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R Stodtmeister

Publications and source records attributed to R Stodtmeister.

At least 19 recordsLinked to original sources
PubMed1995

[The Behavior of Visual Evoked Cortical Potentials during and after an Artificial Increase in Intraocular pressure].

Previously, it has been shown that in healthy persons the function of the eye assessed by visual evoked cortical potential (VECP) amplitudes changes in a characteristic way during stepwise artificial elevation of intraocular pressure (IOP). It has been demonstrated that a stepwise increase in IOP leads to a decrease in the amplitude followed by an increase or a stabilization of the function during a further rise of IOP. At pressure values of 62 mmHg, the amplitude falls to the noise level. In order to examine whether this behaviour can also be observed if the procedure is reversed, we initially increased the IOP to values, at which the VECP amplitudes could not be distinguished from noise (standstill pressure). During a subsequent stepwise decrease in the artificially increased IOP, we investigated 5 persons. The function did not recover before the IOP had reached values below 46 mmHg. Thus, at the same IOP value, the VECP can assume different amplitude values depending on wether the pressure rises or falls. In 24 further persons, the artificial IOP increase was decreased directly to the starting values. The function recovered immediately. Factors influencing the eye shape (e.g. astigmatism), as ascribed at artificially increased IOP, cannot explain the different behaviour of VECP amplitudes in the experiments done here, because mechanical changes are the same in IOP increase and its reverse. But the behaviour observed here is not contradictory and can be explained by the known characteristics of microcirculation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

[Simultaneous registration of VECP and pattern ERG during artificially raised intraocular pressure].

The visual evoked cortical potentials (VECP) are changed by the artificial increase in intraocular pressure (IOP). The exact location of the damage is still unclear. One possibility is that the increased ocular pressure reduces the blood flow in the optic nerve head. The function of the optic nerve fiber function would be decreased by this effect. Another possibility is that the generation of the signals in the retinal ganglion cells could be influenced by the artificial pressure enhancement. We developed a method of simultaneous recording pattern reversal electroretinograms (PERG) and VECP during artificially raised IOP. The PERG was recorded by cutaneous electrodes (Grass, USA; diameter 5 mm), which were positioned close to the lid margins. The pattern reversal rate was 7.9 reversals/s. In a pilot study, we examined 10 healthy volunteers with artificially increased ocular pressure. In 9 cases, amplitudes showed a more stable behavior in the VECP than in the PERG: the mathematical behavior of the amplitude/pressure curves was more stable in the VECP of 6 volunteers and once in the PERG. Signs of very sufficient autoregulation could be found in the VECP of 7 volunteers and once in the PERG. The critical pressure, at which a further increase in IOP causes a continuous amplitude decrease to the noise level, was 9 times more stable in VECP (median 53 mmHg) than in PERG (median 48 mmHg). The results lead to the conclusion that in healthy persons the artificial pressure rise influences the ganglion cells at an earlier timepoint than the signal transmission in the axons.

Adult↗
PubMed1994

[Fourier analysis of transient VECP in artificially increased intraocular pressure].

Usually, amplitudes and latencies are measured to analyze visual evoked cortical potentials (VECP). From the physical point of view this means an analysis in the time domain. Generally it is possible to get important information on oscillations by testing to see which frequency the power is transmitted at (frequency domain). We made such experiments on visual evoked cortical potentials with Fourier analysis during an artificial stepwise rise in the intraocular pressure. We recorded the VECP of 60 healthy young persons at a stimulus rate of 1.9 checkerboard reversals/second and analyzed the curves by Fourier transformations. We proceeded in the same way with 30 volunteers using a stimulus rate of 3.1 checkerboard reversals/second. In comparison to the VECP curves without Fourier analysis, no systemic changes in the amplitude spectra appeared during the rise in intraocular pressure. Because of this we feel that Fourier analysis mostly renders no further information and is probably dispensable for experienced clinicians when testing pressure tolerance of the optic nerve head. On the other hand, the analysis clearly showed the appearance of distortion frequencies. This may be of clinical interest in cases of severe distortion and in patients with almost extinguished VECPs. It might also be helpful to clinicians who are less experienced in electrophysiology.

Adult↗
PubMed1993

Comparison of apraclonidine and timolol in chronic open-angle glaucoma. A three-month study.

PURPOSE: To compare the safety and efficacy of apraclonidine ophthalmic solution 0.25% and 0.5% (both given 3 times daily) to timolol maleate (0.5%) given twice daily, in primary open-angle glaucoma or ocular hypertension. METHODS: This study was a 90-day prospective, multicenter, double-masked, randomized, parallel group trial. Intraocular pressure (IOP) measurements were made between 8:00 and 10:00 AM before the morning dose (i.e., up to 12 hours after the evening dose of glaucoma medication) and at 4:00 PM (i.e., 8 hours after the morning dose of glaucoma medication). Patients with off-therapy IOP of greater than 22 mmHg and less than 35 mmHg were entered into the study and were assessed 14, 30, and 90 days after treatment. RESULTS: Sixty-nine patients were enrolled; there were no significant demographic differences among the three study groups. All three treatments significantly reduced IOP over 90 days (P < 0.011). For apraclonidine 0.5%, IOP reductions from 25.8 +/- 3.2 mmHg (pretreatment) to 20.4 +/- 4.00 mmHg (day 90) were observed; for apraclonidine 0.25%, from 25.7 +/- 3.05 mmHg (pretreatment) to 22.1 +/- 4.24 mmHg (day 90); and for timolol 0.5% from 26.1 +/- 3.79 mmHg to 21.1 +/- 5.91 mmHg (day 90). The 90-day period of therapy was completed by 12 patients treated with apraclonidine 0.5%, 21 patients treated with apraclonidine 0.25%, and 23 patients treated with timolol 0.5%. There were no serious adverse events. Fourteen of 22 patients (0.5% apraclonidine) and 21 of 23 patients (0.25% apraclonidine) tolerated the drug well; ocular allergy developed in the remaining patients treated with apraclonidine, which resolved upon discontinuation. CONCLUSIONS: Apraclonidine effectively lowers IOP associated with open-angle glaucoma or ocular hypertension; these pilot results will need to be confirmed by a larger pivotal study. Long-term therapy for some patients may be inhibited by ocular allergy for which there was a higher incidence to the 0.5% apraclonidine solution than to the 0.25% solution in this study. Apraclonidine may be of value as an additional therapy for open-angle glaucoma in selected patients.

Adult↗
PubMed1992

Averaged steady-state visual evoked cortical potentials at artificially raised intraocular pressure.

By recording steady-state visual evoked cortical potentials while intraocular pressure is artificially increased, information can be obtained on the pressure tolerance of the optic nerve head. Such experiments have previously been performed by a vector voltmeter technique. We studied the visual evoked cortical potentials in 30 healthy volunteers with artificially increased intraocular pressure, but we used an averager instead of a vector voltmeter. The results were similar except that the noise level in averaging was higher than with the vector voltmeter technique. This observation confirms that the signal-to-noise ratio is much better with the vector voltmeter technique than with the averaging technique. Our results show that averaging can be used in pressure tolerance testing, but the amplitude cannot be observed as far down as in the vector voltmeter technique. This limits the clinical value of averagers in this application.

Adult↗
PubMed1992

[Oculopression tonometry after argon laser trabeculoplasty].

A group of 26 patients (14 female and 12 male ranging in age from 49 to 84 years) who had primary open angle glaucoma underwent argon laser trabeculoplasty in one eye each. Shortly before the laser treatment, and one and twelve (7-14) weeks after the treatment suction cup oculopression tonometry was performed with an increase of intraocular pressure according to 1.8 x actual intraocular pressure. A therapeutically significant decrease of intraocular pressure was observed already one week thereafter, but findings become more significant after a longer follow up. The decrease of intraocular pressure and results of oculopression tonometry indicate that the measured resistance to aqueous outflow decreased significantly after argon laser trabeculotomy.

Aged↗
PubMed1992

Retinal capillary hemodynamics, visual-evoked potentials, and pressure tolerance in normal human eyes.

Twenty-three normal adult volunteers underwent single eye visual-evoked potential (VEP) and blue field entoptic studies during suction cup-induced intraocular pressure (IOP) elevation, to determine whether IOP-induced changes in VEP are related to alterations in retinal capillary hemodynamics. VEP pressure tolerance testing through an ascending series of 6-8 IOP levels was carried out using a 7.1 Hz reversing checkerboard grating, with amplitudes averaged by Nicolet Pathfinder. Nineteen of the 23 subjects (83%) showed an increase from baseline in their VEP amplitude at IOP values approximating to central retinal diastolic pressures. All subjects underwent subsequent blue field entoptic hemodynamic studies at each of four IOP values related to their VEP pressure tolerance curve--at baseline IOP, at IOP corresponding to the VEP amplitude peak, and at IOPs corresponding to trough points either side of this peak. Blue field studies were conducted in a masked fashion with pressures generated in semirandom sequence. VEP amplitude pressure tolerance curves were found to vary in strong positive concordance with retinal leukocyte velocity pressure tolerance patterns (P less than 0.001). Leukocyte density initially varied inversely to velocity and VEP amplitude, increasing marginally with initial IOP elevation, but then fell in parallel with velocity at IOP levels exceeding the VEP amplitude peak (P = 0.009). These findings indicate a strong interrelationship between retinal hemodynamics and visual pathway activity as measured by VEP, suggesting that vascular autoregulation may account for the characteristic pattern of the normal VEP pressure tolerance curve.

Adult↗
PubMed1991

[Iris fluorescence angiography findings in oculo-oscillodynamography].

Supported by irisfluorescein angiography it should be examined if systolic ciliary pressure found by oculooscillodynamography is to be seen in every part of the uvea. Iris vessels were found to be perfused at 42 mm Hg (Median, Q1-Q3 = 38-45 mm Hg) whereas oculooscillodynamography displayed systolic ciliary pressure to be 69 mm Hg (62-72 mm Hg). This different blood pressure in different districts of the uvea may be one explanation for the particular vulnerability of iris vessels e.g. in ischemic ophthalmopathy.

Adult↗
PubMed1991

[Standardized determination of pressure tolerance of the optic nerve head].

The early diagnosis of glaucoma relies on the detection of manifest damage in present-day clinical practice. The reason for such damage in glaucoma may be seen in the breakdown of the autoregulation of the circulation in the optic nerve head. This autoregulation can be assessed by the pressure tolerance test devised by ourselves which may detect glaucoma before manifest damage can occur. We demonstrate a standardized method in which the test procedure is controlled by a computer. In particular, the time course of the examination which is of crucial importance is exactly defined. The method is no more difficult to apply than automatic perimetry. We describe six examinations in seven subjects each. The results are analyzed by the estimation of variance components. The intraocular pressure shows an intraclass correlation of 0.41 and the critical pressure an intraclass correlation of 0.27. The intraindividual variability of critical pressure is mainly due to the widely known variability of intraocular pressure. The autoregulation behavior shows a very good constancy, which makes the test clinically useful in the differential diagnosis of glaucoma.

Adult↗
PubMed1990

[Examinations by ocular pressure tonometry].

A new method has recently been suggested for the determination of the outflow resistance in the anterior chamber angle. In this method the intraocular pressure is set to 45 mmHg for 8 minutes. The intraocular pressure is measured after the removal of the suction cup. Values below 7 mmHg are obtained in healthy subjects. Values above 7 mmHg are thought to be indicative for glaucoma. By setting the intraocular pressure to 45 mmHg for the expression of fluid the authors claim to have brought normalization to tonography. We show here in a series of results that we can reproduce the results which have been published by Ulrich et al. For normalization of a tonographic test we need a pressure rise which effects a uniform expression of volume. According to the knowledge presently generally agreed upon a uniform expression of volume is obtained by increasing the intraocular pressure by a constant factor and not by increasing it to a constant level. In 30 healthy volunteers and in 30 glaucoma patients we have increased the intraocular pressure by the constant factor of 1.8. According to our results the glaucoma patients and the healthy subjects can no longer be differentiated. A better differentiation is possible by the initial intraocular pressure. Thus we have shown that the favorable results by ocular pressure tonometry are mainly due to the intraocular pressure before the test. We feel therefore that ocular pressure tonometry should not be incorporated in our diagnostic armamentarium for glaucoma diagnosis.

Diagnosis, Differential↗
PubMed1990

[Suction cup ocular pressure versus Vörösmarthy oculopression. Biometry differences].

In a 20-min follow-up after oculopression, biometric measurements were taken before, immediately after, and 5, 10, 15 and 20 min after finishing oculopression. Thirty-two eyes were measured by ultrasound using the immersion technique with a 10 MHz A-scan probe. Sixteen cataract patients more than 50 years of age and 16 healthy young subjects up to 30 years of age took part in the study. Oculopression was performed either with a Honan Oculopressor or with a Mikuni and Yoneyama suction-cup oculodynamometer. The anterior chamber depth showed higher initial deepening following Honan oculopression, whereas the length of the vitreous was found to be shorter with the same method. Suction-cup oculopression revealed no distinct changes in these compartments. Nevertheless, 10 min after oculopression, there was no statistically significant difference between the two oculopression techniques. When comparing the age groups, the cataract patients showed more express change than the younger subjects.

Adult↗
PubMed1990

[Total average values of transient visual evoked cortical potentials in tests of the pressure tolerance of the optic nerve].

Transient visually evoked cortical potentials were recorded during an artificial stepwise rise of intraocular pressure. At each pressure step one average was taken. The reversal rate was 1.9 Hz. Two groups of 30 healthy volunteers each were examined: in group one 25 sweeps were averaged and in group two 50 sweeps. Thus the recording time in group two was doubled compared to group one. When all subjects were examined the evoked potentials of the 30 subjects were averaged at each pressure step: the results was a "Grand Average" at the different pressure steps applied. The amplitudes of N2-P2 were plotted versus the intraocular pressure. It is seen that a not monotone or weakly monotone function in the amplitude/pressure curve is more clearly seen in the averages of 25 sweeps. We interpret this result as follows: a not monotone or weakly monotone behaviour is a sign of autoregulation in the optic nerve head. This sign is more clearly shown at a short recording time. The majority of healthy persons show autoregulation, the majority of glaucoma patients do not. According to the results presented here it is advisable to apply short recording times in clinical pressure tolerance testing of the optic nerve head. A short recording time enhances the accuracy of the test.

Adult↗
PubMed1990

[The pressure tolerance test--a new technic in the differential diagnosis of glaucoma].

There can be a damage of optic nerve fibers without a known increase of intraocular pressure. This observation has led to the proposition to measure the pressure tolerance of the optic nerve head. An examination which is performing this task is feasible now with a recently introduced technique. In this paper clinically well defined borderline cases are presented in which the pressure tolerance test yields clinically valuable results. As shown paradigmatically the pressure tolerance test shows to be a valuable tool in the differential diagnosis of glaucoma.

Adult↗
PubMed1989

Ocular perfusion pressures in different types of glaucoma.

It is widely accepted that a disturbed blood supply of the optic disc may cause (in addition with an increased intraocular pressure) optic nerve fibre damage. Therefore we measured ocular perfusion pressures in 79 healthy subjects. In 18 patients with low tension glaucoma, in 27 patients suffering from ocular hypertension and in 49 glaucoma (OAG) patients. For measuring perfusion pressures we used the technique of oculo-oscillo-dynamography (OODG) as described by Ulrich. Additionally we measured intraocular pressure and systemic blood pressure. In OODG the IOP is simultaneously increased in both eyes by application of a suction cup. After increase of the IOP the negative pressure in the suction cup is slowly and linearly decreased. During this decrease the pulse-depending oscillations of each eye are recorded on a strip-chart-recorder. By means of this method retinal and ciliary perfusion pressures can be separated. As a result we could show that mean arterial blood pressure and systolic retinal perfusion pressure were comparable and not statistically significantly different between the groups examined. The systolic ocular perfusion pressures in patients with low tension glaucoma showed a highly statistically significant reduction compared with the other groups. Between healthy subjects, OAG-patients and patients suffering from ocular hypertension there was no difference in systolic ciliary perfusion pressure detectable.

Aged↗
PubMed1989

[Relation of negative pressure difference and artificially elevated intraocular pressure using the suction cup method].

This paper presents regressions and the range of scatter of measured values for current standard ophthalmologic suction cups for the first time. The scatter range is similar to that of blood pressure measurements made by the Riva-Rocci method. Using the regressions presented here it is possible to deduce the increase in pressure from the negative pressure difference in the suction cup; this can be done with sufficient accuracy and the amount of time required is acceptable.

Humans↗
PubMed1989

[Effect of carteolol and timolol eyedrops on the pressure tolerance of the optic nerve head].

In a planned, randomized, double blind study ocular perfusion pressures were measured before and after a 3-day regimen of 2% carteolol hydrochloride or 0.5% timolol maleate. A pressure tolerance test was also carried out. The results of this test revealed the critical pressure: it is the artificially increased intraocular pressure at which the visual function (monitored by visually evoked cortical potentials) is reduced to 20% of its initial value. The ocular perfusion pressures are affected by both drugs. They are more clearly reduced by carteolol than by timolol. The critical pressure is affected by both drugs too. After application of carteolol, the critical pressure is clearly lower than after application of timolol. The difference is statistically significant (p less than 0.05).

Adaptation, Physiological↗
PubMed1989

[Leydhecker tonography and Ulrich ocular pressure tonometry in probands with healthy eyes and glaucoma patients].

In the study presented here, we compared two methods of measuring the ocular drainage resistance in patients with primary open angle glaucoma and in healthy subjects: (1) 7-min tonography according to Leydhecker; (2) oculopression tonometry according to Ulrich. We examined 30 healthy subjects and 30 patients suffering from glaucoma. Seven-minute tonography according to Leydhecker and the oculopression tonometry according to Ulrich (OPT) were both performed in these two groups. By means of OPT, we determined the discrimination function D1, i.e. the difference between the intraocular pressure (IOP) before starting the test and the IOP after removing the cup. Using these function results, it was possible to differentiate sufficiently between healthy and glaucomatous eyes. Fifty-Five eyes (92%; 60 people examined) were correctly diagnosed, 3% were classified as false negative; 5% (3) as false positive. In comparison, tonography according to Leydhecker showed 10% (6) false negative and no false-positive cases. The results presented here did not show any significant differences between the two methods used. Therefore both methods are considered to be of equal value in clinical use.

Glaucoma, Open-Angle↗