Comparative study of microtremor analysis methods

During a multidisciplinary microzonation pilot project in the city of Heraklion (Crete, Greece), microtremor data were collected at the top of exploratory boreholes specifically designed for the purposes of the project, over a period of 5 days, for 4 h/day at 125 Hz (continuous recordings). The data were analysed with the SSR and H/V Ratio techniques, using the standard FFT (applied to long data series) and a Multi-variate Maximum Entropy (MV-MAXENT) spectral analysis method. Both techniques, implemented with both spectral analysis methods, identify the same major resonance frequency band, albeit with different amplification levels. The MV-MAXENT however is effective in handling short data lengths while yielding high resolution spectra and addressing several shortcomings of the conventional FFT (windowing, zero padding etc.). Thus, it yields competitively similar results, with only a fraction (a few minutes) of the data required by the lower resolution (FFT) method and appears to be a powerful tool for site effect investigations. Moreover, the results of both microtremor-based techniques are consistent and remarkably similar to the results of microzonation methods that require (expensive) borehole data

A statistical reappraisal in the relationship between global and Greek seismic activity

For the period 1917-1987, Greek seismic activity exhibits a very significant positive correlation to the preceding global activity with a time-lag of 15 years. It seems that all Greece and the two characteristic areas in which we have separated it (Greece without Arc, and the area of the Greek seismic Arc), follow the global seismic activity but with a time-shift of 15 years. Moreover, it seems to exist an intrinsic interaction mechanism between the Greek seismic arc and the rest of Greece, which may be deduced by their different behavior exhibited when they are correlated with the global activity, as well as from the correlation between themselves, where a very significant positive correlation has been found with a time-lag of 3 years, for Greece without arc preceding. A quasi-periodic term of 30-yrs is also observed in these detailed four seismic time-series. The cross-correlation analysis of seismic time-series, as shown, is served as a powerful tool to clarify the complicated space-time pattern of the world wide mosaic of tectonic plate motions. The implications of spring-block model of tectonic plates interaction is invoked, considering the earth's rotation rate changes as their triggering agent. Particular emphasis is given to the potential of such studies in earthquake prediction efforts from local or regional scales to a global scale and vice-versa. © 1995 Kluwer Academic Publishers

Objective documentation of anterior chamber depth following trabeculectomy and its correlation with intraocular pressure and bleb functionality

The purpose of this study was to objectively evaluate the anterior chamber depth (ACD) after trabeculectomy and to correlate its variations with the intraocular pressure (IOP) and bleb functionality. Fifty eyes (46 patients) were included in this prospective study. ACD was documented with the use of a non-contact optical device (IOL Master-Carl Zeiss Meditec) and IOP was measured with the Goldmann applanation tonometer. Ophthalmological examination, IOP, and ACD measurements were performed before surgery, the day after and weekly thereafter. Linear regression Analysis between the 2 variables was performed and correlation coefficients were estimated. A 2-tailed t test was used and a P value < .05 was considered as statistically significant. Correlation coefficients between ACD and IOP, during the follow-up period, resulted in a moderate to strong positive relationship (r = 0.2–0.7), which since the 1st week resulted statistically significant at 5%. Twenty seven eyes (54%) needed at least 1 needling procedure. Considering each group separately, until the 3rd post-op week, the correlation coefficients in the needling group resulted higher than those in the non-needling group. Furthermore, in the needling group, the relationship between ACD and IOP, for the 1st, 2nd, 3rd, and 4th week was statistically significant at 5%. The objective documentation of the ACD in the early post-trabeculectomy period presents a moderate to strong positive correlation with the IOP. Furthermore, the brisk deepening of the ACD during the first 2 to 4 post-operative weeks is strongly correlated with the increase of the IOP and early signs of bleb encapsulation. Abbreviations: DACD = Difference in Anterior Chamber Depth, DIOP = Difference in Intraocular Pressure, ACD = Anterior Chamber Depth, IOP = Intraocular Pressure, POAG = Primary Open Angle Glaucoma, PXG = Pseudoexfoliative Glaucoma. Copyright © 2018 the Author(s)

Phacoemulsification in a patient with small pupil and a large iris cyst

Purpose. Peripheral iris cysts are generally asymptomatic and nonprogressive. They are usually located in the inferotemporal quadrant of the anterior segment, most commonly in the iridociliary sulcus. We report our management strategy in a patient with small pupil and a large iris cyst. Method. Retrospective, case report. Results. A 65-year-old man was referred, reporting blurred vision OS. Best-corrected visual acuity (BCVA) was 6/12 OD and 6/48 OS. Anterior chamber (AC) examination OS revealed an iris cyst protruding inferotemporally occupying almost one-third of AC volume. Intraocular pressure (IOP) was 32 mmHg OS and 19 mmHg OD. Aspiration with a 27-G cannula, without cyst resection, was performed. Phacoemulsification and intraocular lens implantation were uneventful. The BCVA improved to 6/9 1 week postoperatively and to 6/6 a month later. In the first postoperative visit, IOP dropped to 16 mmHg. The cyst was significantly decreased in size. Six months postoperatively, BCVA remained unchanged while AC examination revealed that the cyst remained in place with no signs of enlargement. Conclusions. In this case, cyst aspiration was elected as a treatment procedure that led to significant decrease in size. This management option, combined with an uncomplicated cataract extraction procedure, resulted in an excellent visual and a positive anatomic outcome. © 2011 Wichtig Editore

Visual field examination method using virtual reality glasses compared with the Humphrey perimeter

Stylianos Tsapakis, Dimitrios Papaconstantinou, Andreas Diagourtas, Konstantinos Droutsas, Konstantinos Andreanos, Marilita M Moschos, Dimitrios Brouzas 1st Department of Ophthalmology, National and Kapodistrian University of Athens, Athens, Greece Purpose: To present a visual field examination method using virtual reality glasses and evaluate the reliability of the method by comparing the results with those of the Humphrey perimeter.Materials and methods: Virtual reality glasses, a smartphone with a 6 inch display, and software that implements a fast-threshold 3 dB step staircase algorithm for the central 24° of visual field (52 points) were used to test 20 eyes of 10 patients, who were tested in a random and consecutive order as they appeared in our glaucoma department. The results were compared with those obtained from the same patients using the Humphrey perimeter.Results: High correlation coefficient (r=0.808, P<0.0001) was found between the virtual reality visual field test and the Humphrey perimeter visual field.Conclusion: Visual field examination results using virtual reality glasses have a high correlation with the Humphrey perimeter allowing the method to be suitable for probable clinical use. Keywords: visual fields, virtual reality glasses, perimetry, visual fields software, smartphon

Comparison of goldmann applanation tonometry and pascal dynamic contour tonometry in relation to central corneal thickness and corneal curvature

Purpose: The aim of the study was to assess the influence of central corneal thickness (CCT) and corneal curvature in tonometry measurements taken by Goldmann applanation tonometry (GAT) and Pascal dynamic contour tonometry (DCT). Methods: This was a prospective study of 185 eyes from 97 subjects, attending outpatient ophthalmology appointments, who underwent intraocular pressure measurements by GAT and Pascal DCT. CCT and corneal curvature were obtained using ultrasound pachymetry and Orbscan topography, respectively. All measurements were carried out among males and females during the period 2009-2012. Apart from the usual descriptive and exploratory data analysis, one-way analysis of variance and agreement analysis were performed, linear as well as intraclass correlation coefficients were estimated, and multiple scatter and Bland-Altman plots were produced. Results: Mean IOP measurements obtained were 17.21±4.10 mmHg by DCT and 13.23±4.07 mmHg by GAT. Mean difference between the GAT and DCT measurements was 3.88±2.8 mmHg. Mean CCT and corneal curvature were 522.78±52 μm and 43.83±2.9823 D, respectively. Conclusion: Intraocular pressure measured by GAT was consistently lower when compared with DCT, and this difference was greatest with thinner CCT. Flat corneas seem to influence GAT measurements compared to DCT. © 2016 Andreanos et al

Prospective study comparing Xalatan® eye drops and two similar generics as to the efficacy and safety profile

Purpose: To evaluate the efficacy and safety between two generic prostaglandins Lataz–Xalaprost (Greece) and the corresponding original drops (Xalatan®). Material and methods: In this prospective randomized study, 60 patients diagnosed with open-angle glaucoma or ocular hypertension were enrolled, who had never received antiglaucoma treatment. Subjects were divided randomly into three groups (Xalatan, Lataz, and Xalaprost groups) and they were studied over 16 weeks. At each visit, the mean applanation tonometry values and tear break-up time were measured. The Ocular Surface Disease Index questionnaire was used to evaluate patient’s symptoms. Results: There was a statistically significant difference (p < 0.001) in the mean values of the intraocular pressure between the baseline and the last visit (Xalatan group: from 23.11 ± 1.61 mmHg to 15.81 ± 1.22 mmHg, Lataz group: from 23.26 ± 1.33 mmHg to 15.80 ± 1.47 mmHg, and Xalaprost group: from 23.08 ± 1.45 mmHg to 16.08 ± 1.38 mmHg). Both generic eye drops showed mean percentage intraocular pressure reduction comparable to the standards of prostaglandin analogues (Xalatan: 31.57%, Lataz: 32.06%, and Xalaprost: 30.34%). Xalatan reduced the tear break-up time less, followed by Lataz and then by Xalaprost (Xalatan: from 8.5 to 8 s, Lataz: from 8.2 to 7.4 s, and Xalaprost: from 8.7 to 7.7 s). Xalatan presented the best safety profile, followed by Lataz and least was Xalaprost, according to Ocular Surface Disease Index questionnaire’s results. Conclusion: No significant difference was recorded in the effectiveness of each generic prostaglandin compared to the original. Furthermore, no patient had to change medication. The differences that arose in the safety profile of the three eye drops suggest a prompt closer initial monitoring of patients who are administered generic eye drops. © The Author(s) 2018

Safety and efficacy of phacoemulsification and intraocular lens implantation through a small pupil using minimal iris manipulation

Dimitris Papaconstantinou, George Kalantzis, Dimitris Brouzas, Anastasios Kontaxakis, Chryssanthi Koutsandrea, Andreas Diagourtas, Ilias Georgalas Department of Ophthalmology, National and Kapodistrian University of Athens, Athens, Greece Purpose: The aim of this study was to compare the results of phacoemulsification through a small pupil using minimal iris manipulation versus phacoemulsification through a well-dilated pupil.Methods: This prospective randomized control (comparative) study comprised 78 patients (group I) with a maximally dilated pupil size of ≤4.00 mm and 45 patients (group II) with dilated pupil size of ≥7.00 mm. In group I patients, only viscodilation and minimal push-and-pull iris stretching with two collar-button iris-retractor hooks were utilized without iris manipulation. Phacoemulsification was performed by two senior surgeons and the technique used consisted of either stop and chop or quick chop, infusion/aspiration of lens cortex, capsular bag refill with ocular viscoelastic devices, and implantation of an acrylic foldable intraocular lens. Patients were examined on the first day and 1 month postoperatively.Results: Forty-six eyes of group I patients had pseudoexfoliation syndrome, eleven eyes had previous glaucoma surgery, 14 eyes had angle-closure or open-angle glaucoma, and seven eyes had posterior synechiae with iritis. In group I patients, the mean pupil size measured under an operating microscope was 3.2 mm preoperatively, 4.3 mm after viscoelastic and mechanical pupil dilation, and 4.1 mm at the end of a surgical procedure. Rupture of the zonular fibers occurred in six patients of group I and the intraocular lens was implanted in the sulcus. Small iris-sphincter rupture and small hemorrhages occurred in four eyes during pupillary manipulation, but they were not evident at the end of the surgery. In group II patients, no intraoperative complications occurred. Signs of significant corneal edema and iritis were observed more frequently in group I eyes (26 eyes and 20 eyes, respectively) on the first postoperative day in comparison with group II eyes (ten eyes and six eyes, respectively). Intraocular pressure was <20 mmHg in all eyes of both groups. One month postoperatively, the pupil was round and reactive to light, the anterior chamber was quiet, and the cornea was clear in all eyes. The best-corrected visual acuity on Snellen chart was 20/40 (Monoyer’s scale) or better in both groups.Conclusion: Phacoemulsification through a small pupil using minimal iris manipulation can be safe and exhibits the same results as those obtained with phacoemulsification through normal pupils. Keywords: phacoemulsification, small pupil, safety, iris manipulatio

Comparison of Goldmann applanation tonometry and Pascal dynamic contour tonometry in relation to central corneal thickness and corneal curvature

Konstantinos Andreanos, Chryssanthi Koutsandrea, Dimitris Papaconstantinou, Andreas Diagourtas, Andreas Kotoulas, Panagiotis Dimitrakas, Marilita M Moschos First Department of Ophthalmology, University of Athens, “G. Gennimatas” General Hospital of Athens, Athens, Greece Purpose: The aim of the study was to assess the influence of central corneal thickness (CCT) and corneal curvature in tonometry measurements taken by Goldmann applanation tonometry (GAT) and Pascal dynamic contour tonometry (DCT).Methods: This was a prospective study of 185 eyes from 97 subjects, attending outpatient ophthalmology appointments, who underwent intraocular pressure measurements by GAT and Pascal DCT. CCT and corneal curvature were obtained using ultrasound pachymetry and Orbscan topography, respectively. All measurements were carried out among males and females during the period 2009–2012. Apart from the usual descriptive and exploratory data analysis, one-way analysis of variance and agreement analysis were performed, linear as well as intraclass correlation coefficients were estimated, and multiple scatter and Bland–Altman plots were produced.Results: Mean IOP measurements obtained were 17.21±4.10 mmHg by DCT and 13.23±4.07 mmHg by GAT. Mean difference between the GAT and DCT measurements was 3.88±2.8 mmHg. Mean CCT and corneal curvature were 522.78±52 µm and 43.83±2.9823 D, respectively.Conclusion: Intraocular pressure measured by GAT was consistently lower when compared with DCT, and this difference was greatest with thinner CCT. Flat corneas seem to influence GAT measurements compared to DCT. Keywords: glaucoma, Goldmann, Pascal, tonometr