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Mean Sensitivity (mean + sensitivity)

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Medical Sciences	80%

Selected Abstracts

Retinal sensitivity and fixation changes 1 year after triamcinolone acetonide assisted internal limiting membrane peeling for macular hole surgery , a MP-1 microperimetric study

ACTA OPHTHALMOLOGICA, Issue 6 2010
Hakan Ozdemir
Acta Ophthalmol. 2010: 88: e222,e227 Abstract. Purpose:, To evaluate microperimetric changes 1 year after macular hole surgery with triamcinolone acetonide assisted internal limiting membrane (ILM) peeling. Methods:, Twenty-two eyes of 22 patients with stage 3 and 4 idiopathic macular holes of <6 months' duration underwent vitrectomy with triamcinolone acetonide assisted ILM peeling. Best corrected visual acuity (BCVA) (logarithm of the minimum angle of resolution), and central retinal sensitivity were documented before and 1, 3, 6, and 12 months after surgery. Macular sensitivity (mean sensitivity in decibels -dB), and stability and location of fixation (preferred retinal locus) were determined using MP-1 microperimetry (Nidek). The MP-1 microperimetry sensitivity map was overlaid onto infrared images recorded on a Heidelberg scanning laser ophthalmoscope using dedicated MP-1 software to evaluate the fixation location before surgery. Anatomical success was evaluated with optical coherence tomography (OCT). Optical coherence tomography scans were recorded on an OCT 3000 scanner. Results:, Anatomical success was achieved in all 22 eyes. All patients completed 1 year follow-up. No recurrence of macular hole was seen in any patients in the follow-up period. The mean BCVA improved from 0.75 ± 0.2 before surgery to 0.31 ± 0.1 logMAR at the last visit (p < 0.001). Mean sensitivity improved from 3.7 ± 0.6 to 5.3 ± 1.0 dB at the last visit (p < 0.001). Before surgery, the preferred retinal locus was located on the margin of the hole in all, in 18 eyes on its upper part and in four eyes to the side or on its lower part. Preoperatively, 12 eyes were stable and 10 were relatively unstable, but 12 month after surgery, fixation stability had improved, and 20 eyes were stable and two were relatively unstable. Conclusions:, MP-1 microperimetry sensitivity map overlaid onto an infrared image using dedicated MP-1 software can be used successfully to evaluate fixation location in patients with a macular hole before surgery. With microperimetry findings, we can also measure functional macular changes more precisely than using BCVA alone after macular hole surgery. Our results also showed that retinal sensitivity and fixation properties were improved after vitrectomy with triamcinolone acetonide assisted ILM peeling in patients with idiopathic macular hole. [source]

Practical identifiability of biokinetic parameters of a model describing two-step nitrification in biofilms

BIOTECHNOLOGY & BIOENGINEERING, Issue 3 2008
D. Brockmann
Abstract Parameter estimation and model calibration are key problems in the application of biofilm models in engineering practice, where a large number of model parameters need to be determined usually based on experimental data with only limited information content. In this article, identifiability of biokinetic parameters of a biofilm model describing two-step nitrification was evaluated based solely on bulk phase measurements of ammonium, nitrite, and nitrate. In addition to evaluating the impact of experimental conditions and available measurements, the influence of mass transport limitation within the biofilm and the initial parameter values on identifiability of biokinetic parameters was evaluated. Selection of parameters for identifiability analysis was based on global mean sensitivities while parameter identifiability was analyzed using local sensitivity functions. At most, four of the six most sensitive biokinetic parameters were identifiable from results of batch experiments at bulk phase dissolved oxygen concentrations of 0.8 or 5 mg O2/L. High linear dependences between the parameters of the subsets and resulted in reduced identifiability. Mass transport limitation within the biofilm did not influence the number of identifiable parameters but, in fact, decreased collinearity between parameters, especially for parameters that are otherwise correlated (e.g., µAOB and , or µNOB and ). The choice of the initial parameter values had a significant impact on the identifiability of two parameter subsets, both including the parameters µAOB and . Parameter subsets that did not include the subsets µAOB and or µNOB and were clearly identifiable independently of the choice of the initial parameter values. Biotechnol. Bioeng. 2008;101: 497,514. © 2008 Wiley Periodicals, Inc. [source]

Detecting language problems: accuracy of five language screening instruments in preschool children

DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 2 2007
H M E Van Agt MA
To identify a simple and effective screening instrument for language delays in 3-year-old children the reliability, validity, and accuracy of five screening instruments were examined. A postal questionnaire sent to parents of 11423 children included the Dutch version of the General Language Screen (GLS), the Van Wiechen (VW) items, the Language Screening Instrument for 3- to 4-year-olds, consisting of a parent form (LSI-PF) and a child test (LSI-CT), and parents' own judgement of their child's language development on a visual analogue scale (VAS). The response rate was 78% or 8877 children. Reliability (internal consistency) was found to be acceptable (,=0.67,0.72) for all instruments. Significant correlations between the screening instruments (r=0.29,0.55, p<0.01) indicated good concurrent validity. Accuracy was estimated by the sensitivity, specificity, and receiver operating characteristic (ROC) curves against two reference tests based on parent report and specialists' judgement. If the test would classify approximately 5% of the population as screen-positive, the mean sensitivity was 50%; assigning between 20% and 30% of the population as screen-positive, the mean sensitivity was 77%. The sensitivity was lowest for the LSI-CT (range 43,62%), whereas short instruments like the LSI-PF, VW, and the one-item VAS exhibited high levels of sensitivity (range 50,86%). The area under the ROC curves, ranged from 0.75 to 0.87. Apparently, short and simple parent report instruments like the LSI-PF and the one-item VAS perform remarkably well in detecting language delays in preschool children. [source]

Stimulus size and the variability of the threshold response in the central and peripheral visual field

OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 6 2002
L. S. Kim
Purpose:, The investigation of the peripheral visual field has shown considerable interest for the investigation of field loss attributed to anticonvulsant therapy. The purpose was to determine the within-visit between-subject, the between-visit between-subject, and the between-location variability of the threshold response in the normal eye with increase in stimulus eccentricity out to 60° as a function of stimulus size. Methods:, Forty-eight normal subjects attended for a total of three visits (mean age = 49.5 years, SD = 18.9, range 22,84 years). At the first visit, one randomly assigned eye of each subject was examined with the Humphrey Field Analyzer 750 (Carl Zeiss, Jena, Germany) and the Full Threshold algorithm using Programs 30,2 and 60,4 and stimulus sizes III and V. The combination of stimulus size and of program, and the order of the combination within- and between-sessions, were randomized for each subject. The results of the first visit were considered as a familiarization period and were discarded. The protocol at the second and third visits was identical to that at the first visit for each subject. Results:, The ratio of the SD of the group mean sensitivity was determined at each stimulus location for stimulus size III compared with stimulus size V for Programs 30,2 and 60,4 at visit 3. The SDs were greater than unity for Program 30,2 (p < 0.0001) and for Program 60,4 (p < 0.0001) indicating greater variability for the size III stimulus. The SDs were also greater than unity for the central inner zone (p < 0.0001), central outer zone (p < 0.0001) and peripheral inner zone (p < 0.0001). The ratios in the peripheral outer zone were not quite greater than unity (p = 0.054). The ratios increased with increase in eccentricity by up to 2.7 times between 15° and 30° eccentricity and by up to 2.7 times between 30° and 60° eccentricity. The group mean ratio did not vary significantly between the two visits for Program 30,2 stimulus size III (p = 0.563), Program 60,4 stimulus size III (p = 0.935) and for Program 60,4 stimulus size V (p = 0.005). However, the group mean SD was lower at visit 3 compared with visit 2 for Program 30,2 stimulus size V (p = 0.0004). The SDs associated with the extreme peripheral locations in the superior and nasal fields were smaller for stimulus size III because the threshold was frequently attenuated by lid and facial contour. Conclusions:, Considerably narrower confidence limits for normality for the peripheral regions of Program 30,2 and for 60,4 are demonstrated with the use of Goldmann size V. [source]

Retinal sensitivity and fixation changes 1 year after triamcinolone acetonide assisted internal limiting membrane peeling for macular hole surgery , a MP-1 microperimetric study