Pulse Amplitude Measurements Research Articles

Evaluation of the effects on choroidal thickness of bimatoprost 0.03% versus a brinzolamide 1.0%/timolol maleate 0.5% fixed combination

Objective: To investigate the effects of two different medical treatment options on choroidal thickness (CT) in cases of open-angle glaucoma (OAG).Methods: Sixty-seven eyes newly diagnosed with OAG and 52 healthy eyes constituting the control group were included in the study. Glaucomatous eyes were randomly divided into two subgroups; Group I was started on bimatoprost 0.03% and Group II on a brinzolamide 1.0%/timolol maleate 0.5% fixed combination (BTFC). Intraocular pressure (IOP), ocular pulse amplitude (OPA) and subfoveal CT measurements were performed in all eyes in the study before treatment and on weeks 2, 4 and 8 after treatment.Results: Mean initial IOP values in groups I and II and the control group were 25.5 ± 4.7, 25.1 ± 5.2 and 16.1 ± 2.9 mmHg, mean OPA values were 3.7 ± 1, 3.6 ± 1.4 and 2.4 ± 0.6 mmHg and mean CT values were 269.4 ± 83, 264.5 ± 84.4 and 320.1 ± 56.6 μm, respectively. Eight weeks after treatment, mean IOP values in Groups I and II and the control group were 18.3 ± 2.6, 18.1 ± 3.4 and 15.7 ± 2.9 mmHg, mean OPA values were 2.9 ± 1.2, 2.8 ± 1.5 and 2.3 ± 0.8 mmHg and mean CT values were 290.2 ± 87.3, 271.8 ± 82.5 and 319.3 ± 56.8 μm, respectively. No significant difference was determined in terms of the decrease in IOP and OPA obtained after treatment in Group I and Group II. However, a significant difference was observed between the two groups in terms of choroidal thickening after treatment.Conclusion: The use of topical ocular hypotensive medication in eyes with OAG results in an increase in CT. This increase is relatively greater with bimatoprost 0.03% therapy compared to BTFC.

Mapping cerebral pulse pressure and arterial compliance over the adult lifespan with optical imaging.

Cerebrovascular health is important for maintaining a high level of cognitive performance, not only in old age, but also throughout the lifespan. Recently, it was first demonstrated that diffuse optical imaging measures of pulse amplitude and arterial compliance can provide estimates of cerebral arterial health throughout the cortex, and were associated with age, estimated cardiorespiratory fitness (eCRF), neuroanatomy and cognitive function in older adults (aged 55–87). The current study replicates and extends the original findings using a broader age range (a new adult sample aged 18–75), longer recording periods (360 s), and a more extensive optical montage (1536 channels). These methodological improvements represent a 5-fold increase in recording time and a 4-fold increase in coverage compared to the initial study. Results show that reliability for both pulse amplitude and compliance measures across recording blocks was very high (r(45) = .99 and .75, respectively). Pulse amplitude and pulse pressure were shown to correlate with age across the broader age range. We also found correlations between arterial health and both cortical and subcortical gray matter volumes. Additionally, we replicated the correlations between arterial compliance and age, eCRF, global brain atrophy, and cognitive flexibility. New regional analyses revealed that higher performance on the operation span (OSPAN) working memory task was associated with greater localized arterial compliance in frontoparietal cortex, but not with global arterial compliance. Further, greater arterial compliance in frontoparietal regions was associated with younger age and higher eCRF. These associations were not present in the visual cortex. The current study not only replicates the initial one in a sample including a much wider age range, but also provides new evidence showing that frontoparietal regions may be especially vulnerable to vascular degeneration during brain aging, with potential functional consequences in cognition.

Interoceptive Awareness Moderates the Relationship Between Perceived and Physiological Genital Arousal in Women

IntroductionIn general, laboratory studies have shown low correlations between subjective (ie, self-report) and physiologic (ie, vaginal pulse amplitude) measurements of sexual arousal in women. One explanation for this presumed low concordance is that women might not be attending to their genital responses and/or might be unable to accurately perceive their genital responses. AimTo examine the extent to which women can perceive their genital arousal sensations, the role that interoceptive awareness plays in this ability, and whether interoceptive awareness influences sexual concordance in women. MethodsTwenty-six sexually functional women viewed an erotic film while their physiologic and perceived genital sexual arousal levels were measured continuously. Self-report measurements of sexual function and bodily awareness also were administered. Main Outcome MeasuresPhysiologic sexual arousal was measured with a vaginal photoplethysmograph, and perception of genital arousal was measured with an arousometer. Degree of bodily awareness was measured with the Multidimensional Assessment of Interoceptive Awareness questionnaire. ResultsWomen exhibited a significant degree of agreement between physiologic and perceived genital arousal (P < .05). Interoceptive awareness was found to significantly moderate this relation (P < 0.05), such that a greater degree of interoceptive awareness facilitated greater agreement between physiologic and perceived genital arousal. Interoceptive awareness also was found to facilitate greater concordance between subjective and physiologic sexual arousal (P < .05). ConclusionWomen can perceive their genital response, and interoceptive awareness influences this ability and the relation between subjective and physiologic sexual arousal. Increasing bodily awareness could be a plausible route for treatment development.

A new digital pulse processing method for 2πα and 2πβ emitter measurement

Digital pulse processing has developed rapidly during recent years. Moreover, it has been widely applied in many fields. In this study, we introduce a digital pulse processing method for 2πα and 2πβ emitter measurement. Our digital pulse processing method for 2πα and 2πβ emitter measurement is comprised of a field-programmable gate-array-based acquisition card and a pulse-height analysis routine. We established two channels (one for the α emitter and one for the β emitter) on an acquisition board using an analog-to-digital converter with a 16-bit resolution at a speed of 100 million samples per second. In this study, we used captured and stored data to analyze emission rate counts and spectrums. The method we established takes into account noise cancelation, dead-time correction, background subtraction, and zero-energy extrapolation. We carefully designed control procedures in order to simplify pulse-width fitting and threshold-level setting. We transmitted data and commands through a universal serial bus between the acquisition board and the computer. The results of our tests prove that our method performs well in pulse reconstruction fidelity and amplitude measurement accuracy. Compared with the current standard method for measuring 2πα and 2πβ emission rates, our system demonstrates excellent precision in emission rate counting.

Relationship between blood pressure and retrobulbar blood flow in dipper and nondipper primary open-angle glaucoma patients.

To evaluate the relationship between retrobulbar hemodynamic parameters in the ophthalmic artery (OA), central retinal artery, and short posterior ciliary artery and 24-hour blood pressure (BP) measurements in dipper and nondipper patients with primary open-angle glaucoma (POAG). A prospective, cross-sectional, and observational study was conducted on consecutive patients, referred or recruited, attending the outpatient service of our ophthalmology department. Ambulatory BP monitoring, Doppler imaging, and ocular pulse amplitude measurements were performed on the same day. Patients with nocturnal BP decrease up to 10% of the diurnal BP were defined as dippers and those with BP decrease less than 10% were defined as nondippers. A total of 114 patients (36 nondippers and 78 dippers) were included in the study. The end-diastolic velocity was significantly lower and the resistivity index (RI) was significantly higher in the dippers than in the nondippers (p&lt;0.0001 and p&lt;0.0001, respectively). The RI in the OA was significantly correlated with daytime and nighttime systolic BP and with the daytime mean arterial pressure in the dippers. The RI in the OA significantly correlates with BP in patients with POAG with nocturnal BP dips. Additionally, retrobulbar blood flow parameters are reduced in dippers as compared with nondippers with POAG.

Optical measures of changes in cerebral vascular tone during voluntary breath holding and a Sternberg memory task

The human cerebral vasculature responds to changes in blood pressure and demands for oxygenation via cerebral autoregulation. Changes in cerebrovascular tone (vasoconstriction and vasodilation) also mediate the changes in blood flow measured by the BOLD fMRI signal. This cerebrovascular reactivity is known to vary with age. In two experiments, we demonstrate that cerebral pulse parameters measured using optical imaging can quantify changes in cerebral vascular tone, both globally and locally. In experiment 1, 51 older adults (age range=55–87) performed a voluntary breath-holding task while cerebral pulse amplitude measures were taken. We found significant pulse amplitude variations across breath-holding periods, indicating vasodilation during, and vasoconstriction after breath holding. The breath-holding index (BHI), a measure of cerebrovascular reactivity (CVR) was derived and found to correlate with age. BHI was also correlated with performance in the Modified Mini-Mental Status Examination, even after controlling for age and education. In experiment 2, the same participants performed a Sternberg task, and changes in regional pulse amplitude between high (set-size 6) and low (set-size 2) task loads were compared. Only task-related areas in the fronto-parietal network (FPN) showed significant reduction in pulse amplitude, indicating vasodilation. Non-task-related areas such as the somatosensory and auditory cortices did not show such reductions. Taken together, these experiments suggest that optical pulse parameters can index changes in brain vascular tone both globally and locally, using both physiological and cognitive load manipulations.

Terahertz Detection of Wavelength-Size Metal Particles in Pressboard Samples

Results of a theoretical and experimental investigation of THz detection of randomly-oriented metal particles smaller than 1 mm embedded in pressboard are reported and critically compared with X-ray scanner results. A theoretical description based on Gaussian beam theory and a transfer function approach enabled simulation of signals transmitted around and reflected from real particles and was able to predict signal detectability. Simulated signals and detection limits were compared with experimental transmission and reflection time domain spectroscopy (TDS) raster scanning data. Simulated and measured pulse amplitude and shape were in agreement. Reflection mode was superior to transmission mode in terms of both particle visibility and hit ratio. Imaging of particles was also possible in “reflection in transmission” mode, which can be used to complement classical transmission mode. X-ray images did not detect the smallest particles sufficiently and, therefore, could not be used as reference data for comparison with THz data. The results demonstrate that TDS reflection scanning is able to determine the position of small metal particles and the technique could be possibly used for quality control of pressboard insulation.

Impact of colored noise in pulse amplitude measurements: A time-domain approach using differintegrals

In particle detectors, pulse shaping is the process of changing the waveform of the pulses in order to maximize the signal to noise ratio. This shaping usually only takes into account white, pink (flicker) and red (Brownian) noise. In this paper, a generalization of noise indexes as a function to an arbitrary fβ noise type, where β is a real number, is presented. This generalization has been created using the differintegral operator, defined in Fractional Calculus. These formulas are used to calculate the Equivalent Noise Change (ENC) in detector particle systems.

Evaluation of ocular pulse amplitude and choroidal thickness in diabetic macular edema.

The aim of this study is to evaluate the ocular pulse amplitude (OPA) and choroidal thickness (CT) measurements in patients with diabetic macular edema (DME) and healthy subjects. A total of 34 patients (12 male and 22 female) who had type 2 diabetes mellitus with DME and 34 sex-matched healthy subjects (13 male and 21 female) were included in this prospective study. The intraocular pressure (IOP) and OPA were measured with Dynamic contour tonometer (Pascal DCT, Switzerland). The subfoveal CT was measured using the Cirrus HD-OCT (Carl Zeiss Meditec). The CT at 1500 μm and 3000 μm nasal and temporal to the central fovea was also measured. The mean IOP values were 18.4±3.5 and 17.1±2.1 mm Hg in DME patients and healthy controls, respectively (P= 0.091). The mean OPA values in patients with DME (2.58±0.96) and controls (3.52±1.03) were statistically different (P<0.001). The mean subfoveal CT value was 273.5±30.2 μm in the eyes with DME and 321.4±36.5 μm in the control group (P< 0.001). In both groups, linear regression analysis showed no significant association between OPA and CT measurements. The IOP showed a significantly positive correlation with OPA in both DME (P=0.002, r=0.526) and controls (P=0.004, r=0.483). The current study suggests that both pulsatile choroidal blood flow and CT are decreased in patients with DME.

Acute effects of caffeine on choroidal thickness and ocular pulse amplitude

Objective: To explore ocular changes in healthy people after caffeine consumption.Methods: This prospective observational study was carried out with students of the Turgut Özal University Medical Faculty from May 15 to 15 December 2014. Enrolled in the study were 17 healthy subjects (n = 17 eyes), with a median age of 24 (IQR 1), ranging between 21 and 26 years. The control group (6 females, 11 males) aged between 23 and 28 (median 25 years [IQR 4.75]). For study, one eye from each participant was randomly selected. To obviate the effect of diurnal variations, tests were performed at the same time of the day (10:00 a.m.–12:00 p.m.). Each subject was given an ophthalmologic examination before the study to exclude those with undiagnosed ocular disease. Version 6.0 Cirrus high-definition optical coherence tomography (HD-OCT) (Carl Zeiss Meditec, Dublin, CA) was used to measure CT at the fovea, and 1500 μm nasal and 1500 μm temporal to the fovea. After baseline OCT measurements, participants were asked to have 200 mg oral caffeine intake or a placebo capsule (200 mg lactose powder). Two further OCT measurements were applied at the first and fourth hours of caffeine intake. All participants also had intraocular pressure (IOP) and ocular pulse amplitude (OPA) measurements recorded before, first and fourth hours of caffeine intake. IOP and OPA were measured using the dynamic contour tonometry (DCT) (Swiss Micro Technology AG, Port, Switzerland).Results: The groups showed no significant difference by means of age, gender, spherical refraction and axial length (p > 0.05). Baseline choroidal thickness measurements of the study and control group showed no significant difference. Oral caffeine intake caused a significant reduction in choroidal thickness compared with baseline, at all three measurement points, (p < 0.05). There were no significant changes in IOP and OPA measurements compared with the baseline values (p > 0.05). The choroidal thickness still continued to decrease for at least 4 h following caffeine intake; whereas, the difference between 1 and 4 h was not statistically significant (p > 0.05). However, choroidal thicknesses, IOP and OPA values of the control group revealed no significant difference at all points when comparing measurements at baseline with 1 and 4 h after placebo intake (p > 0.05).Conclusions: We found no significant change in IOP and OPA following oral 200 mg caffeine intake, while CT significantly decreased, for at least 4 h.

Subfoveal Choroidal Thickness Is Associated with Blood Hematocrit Level

Purpose: To compare subfoveal choroidal thickness (SFCT), retinal vessel caliber, and ocular pulse amplitude between treated polycythemia vera (PV) patients and healthy adults. Methods: Forty patients with PV and 40 age- and sex-matched healthy controls were recruited for this cross-sectional study. Spectral-domain optical coherence tomography was used for SFCT and retinal vessel caliber measurements. The Pascal dynamic contour tonometer was used for ocular pulse amplitude measurements. The correlations of blood hematocrit levels with the studied ocular parameters were analyzed. Results: There were no statistically significant differences between the PV patients and controls in SFCT, retinal vessel caliber, and ocular pulse amplitude (p > 0.05). SFCT was associated with hematocrit level in both PV patients and healthy adults (p < 0.05). Conclusions: Although SFCT, retinal vessel caliber, and ocular pulse amplitude parameters are similar in treated PV patients and healthy controls, SFCT is associated with hematocrit level.

Role of ocular pulse amplitude in glaucoma

The ocular pulse amplitude is defined as the difference between diastolic and systolic intraocular pressure. The ocular pulse is generated by the pulsatile ocular blood flow in the choroid. It is dependent on the dynamics of the cardiovascular system, the rigidity of the ocular vessels on one side and the biomechanical properties of the eye on the other side. In addition the influence of outflow facility of the aqueous humor, the level of the intraocular pressure itself and last but not least the rigidity of the sclera on the ocular pulse amplitude is until now not clear. Dynamic contour tonometry (Pascal®) does not only measure intraocular pressure almost independent of corneal thickness and curvature but also allows easy and fast measurement of ocular pulse amplitude on the slit lamp. The ocular pulse amplitude in healthy subjects is between 1.2 and 4 mmHg. If the ocular pulse amplitude is larger than 1.2 mmHg spontaneous pulsations of the central retinal vein are visible on fundoscopy. In patients with ocular hypertension the ocular pulse amplitude is larger than in normal subjects but this is mainly due to higher IOP levels. In patients with manifest open-angle glaucoma the ocular pulse amplitude stays initially within the normal range. In more advanced stages of the disease and especially in patients with ocular perfusion pressure dependent optic neuropathy the ocular pulse amplitude is gradually reduced. Due to the various factors influencing ocular pulse amplitude a direct correlation between reduced ocular pulse amplitude and reduced ocular perfusion pressure has not been established as yet. New approaches investigating the variations of the ocular pressure Fourier spectral analysis are promising, especially when simultaneous analysis of the arterial blood pressure is performed. These techniques may allow a fast and easy discrimination between healthy and glaucomatous patients in the near future. If ocular pulse amplitude exhibits a massive inter-ocular asymmetry in the presence of symmetrical ocular findings of extraocular vascular pathologies (i.e. carotid stenosis) are the most likely cause and therefore should be excluded.

전기자극의 강도와 측정전극의 간격이 감각신경신호의 파라미터에 미치는 영향 연구

Abstract: This study was designed to investigate the effects of stimulation intensity and inter-electrode distanceon the parameters of the measured sensory nerve signal. 30 healthy subjects participated in this study. Sensory nervesignals were elicited by four different pulse amplitudes, i.e., 3, 6, 9, 12 mA, with the pulse width fixed at 500μs. Thesensory nerve signals elicited by the four different pulse amplitudes were measured by four different inter-electrodedistances (20, 30, 40, and 50 mm). We extracted four parameters (pulse amplitude, pulse width, pulse area, andlatency time from stimulation) from the sensory nerve signals. The measured pulse amplitude and pulse width wereincreased when the measuring inter-electrode distance was increased while the stimulating pulse amplitude wasfixed. The measured pulse amplitude was saturated with the stimulating pulse amplitudes of over 6 mA while mea-suring inter-electrode distance. Under the same condition, measured pulse width was increased, and sensory nervesignal was initiated early. Sensory nerve signals, specially those of pulse amplitude, were distorted by a differentialamplification method that commonly measures the human body signal. The experimental results indicate that thedifferential amplification method is required to be replaced when measuring nerve signals. Our observations sug-gested that the hyperpolarization of the action potential of the sensory nerve signal for preventing distortion couldbe used to clarify the correlation between the parameters of the sensory nerve signals and quantification of sen-sations.Key words: Sensory nerve signal, Stimulation intensity, Inter-electrode distance, Parameter

Choroid thickness and ocular pulse amplitude in migraine during attack.

To compare the choroidal thickness and ocular pulse amplitude (OPA) measurements obtained during the attack period in migraine patients and age and gender matched control group participants using high definition optical coherence tomography (OCT). Thirty eyes at the side of the headache of 30 subjects with a diagnosis of migraine with or without aura and unilateral migraine and 29 age and gender matched healthy participants were enrolled in this observational, cross-sectional study. OCT scans were performed to all participants. Choroidal thicknesses were measured at the fovea, 1500 μm nasal and 1500 μm temporal to the fovea. Intraocular pressure (IOP) and OPA were also measured. The choroidal thickness measurements obtained during the attack period in migraine patients were (mean±SD) 279.82±35.87, 250.05±29.49, and 239.58±27.92 and in control group were 308.20±44.97, 276.95±41.39, and 281.60±41.38 at foveal, nasal, and temporal measurement points, respectively. Choroidal thickness significantly decreased according to the control group (P<0.05) at all measured points in migraine patients during attack. IOP (mean±SD) values were 16.71±3.26 and17.40±3.19 and OPA (mean±SD) values were 2.26±0.81 and 2.64±1.03 in migraine and control groups, respectively, and did not seem to be changed (P>0.05). Choroidal thickness was found to be significantly decreased in unilateral migraine patients during the attack period when compared with the control group, whereas OPA did not change. The possible implications of these findings on the association between migraine and glaucoma are discussed.

Real-time single-shot measurement and correction of pulse phase and amplitude for ultrafast lasers

The transition of femtosecond lasers from the laboratory to commercial applications requires real-time automated pulse compression, ensuring optimum performance without assistance. Single-shot phase measure- ments together with closed-loop optimization based on real-time multiphoton intrapulse interference phase scan are demonstrated. On-the-fly correction of amplitude, as well as second- and third-order phase distortions based on the real-time measurements, is accomplished by a pulse shaper.© 2014 Society of Photo-Optical Instrumentation Engineers

Dynamic contour tonometry over silicone hydrogel contact lens

PurposeThis study compared the measurements of intraocular pressure (IOP) and ocular pulse amplitude (OPA) using the Dynamic Contour Tonometry (DCT) over silicone hydrogel contact lenses of different modulus. Corneal biomechanics were also measured using the Ocular Response Analyzer (ORA). MethodsForty-seven young (mean age 22.3 years, standard deviation 1.2 years) subjects had IOP, OPA, corneal hysteresis (CH) and corneal resistance factor (CRF) measured without lens and with two brands of silicone hydrogel contact lenses. Each eye wore one brand followed by another, randomly assigned, and then the lenses switched over. Difference and agreement of IOP and OPA with and without silicone hydrogel contact lens were studied. ResultsThe right and left eyes had similar corneal curvatures, central corneal thicknesses, IOP, OPA and corneal biomechanics at baseline. No significant difference was found in CH and CRF when they were measured over different contact lenses. IOP demonstrated a greater difference (95% limits of agreement: 2.73mmHg) compared with no lens when it was measured over high modulus silicone hydrogel lenses. Agreement improved over low lens modulus silicone hydrogel lenses (95% limits of agreement: 2.2–2.4mmHg). 95% limits of agreement were within 1.0mmHg for OPA. ConclusionsThis study demonstrated the feasibility of DCT over silicone hydrogel lenses. Low lens modulus silicone hydrogel contact lens in situ has no clinical effect on DCT.

Prototype 250 GHz Bandwidth Chip to Chip Electrical Interconnect, Characterized With Ultrafast Optoelectronics

We have connected two optoelectronic chips with air-spaced two-wire transmission lines and have observed essentially undistorted transmission of 1.8 ps (FWHM) electrical pulses over propagation distances up to 200 cm. The lines consist of two 0.4 mm (or 0.5 mm) diameter copper wires with centers separated by 1.0 mm. The air spaced two-wire lines show transform-limited TEM mode pulse propagation with very small group velocity dispersion (GVD), and relatively low attenuation. Our achieved performance with a power loss of 5.8 dB/m approaches that needed for mm-wave and THz interconnects. The coupling was enabled by two tungsten probes with 1 μm diameter tips in near-contact (5 μm gap) with the coplanar transmission lines on the transmitting and receiving optoelectronic chips. The air spaced two-wire line's relatively small, measured pulse amplitude attenuation coefficient was 1.31 times larger than the theoretical prediction for the TEM mode. This discrepancy is considered to be primarily due to reduction of the Cu conductivity in the THz skin-depth layer.

Cochlear implant artifact attenuation in late auditory evoked potentials: A single channel approach

Recent evidence suggests that late auditory evoked potentials (LAEP) provide a useful objective metric of performance in cochlear implant (CI) subjects. However, the CI produces a large electrical artifact that contaminates LAEP recordings and confounds their interpretation. Independent component analysis (ICA) has been used in combination with multi-channel recordings to effectively remove the artifact. The applicability of the ICA approach is limited when only single channel data are needed or available, as is often the case in both clinical and research settings. Here we developed a single-channel, high sample rate (125 kHz), and high bandwidth (0–100 kHz) acquisition system to reduce the CI stimulation artifact. We identified two different artifacts in the recording: 1) a high frequency artifact reflecting the stimulation pulse rate, and 2) a direct current (DC, or pedestal) artifact that showed a non-linear time varying relationship to pulse amplitude. This relationship was well described by a bivariate polynomial. The high frequency artifact was completely attenuated by a 35 Hz low-pass filter for all subjects (n = 22). The DC artifact could be caused by an impedance mismatch. For 27% of subjects tested, no DC artifact was observed when electrode impedances were balanced to within 1 kΩ. For the remaining 73% of subjects, the pulse amplitude was used to estimate and then attenuate the DC artifact. Where measurements of pulse amplitude were not available (as with standard low sample rate systems), the DC artifact could be estimated from the stimulus envelope. The present artifact removal approach allows accurate measurement of LAEPs from CI subjects from single channel recordings, increasing their feasibility and utility as an accessible objective measure of CI function.

Estimation of Ocular Rigidity in Glaucoma Using Ocular Pulse Amplitude and Pulsatile Choroidal Blood Flow

Theoretical models and animal studies have suggested that scleral rigidity plays an important role in the pathogenesis of glaucoma. The aim of this study was to present a noninvasive technique for estimating ocular rigidity (E) in vivo, and to compare the estimated rigidity between patients with open-angle glaucoma (OAG); ocular hypertension (OHT); suspect glaucomatous disc (GS); and normal subjects (N). We hypothesized that OHT patients would have higher rigidity. All patients underwent measurements of ocular pulse amplitude (OPA) using dynamic contour tonometry, pulsatile choroidal blood flow (ChBFP) using laser Doppler flowmetry; axial length (AL); and assessment of automated visual field mean deviation (MD). The ratio between OPA and ChBFP was calculated according to the Friedenwald's equation of ocular rigidity. The calculated ratio is denoted as (ER). The average ER values of the four diagnostic groups were compared using nonparametric tests. The relationship between ER and other ocular and systemic factors was examined using correlation and regression analysis. A total of 257 subjects were included in the study (56 N, 108 OAG, 48 GS, and 45 OHT). ER correlated negatively with AL and positively with MD, signifying that a lower rigidity was associated with a longer eye and a worse (more negative) MD. ER was also found to be highest in OHT (0.235 ± 0.16) and lowest in OAG (0.188 ± 0.14; P = 0.01). Estimated coefficient of ocular rigidity by OPA and ChBFP suggested that glaucoma patients had the lowest rigidity and OHT the highest. It supports the idea that a more compliant ocular shell may predispose the optic nerve head to intraocular pressure (IOP)-related damage.

The Accuracy of Dynamic Contour Tonometry Over Soft Contact Lenses

Dynamic contour tonometry (DCT) has been shown to measure the intraocular pressure (IOP) independently of corneal thickness. This study aimed to investigate if DCT remains accurate when the IOP measurement is taken over soft contact lenses (CLs) of different thicknesses and material characteristics. This was a prospective clinical study that included 42 patients. Subject age was 22 to 59 years (26.5 ± 6.3 years). Intraocular pressure and ocular pulse amplitude (OPA) measurements were taken under topical anesthesia without CLs and over various daily disposable CLs with -0.50, +5.00, and -5.00 diopters (D) in hydrogel (Nelfilcon A) and in silicone hydrogel (Narafilcon A) materials. No statistically significant differences were found when comparing the IOP measurements obtained using either of the different CL powers of -0.50 or -5.00 D, irrespective of which CL material was being used. However, the difference of 0.62 mm Hg observed when the Nelfilcon A with a power of +5.00 D was used turned out to be highly statistically significant (p = 0.0002), whereas the Narafilcon A with the same power of +5.00 D, with a small difference of -0.16 mm Hg, was not. Regarding OPA measurements, no significant differences were found between measurements with and without CL neither for different materials nor for change in dioptrical power (F = 0, p = 1.000). This study showed good reliability of IOP and OPA measurements over CLs with varying thickness profiles and different soft materials when using the DCT. Only a small but statistically significant difference of 0.62 mm Hg was found for the IOP measurement with the hydrogel CL of +5.00 D compared with "no CL."