PubMed Health⌕ Search

Biomedical subjects

I M Velten

Publications and source records attributed to I M Velten.

10 recordsLinked to original sources
PubMed2002

[Multifocal ERG with 30 Hz flicker stimulation in glaucoma patients and normal probands].

BACKGROUND: It was the aim of the present study to investigate the value of multifocal ERG with 30 Hz flicker stimulation for glaucoma diagnosis. METHODS: Multifocal ERGs with 30 Hz flicker stimulation were recorded with a mean luminance of 50 cd/m2 and a contrast of 99% from the central 60 degrees of the retina which were stimulated by 61 hexagons. From 30 patients with primary and secondary open-angle and low-tension glaucomas with reproducible visual field losses and glaucomatous optic disc atrophy and 21 normal subjects, one eye was included in the study. The first harmonic wave, the basewave and the ratio of these two parameters were ana-lysed. The responses of seven neighbouring hexagons were averaged for the intraocular comparison between areas with and without perimetric defects and for the comparison between glaucomas and normal subjects. RESULTS: In the glaucoma group, the ratio of the first harmonic wave and the basewave was significantly lower in an area within a perimetric defect than outside the defect (p < 0.001) when compared intraocularly. The extent of ERG changes however did not correlate with the extent of perimetric defects. Comparing the glaucoma with the normal group, the ratio of the first harmonic and the basewave was significantly lower in an area within the perimetric defect in the glaucoma group than in corresponding areas of the normal group (p = 0.002). The first harmonic and the basewave did not differ significantly. DISCUSSION: These results show that the method is not appropriate to objectively indicate visual field losses although it statistically separates glaucomas from normal subjects.

Adult↗
PubMed2001

The a-wave of the dark adapted electroretinogram in glaucomas: are photoreceptors affected?

AIMS: To evaluate whether the a-wave of the dark adapted flash electroretinogram (ERG) is affected by glaucomatous damage. METHODS: ERGs were recorded in 20 patients (age 33-65 years) with advanced glaucomas (primary and secondary open angle and low tension glaucomas) and 20 normals using a ganzfeld stimulus. After 30 minutes of dark adaptation and pupil dilatation to at least 7.5 mm in diameter, luminance response functions were obtained presenting white flashes of increasing scotopic luminance (the highest flash intensity being 9.4 cd/s/m2, the lowest being 5.75 log units below it) with an interflash interval of 5 seconds. For each scotopic luminance, the responses of four flashes were averaged. The a-wave's amplitude was measured at 10, 11, and 12 ms. Within the glaucoma group, correlations between the interocular differences of the a-wave's amplitude and the mean deviation of a static perimetry (Octopus 500 perimeter, program G1) were computed for all flash intensities. Between normals and glaucomas, the a-wave's amplitude was compared for all flash intensities (paired t test). RESULTS: Within the glaucoma group, the interocular differences of the a-wave's amplitudes correlated significantly with the differences of the MD for flash intensities of 9.4, 5.3, 1.7, and 0.5 cd/s/m2. The a-wave's amplitude was significantly lower in the glaucoma compared with the normal group (p <0.005) for flash intensities of 9.4 and 5.3 cd/s/m2. CONCLUSION: These electrophysiological results imply that also the outer retinal structures, especially the photoreceptors, may be affected by glaucomatous damage.

Adaptation, Ocular↗
PubMed2001

The b-wave of the dark adapted flash electroretinogram in patients with advanced asymmetrical glaucoma and normal subjects.

AIMS: To evaluate whether the b-wave of the dark adapted flash electroretinogram (ERG) is affected by glaucomatous damage. METHODS: ERGs were recorded in 35 patients aged 33-65 years with advanced asymmetrical glaucomas (interocular difference of perimetric defects (mean deviation) >2 dB between the two fellow eyes of the glaucoma patients, primary and secondary open angle and low tension glaucomas) and 17 normal subjects matched for age and sex using white flashes of a xenon discharge tube in a Ganzfeld stimulator. After 30 minutes of dark adaptation luminance response functions were obtained using flashes of increasing scotopic luminance (highest 9.4 cd/s/m2, lowest 5.5 log units below it). The parameters Vmax, n, and K of the Naka-Rushton equation were computed from the measurement values based on the usual fitting procedure. These parameters, together with b-wave amplitudes and implicit times for all flash intensities, were compared interocularly and between the normal subjects and those with glaucoma. Correlations were computed between interocular differences of the mean deviation and interocular differences of Vmax, n, K, b-wave amplitudes, and implicit times between the two fellow eyes of the patients with asymmetrical glaucomatous damage. RESULTS: Implicit times were significantly longer (p<0.005) in the glaucoma patients than in the normal group for flash intensities of 9.4, 5.3, 1.7, 0.53, and 0.17 cd/s/m2. b-Wave amplitudes did not differ significantly between the two study groups. Comparing the two fellow eyes of each patient with glaucoma, Vmax was significantly higher in the less damaged eye than in the more damaged eye. The interocular differences in the mean deviation correlated significantly with the interocular differences in the b-wave amplitudes, implicit times, and Vmax. CONCLUSIONS: These results suggest that glaucomas can lead to electrophysiologically measurable damage of the inner nuclear layer.

Adaptation, Ocular↗
PubMed2000

[Central corneal thickness in normal eyes, patients with ocular hypertension, normal-pressure and open-angle glaucomas--a clinical study].

BACKGROUND: The relation between Goldmann applanation tonometry and central corneal thickness (CCT) was investigated in several studies during the last thirty years. It was the aim of the present study to evaluate CCT in normals, patients with ocular hypertension, low-tension, and open-angle glaucomas. PATIENTS AND METHODS: CCT was measured in 135 normal eyes, 137 with ocular hypertension, 65 with low-tension, and 94 with primary and secondary open-angle glaucomas using the AL-11000-pachymeter (Tomey). The results were compared using the unpaired t-test. RESULTS: CCT was significantly higher in the patients with ocular hypertension (586 +/- 43 microns) than in the normal group (566 +/- 37 microns, p < 0.0001), in low-tension glaucomas (555 +/- 46 microns, p < 0.0001), and in open-angle glaucomas (558 +/- 31 microns, p < 0.0001). The latter three groups did not differ significantly. There was no significant correlation between CCT and age, the actually measured IOP, the highest IOP in the patient's history, or the spherical equivalent. CONCLUSIONS: Only patients with ocular hypertension showed a significant difference in CCT compared with normals. Pachymetry thus should be conducted in those patients to avoid overestimation of the IOP by applanation tonometry. In most of the patients with low-tension and open-angle glaucomas however, CCT regarded without other parameters (e.g. corneal or scleral rigidity) plays a minor role in detection of elevated IOP according to the results of this study.

Adolescent↗
PubMed2000

[Diplopia as first symptom of a bronchogenic carcinoma].

BACKGROUND PATIENTS: In about 30% of patients with orbital metastases, these metastases are detected before the primary tumour is known. Less than 5% of orbital metastases are located in extraocular muscles. We report on a patient with diplopia caused by diminished abduction of the left eye as first symptom of a bronchogenic carcinoma. PATIENT: A 86-year-old patient presented with a newly developed diplopia. On examination, the left eye showed a diminished abduction, ptosis and miosis. Pharmacological testing revealed peripheral Horner's syndrome. On cranial magnet resonance tomography, the lateral rectus muscle belly was enlarged. A chest X-ray showed a large tumour (6 cm in diameter) of the left upper lobe with multiple metastases to the lungs. Further examinations revealed a large cell bronchogenic carcinoma with metastases to the lungs, adrenal glands, and the lateral rectus muscle. CONCLUSIONS: Diplopia caused by metastases to extraocular muscles is rare as first sign of a bronchogenic carcinoma. The combination of peripheral Horner's syndrome with diminished abduction of the homolateral eye primarily suggests a lesion of the cavernous sinus. The bronchogenic carcinoma could not be causative for Horner's syndrome in the patient presented here, however an undetected tumor-infiltration of the postganglionic region cannot be excluded. This case demonstrates that in all patients with newly developed diplopia and Horner's syndrome, even in absence of orbital signs, apart from a ophthalmological examination detailed radiographic or magnetic resonance tomographic imaging is necessary of both skull base and orbita.

Aged↗
PubMed1999

The full-field flicker test in glaucomas: influence of intraocular pressure and pattern of visual field losses.

BACKGROUND: The purpose of this study was to evaluate how temporal contrast sensitivity (TCS) determined with full-field flicker stimuli is influenced by intraocular pressure and whether TCS is reduced in glaucoma patients with diffuse perimetric losses as well as in patients with localized visual field deficits. METHODS: TCS was determined with sinusoidally flickering light (37.1 Hz) in a full-field bowl. Perimetric mean defect (MD) and cumulative defect curves (Octopus G1) were used to distinguish between patients with localized and diffuse field deficits. Normal subjects (296), low-tension glaucoma patients (98) and open-angle glaucoma patients with previously elevated intraocular pressure (541) were classified into five subgroups taking into account the depth of their visual field losses. RESULTS: No significant correlation between full-field flicker sensitivity and prevailing intraocular pressure was found in normals (Y=1.36+0.006 X) or in patients (Y=0.95-0.0002 X). Analyses of validity at a predefined specificity of 90% reveal a reduction of TCS in patients with early (MD<5 dB) diffuse perimetric losses (sensitivity 69%) as well as in those showing localized visual field defects (sensitivity 65%). Sensitivity was 87% in patients with diffuse perimetric defects (MD 5-10 dB), 93% in a group of patients with both types of losses, and 100% in advanced glaucomas (MD>20 dB). The lack of TCS is similar in open-angle glaucomas and in field-loss-matched normal-tension glaucoma patients. CONCLUSIONS: Significantly reduced TCS in patients with early diffuse perimetric losses as well as in those showing localized visual field defects indicates that localized damages can be associated with general deterioration of the ability to perceive flickering stimuli. Thus, this flicker test can be performed in a full-field bowl with no need for fixation. Considering its other clinical qualities (photopic conditions, low influence of prevailing intraocular pressure and media opacity) the test may be a useful, convenient supplementary procedure in glaucoma screening.

Chronic Disease↗
PubMed1999

[Does corneal ocular "pseudo-hypertension" exist?].

BACKGROUND: The relation between Goldmann applanation tonometry and central corneal thickness (CCT) was evaluated in several studies during the last thirty years. Patients with ocular hypertension were found to have a significantly higher CCT compared with normals and glaucomas. PATIENTS: To report on two sisters with elevated CCT and ocular hypertension diagnosed by raised intraocular-pressure (IOP) readings on Goldmann applanation tonometry. RESULTS: In both patients, there were no signs for early functional or morphological glaucomatous changes. Maximum IOP was 30 mm Hg and 26 mm Hg. The corneal pachymetry revealed an increased CCT in both patients (700 and 680 microns, respectively), while corneal morphology was normal. CONCLUSIONS: Ocular hypertension can be misdiagnosed by too high applanation tonometer readings in patients with markedly elevated CCT. Before the onset of treatment thus, corneal pachymetry should be performed in patients with ocular hypertension to exclude ocular "pseudohypertension" and to avoid unneccessary treatment.

Adolescent↗
PubMed1999

Temporal contrast sensitivity with peripheral and central stimulation in glaucoma diagnosis.

AIMS: To evaluate temporal contrast sensitivity with full field, peripheral, and central stimulation and to determine the most sensitive corresponding retinal area for glaucoma damage. METHODS: Temporal contrast sensitivity was determined either with a full field, a peripheral annular area from 30 degrees to 90 degrees, or a central area from 0 degree to 30 degrees at a frequency of 37.1 Hz. 232 eyes of 232 subjects were included. They were classified into four groups: eyes with ocular hypertension (OHT, n = 54), "preperimetric" glaucomas (n = 73) with glaucomatous optic disc abnormalities but no visual field loss, "perimetric" glaucomas (n = 53) with visual field loss, and 52 normals. RESULTS: In all four groups, temporal contrast sensitivity was almost equal with full field and peripheral, but significantly higher than with central stimulation (p < 0.001). With regard to the diagnostic power of the three different stimulus areas, OHTs and glaucomas were found to be best discriminated from normals by peripheral stimulation. CONCLUSIONS: According to these results, temporal contrast sensitivity seems to be determined by peripheral retinal areas. As the diagnostic power of the three different stimulus areas was best with the peripheral stimulation, this condition should be used for early glaucoma diagnosis.

Adult↗