scholarly journals Enhancement of Visual Field Predictions with Pointwise Exponential Regression (PER) and Pointwise Linear Regression (PLR)

2016 ◽  
Vol 5 (2) ◽  
pp. 12 ◽  
Author(s):  
Esteban Morales ◽  
John Mark S. de Leon ◽  
Niloufar Abdollahi ◽  
Fei Yu ◽  
Kouros Nouri-Mahdavi ◽  
...  
Keyword(s):  
Visual Field ◽  
Linear Regression ◽  
Exponential Regression

scholarly journals CO<sub>2</sub> flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

2007 ◽  
Vol 4 (6) ◽  
pp. 1005-1025 ◽  
Author(s):  
L. Kutzbach ◽  
J. Schneider ◽  
T. Sachs ◽  
M. Giebels ◽  
H. Nykänen ◽  
...  
Keyword(s):  
Linear Regression ◽  
Nonlinear Regression ◽  
Co2 Flux ◽  
Exponential Model ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Closed Chamber ◽  
Exponential Regression ◽  
Closure Time ◽  
Over Time

Abstract. Closed (non-steady state) chambers are widely used for quantifying carbon dioxide (CO2) fluxes between soils or low-stature canopies and the atmosphere. It is well recognised that covering a soil or vegetation by a closed chamber inherently disturbs the natural CO2 fluxes by altering the concentration gradients between the soil, the vegetation and the overlying air. Thus, the driving factors of CO2 fluxes are not constant during the closed chamber experiment, and no linear increase or decrease of CO2 concentration over time within the chamber headspace can be expected. Nevertheless, linear regression has been applied for calculating CO2 fluxes in many recent, partly influential, studies. This approach has been justified by keeping the closure time short and assuming the concentration change over time to be in the linear range. Here, we test if the application of linear regression is really appropriate for estimating CO2 fluxes using closed chambers over short closure times and if the application of nonlinear regression is necessary. We developed a nonlinear exponential regression model from diffusion and photosynthesis theory. This exponential model was tested with four different datasets of CO2 flux measurements (total number: 1764) conducted at three peatlands sites in Finland and a tundra site in Siberia. Thorough analyses of residuals demonstrated that linear regression was frequently not appropriate for the determination of CO2 fluxes by closed-chamber methods, even if closure times were kept short. The developed exponential model was well suited for nonlinear regression of the concentration over time c(t) evolution in the chamber headspace and estimation of the initial CO2 fluxes at closure time for the majority of experiments. However, a rather large percentage of the exponential regression functions showed curvatures not consistent with the theoretical model which is considered to be caused by violations of the underlying model assumptions. Especially the effects of turbulence and pressure disturbances by the chamber deployment are suspected to have caused unexplainable curvatures. CO2 flux estimates by linear regression can be as low as 40% of the flux estimates of exponential regression for closure times of only two minutes. The degree of underestimation increased with increasing CO2 flux strength and was dependent on soil and vegetation conditions which can disturb not only the quantitative but also the qualitative evaluation of CO2 flux dynamics. The underestimation effect by linear regression was observed to be different for CO2 uptake and release situations which can lead to stronger bias in the daily, seasonal and annual CO2 balances than in the individual fluxes. To avoid serious bias of CO2 flux estimates based on closed chamber experiments, we suggest further tests using published datasets and recommend the use of nonlinear regression models for future closed chamber studies.

scholarly journals Trends in the Retinal Nerve Fiber Layer Thickness Changes with Different Degrees of Visual Field Defects

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Wenhui Geng ◽  
Dabo Wang ◽  
Jing Han
Keyword(s):  
Regression Analysis ◽  
Visual Field ◽  
Linear Regression ◽  
Nerve Fiber ◽  
Retinal Nerve Fiber Layer ◽  
Linear Regression Analysis ◽  
Simple Linear Regression ◽  
Fiber Layer ◽  
Simple Linear Regression Analysis ◽  
Rnfl Thickness

Purpose. To explore the disease progression of primary open-angle glaucoma (POAG) in individuals with different degrees of VF defects by analyzing the trends in retinal nerve fiber layer (RNFL) changes at each stage. Methods. A total of 39 patients (77 eyes) were divided into three groups based on the severity of glaucomatous visual field (VF) loss: the first group included patients with mild baseline VF defects (mild group; n = 21 eyes). The second group included patients with moderate VF defects (moderate group; n = 18 eyes). The third group included patients with severe baseline VF defects (severe group; n = 38 eyes). For all patients, slit-lamp biomicroscopy of the anterior and posterior segments and detailed fundus and optic disc inspections were performed, the intraocular pressure (IOP) was measured by Goldman tonometry, best-corrected visual acuity (BCVA) was measured, the RNFL thickness was measured by OCT, and the VF was assessed by the Octopus perimeter. All the groups were followed up postoperatively for 18 months. Results. The mean RNFL thickness was recorded for all the visits. Using simple linear regression analysis, we found that the R2 values of the three groups were 0.988, 0.982, and 0.814, respectively, and the slopes of mean RNFL thickness changes for mild, moderate, and severe baseline VF defects were −0.088, −0.082, and −0.015, respectively. Moreover, we used simple linear regression analysis to explore whether and how the speed of RNFL thinning differs across groups. The R2 values of the three groups were 0.982, 0.978, and 0.805, respectively, and the slopes for mild, moderate, and severe baseline VF defects were 0.089, 0.085, and 0.017, respectively. Conclusion. The rate of RNFL thinning is linear; RNFL thinning is the fastest in individuals with mild baseline VF defects, followed by those with moderate baseline VF defects. In individuals with severe VF defects, changes in the RNFL thickness do not appropriately reflect the progression of the disease. The clinical trial is registered with ChiCTR2000028975.

Comparing the usefulness of a new algorithm to measure visual field using the variational Bayes linear regression in glaucoma patients, in comparison to the Swedish interactive thresholding algorithm

2021 ◽  
pp. bjophthalmol-2020-318304
Author(s):  
Hiroshi Murata ◽  
Ryo Asaoka ◽  
Yuri Fujino ◽  
Masato Matsuura ◽  
Kazunori Hirasawa ◽  
...  
Keyword(s):  
Visual Field ◽  
Linear Regression ◽  
Open Angle Glaucoma ◽  
Variational Bayes ◽  
Mean Deviation ◽  
Test Duration ◽  
Field Analyser ◽  
Measurement Duration ◽  
Measurement Algorithm ◽  
Thresholding Algorithm

Background/aimsWe previously reported that the visual field (VF) prediction model using the variational Bayes linear regression (VBLR) is useful for accurately predicting VF progression in glaucoma (Invest Ophthalmol Vis Sci. 2014, 2018). We constructed a VF measurement algorithm using VBLR, and the purpose of this study was to investigate its usefulness.Method122 eyes of 73 patients with open-angle glaucoma were included in the current study. VF measurement was performed using the currently proposed VBLR programme with AP-7700 perimetry (KOWA). VF measurements were also conducted using the Swedish interactive thresholding algorithm (SITA) standard programme with Humphrey field analyser. VF measurements were performed using the 24–2 test grid. Visual sensitivities, test–retest reproducibility and measurement duration were compared between the two algorithms.ResultMean mean deviation (MD) values with SITA standard were −7.9 and −8.7 dB (first and second measurements), whereas those with VBLR-VF were −8.2 and −8.0 dB, respectively. There were no significant differences across these values. The correlation coefficient of MD values between the 2 algorithms was 0.97 or 0.98. Test–retest reproducibility did not differ between the two algorithms. Mean measurement duration with SITA standard was 6 min and 02 s or 6 min and 00 s (first or second measurement), whereas a significantly shorter duration was associated with VBLR-VF (5 min and 23 s or 5 min and 30 s).ConclusionVBLR-VF reduced test duration while maintaining the same accuracy as the SITA-standard.

scholarly journals Hubungan Kecepatan Pendinginan Air dengan Kecepatan Tiupan Udara

2017 ◽  
Vol 2 ◽  
pp. 241
Author(s):  
Taat Guswantoro ◽  
Manogari Sianturi ◽  
Nurafni Prapitasari ◽  
Areli Elona
Keyword(s):  
Regression Analysis ◽  
Wind Speed ◽  
Linear Regression ◽  
Water Temperature ◽  
Rate Of Change ◽  
Hot Water ◽  
Water Cooling ◽  
Exponential Regression ◽  
The Relationship

<p class="AbstractEnglish"><strong>Abstract</strong>: In this study hot water was placed in two erlenmeyer scale 100 ml clogged and without plug, each filled with 150 ml hot water and allowed to cool in air. Measurement of water temperature using sensor connected to the interface and recorded using the pasco capstone 14.1. The wind is raised with the fan, to adjust the wind speed by adjusting the fan distance, the speed is measured using an anemometer. The water cooling constant is obtained by a decay exponential regression analysis of temperature vs time. The relationship between water colling coefficient with wind speed is used linear regression. From the research, the water cooling coefficient naturally for clogging erlenmeyer is 3,1 x 10<sup>-4</sup> s<sup>-1</sup> and for erlenmeyer without plug 3.8 x 10<sup>-4</sup> s<sup>-1</sup>, the rate of change of water cooling constant to wind speed is 1 , 4 x 10<sup>-4</sup> m<sup>-1</sup>.</p><p class="KeywordsEngish"> </p><p class="AbstrakIndonesia"><strong>Abstrak: </strong>Pada penelitian ini air panas ditempatkan dalam dua buah erlenmeyer berskala 100 ml bersumbat dan tanpa sumbat, masing-masing diisi air panas dengan volume 150 ml dan dibiarkan mendingin di udara. Pengukuran suhu air dengan menggunakan sensor panas yang dihubungkan ke interface dan dicatat menggunakan program pasco capstone 14.1. Angin dibangkitkan dengan kipas, untuk mengatur kecepatan angin dengan cara mengatur jarak kipas, kecepatan angin diukur menggunakan anemometer. Konstanta pendinginan air diperoleh dengan analisis regresi eksponensial meluruh dari data suhu dan waktu. Hubungan antara koefisien pendinginan air dengan kecepatan angin digunakan regresi linier. Dari penelitian diperoleh koefisien pendinginan air secara alami untuk erlenmeyer tersumbat sebesar 3,1 x 10<sup>-4</sup> s<sup>-1</sup> dan untuk erlenmeyer tanpa sumbat sebesar  3,8 x 10<sup>-4</sup> s<sup>-1</sup>, laju perubahan konstanta pendinginan air terhadap kecepatan angin adalah sebesar 1,4 x 10<sup>-4</sup> m<sup>-1</sup><sub>.</sub></p>

Author Response: On Alternative Methods for Measuring Visual Field Decay: Tobit Linear Regression

2012 ◽  
Vol 53 (1) ◽  
pp. 118 ◽  
Author(s):  
Joseph Caprioli ◽  
Dennis Mock ◽  
Elena Bitrian ◽  
Abdelmonem Afifi ◽  
Fei Yu ◽  
...  
Keyword(s):  
Visual Field ◽  
Linear Regression ◽  
Alternative Methods ◽  
Author Response ◽  
Field Decay

Validating the efficacy of the binomial pointwise linear regression method to detect glaucoma progression with multicentral database

2019 ◽  
Vol 104 (4) ◽  
pp. 569-574
Author(s):  
Shotaro Asano ◽  
Hiroshi Murata ◽  
Masato Matsuura ◽  
Yuri Fujino ◽  
Atsuya Miki ◽  
...  
Keyword(s):  
Visual Field ◽  
Linear Regression ◽  
Trend Analysis ◽  
Predictive Value ◽  
False Positive Rate ◽  
Linear Regression Method ◽  
Trend Analyses ◽  
Total Deviation ◽  
Positive Rate ◽  
Test Points

Background/aimWe previously reported the benefit of applying binomial pointwise linear regression (PLR: binomial PLR) to detect 10–2 glaucomatous visual field (VF) progression. The purpose of the current study was to validate the usefulness of the binomial PLR to detect glaucomatous VF progression in the central 24°.MethodsSeries of 15 VFs (Humphrey Field Analyzer 24–2 SITA-standard) from 341 eyes of 233 patients, obtained over 7.9±2.1 years (mean±SD), were investigated. PLR was performed by regressing the total deviation of all test points. VF progression was determined from the VF test points analyses using the binomial test (one side, p<0.025). The time needed to detect VF progression was compared across the binomial PLR, permutation analysis of PLR (PoPLR) and mean total deviation (mTD) trend analysis.ResultsThe binomial PLR was comparable with PoPLR and mTD trend analyses in the positive predictive value (0.18–0.87), the negative predictive value (0.89–0.95) and the false positive rate (0.057–0.35) to evaluate glaucomatous VF progression. The time to classify progression with binomial PLR (5.8±2.8 years) was significantly shorter than those with mTD trend analysis (6.7±2.8 years) and PoPLR (6.6±2.7 years).ConclusionsThe binomial PLR method, which detected glaucomatous VF progression in the central 24° significantly earlier than PoPLR and mTD trend analyses, shows promise for improving our ability to detect visual field progression for clinical management of glaucoma and in clinical trials of new glaucoma therapies.

Low-cost, smartphone-based frequency doubling technology visual field testing using a head-mounted display

2019 ◽  
pp. bjophthalmol-2019-314031 ◽  
Author(s):  
Karam AlRahman Alawa ◽  
Ryan P Nolan ◽  
Elaine Han ◽  
Alejandro Arboleda ◽  
Heather Durkee ◽  
...  
Keyword(s):  
Visual Field ◽  
Linear Regression ◽  
Open Angle Glaucoma ◽  
Low Cost ◽  
Frequency Doubling ◽  
Regression Analyses ◽  
Field Screening ◽  
Head Mounted Display ◽  
Frequency Doubling Technology ◽  
Significant Difference

BackgroundCurrent visual field screening machines are bulky and expensive, limiting their accessibility, affordability and use. We report the design and evaluation of a novel, portable, cost-effective system for glaucoma screening using smartphone-based visual field screening using frequency doubling technology (FDT) and a head-mounted display.MethodsNineteen eyes of 10 subjects with new-onset or chronic primary open angle glaucoma were tested and compared with the Humphrey Zeiss FDT and the newly developed Mobile Virtual Perimetry (MVP) FDT with the C-20 testing pattern. Mann-Whitney, Bland-Altman and linear regression analyses were performed to assess statistical difference, agreement and correlation, respectively, between the two devices.ResultsThe average age of the participants was 58±15 years. No statistically significant difference was found between the MVP FDT and the Humphrey Zeiss FDT (p>0.05). Bland-Altman and linear regression analyses demonstrated good agreement and correlation between the two devices.ConclusionThe MVP FDT is a low-cost, portable visual field screening device that produces comparable results to the Humphrey Zeiss FDT and may be used as an easily accessible screening tool for glaucoma.

Sign in / Sign up

Export Citation Format

Share Document