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R Stodtmeister

Publications and source records attributed to R Stodtmeister.

At least 19 recordsLinked to original sources
PubMed2006

[The role of pachymetry in routine glaucoma diagnosis].

The influence of corneal thickness on the precision of Goldman applanation tonometry is highly disputed. Goldmann and Schmidt assumed that the physiological variation of corneal thickness does not influence the measurement. But they indicated that an "abnormal" deviation of corneal thickness can lead to a false measurement. In the last 30 years many investigations have reliably demonstrated that thick corneas produce elevated applanation values and thin corneas lower values. The correction value is 1 mm Hg per 25 microm change in corneal thickness. The accuracy of intraocular pressure measurement is important for the detection and monitoring of glaucoma. Therefore it is necessary to recalculate applanation values based on corneal thickness in every patient, especially after refractive surgery. It is also necessary to keep in mind that with applanation tonometry we measure a force. From the force readings we deduce the value of the intraocular pressure. This conclusion is only correct if the theory of Goldmann applanation tonometry is right. But between force measurement and intraocular pressure there is the individual cornea with special properties like thickness, rigidity and astigmatism which can influence the correctness of the measurement. So we can understand why knowledge of corneal thickness can improve the deduction from force measurement of intraocular pressure. It is also reasonable that other individual corneal properties we do not measure or do not know so far can influence the deduction. This means that the corneal thickness is not the only variable. Pachymetry allows us to estimate the intraocular pressure with higher precision. Therefore it should be clinically used.

Artifacts↗
PubMed2004

[Non-invasive determination of intracranial pressure. Physiological basis and practical procedure].

It has been shown in some recently published papers that the intracranial pressure can be determined by dynamometric measurement of the outflow pressure of the central retinal vein (VOP). The knowledge gained by the basic experiments of Baurmann in 1925 has been forgotten by the ophthalmic community for many years. In this paper the basic phenomena of venous collapse are outlined which are fundamentally different from the biomechanics of the arterial collapse phenomenon observed by ophthalmodynamometry. A practical guideline is given for the dynamometric measurement of venous outflow pressure which equals the intracranial pressure. Performing dynamometry of the central retinal vein enables the ophthalmologist to determine intracranial pressure in a non-invasive way.

Humans↗
PubMed1998

Applanation tonometry and correction according to corneal thickness.

PURPOSE: In previous studies, it has been shown that the central corneal thickness influences the measurement values of applanation tonometry. The aim of this study is to answer the question as to which values and with what frequency the tonometer readings as based on corneal thickness have to be corrected in the patients attending an ophthalmic practice. SUBJECTS AND METHODS: The corneal thickness was measured in 579 patients using ultrasound pachymetry under the conditions prevailing in a medical practice; from the thickness obtained, the correction values for intraocular pressure were calculated. RESULTS: Correction values of +/-2 mm Hg and above were found in half of the patients examined, and correction values of +/-3 mm Hg and above in a good quarter of the patients. The correction value was +/-4 mm Hg and more in every fifth patient. CONCLUSIONS: Corneal thickness does, in fact, influence the results of applanation tonometry to a clinically relevant degree.

Aged↗
PubMed1997

Retinal capillary hemodynamics and VEP/pressure tolerance: evidence of retinal microcirculatory compromise in treated glaucomatous eyes.

Measurements of retinal leukocyte velocity were made in single eyes of 6 glaucomatous adults and 9 normal subjects at each of 4 discrete levels of IOP elevation assigned according to the characteristics of prior pattern-evoked cortical potential pressure tolerance measurements. Glaucomatous eyes failed to demonstrate any stabilization in retinal leukocyte velocity at pressures above 45 mm Hg, with velocities 33% lower than normal for a comparable degree of IOP elevation (p < 0.012). Even at baseline IOP, leukocyte velocity was 27.2% slower in the treated glaucomatous eyes than in normal control eyes (p < or = 0.013), despite comparable baseline IOP levels in both groups.

Adrenergic beta-Antagonists↗
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↗