Interactive Threshold Research Articles

Risk Factors for Visual Field Progression in Treated Glaucoma

To determine intraocular pressure (IOP)-dependent and IOP-independent variables associated with visual field (VF) progression in treated glaucoma. Retrospective cohort of the Glaucoma Progression Study. Consecutive, treated glaucoma patients with repeatable VF loss who had 8 or more VF examinations of either eye, using the Swedish Interactive Threshold Algorithm (24-2 SITA-Standard, Humphrey Field Analyzer II; Carl Zeiss Meditec, Inc, Dublin, California), during the period between January 1999 and September 2009 were included. Visual field progression was evaluated using automated pointwise linear regression. Evaluated data included age, sex, race, central corneal thickness, baseline VF mean deviation, mean follow-up IOP, peak IOP, IOP fluctuation, a detected disc hemorrhage, and presence of beta-zone parapapillary atrophy. We selected 587 eyes of 587 patients (mean [SD] age, 64.9 [13.0] years). The mean (SD) number of VFs was 11.1 (3.0), spanning a mean (SD) of 6.4 (1.7) years. In the univariable model, older age (odds ratio [OR], 1.19 per decade; P=.01), baseline diagnosis of exfoliation syndrome (OR, 1.79; P=.01), decreased central corneal thickness (OR, 1.38 per 40 μm thinner; P<.01), a detected disc hemorrhage (OR, 2.31; P<.01), presence of beta-zone parapapillary atrophy (OR, 2.17; P<.01), and all IOP parameters (mean follow-up, peak, and fluctuation; P<.01) were associated with increased risk of VF progression. In the multivariable model, peak IOP (OR, 1.13; P<.01), thinner central corneal thickness (OR, 1.45 per 40 μm thinner; P<.01), a detected disc hemorrhage (OR, 2.59; P<.01), and presence of beta-zone parapapillary atrophy (OR, 2.38; P<.01) were associated with VF progression. IOP-dependent and IOP-independent risk factors affect disease progression in treated glaucoma. Peak IOP is a better predictor of progression than is IOP mean or fluctuation.

Single-Session vs Multiple-Session Pattern Scanning Laser Panretinal Photocoagulation in Proliferative Diabetic Retinopathy

To investigate the effects of pattern scanning laser (Pascal; OptiMedica, Santa Clara, California) multispot panretinal photocoagulation given in a single-session (SS-PRP) vs single-spot multiple-session PRP (MS-PRP) on proliferative diabetic retinopathy (PDR). Single-center, randomized clinical trial of 40 eyes. Proliferative diabetic retinopathy was treated with a 400-mum spot size in 1500 burns given either as Pascal in 20-millisecond SS-PRP or in 3 sessions (100-millisecond MS-PRP) during a 4-week period. Visual acuity, central subfield retinal thickness (CRT), and 24-2 Swedish interactive thresholding algorithm visual fields were recorded at baseline and 4 and 12 weeks. Central subfield retinal thickness, mean deviation, and PDR grade at 12 weeks. There was a significant increase in mean CRT with MS-PRP (22 mum at 4 weeks, 95% CI, -32.25 to -10.75; 20 mum at 12 weeks, 95% CI, -28.75 to -10.82; P < .001) and no significant increase in the SS-PRP group. The mean deviation increased significantly in the SS-PRP group after 4 weeks (0.73 dB, P = .048), with no significant changes in either group at other points. A positive effect on PDR was observed in 74% of eyes in the SS-PRP group vs 53% in the MS-PRP group (P = .31). Mean treatment time for SS-PRP was 5.04 minutes (SD, 1.5 minutes) compared with 59.3 (SD, 12.7 minutes) in the MS-PRP group (P < .001). There were no adverse outcomes (CRT, visual acuity, or visual field) from using multispot SS-PRP vs single-spot MS-PRP at 12 weeks postlaser, and treatment times were significantly shorter for multispot SS-PRP. Pascal SS-PRP was as effective as MS-PRP in the treatment of PDR. Twenty-millisecond Pascal SS-PRP may be safely and rapidly performed in 1500 burns with a similar efficacy to conventional MS-PRP. TRIAL IDENTIFIER: Research and Development Office PIN R00037, Central Manchester University Hospitals Foundation Trust.

Population Growth and Its Expression in Spatial Built-up Patterns: The Sana’a, Yemen Case Study

In light of rapid global urbanisation, monitoring and mapping of urban and population growth is of great importance. Population growth in Sana’a was investigated for this reason. The capital of the Republic of Yemen is a rapidly growing middle sized city where the population doubles almost every ten years. Satellite data from four different sensors were used to explore urban growth in Sana’a between 1989 and 2007, assisted by topographic maps and cadastral vector data. The analysis was conducted by delineating the built-up areas from the various optical satellite data, applying a fuzzy-rule-based composition of anisotropic textural measures and interactive thresholding. The resulting datasets were used to analyse urban growth and changes in built-up density per district, qualitatively as well as quantitatively, using a geographic information system. The built-up area increased by 87 % between 1989 and 2007. Built-up density has increased in all areas, but particularly in the northern and southern suburban districts, also reflecting the natural barrier of surrounding mountain ranges. Based on long-term population figures, geometric population growth was assumed. This hypothesis was used together with census data for 1994 and 2004 to estimate population figures for 1989 and 2007, resulting in overall growth of about 240%. By joining population figures to district boundaries, the spatial patterns of population distribution and growth were examined. Further, urban built-up growth and population changes over time were brought into relation in order to investigate changes in population density per built-up area. Population densities increased in all districts, with the greatest density change in the peripheral areas towards the North. The results reflect the pressure on the city’s infrastructure and natural resources and could contribute to sustainable urban planning in the city of Sana’a.

Effect of Cataract Extraction on the Glaucoma Progression Index (GPI) in Glaucoma Patients

To determine the effect of cataract extraction on the glaucoma progression index (GPI) in glaucoma patients with coexisting cataract. This is a retrospective noncomparative study. Consecutive eligible patients with glaucoma who underwent phacoemulsification alone or in combination with augmented trabeculectomy were included. All patients had Swedish Interactive Threshold Algorithm-standard 24-2 visual fields within 10 months of surgery. Exclusion criteria included other ocular morbidity, intraoperative complications, and perimetric reliability indices greater than 33%. Comparison was made between the immediate visual fields before and after surgery. The main outcome measure was the change in GPI. Changes in the pattern standard deviation (PSD) and mean deviation (MD) were also assessed. Comparison of means was performed with the paired t test. Thirty-three eyes of 33 patients (all Whites) were analyzed. The mean age at surgery was 77.0+/-8.7 years. Visual field tests were performed 3.3+/-3.0 months SD before surgery and 5.4+/-2.6 months after surgery. There was a statistically significant increase in the GPI after cataract surgery (from 71.5+/-18.5% to 74.6+/-17.1%; P=0.02). The improvement in MD was also statistically significant (from -11.8+/-5.3 to -10.2+/-5.3 dB; P <0.01), but the change in PSD did not reach statistical significance. Uncomplicated cataract extraction resulted in a statistically significant improvement in the 24-2 Swedish Interactive Threshold Algorithm-standard GPI and MD, but not in PSD. Both the MD and the GPI may be influenced by lens opacities, which could make detection of glaucoma visual field progression more difficult for clinicians in glaucoma patients with concurrent cataract.

Screen-Film Mammographic Density and Breast Cancer Risk: A Comparison of the Volumetric Standard Mammogram Form and the Interactive Threshold Measurement Methods

Mammographic density is a strong risk factor for breast cancer, usually measured by an area-based threshold method that dichotomizes the breast area on a mammogram into dense and nondense regions. Volumetric methods of breast density measurement, such as the fully automated standard mammogram form (SMF) method that estimates the volume of dense and total breast tissue, may provide a more accurate density measurement and improve risk prediction. In 2000-2003, a case-control study was conducted of 367 newly confirmed breast cancer cases and 661 age-matched breast cancer-free controls who underwent screen-film mammography at several centers in Toronto, Canada. Conditional logistic regression was used to estimate odds ratios of breast cancer associated with categories of mammographic density, measured with both the threshold and the SMF (version 2.2beta) methods, adjusting for breast cancer risk factors. Median percent density was higher in cases than in controls for the threshold method (31% versus 27%) but not for the SMF method. Higher correlations were observed between SMF and threshold measurements for breast volume/area (Spearman correlation coefficient = 0.95) than for percent density (0.68) or for absolute density (0.36). After adjustment for breast cancer risk factors, odds ratios of breast cancer in the highest compared with the lowest quintile of percent density were 2.19 (95% confidence interval, 1.28-3.72; P(t) <0.01) for the threshold method and 1.27 (95% confidence interval, 0.79-2.04; Pt = 0.32) for the SMF method. Threshold percent density is a stronger predictor of breast cancer risk than the SMF version 2.2beta method in digitized images.

Glaucoma Surgery Decreases the Rates of Localized and Global Visual Field Progression

Incisional glaucoma surgical procedures produce greater intraocular pressure (IOP) reduction and less IOP variability than medical treatment. We sought to determine the efficacy of glaucoma surgery in decreasing localized and global rates of visual field (VF) progression. Retrospective, interventional case series. Subjects in the New York Glaucoma Progression Study with glaucomatous optic neuropathy, repeatable VF loss, and 10 or more Swedish interactive threshold algorithm standard VF examinations were assessed for eligibility. Patients who underwent successful glaucoma surgery (not requiring further surgical intervention and IOP < 18 mm Hg) in either eye and who were followed up for at least 2 years before and after surgery were enrolled. Automated pointwise linear regression analysis was used to calculate global and localized rates of progression before and after surgery. Eyes with other ocular conditions likely to affect the VF and an insufficient number of VF to create a slope before and after surgery were excluded. Comparisons were performed within the same eyes before and after surgery (Student paired t test). We enrolled 28 eyes of 28 patients (mean age, 61.2 +/- 14.5 years). The mean number +/- standard deviation of VF was 13.4 +/- 2.3, spanning 7.1 +/- 1.2 years (range, 4 to 9 years). Mean IOP +/- standard deviation decreased from 19.0 +/- 3.9 mm Hg before surgery to 11.3 +/- 3.7 mm Hg after surgery (40% reduction; P < .01). Mean global progression rates decreased from -1.48 +/- 1.4 dB/year before surgery to -0.43 +/- 0.8 dB/year after surgery (70% reduction; P = .01). Twelve eyes (42.8%) had at least 1 significantly progressing point before surgery, whereas only 2 (7.1%) had at least 1 progressing point after surgery. Each 1 mm Hg of IOP reduction after surgery resulted in a 0.1 dB/year decrease in the global rate of progression. Successful IOP reduction after glaucoma surgery greatly reduces both the number of progressing points and the localized and general rates of VF progression.

Detection of pathological areas and estimation of viability parameters in late-enhancement cardiac MRI

Methods The first step consists to analyse myocardium intensity with a specifically tailored Expectation-Maximization algorithm [2]. Estimated distributions of both normal and abnormal tissues are then exploited to generate a fuzzy map indicating, for every pixel, the membership degree to the abnormal tissue class. As false positives remain, we design a fast version of the region competition [3] algorithm to rapidly obtain well-defined regions corresponding to pathological areas and the membership values of all their pixels. To quantify these areas, we calculate the percentage of abnormal tissue and use normalized representations independent of myocardium shape and size to automatically compute the thickness of pathological regions. Results The method was tested on 11 short-axis LECMR volumes (100 slices) acquired in a multi-center study between 2004-2007 (Philips Intera scanner 1.5 T, M FFE sequence, TE = 1.1 ms, TR = 3.8 ms, flip angle = 15°). All slices are 256 × 256, spaced with 10 mm and with pixel size around 1.5 mm. An experienced operator used the interactive thresholding procedure available in the Philips ViewForum 4.3 Cardiac Package to locate pathological areas. To automatically detect these areas we used: (1) our method (see results in Figure 1), (2) thresholding at average normal myocardium value plus two standard deviations (SD) and (3) thresholding at average normal myocardium value plus three SD. Following segmentation, we quantified the volumetric fraction of pathologic areas and the distance between the damaged region and the epicardium. We compared the results obtained from automatic segmentation to the results obtained from manual segmentation (Figure 2). Our method gives the smallest error with respect to manual detections (detected tissue error = 3.5 +/5.6% of heart volume, distance error = 12 +/11% of myocardium thickness) and always avoided false detections contrary to thresholding approaches.

Prediction of Glaucomatous Visual Field Loss by Extrapolation of Linear Trends

To investigate how well short-term progression rates can predict long-term visual field outcomes in patients with glaucoma. We calculated visual field rates of progression using linear regression analysis of the Visual Field Index (VFI) for 100 consecutive patients with glaucoma having 10 or more Swedish Interactive Thresholding Algorithm standard field tests. Final VFI was predicted on the basis of linear extrapolation of the slope defined by the initial 5 field test results. Final VFI also was estimated using linear regression of all qualifying examination results for each patient. Primary outcome measures were the absolute difference and the correlation between predicted and estimated final VFI values. Patient follow-up averaged 8.2 years and 11 field examinations. Median VFI progression rate was -1.1% per year both for the initial 5 test results and also for the complete series. Seventy percent of patients had a predicted final VFI within +/-10% of the estimated final VFI, and the 2 VFI calculations had a correlation coefficient of 0.84. Linear extrapolation based on 5 initial visual field test results was a reliable predictor of future field loss in most patients. Patients in whom linear regression analysis suggests dangerously rapid rates of visual field progression may be candidates for significant alterations in therapy.

Factors Affecting Rates of Visual Field Progression in Glaucoma Patients with Optic Disc Hemorrhage

Optic disc hemorrhage (DH) is an important risk factor for glaucoma progression. We sought to investigate factors affecting the rate of visual field (VF) progression after DH in glaucomatous eyes. Retrospective cohort study. Consecutive glaucoma patients from our Glaucoma Progression Study with > or =5 Swedish interactive threshold algorithm standard 24-2 VFs from 1999 through 2008. Disc photographs of all patients were evaluated for the presence of DH. Exclusion criteria were conditions other than glaucoma likely to affect the VF and insufficient number of VFs to create a slope after DH detection. Automated pointwise linear regression was used to determine the rate of VF loss after DH detection. Fast progression was defined as a global VF loss of > or =1.5 dB/year. Factors associated with a fast rate of VF loss after the detection of the DH were evaluated. Assessed variables included baseline (age, gender, intraocular pressure [IOP], central corneal thickness, VF mean deviation [MD], presence of migraine, Raynaud's phenomenon, low blood pressure, and exfoliation syndrome) and intercurrent data (DH recurrence, fellow eye involvement, glaucoma surgery, and IOP reduction). Odds ratios (ORs) and 95% confidence intervals (CIs) were determined for each variable. Seventy-six eyes (76 patients; mean age, 68.3+/-10.9 years) were enrolled. Mean IOP and VF MD at the time of the DH detection were 16.6+/-3.8 mmHg and -5.6+/-5.7 dB, respectively. The mean global progression rate after DH was -1.1+/-1.3 dB/year (mean follow-up, 3.8+/-2.8 years). A rate of progression of > or =1.5 dB/year was found in 20 (26%) eyes. Multivariate logistic regression analysis revealed larger baseline MD (OR, 1.11; 95% CI, 1.01-1.20; P = 0.03) and older age (OR, 1.06; 95% CI, 1.01-1.13; P = 0.04) to be significant risk factors for fast progression after DH. Eyes with a baseline MD worse than -4.0 dB had a 270% increased risk of fast progression compared with those with an MD better than -4.0 dB. The presence of a DH in older subjects with a worse VF predicted further VF global MD deterioration by more than 5 dB within 4 years. These eyes should undergo careful and frequent disease surveillance and consideration should be given to more aggressive treatment.

The effects of bazedoxifene on mammographic breast density in postmenopausal women with osteoporosis

This study aimed to assess quantitative changes in mammographic breast density after 24 months of therapy with bazedoxifene compared with raloxifene or placebo in postmenopausal women with osteoporosis. This was a retrospective, ancillary study of a subset of women enrolled in a multicenter, double-blind, randomized, placebo- and active-controlled phase 3 trial evaluating bazedoxifene for the treatment of postmenopausal osteoporosis. Participants were randomly assigned to receive bazedoxifene 20 or 40 mg, raloxifene 60 mg, or placebo once daily for 3 years. To be eligible for breast density evaluation, participants had to be 62 years or younger and completed 24 months of treatment, with mammograms at baseline and 24 months. Original mammogram pairs (left craniocaudal views) for each participant were digitized and analyzed by a radiologist. Breast density was measured using interactive thresholding to segment the mammogram, and percent density was determined using a validated software program. Mammogram pairs were obtained from 444 participants. Baseline and demographic characteristics were similar among groups (mean age, 58.7 y). After 24 months, the mean percent changes in breast density from baseline were low (bazedoxifene 20 mg, -1.2%; bazedoxifene 40 mg, -0.4%; raloxifene 60 mg, -0.5%; placebo, -0.2%) and not significantly different among groups. Treatment with bazedoxifene for 2 years did not affect age-related changes in breast density in this population of postmenopausal women with osteoporosis. The changes in breast density with bazedoxifene 20 or 40 mg were similar to those with raloxifene 60 mg or placebo.

Glaucoma With Early Visual Field Loss Affecting Both Hemifields and the Risk of Disease Progression

To evaluate whether damage to both hemifields in glaucomatous eyes predicts more rapid disease progression than does single-hemifield involvement. We reviewed the medical records of 43 660 consecutive patients. Eyes with glaucomatous optic neuropathy, 10 or more Swedish Interactive Threshold Algorithm standard 24-2 visual fields in at least 5 years, and mean deviation (MD) smaller than -6.0 dB were included. Pointwise linear regression was used to determine progression. Cox proportional hazards analysis was used to calculate risk of progression based on different baseline covariates. We enrolled 205 eyes (205 patients; mean [SD] age, 64.2 [11.0] years; follow-up, 6.5 [1.8] years; number of visual fields, 12.3 [2.9]). Patients were divided into 3 groups: initial superior defect (group A; n = 79; MD, -3.4 [1.9] dB), initial inferior defect (group B; n = 61; MD, -3.4 [1.8] dB), and both hemifields affected (group C; n = 65; MD, -4.2 [1.5] dB). Group C progressed faster than did groups A and B (P < .02). Multivariate analysis showed significant effect of higher baseline intraocular pressure, thinner central corneal thickness, and initial damage to both hemifields. Initial damage to both hemifields increases the risk of glaucoma progression. More aggressive therapy should be considered for these eyes.

Functional correlation between retinal sensitivity threshold values of standard automated perimetry in glaucoma

Abstract Purpose To study the interrelationship among the 52 retinal sensitivity threshold values of the Humphrey visual field analyzer with the 24‐2 Swedish interactive threshold algorithm (SITA) standard strategy in glaucoma patients. Methods Prospective cross‐sectorial study. 104 eyes of 104 patients with diagnosed glaucoma by means of optic disc stereophotographs were evaluated. Each 52 threshold points of the SITA Standard 24.2 program in the standard automated perimetry (SAP) were obtained. The upper and the lower hemifield were studied separately. Pearson correlation coefficients were calculated between each of the mean threshold values at each point of the visual hemifield and the rest of the threshold points. Results Perimetric correlation maps between threshold values in the same hemifield were obtained. Most of the points had moderate and high correlations (r ≥ 0,65) with neighboring points and distant points corresponding to the retinotopic distribution of the retinal nerve fibers. Conclusion There is a functional relationship, in glaucoma patients SAP, between neighboring and distant threshold points in corresponding to the anatomical arrangement of ganglion cells axons. This enables to achieve perimetric patterns of glaucoma defects.

Discordance between structure and function in glaucoma: Possible anatomical explanations

Purpose The aim of this study was to analyze glaucomatous eyes that show discordance between structure and function and hypothesize plausible anatomical explanations for discordance. Methods Fifty eyes from 50 consecutive subjects with glaucoma (which was diagnosed according to multicenter criteria) were studied. One eye from each subject was selected randomly for inclusion, counterbalancing right eye (O.D.) and left eye (O.S.). By comparing the available structural information (from clinical disc assessment as well as GDx retinal nerve fiber layer [RNFL] measurements) to the Swedish Interactive Threshold Algorithm (SITA) Standard 24-2 (SS24-2) visual field results, study eyes were assigned to the following categories: (1) positive structure-function correlation, (2) structural abnormalities with no functional deficits, and (3) functional abnormalities with no structural deficits. Structure and function also were compared on a statistical basis, utilizing the nerve fiber indicator (NFI) of the GDx and the mean deviation (MD) and pattern standard deviation (PSD) of SS24-2 visual fields. Results Forty-four eyes were classified in category 1, 5 eyes in category 2, and 1 eye in category 3. Scatter plots showing the relationship between the NFI and MD and between the NFI and PSD depict a positive correlation in the 44 category 1 eyes with R 2 values of 0.465 and 0.322, respectively. The remaining 6 eyes with discordant structural and functional findings were analyzed in detail. Conclusion The majority (88%) of glaucoma cases show concordance between structural loss and functional deficits. The primary proposed explanations for discordance include (1) visual field sampling and test selection limitations (i.e., the SS24-2 samples only axons that are anatomically connected to photoreceptors in the central retina, whereas the GDx samples virtually all axons) and (2) GDx measurement limitations in the papillo-macula bundle (i.e., the GDx has difficulty differentiating the normally thin RNFL from the pathologically even thinner RNFL). Tests of both structure and function are recommended in glaucoma suspects and patients, as neither mode is capable of identifying all glaucomatous deficits. Due to the apparent diagnostic benefit that the peripheral functional data may provide, we strongly recommend that future studies evaluating the structure–function relationship in glaucoma record peripheral (60-4) visual fields for all subjects at the outset of the study.

Diagnostic accuracy of Heidelberg Retina Tomograph III classifications in a Turkish primary open-angle glaucoma population

This study aimed to evaluate the diagnostic accuracy of Moorfields regression analysis (MRA) and the glaucoma probability score (GPS) in primary open-angle glaucoma (POAG) and to measure the level of agreement between the two algorithms in classifying eyes as normal or abnormal in a Turkish population. We prospectively selected 184 healthy subjects and 158 subjects with POAG, who underwent an ophthalmological examination, visual field analysis and imaging with the Heidelberg Retina Tomograph II, using HRT III software, Version 3.0. The diagnostic accuracies of the two classifications were measured when the borderline was taken as either normal (highest specificity criteria) or abnormal (highest sensitivity criteria). The agreement between them was calculated using the unweighted kappa (kappa) coefficient. Optic nerve head topographic parameters showed statistically significant differences between the control and POAG groups (p < 0.001). The parameters with the highest area under the receiver operating characteristic curves were global GPS (0.86), cup : disc area (0.85), rim : disc area (0.85) and vertical cup : disc (0.85). According to the highest specificity criteria, MRA had a sensitivity of 67.7% and a specificity of 95.1%, whereas the GPS had a sensitivity of 70.9% and a specificity of 88.0%. According to the highest sensitivity criteria, MRA had a sensitivity of 81.0% and a specificity of 75.0%, whereas the GPS had a sensitivity of 89.2% and a specificity of 57.6%. A moderate agreement of 68% (233 eyes) with a kappa coefficient of 0.51 was found between MRA and the GPS. The GPS automated classification showed similar sensitivity to MRA, but considerably lower specificity, when applied in a Turkish population.

Snackchips in China

This case is intended to work well as an exam or a capstone for a course on decision analysis, simulation, real options, and game theory. It explores a conventional snack-chip marketer's strategy in China for promoting and advertising a recently acquired healthy snack-chip brand in mid-2002. The marketer has some key decisions to make, now and in the future, about a range of marketing expenditures in the context of an exciting emerging market and in the face of a formidable competitive threat from its chief rival. The case allows students to consider how two parties' decisions about marketing expenditures and market entry interact and to extend the notion of a single party's downstream decision (or real option) to multiple parties' interactive real options. The case's competitive situation can be modeled as a dynamic game of imperfect information, or a multiperiod decision situation with continuous uncertainties and a strategic interaction embedded downstream. Monte Carlo simulation of both parties' payoffs under equilibrium play in the downstream subgame yields a subgame perfect Nash equilibrium, which entails interactive threshold policies for both parties.

Use of a Continuous Probability Scale to Display Visual Field Damage

To derive and display the percentile score (1st-99th percentile) at each perimetric location of a standard automated perimetry test to determine whether this technique will uncover patterns of loss not visible in standard (StatPac) probability maps. We computed continuous scale probability plots of data collected from testing 305 visually healthy participants with standard automated perimetry (24-2 Swedish interactive thresholding algorithm). The age-corrected thresholds were sorted by sensitivity at each visual field location. Percentiles were derived in single increments from the 1st to the 99th. We displayed the percentiles as a color scale and then interpreted visual field plots from healthy control subjects and patients with visual system disorders. Added information was achieved for identifying patterns of visual loss by using the 5th- to 20th-percentile range in conjunction with the lower range below the 5th percentile that is typically used. The extent of contiguous regional defects appeared larger using this method. Healthy control subjects often have threshold results within the 5th- to 20th-percentile range, but these test locations usually appeared randomly spaced rather than in contiguous patterns commonly seen in patients at the border of visual field defects. Continuous scale probability plots are a potentially useful adjunct for interpretation of perimetry results.

Effects of noise and confidence thresholds in nominal and metric Axelrod dynamics of social influence

We study the effects of bounded confidence thresholds and of interaction and external noise on Axelrod's model of social influence. Our study is based on a combination of numerical simulations and an integration of the mean-field master equation describing the system in the thermodynamic limit. We find that interaction thresholds affect the system only quantitatively, but that they do not alter the basic phase structure. The known crossover between an ordered and a disordered state in finite systems subject to external noise persists in models with general confidence threshold. Interaction noise here facilitates the dynamics and reduces relaxation times. We also study Axelrod systems with metric features and point out similarities and differences compared to models with nominal features.

Scanning Laser Polarimetry with Variable Corneal Compensation to Detect Preperimetric Glaucoma Using Logistic Regression Analysis

Background/Aims: To define if a new function improves the capability of the scanning laser polarimetry with variable corneal compensation (GDx-VCC) nerve fiber analyzer in detecting preperimetric glaucoma using 12 retinal nerve fiber layer (RNFL) peripapillary sectors. Methods: Data were obtained in a cross-sectional, hospital-clinic-based study in which 478 eyes from 478 glaucoma suspects were enrolled. All of them underwent ophthalmological examination, static automated perimetry (Humphrey 24-2 Swedish interactive threshold algorithm), optic nerve stereoscopic photography, red-free digital RNFL photography and GDx-VCC examination. The overall intake included 391 normal eyes and 60 preperimetric glaucoma eyes with defects in the fiber layer photographs. Results: The mean values of inferior average, temporal-superior-nasal-inferior temporal average, superior average and the number (nerve fiber indicator) were significantly lower in the eyes with RNFL defects than in the control group, when compared with the obtained linear discriminating function. The area under the curve values for receiver-operating characteristics analysis of the new parameter were 5% better than the best GDx-VCC standard values. Conclusions: Our results confirm that the new function has a better diagnostic reliability in preperimetric glaucoma and confirms the usefulness of morphological diagnosis between normal and early damaged RNFLs.

Glaucoma Monitoring in a Clinical Setting

To compare prospectively 2 perimetric progression detection algorithms for glaucoma, the Early Manifest Glaucoma Trial algorithm (glaucoma progression analysis [GPA]) and a nonparametric algorithm applied to the mean deviation (MD) (nonparametric progression analysis [NPA]). Patients with a reproducible glaucomatous visual field defect at baseline in at least 1 eye were followed up prospectively using perimetry (Humphrey field analyzer 30-2 Swedish interactive thresholding algorithm). Classifications by GPA and by NPA at the end of the follow-up period were compared. Two hundred twenty-one patients met the inclusion criteria; 1 eye per patient was analyzed. On average, 7.1 reliable fields were available after a mean follow-up period of 5.3 years. The mean MD at baseline was -9.4 dB; the mean MD slope during the follow-up period was -0.25 dB/y. Fifty-six eyes showed progression by GPA and 89 eyes by NPA (P < .001); 42 eyes showed progression by both techniques (kappa = 0.39). In eyes with progression detected by NPA only, baseline MD was worse than that in eyes with progression detected by GPA (-12.5 vs -8.2 dB, P = .002), and GPA more often gave a reading of "baseline MD out of range" (P < .001). After exclusion of eyes with baseline MD out of range, the measure of agreement was kappa = 0.50. Nonparametric progression analysis had fairly good agreement with GPA. Especially in cases of more advanced disease, NPA labeled more eyes as having progression than GPA.

Detectability of Glaucomatous Changes Using SAP, FDT, Flicker Perimetry, and OCT

To compare the detectability between glaucomatous visual field changes using standard automated perimetry (SAP), frequency doubling technology (FDT), short-wavelength automated perimetry (SWAP), and flicker perimetry and structural changes using optical coherence tomography (OCT). Fifty-nine eyes of fifty-nine patients with open-angle glaucoma, 24 eyes of 24 glaucoma suspects (GSs), and 40 eyes of 40 healthy age-matched subjects. All subjects underwent Humphrey visual field analyzer II 24-2 full threshold (SAP), Swedish interactive threshold algorithm-SWAP, FDT (30-1, 30-5, 24-2-1, 24-2-5), flicker perimetry on Octopus 311 (4-zone probability 38S), and Stratus OCT [fast retinal nerve fiber layer thickness (NFLT) and fast optic disc]. To evaluate the visual field, FDT and flicker used the number of abnormal points, whereas SAP used mean deviation (MD) and SWAP used both the number of abnormal points and MD. The areas under the receiver operating characteristic curves [area under the curve (AUCs)] and sensitivities at fixed specificities were used to assess the detectability of glaucoma. The AUC for FDT 30-1, 30-5, 24-2-1, 24-2-5, flicker perimetry, SWAP (MD), and SWAP (number of abnormal points) were 0.95, 0.94, 0.88, 0.89, 0.99, 0.88, and 0.88 in the early glaucoma group and 0.67, 0.69, 0.65, 0.70, 0.80, 0.64, and 0.66 in the GS group, respectively. In the early glaucoma and GS groups, all OCT parameters had an AUC >0.81 except the disc area parameter. Especially, average NFLT had the highest AUC of 0.94 in the OCT parameters. FDT, SWAP, flicker perimetry, and OCT are all useful methods for discriminating between healthy eyes and eyes with early glaucoma. Among all 10 OCT parameters, NFLT has the highest sensitivity for detecting early glaucomatous changes in GS patients.