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| 2. |
- Sharif, Ali, 1986-, et al.
(författare)
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Inter-observer Reliability of Counting Retinal Microaneurysms and Haemorrhages in Elderly with Diabetes
- 2023
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Ingår i: European Journal of Ophthalmology. - : Sage Publications. - 1120-6721 .- 1724-6016. ; 33:1 Suppl., s. 20-20
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- DESIGN: Cross-sectional retrospective cohort study.PURPOSE: To investigate if quantifying retinal microvascular lesions is a reliable outcome measure in elderly.METHODS: Fundus photographs from all patients with type 2 diabetes, age ≥80 years, visiting the screening program 2008 in Region Värmland Sweden, n = 668, were reviewed. Inclusion criteria were mild/moderate diabetic retinopathy (DR) according to the International Diabetic Retinopathy Severity Scale. Exclusion criteria were hard exudates within two disc-diameters, and microaneurysms or haemorrhages within one-disc diameter, from the centre of the macula. Two observers counted microaneurysms and haemorrhages independently. Outcome measures were the total sum of microaneurysms and the total sum of haemorrhages per patient. Correlation, agreement and reliability between the counts of the observers was assessed. Analyses microaneurysm counts utilized all included patients while analyses of haemorrhages those with at least moderate DR in one eye.RESULTS: In total 101 patients met the inclusion/exclusion criteria, median age 82 years and 50.5% were of female sex. Moderate DR in at least one eye was present in 59 patients. In all patients the number of microaneurysms ranged from 1-82, and among patients with at least moderate DR the haemorrhages ranged from 1–29. For microaneurysm count the Pearson correlation coefficient was 0.896 p < 0.001 and intraclass correlation coefficient (ICC) was 0.944 (95% CI 0.917–0.962) between the two observers. For haemorrhage count the Pearson correlation coefficient was 0.897 p < 0.001 and ICC was 0.94 (95% CI: 0.893–0.965) between the two observers.CONCLUSIONS: Retinal microaneurysm count and haemorrhage count was assessed with excellent reliability. The results suggests that retinal microvascular lesions in elderly with diabetes can be manually quantified but the usefulness of such measures needs further evaluation.
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| 3. |
- Woxenius, Johan, 1967, et al.
(författare)
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A combined approach to technology
- 1996
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Ingår i: European intermodal yearbook : directory of intermodal transport, equipment and services. - 1362-5438. ; , s. 18-20
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Hellgren, Johan, 1966-
(författare)
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Compensation for hearing loss and cancellation of acoustic feedback indigital hearing aids
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of integrated circuits during the last decades has made it possible to incorporate digital signal processing in hearing aids that fit into the ear canal and are powered by small zink-air batteries. The digital signal processing provides new possibilities for the hearing aid to modify the signal to fit the impaired ear. A linear phase filter bank that is intended as a basic building block of the signal processing in digital hearing aids is introduced in this dissertation. The filterbank is computationally very efficient and divides the input signal into a number of narrow band signals for further signal processing. The filter bank was combined with band specific gains and two compressors to form the signal processing of a hearing aid. The compressors allow leveldependent gain. Three alternative fitting strategies used to adjust the characteristics of this hearing aid to the individual hearing impaired listener were evaluated. The three fitting strategies differed mainly in the characteristics of the compressors. The strategies were evaluated by hearing impaired subjects in a field test and in laboratory tests. When the subjects were grouped according to their preference among the fitting strategies, the results showed significant differences in the hearing loss configuration between the groups.One of the main tasks of a hearing aid is to amplify the signal to make it audible for the hearing impaired user. The maximum gain that can be used in a hearing aid will be controlled by the feedback from the output to the microphone, as the hearing aid will be a part of a closed loop system. The feedback path depends on several factors such as the position of the microphone (differs between hearing aid categories), size of vent, and the acoustics around the hearing aid. The feedback, and thus the maximum gain that can be used in a hearing aid, has been identified with a number of different hearing aids in a number of conditions that can be expected when the hearing aid is used under real-life conditions.Feedback cancellation can be used to reduce the negative effects of feedback on the performance of the hearing aid. An internal feedback in the hearing aid that is an estimate of the external feedback is then used to cancel the feedback signal. The external feedback path will vary as the hearing aid is used ( e.g. when a telephone set is placed by the ear). It is thus desirable to continuously identify the feedback path. One approach to do this is to utilize closed loop identification with the direct method and some recursive identification method. The output and input signals of the hearing aid are then considered as input and output signal of the system to be identified, i.e. the feedback path. An advantage with this method is that the identification can be done without modifying the output signal. A drawback is that the estimate may be biased, depending on the characteristics of the input signal. A difference from many other closed loop identification problems is that the data used for identification will depend on previous estimates of the system. A feedback cancellation algorithm where Filtered-X LMS is used with the direct method has been analyzed. Filtered-XLMS is computationally efficient and gives a possibility to incorporate known characteristics of the feedback path in the model set used. Prefiltering was also used in the algorithm as it can provide an unbiased estimate if the spectrum of the input signal is known.
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| 6. |
- Hellgren, Johan, 1965
(författare)
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Kronisk rinit och innemiljö.
- 2012
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Ingår i: Allergi i praxis. - 0806-5462. ; 4, s. 6-11
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 7. |
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| 8. |
- Hellgren, Johan, 1965
(författare)
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Non-infectious rhinitis. Epidemiology and clinic
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- We have assessed self-reported rhinitis in the absence of common cold, called "Non-infectious rhinitis", (NIR). The occurrence of NIR was investigated in a population sample of 2,044 individuals, aged 21-51, in an industrialised county in Sweden who answered a questionnaire relating to NIR and occupational exposure to potential irritants and sensitisers. For the clinical evaluation of NIR we compared four different, objective methods to assess nasal obstruction in 41 subjects without current nasal symptoms. Two of these methods, peak nasal inspiratory flow (PNIF) and acoustic rhinometry were used to assess objective signs of rhinitis in 37 workers exposed to paper dust compared with 36 controls in a soft-paper industry. Finally we assessed subjective and objective signs of rhinitis, including the quality of life, in a population sample of 184 individuals with asthma, compared with controls.The prevalence of NIR in a general population was 40% while the incidence rate was 13.5/1,000 person-years. Smokers, subjects with atopy and women had a higher incidence rate of NIR. Men exposed to fire fumes, male cleaners and women exposed to paper dust also ran an increased risk of NIR. The clinical study confirmed that workers exposed to paper dust had more symptoms of nasal blockage and nasal crusts that deteriorated during the working day, but we found no objective signs of nasal inflammation. Among the subjects with asthma we found an increased reversible swelling of the nasal mucosa. Subjects with asthma and NIR also experienced more deterioration in their quality of life than those without NIR.Conclusion; these results indicate that NIR is common in a general population. Occupational exposure to paper dust and asthma was associated with an increased risk of NIR.
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| 9. |
- Hellgren, Johan, 1965, et al.
(författare)
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Rinit och astma: dags att tänka nytt.
- 2014
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Ingår i: Allergi i Praxis. - Oslo, Norge : Oslo. - 0806-5462. ; 2014:1, s. 28-31
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Hellgren, Karl-Johan
(författare)
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A New Model for Assessment of Change in Visual Function in Diabetes
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this thesis was to determine whether perimetry using a new model to interpret deterioration or improvement in the visual field can be employed to assess change in visual function over time in diabetes. Diabetic retinopathy has long been considered a microvascular disease, but it is still a matter of debate to what extent diabetes also affects retinal neurons. Visual acuity is routinely tested to evaluate visual function in diabetes, but can vary for no obvious reasons and even be normal despite severe vessel abnormalities, and hence less useful for early detection of visual impairment. Until now, no measure has proven to be suitable for identifying early changes in retinal function in diabetes. Two cohorts were investigated. The first cohort comprised 55 diabetic patients with various degrees of diabetic retinopathy. Using a cross-sectional design, we studied how refraction and visual acuity varied in patients under routine care (Study I), and we assessed limits for significant change in visual fields by use of standard automated perimetry (SAP) and short-wavelength automated perimetry (SWAP) based on short-term test–retest variability (Study II). The second cohort consisted of 81 diabetic subjects with no or mild/moderate diabetic retinopathy. We applied a longitudinal prospective design to explore the correlation between functional change and progression of microvascular abnormalities (Study III), and examined the usefulness of SAP with our limits of significant change for detecting early retinal dysfunction over 3–5 years (Study IV). In Study I, we demonstrated that refraction was stable in most eyes, and assessments of visual acuity were highly reproducible despite substantial fluctuations in blood glucose levels. In Study II, we defined limits of significant change for SAP and SWAP for diabetic subjects. In Study III, we used the defined limits for change to monitor visual function in diabetes by SAP. After 18 months of follow-up, deterioration was common but improvement was rare, and deteriorated fields were reproducible despite an unchanged degree of retinopathy. In Study IV, up to five years of follow-up, confirmed visual field deterioration in eyes without any retinopathy or with stable mild/moderate retinopathy. Standard automated perimetry with our new model for detecting change can successfully determine early retinal dysfunction over time in diabetes, which can represent early signs and progression of retinal neurodegeneration.
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