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Biomedical subjects

R Stodtmeister

Publications and source records attributed to R Stodtmeister.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1988

[Ulrich and Ulrich oculo-oscillodynamography: results in patients with healthy eyes].

Ulrich and Ulrich's method of oculo-oscillodynamography (OODG) is a relatively new method which enables the systolic retinal, systolic ciliary, and systolic ocular perfusion pressure or respectively blood pressure to be measured. The results obtained by the present authors are in good agreement with those of Ulrich and Ulrich (n = 30). The intraocular pressure values obtained with this method correlate somewhat less well with the systemic blood pressure than is the case with suction cup ophthalmodynamometry. However, the correlation coefficients are sufficiently high to permit their application in ophthalmological diagnosis. The results presented here indicate that the diastolic ocular pressure should be determined by applying the formoscillatory criterion. The positive intercept in the regression equations can be explained by the assumption that the regression is curvilinear at systemic blood pressure values which are generally not encountered in humans in whom OODG is of diagnostic importance. It is suggested that the linear regression is a sufficiently exact model at the systemic blood pressures most frequently measured. Normal OODG values can be read off easily from the diagrams published here.

Adult↗
PubMed1988

[Quantitative assessment of the clinical electroretinogram].

The clinical application of electroretinography has been limited until now by the lack of standardisation, especially of stimulus conditions. Normal values for the electroretinographic response parameters can only be used if patients are examined under the conditions which were given for the examination of healthy subjects. It is shown in this paper that the inexpensive apparatus designed by Kooijman and Damhof (1981) can be calibrated by any user simply and at justifiable expense. Normal values for the amplitudes and peak times for the a- and b-wave are presented. The normal range of the values has been defined with regard to the frequency distribution. According to the authors' results, methods of descriptive statistics in skewed distributions are mainly necessary at low stimulus intensities. The descriptive methods for normal distributions were regularly applied at higher stimulus intensities. In general, however, ERG parameters are normally distributed as shown by the distribution of the residuals between the linear regression of the parameter to the logarithm of the corneal illuminance and the measured values. The influence of age on the amplitude was calculated according to the results of Lehnert and Wünsche (1966) and the lower limits of the normal range are given for four age groups. The data presented here may be used as normal values provided that the simple calibration methods are applied. Thus electroretinography is no longer a method merely for the laboratory, but can be used in clinics and offices as well. However, a prerequisite is that the physician has sufficient experience in ophthalmological electrophysiology.

Adult↗
PubMed1988

[Ocular hemodynamics following suction cup oculopression].

In the study reported here the authors investigated the influence on ocular perfusion pressures of suction-cup oculopression, a procedure which permits oculopression without orbital compression. Patients over 50 years of age were examined before cataract extraction. Ulrich's method of ocular oscillodynamography was used to determine ocular perfusion pressures. A Mikuni and Yoneyama suction-cup dynamometer was applied for suction-cup oculopression. Ocular hypotonia following suction-cup oculopression was adequate and comparable to that achieved by other oculopression methods. After oculopression a significant increase in ocular perfusion pressures (retinal, ciliary, and diastolic) was found. However, ocular blood pressure remains constant after oculopression. Moreover, the increase in ocular perfusion pressure could not be explained by oculocardiac reflexes, because there was no change in systemic arterial blood pressure. It must be assumed, therefore, that the increase in ocular perfusion pressures is caused by a lowering of resistance, i.e., a drop in intraocular pressure.

Blood Pressure↗
PubMed1988

[Ocular hemodynamics following local administration of clonidine].

The influence of topically applied clonidine 0.125% on ocular hemodynamics was investigated in ten patients with open-angle glaucoma and ten healthy volunteers, using a new, differentiated method. Ocular perfusion pressures were determined by Ulrich's method of oculo-oscillodynamography. Following monocular application of clonidine 0.125% eye drops a clear decrease in systemic blood pressure and a somewhat less pronounced reduction of ocular perfusion pressure was observed in both groups of patients. The reduction in ocular perfusion pressures was higher in the eye after drop application than in the untreated control eye. It must therefore be assumed that clonidine 0.125% eye drops have a local perfusion pressure-reducing effect in addition to their systemic effect.

Adult↗
PubMed1988

Effect of different antiglaucomatous drugs on ocular perfusion pressures.

In an attempt to elucidate whether antiglaucomatous drugs, especially beta-blockers, affect systemic and/or ocular blood flow, we measured ocular perfusion pressures (PP), systemic blood pressure (BP) and heart rate in 50 healthy subjects before and after topical instillation of the following eye drops: timolol 0.5% (n = 10), betaxolol 0.5% (n = 10), carteolol 2% (n = 10), pilocarpine 2% (n = 10) and acetazolamide 750 mg per os (n = 10). The ocular perfusion pressures were measured by OODG as described by Ulrich. By means of this method--retinal and ciliary perfusion pressure can be recorded separately and simultaneously. Our results indicated that, in spite of a statistically significant decrease in IOP in all 5 groups, there was no change in retinal or ciliary perfusion pressure, heart rate or blood pressure in any of the groups except the carteolol subjects. The ocular perfusion pressures should be increased with reduction of the IOP when the systemic parameters remain unchanged. This was not the case in our experiments and therefore it can be suggested that a relative reduction in ocular perfusion pressure occurs with all agents and, in this respect, timolol and betaxolol did not affect ocular perfusion pressure more than pilocarpine and acetazolamide. Carteolol, however, produced a slight decrease (alpha less than 0.02) in ocular perfusion pressure, in spite of lowering of the IOP.

Adrenergic beta-Antagonists↗
PubMed1988

[Assessment of aqueous humor dynamics with Ulrich oculopressure tonometry].

Oculopression tonometry according to Ulrich can be used for the judgement of the facility of outflow like the tonography according to Grant. As shown by us for the first time, oculopression tonometry can also serve to evaluate aqueous humor formation. The results of a planned prospective study in 30 glaucoma patients and in 30 healthy volunteers are shown. It can be concluded that the recovery time of the intraocular pressure seems to be a better criterion for the diagnosis of glaucoma than the intraocular pressure measured immediately after the artificial pressure enhancement.

Aqueous Humor↗
PubMed1988

[Effect of nonspecific and cardioselective beta receptor blockers on the formation of aqueous humor. An oculopressure tonometry study].

The aim of the present study was to show the effect of different topical beta-blocking agents on aqueous humor formation with a clinically practicable method. In a clinical, randomized, prospective double-blind study, 60 healthy volunteers were examined by means of oculopression tonometry according to Ulrich. The placebo was applied to 29 subjects; a nonselective beta-blocker (timolol maleate 0.5%) was given to 14 volunteers and 17 subjects received a cardioselective, beta-1-blocking agent (betaxolol-HCl 0.5%). On the 1st day, intraocular pressure (IOP) was lowered by the suction cup method and then we measured the time required for IOP to return to the initial value. The examination procedure of the 1st day was repeated on the 2nd day 3 h after application of the ophthalmic solution. After evaluation of the different groups, we could show that the recovery times in the placebo groups were comparable. Furthermore, we showed that both beta-blockers slow down the increase of IOP to the initial value. There was a statistically significant difference in recovery time between timolol and placebo. This difference was statistically not significant between betaxolol and placebo.

Adult↗
PubMed1988

Nd:YAG laser shock waves in artificial eyes.

Nd:YAG laser surgery is performed by inducing optical breakdown in the interior of the eye. The optical breakdown is accompanied by shock waves which expand throughout the entire eye. In our experiments, we measured the amplitudes of shock waves at the walls of artificial eyes caused by single and multiple pulses of optical energy originating from an Nd:YAG laser at a wavelength of 1.064 micron. We have shown that the effects observed are not caused by mechanical resonance. We believe that similar results can be expected for human eyes. The peak pulse amplitudes in artificial eyes of different length were found to increase linearly as a function of the energy transferred into the eye. The peak amplitudes of pulse sequences were found to be only half of those for single pulses of comparable energy. In laser surgery, such sequences can be preferable if they achieve the same effect.

Energy Transfer↗