Travoprost- and Tafluprost-induced Changes in Intraocular Pressure and Ocular Pulse Amplitude

Purpose: To compare the intraocular pressure reduction and changes in ocular pulse amplitude of travoprost 0.003% and tafluprost 0.0015%. Methods: We assessed patients who were diagnosed with open-angle glaucoma from January 2017 to July 2019 for the first time at our hospital. Forty-two eyes were assigned to the travoprost group (23 patients) and 26 eyes were assigned to the tafluprost group (14 patients). Changes in intraocular pressure were measured by Goldmann applanation tonometry (GAT), and corrected ocular pulse amplitude (cOPA) was measured using dynamic contour tonometry. Changes in these parameters were observed and compared for 1 year. Results: No significant differences were observed between the GAT measurements and the cOPA of patients treated with travoprost and tafluprost for 1 year (p = 0.512, p = 0.105). The change in initial intraocular pressure on GAT observed after 1 week was -5.32 ± 2.63 mmHg for travoprost and -3.79 ± 3.19 mmHg for tafluprost (p = 0.0457). The initial change in cOPA was +0.04 ± 0.9 mmHg in the travoprost group and -0.76 ± 0.97 mmHg in the tafluprost group (p = 0.0028). Conclusions: Travoprost and tafluprost reached the targeted intraocular pressure with no difference in the long-term effects of reduced intraocular pressure. However, travoprost was initially better at lowering intraocular pressure faster, and tafluprost had a greater effect on lowering OPA. Prostaglandin analogs can be selected individually by considering the aforementioned factors.

Non-invasive Clinical Measurement of Ocular Rigidity and Comparison to Biomechanical and Morphological Parameters in Glaucomatous and Healthy Subjects

Purpose: To assess ocular rigidity using dynamic optical coherence tomography (OCT) videos in glaucomatous and healthy subjects, and to evaluate how ocular rigidity correlates with biomechanical and morphological characteristics of the human eye.Methods: Ocular rigidity was calculated using Friedenwald's empirical equation which estimates the change in intraocular pressure (IOP) produced by volumetric changes of the eye due to choroidal pulsations with each heartbeat. High-speed OCT video was utilized to non-invasively measure changes in choroidal volume through time-series analysis. A control-case study design was based on 23 healthy controls and 6 glaucoma cases. Multiple diagnostic modalities were performed during the same visit including Spectralis OCT for nerve head video, Pascal Dynamic Contour Tonometry for IOP and ocular pulse amplitude (OPA) measurement, Corvis ST for measuring dynamic biomechanical response, and Pentacam for morphological characterization.Results: Combining glaucoma and healthy cohorts (n = 29), there were negative correlations between ocular rigidity and axial length (Pearson R = −0.53, p = 0.003), and between ocular rigidity and anterior chamber volume (R = −0.64, p = 0.0002). There was a stronger positive correlation of ocular rigidity and scleral stiffness (i.e., stiffness parameter at the highest concavity [SP-HC]) (R = 0.62, p = 0.0005) compared to ocular rigidity and corneal stiffness (i.e., stiffness parameter at the first applanation [SP-A1]) (R = 0.41, p = 0.033). In addition, there was a positive correlation between ocular rigidity and the static pressure-volume ratio (P/V ratio) (R = 0.72, p < 0.0001).Conclusions: Ocular rigidity was non-invasively assessed using OCT video and OPA in a clinic setting. The significant correlation of ocular rigidity with biomechanical parameters, SP-HC and P/V ratio, demonstrated the validity of the ocular rigidity measurement. Ocular rigidity is driven to a greater extent by scleral stiffness than corneal stiffness. These in vivo methods offer an important approach to investigate the role of ocular biomechanics in glaucoma.

The Effect of Corneal Thickness, Densitometry and Curvature on Intraocular Pressure Measurements Obtained by Applanation, Rebound and Dynamic Contour Tonometry

Evaluate the effect of corneal thickness, densitometry and curvature on intraocular pressure (IOP) measurements obtained by Goldmann applanation tonometry (GAT), non-contact tonometry (NCT), rebound tonometry (RT), and dynamic contour tonometry (DCT). A cross-sectional prospective study involving 40 participants was performed. Corneal measurements were obtained using Pentacam (Oculus GMbH, Wetzlar, Germany), densitometry was measured at annuli of 0–2, 2–6, 6–10 and 10–12 mm. The relationship between corneal thickness (central, 4 and 6 mm), corneal astigmatism and corneal densitometry and IOP was examined. There was a significant relationship between corneal thickness (central, 4 and 6 mm) and GAT180, GAT90, RT, and NCT (P < 0.001 for all comparisons) but not for DCT. Higher corneal densitometry (6–10 mm and 10–12 mm zones) was associated with higher IOP from GAT180 and GAT90, and higher densitometry in the 6–10 mm zone correlated with higher IOP from NCT, however corneal densitometry increased with age. Accounting for age, the relationship between corneal densitometry and IOP measurements was not significant. In eyes with greater corneal astigmatism there was a greater difference between GAT90 and GAT180 measurements. IOP measurements may be affected by corneal thickness, densitometry and curvature. DCT was less affected by properties of the cornea compared to other devices.

Correlation of ocular rigidity with intraocular pressure spike after intravitreal injection of bevacizumab in exudative retinal disease

Background/aimsTo evaluate the non-invasive measurement of ocular rigidity (OR), an important biomechanical property of the eye, as a predictor of intraocular pressure (IOP) elevation after anti-vascular endothelial growth factor (anti-VEGF) intravitreal injection (IVI).MethodsSubjects requiring IVI of anti-VEGF for a pre-existing retinal condition were enrolled in this prospective cross-sectional study. OR was assessed in 18 eyes of 18 participants by measurement of pulsatile choroidal volume change using video-rate optical coherence tomography, and pulsatile IOP change using dynamic contour tonometry. IOP was measured using Tono-Pen XL before and immediately following the injection and was correlated with OR.ResultsThe average increase in IOP following IVI was 19±9 mm Hg, with a range of 7–33 mm Hg. The Spearman correlation coefficient between OR and IOP elevation following IVI was 0.796 (p<0.001), showing higher IOP elevation in more rigid eyes. A regression line was also calculated to predict the IOP spike based on the OR coefficient, such that IOP spike=664.17 mm Hg·µL×OR + 4.59 mm Hg.ConclusionThis study shows a strong positive correlation between OR and acute IOP elevation following IVI. These findings indicate that the non-invasive measurement of OR could be an effective tool in identifying patients at risk of IOP spikes following IVI.

Intraocular Pressure Elevation in Keratoconus with Coexisting Pseudoexfoliation Glaucoma: How Important is the Method of Measurement?

Objective In this report, we investigated the association between the intraocular pressure (IOP) values by two different measurement methods and the corneal biomechanical properties in a patient with keratoconus and secondary glaucoma due to pseudoexfoliation syndrome who developed a marked elevation of intraocular pressure in the right eye. Methods IOP was measured over a period of 3 days with Goldmann applanation tonometry (GAT) and dynamic contour tonometry (Pascal tonometry, DCT). Corneal hysteresis (CH) and corneal resistance factor (CRF) were estimated with the aid of an ocular response analyzer (ORA). Results CH and CRF were significantly reduced in the right eye compared to the left eye throughout the period of observation (paired t-test, p < 0.001). The difference between both methods of IOP measurement in the right eye was statistically significant for IOP < 30 mmHg by GAT (Wilcoxon test, p = 0.004). For IOP values > 30 mmHg by GAT, there was no statistically significant difference between DCT and GAT (Wilcoxon test, p = 0.0625). Conclusions This observation supports the clinical hypothesis that a significant decrease in CH translates to a decreased correlation of CH and IOP recordings by GAT and, furthermore, suggests that after a critical point of CH reduction, the impact of CH on GAT may be comparable to that on DCT.

First-in-human continuous 24-hour measurement of intraocular pressure and ocular pulsation using a novel contact lens sensor

Background/AimsThis study assessed the feasibility of a novel contact lens device for intraocular pressure (IOP) and ocular pulse amplitude (OPA) continuous measurements over 24 hours.MethodsThis prospective, open-label, single-centre, non-randomised study included glaucoma and healthy subjects. IOP and OPA values acquired by the pressure-measuring contact lens (PMCL) device in one patient’s eye at the beginning of the measurement were compared with tonometry values (Goldman applanation tonometry (GAT) and dynamic contour tonometry (DCT)) in the same eye just before PMCL placement. Furthermore, IOP and OPA values measured with PMCL on the study eye during a water drinking test (WDT) were compared with DCT values in the fellow eye. Comparisons were performed using t-tests with 95% Confidence Intervals.ResultsTwenty-four-hour IOP and OPA curves were obtained for eight subjects. The mean IOP difference between PMCL and tonometry on the same eye was within ±5 mm Hg in 75% (GAT) and 87.5% (DCT) of subjects. IOP variations due to WDT were detected by PMCL and DCT, showing an average increase of 2.43 and 1.85 mm Hg, respectively. Differences between PMCL and DCT for IOP variations in fellow eyes were within ±5 mm Hg for 97.2% of time points. The difference between OPA in fellow eyes was within ±5 mm Hg for 85.5% of the time points.ConclusionsThis first-in-human study is a proof-of-concept for 24-hour continuous measurements of IOP and OPA with the PMCL. This device is non-invasive and has good comparability with standard tonometry.

Accuracy of dynamic contour tonometry, Goldmann applanation tonometry, and Tono-Pen XL in edematous corneas

Purpose: To investigate in vitro the accuracy of dynamic contour tonometry, Goldmann applanation tonometry, and Tono-Pen XL in edematous corneas. Methods: Experimental study included 20 freshly enucleated porcine eyes. Epithelium was debrided, and eyes were divided in four groups. Groups were immersed in 35%, 40%, 50%, and 60% glycerin solutions for 3 hours. Subsequently, globes were mounted in a special holder, and their intraocular pressure was hydrostatically adjusted. Intraocular pressure was measured by means of dynamic contour tonometry, Goldmann applanation tonometry, and Tono-Pen XL while adjusting true intraocular pressure to 17, 33, and 50 mm Hg. Ultrasound pachymetry was performed. Results: Mean corneal thickness was 914.5 ± 33.3 μm (730–1015 μm). In true intraocular pressure of 33 mm Hg, Goldmann applanation tonometry and dynamic contour tonometry significantly underestimated true intraocular pressure (mean Goldmann applanation tonometry: 14.7 ± 4.8 mm Hg, p < 0.001, mean dynamic contour tonometry: 21.6 ± 6.8, p < 0.001). Tono-Pen XL also underestimated, but difference was not statistically significant (Tono-Pen XL: 27.9 ± 9.7, p = 0.064). In true intraocular pressure of 50 mm Hg, all three methods significantly underestimated (Goldmann applanation tonometry: 17.6 ± 5.3 mm Hg, p < 0.001, dynamic contour tonometry: 26.8 ± 6.3 mm Hg, p < 0.001, Tono-Pen XL: 35.6 ± 8.4 mm Hg, p < 0.001). The error in measured intraocular pressure for each method (true minus measured intraocular pressure) was significantly correlated to true intraocular pressure ( p < 0.001). The intraocular pressure measurements of each eye taken under true intraocular pressure of 17 and 33 mm Hg with the three methods were correlated to each other. Measurements taken under intraocular pressure of 50 mmHg were not correlated to each other. Corneal thickness was not correlated to intraocular pressure measurement. Conclusion: Goldmann applanation tonometry, dynamic contour tonometry, and Tono-Pen XL underestimate intraocular pressure when measured under edematous conditions. Tono-Pen XL showed better accuracy, especially in lower true intraocular pressure. The measurement error increases when true intraocular pressure increases in all three methods.

Ocular Pulse Amplitude in Non-Diabetic Patients with End Stage Renal Disease and Normal Individuals Using Dynamic Contour Tonometry

Introduction: Ocular Pulse Amplitude (OPA) is the fluctuation of IOP with the cardiac cycle which is equal to the difference between systolic and diastolic IOP. These variations in IOP are thought to be caused by the blood volume that is pumped into the eye, mainly the choroidal bed during each cardiac cycle. In patients with end stage renal disease (ESRD), Choroidal perfusion has been found to be reduced as determined by Indocyanine Green Angiography (ICG) which is an invasive procedure. OPA is recorded by Dynamic Contour Tonometer (DCT) which represents a potential new technology for measuring choroidal blood flow indirectly & non-invasively especially in patients with suspected compromise in perfusion as in ESRD. In this study we postulate that measurement of OPA can be used to assess the choroidal perfusion inpatients with ESRD. Objectives: To measure OPA in non-diabetic patients with ESRD on hemodialysis and to compare it with that of OPA in age matched normal individuals. Materials & Methods: It was a prospective Cross-sectional study and was done in a clinical set up during the period of January 2013 to October 2013. OPA among 44exposed and 44 non exposed individuals were measured using Dynamic Contour Tonometry (DCT) and analysis done. Results: The mean OPA in non diabetic patients with ESRD was 1.945mm Hg (CI:1.847 – 2.043) and the mean OPA in age matched normals was 2.16mm Hg (CI: 2.08– 2.24). Conclusion: OPA in non diabetic ESRD patients was statistically significantly lower than that of age matched normals (p=0.03). There was no correlation between OPA and other parameters like age, gender, intraocular pressure, blood pressure or serumcreatinine levels.