular pulse amplitude measurements are influenced by oral administration of acetazolamide. There was a decrease in the pulsatile component of choroidal blood flow and in IOP in both htPOAG and healthy controls. This needs to be taken into account for measurement of OPA with dynamic contour tonometry.