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S Demirel

Publications and source records attributed to S Demirel.

29 records · Page 2Linked to original sources
PubMed1998

False-response monitoring during automated perimetry.

PURPOSE: To ascertain the accuracy and precision of the catch-trial monitor used to estimate the false-response rate in automated perimetry. METHODS: False responses were automatically injected at various rates by modified perimetric software while reliable perimetric subjects underwent visual field thresholding. Four repeat tests were conducted within a 1-hour period to quantify the variability and bias inherent in the catch-trial technique. RESULTS: The catch-trial method gave a very accurate estimate of the average false-response rate. Precision, however, was quite poor because of the small sample of catch trials. Outcomes were predicted using a binomial model, and we demonstrated good concordance between the model and empirical data. When the true false-response rate was 33%, estimates derived from catch trials ranged from 7 to 57%. CONCLUSIONS: Although the catch-trial method gave an accurate estimate of the false-response rate, confidence intervals were too wide to provide a high level of precision. Our data suggest that tests with reported false-response rates < 20% may be considered reliable.

Adult↗
PubMed1998

Improvement of uremic autonomic dysfunction after renal transplantation: a heart rate variability study.

Autonomic dysfunction in hemodialysis patients is one of the components of uremic neuropathy. In this prospective study, we investigated the effect of renal transplantation on uremic autonomic dysfunction with long-term time-domain and frequency-domain heart rate variability. Fourteen hemodialysis patients (10 male, 4 female; mean age 33 +/- 11 (range 16-50) years) were examined before and at the early after transplantation period (mean 4.6 +/- 1.5 (range 3-7. 5) months). The mean time spent on hemodialysis was 16.7 +/- 15.6 (range 6-65) months. In time-domain analysis, significant increases in all parameters except pNN50 (SD, SDANN, SDNN, rMSSD) were observed after renal transplantation (p < 0.01). In frequency-domain analysis, low-frequency (LF) (0.04-0.15 Hz) and high-frequency (HF) (0.15-0.40 Hz) spectral power were found to be significantly increased after renal transplantation (4.54 +/- 1.04 vs. 12.58 +/- 8. 69 for LF (p = 0.005), 2.80 +/- 1.0 vs. 6.50 +/- 3.55 for HF (p = 0. 005)), but the LF/HF ratio was not different from a pretransplant period (1.71 +/- 0.349 vs. 1.85 +/- 0.49, p = 0.26). It was concluded that autonomic dysfunction in hemodialysis patients is reversible and renal transplantation reverses the sympathetic and parasympathetic autonomic dysfunction simultaneously and at a relatively early stage.

Adolescent↗
PubMed1997

Multiple vascular leiomyomas involving bilateral adrenal glands, spleen, and epicardium, associated with bilateral testicular microlithiasis and empty sella turcica.

Leiomyomas can arise from any tissue having smooth muscle as one of its constituents, especially gastrointestinal and genitourinary systems, less frequently in the skin, and rarely in deep soft tissue. An unusual case of multiple vascular leiomyomas involving bilateral adrenal glands, spleen, and epicardium, associated with bilateral testicular microlithiasis, and empty sella turcica is reported in a 15-year-old boy. The adrenal masses were incidentally discovered by ultrasonography. These three findings, taken individually are rare, and the constellation of the three, to the best of our knowledge, is the first recorded example. Furthermore, bilateral involvement of the adrenal glands with leiomyomas is, by itself, very uncommon. The tumors considered benign were surgically removed. Orchiectomy wasn't performed. The boy is well after 1.5-year follow-up under cortisone, 9alpha-fludrocortisone, and testosterone therapy.

Adolescent↗
PubMed1997

The frequency of consanguinity in Konya, Turkey, and its medical effects.

This study was conducted in the town of Konya, Turkey, on 1120 randomly selected women to find out the overall rate of consanguineous marriages among couples. The frequency of consanguineous marriages was found to be 23.2%. It was found that 14.6% of this figure was first cousin marriages and the rest was 8.6%. Consanguineous marriages were higher among women born in villages compared to those born in provinces and the town center. Based on the findings, it was not too difficult to say: the higher the level of education of women, the lower the rate of consanguineous marriages. The number of children with an abnormality was high in consanguineous marriages, while the frequency of spontaneous abortion, still-birth and infant death remained the same.

Abortion, Spontaneous↗
PubMed1997

Heart rate variability in patients with secondary amyloidosis.

Heart rate variability (HRV) is increasingly being used to evaluate the function of the autonomic nervous system. Although autonomic dysfunction has been described in primary amyloidosis patients, this has not been established for patients with secondary amyloidosis. This study examines the autonomic function of 23 biopsy-proven secondary amyloidosis patients (10 male, 13 female) and compares it with 19 healthy (8 male, 11 female) sex- and age-matched controls (Group III), using frequency- and time-domain HRV analysis. The study group was further divided according to renal function; Group I (14 nonuremic patients with serum creatinine level < 1.4 mg/dl) and Group II (9 uremic patients with serum creatinine level > 1.4 mg/dl). In time domain analysis, standard deviation and mean of the standard deviation of all normal R to R intervals, and standard deviation of the average normal R to R interval were significantly lower in Groups I and II as compared to Group III. In frequency domain analysis, low frequency power (LF), representing sympathetic function, was significantly lower in Groups I and II as compared to Group III, but high frequency power (HF), representing parasympathetic function, and the LF/HF ratio, as an index of sympathovagal balance, were not different among the groups. In conclusion, in patients with secondary amyloidosis, sympathetic components of heart rate variables decreased before the onset of uremia and the change became more prominent with the appearance of uremia despite not reaching statistical significance.

Adult↗
PubMed1996

Transcranial magnetic stimulation: delays in visual suppression due to luminance changes.

Transcranial magnetic stimulation (TMS) was used to investigate the delays in visual processing time produced by changes in luminance. By administering a magnetic pulse over the occipital pole 80-140 ms after the onset of visual stimuli, we could suppress perception of a four-digit number within a 30 ms time window. Commensurate with previous studies of visual processing latencies, a drop in luminance from 3.52 logTd to 2.61 logTd delayed the peak of the suppression window by 8.9 ms, while a further drop from 2.61 logTD to 1.75 logTd delayed the peak by an additional 15.4 ms. This study validates the use of TMS as a psychophysical tool.

Adult↗
PubMed1996

Short wavelength automated perimetry (SWAP) in ophthalmic practice.

BACKGROUND: Short Wavelength Automated Perimetry (SWAP) uses a two-color increment threshold procedure (blue-on-yellow) to assess the functional status of short-wavelength-sensitive (SWS) mechanisms. This functional test has been shown to detect visual field abnormalities in patients at high risk of developing glaucoma and in patients with optic neuritis when standard (white-on-white) visual fields are still within normal limits. Often times, damage uncovered by SWAP precedes standard field loss by three or more years. SWAP also reveals a greater spatial extent of visual field damage in glaucoma patients than standard perimetry and can herald progression of standard visual field damage into the areas already classified as abnormal by SWAP. METHODS/RESULTS: This paper describes the SWAP technique and briefly discusses the current theories that account for SWAP's ability to detect visual field damage at an earlier stage than standard perimetry. Several cases that demonstrate the usefulness of this technique are reported. CONCLUSIONS: SWAP testing appears to be the most sensitive functional test for early detection of glaucomatous damage currently available. Although SWAP testing has a few disadvantages, none of them significantly restrict the clinical application of SWAP for glaucoma evaluation.

Aged↗
PubMedDate not supplied

Heart rate variability in diabetes patients.

Diabetes mellitus can cause cardiovascular autonomic neuropathy and is associated with increased cardiovascular deaths. We investigated cardiovascular autonomic neuropathy in diabetics and healthy controls by analysis of heart rate variability. Thirty-one diabetics and 30 age- and sex-matched controls were included. In the time domain we measured the mean R - R interval (NN), the standard deviation of the R - R interval index (SDNN), the standard deviation of the 5-min R - R interval mean (SDANN), the root mean square of successive R - R interval differences (RMSSD) and the percentage of beats with a consecutive R - R interval difference > 50 ms (pNN50). In the frequency domain we measured high-frequency power (HF), low-frequency power (LF) and the LF/HF ratio. Diabetes patients had lower values for time-domain and frequency-domain parameters than controls. Most heart rate variability parameters were lower in diabetes patients with chronic complications than in those without chronic complications.

Adult↗