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János Németh

Publications and source records attributed to János Németh.

11 recordsLinked to original sources
PubMed2006

[Nucleotide sequence variants of the glucocorticoid receptor gene and their significance in determining glucocorticoid sensitivity].

Nucleotide sequence variants of the glucocorticoid receptor gene and their significance in determining glucocorticoid sensitivity. The physiologic response and sensitivity to glucocorticoids may significantly differ among species, individuals, tissues and cell types. The variability of the effect of endogenous and exogenous glucocorticoids is largely determined by genetic components, of which the authors review the knowledge on the glucocorticoid receptor gene. The authors describe the genomic and non-genomic pathways of receptor function, the significance of isoforms produced during receptor protein formation, the pathomechanism of glucocorticoid resistance syndrome and the results of clinical investigations related to receptor gene polymorphisms. Through subtle alteration of receptor function, the gene polymorphisms may increase or diminish sensitivity to glucocorticoids and may play a role in the pathogenesis of metabolic disorders. In their own studies the authors found, that the N363S polymorphism, which increases glucocorticoid sensitivity, may play a role in the pathogenesis of bilateral adrenal adenomas, it may modify the clinical phenotype of patients with congenital adrenal hyperplasia, and may have an impact on steroid-induced ocular hypertension. It is presumed that further research in other diseases will continue to complete our knowledge on the pathophysiology of glucocorticoid receptor gene polymorphisms.

Adenoma↗
PubMed2006

In vivo confocal laser scanning microscopy of the cornea in dry eye.

BACKGROUND: We carried out an investigation into the morphological and quantitative corneal properties in dry eye with various underlying pathologies. METHODS: Ten patients with aqueous tear deficiency, 8 with dysthyroid ophthalmopathy, 8 with chronic lagophthalmos and 10 normal participants were examined. Confocal microscope images were taken at the centre and at the lower and upper periphery of the cornea. Quantitative and morphological assessments of the epithelium, of the sub-basal nerves, of the stroma and the endothelium were made. The epithelial and corneal thicknesses were measured. RESULTS: The mean superficial and intermediate epithelial cell densities in the central cornea in the patient groups were significantly lower than in normal participants (p<0.01). The peripheral epithelial thickness was smaller (p<0.01); it was smallest in the lagophthalmos group. The cornea was thinner in the patient groups (p<0.01). For sub-basal nerves, the density had decreased (p<0.05), and in lagophthalmos the number of beadlike formations had increased (p<0.001); in some patients we found irregular branching patterns. CONCLUSIONS: Dry eye patients showed significant alterations in the cornea, presumably due to increased desquamation of the superficial cell layer. This was most pronounced at the lower periphery of the cornea in patients with exposure keratopathy.

Aged↗
PubMed2006

Dynamics of ocular surface topography in healthy subjects.

Our topography system is an enhancement of a standard TMS-1 corneal topograph instrument (Computed Anatomy Inc., New York, NY, USA). Topographic images are captured at a rate of 4 s(-1), allowing the recording of a series of 120 images in 30 s after a complete blink. In this prospective preliminary study 15 healthy volunteers were examined. The main outcome measures were the time profile of changes in surface regularity index (SRI), surface asymmetry index (SAI) and simulated keratometry values (K1, K2). After a blink there was a tendency for improvement in ocular surface regularity. Later trends were less clear. Our topography system makes possible the detailed evaluation of tear-film dynamics in the post-blink period. The new technique may play an important role in the diagnosis of various tear-film abnormalities; the results may also have significant implications in the planning of refractive surgeries.

Adult↗
PubMed2005

[Evaluation of color Doppler imaging of ophthalmic tumors based on histopathologic findings].

PURPOSE: To examine retrospectively the diagnostic and differential diagnostic value of color Doppler imaging (CDI) in cases of suspected intraocular and orbital tumors. PATIENTS AND METHODS: Color Doppler examination (using Acuson 128, Philips-ATL UM-9, HDI 3000, 5000, Siemens Elegra, GE Logiq9) was performed in a total of 194 patients (177 intraocular, 17 orbital tumors). The results were compared to the clinical findings (routine examination, conventional ultrasound examination) and the results of angiography (FLAG, ICG). Furthermore, in 73 cases histopathology records were obtained for comparison. RESULTS: Signs of blood flow could be detected in 137 cases (71%); the Doppler spectrum was low resistance in the large majority (130) of these cases. In cases where histopathology records were available, 60 of the 73 (82%) showed good concordance between the CDI diagnosis and the pathological results. CDI gave false positive results in 3, and false negative findings in 10 cases; the latter occurred mainly in small iris or ciliary body tumors. CONCLUSIONS: Using CDI, blood flow is demonstrable in the majority of intraocular and orbital tumors, especially if the tumor diameter is larger than 3 mm. CDI flow detection, however, is less reliable for iris or ciliary body tumors.

Adult↗
PubMed2005

Spontaneous alterations of the corneal topographic pattern.

PURPOSE: To assess whether the type of corneal topographic pattern is stable during a 1-minute pause in blinking in healthy subjects. SETTING: First Department of Ophthalmology, Semmelweis University, Budapest, Hungary. METHODS: Corneal topographic images were recorded 5, 15, 30, and 60 seconds after a complete blink in the right eyes of 36 healthy subjects using the TMS-1 instrument in a prospective observational study. The topographic pattern of each image was assessed from the color-coded topographic map and classified into 5 groups (in order of decreasing regularity: round, oval, symmetric bow-tie, asymmetric bow-tie, and irregular). RESULTS: During the 60-second period, a change in the type of topographic pattern was found in 19 subjects (53%), whereas in 17 subjects (47%) the pattern was stable. The alteration of the topographic pattern was statistically significant (P<.001). CONCLUSIONS: Immediately after blinking, the ocular surface regularity improves, possibly due to the building up of the tear film. This is followed later by the distortion of the ocular surface, which is the precursor of the tear-film break up phenomenon. Because of these changes, even in healthy eyes, the optimization and standardization of the postblink time of topographic image capture are very important, especially for planning refractive surgery.

Adult↗
PubMed2003

Optical and ultrasound measurement of axial length and anterior chamber depth for intraocular lens power calculation.

PURPOSE: To evaluate the precision, reproducibility, and applicability of an optical method based on partial coherence interferometry for intraocular lens (IOL) power calculation. SETTING: Ultrasound laboratory of a university eye hospital. METHODS: A prospective comparison of measurements made by the IOLMaster optical instrument (Carl Zeiss) and Ultrascan Digital 2000 contact ultrasound A-scan (Alcon) for IOL calculations was performed. Examined were 255 eyes of 134 persons (204 phakic, 47 pseudophakic, and 4 aphakic). The mean age of the patients was 67.9 years (range 7 to 94 years). RESULTS: The IOLMaster measurements were successful in more than 80% of cases: in 82%, 99%, and 99% for axial length (AL), anterior chamber depth (ACD), and keratometry measurements, respectively. The reproducibility of the AL and ACD measurements was very high (coefficient of variation 0.13% and 2.20%, respectively). The AL and ACD values were significantly larger with the IOLMaster (P <.001) than with the Ultrascan Digital 2000. The correlation between ultrasound and optical AL measurements was high (r = 0.985; P <.001); however, there was no correlation between ACD measurements (r = 0.079; P =.397). The corneal refractive power measurements of a Javal-type keratometer and the IOLMaster were highly correlated (r = 0.955; P <.001), with a mean difference of 0.2 diopter. CONCLUSIONS: The results show that measurements for IOL calculation are easy and precise with the optical method. It is a noncontact method, so no anesthesia is needed and there is no risk of infection.

Adolescent↗
PubMed2003

The diameters of the human retinal branch vessels do not change in darkness.

PURPOSE: To examine whether the diameters of retinal branch vessels of the human eye change during dark and light adaptation. METHODS: Images (S-VHS recordings) were obtained of the peripapillary region in 11 eyes of 11 healthy young adults (seven women, four men; mean age, 26.4 years). The images were made under a sequence of different illumination conditions (light, 30 minutes of darkness, light) with a scanning laser ophthalmoscope (SLO), using near-infrared illumination (785 nm). The recordings were then analyzed with a retinal vessel analyzer (RVA), and the caliber changes of one branch artery and one vein were measured in each eye. RESULTS: For arteries, the changes of diameter under different illumination conditions showed no clear trend, and comparisons between the different time sections revealed no statistically significant changes (P = 0.933; repeated measures ANOVA). There was a slight dilation (average, 0.9%; range, -3.9% to +5.1%) in darkness, and a return to baseline (range, -2.9% to + 2.9%) on restoring normal illumination. Veins during darkness showed a small but fairly consistent constriction (average, 1.5%; range -5.4% to +3.9%; significant P = 0.05), again returning to baseline (range, -2.1% to +2.6%) in normal light. CONCLUSIONS: The small changes of retinal branch vessel diameters under different light conditions probably have little influence on the possible changes of retinal blood flow in healthy subjects.

Adult↗
PubMed2002

Different autoregulation response to dynamic exercise in ophthalmic and central retinal arteries: a color Doppler study in healthy subjects.

PURPOSE: Prospective examination of the influence of changes in heart rate, arterial blood pressure and intraocular pressure induced by short dynamic exercise on orbital blood-flow velocities, and comparison of the autoregulation response in the ophthalmic artery and the central retinal artery. METHODS: Twelve young healthy volunteers were involved in the ophthalmic artery study and 12 others in the central retinal artery study. Blood-flow velocities were measured using color Doppler imaging before and after exercise. RESULTS: After exercise systolic blood pressure and heart rate were higher ( P<0.004) and intraocular pressure was lower ( P<0.006). However, in the central retinal artery the mean flow velocity, end-diastolic velocity and resistive indices remained stable, while in the ophthalmic artery these velocities actually decreased, and resistive indices increased significantly ( P<0.005). In the central retinal vein the velocities showed no significant change. CONCLUSION: Our results confirm the presence of an effective compensatory autoregulation for the retinal circulation, in connection with an increase in the ocular perfusion pressure induced by exercise. However, we found that in the ophthalmic artery some over-compensation occurs (significant decrease in some velocity parameters), whereas in the central retinal artery important flow parameters (mean velocity, end-diastolic velocity and resistive indices) appear to be successfully stabilized. Exercise history, heart rate, blood pressure and intraocular pressure all have to be monitored in orbital blood flow studies, as these variables are strongly affected by the changes in the autonomic nervous system and in turn significantly influence the measured flow velocity and resistivity values.

Adult↗
PubMed2002

High-speed videotopographic measurement of tear film build-up time.

PURPOSE: To detect tear film regularity changes in the 15 seconds after a blink, by using a new high-speed videotopographic method. METHODS: The new system, based on a standard corneal topograph, allows registration of four photokeratoscopic images per second. Altogether, 15 eyes of 15 healthy volunteers and 7 eyes of 7 patients with dry eye were examined in this prospective preliminary study. The main outcome measures were changes in surface regularity index (SRI), surface asymmetry index (SAI), and corneal power. RESULTS: The corneal surface became more regular in the first few seconds after a blink. In healthy eyes, the trend line of SRI and SAI decreased (improved) significantly (P < 0.001) after a blink, in 10 of 15 eyes for the SRI and in 13 of 15 for the SAI. In the typical cases, the trend line for SRI reached its minimum level, on average, at 7.1 +/- 3.9 seconds after a blink and that for the SAI at 5.4 +/- 2.7 seconds. Similar trends were found in the dry-eye group. The changes in keratometric measures were small (mean range, <1.5% of the absolute value) and showed no definite trends. CONCLUSIONS: High-speed videotopography provides the possibility of quantitative measurement of tear-film dynamics and may have clinical value in the management of ocular surface disorders. After a blink, it takes the tear film approximately 3 to 10 seconds (tear film build-up time) to reach the most regular state. However, despite surface-regularity changes, the measured corneal powers are stable.

Adult↗
PubMedDate not supplied

Observer experience improves reproducibility of color Doppler sonography of orbital blood vessels.

PURPOSE: The study investigated the reproducibility of orbital blood flow measurements with color Doppler imaging (CDI) at different stages of observer experience. METHODS: The subjects were 31 healthy volunteers and 2 sequential groups of 25 glaucoma patients each. Repeated blood flow measurements (usually 3 sets) in orbital vessels (ophthalmic artery, short posterior ciliary arteries, central retinal artery, and central retinal vein) were performed by the same observer in a single session in each subject. RESULTS: The parameters with the best reproducibility were the resistance index (mean coefficient of variation [COV], 3.3-8.8%), the peak systolic velocity (mean COV, 6.9-13.7%), the time-averaged velocity (mean COV, 7.2-16.0%), and the systolic acceleration time (mean COV, 8.8-12.3%). The mean COV was greater (9.9-20.3%) for the other arterial flow parameters (end-diastolic velocity and systolic acceleration) and for the venous flow velocities (maximum and minimum). The COVs of the parameters were improved by 20-40% as the observer became more experienced in ophthalmic CDI. CONCLUSIONS: We confirm the general reliability of CDI measurements in orbital vessels and show that observer experience improves reproducibility. It appears, however, that observer performance in these measurements is vessel specific.

Adolescent↗