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Biomedical subjects

L E Pillunat

Publications and source records attributed to L E Pillunat.

At least 19 recordsLinked to original sources
PubMed2001

[Papillary hemodynamics in patients with normal pressure glaucoma and hemorrhage of the optic papilla circumference].

BACKGROUND: Optic disc hemorrhages in patients with normal-pressure glaucoma (NPG) are usually regarded as a sign of vascular dysfunction and as an indicator for glaucoma damage progression. METHODS: Optic nerve head blood flow was measured in 21 patients suffering from NPG with acute optic disc hemorrhages by scanning laser Doppler flowmetry at various locations of the optic disc. Intraocular pressure and mean deviation of the visual field were also monitored. Two groups served as control: 21 patients with NPG matched for age, sex, and stage of the disease and in addition the contralateral eye without any hemorrhages. RESULTS: Optic nerve head blood flow as a mean of several locations was significantly lower in eyes with optic disc hemorrhages than in controls and differed significantly from the contralateral eye. CONCLUSION: Optic nerve blood flow was lower in NPG eyes with optic disc hemorrhages than in the contralateral eye and in controls.

Aged↗
PubMed2001

[Ocular hemodynamics and visual field in glaucoma treated with dorzolamide].

OBJECTIVE: It has been shown that oral carbonic anhydrase inhibitors improve visual function in glaucoma. Furthermore topical dorzolamide might improve ocular hemodynamics, as was demonstrated previously. This study was undertaken to evaluate whether topical dorzolamide affects visual function and ocular hemodynamics in glaucoma. METHODS: In a retrospective, open clinical trial, dorzolamide eye drops were administered to 28 patients with confirmed primary open angle glaucoma (POAG) in both eyes, 3 times daily for a mean follow up of 9 months. One eye was randomly chosen for evaluation. IOP, blood pressure, heart rate, pulsatile ocular blood flow (POBF) and Humphrey 30-2 visual fields were measured at baseline and after the start of the therapy. POBF was determined by pneumotonography. For statistical analysis the Wilcoxon-matched-paired test and the Bonferoni-Holm adjustment were used. RESULTS: In dorzolamide-treated patients the IOP dropped from 18 mmHg to 15.5 mmHg after 9 months therapy (p < 0.01) and the visual field improved significantly by 18% (p < 0.05). A statistically significant change was found for POBF from 543 microliters/min to 675 microliters/min (p < 0.05). CONCLUSIONS: The results showed the expected drop in intraocular pressure. Visual function and pulsatile ocular blood flow improved significantly which might be explained by an analogous, vasodilatory effect as was observed in orally applied carbonic anhydrase inhibitors.

Aged↗
PubMed2001

[Retinal nerve fiber layer thickness and peripapillary blood flow in glaucoma patients and healthy probands].

BACKGROUND: In progressive glaucoma there is increasing loss of retinal nerve fibers and therefore decreasing nerve fiber layer thickness. As measurements of capillary blood flow have been reported to depend on nerve fiber layer thickness, this could result in incorrectly high blood flow measurements in patients with advanced glaucoma. METHODS: In 33 healthy controls and 59 glaucoma patients we measured retinal nerve fiber layer thickness by laser polarimetry and relative capillary blood flow by scanning laser doppler flowmetry three times on the nasal and temporal peripapillary retina. For statistical analysis a regression analysis was used. RESULTS: The correlation coefficients for volume, velocity, and flow with nerve fiber layer thickness at the same location were 0.02/-0.03/-0.02 in the temporal retina and -0.22/-0.07/-0.19 in the nasal retina (all correlations nonsignificant). CONCLUSION: No correlation was found between nerve fiber layer thickness and capillary blood flow. Measurement of capillary blood flow in glaucoma patients thus does not appear to be affected by decreasing nerve fiber layer thickness.

Adolescent↗
PubMed2001

Ocular pulse amplitude is reduced in patients with advanced retinitis pigmentosa.

BACKGROUND/AIMS: The choroid, a low resistance vascular structure carrying 85% of the ocular blood flow, provides nourishment to and removal of potential toxic waste products from the adjacent non-vascularised outer layers of the retina, macula, and optic disc regions. Choroidal perfusion may be reduced in retinitis pigmentosa (RP) and might contribute to retinal pigment epithelium (RPE) degeneration. The aim of this study was to determine whether choroidal perfusion is reduced in RP and whether this is correlated with the stage of disease. METHODS: Ocular pulse amplitude (OPA) evaluated with the ocular blood flow (OBF) system, applanation intraocular pressure (IOP), visual fields, blood pressure (BP), and heart rate (HR) were measured in 75 RP patients having stage RP-I (stage I: visual field size: 7.85-14.67 cm(2); n = 22), stage RP-II (stage II: visual field size: 2.83-7.84 cm(2); n = 29), or stage RP-III (stage III: visual field size: 0.52-2.82 cm(2); n = 24) were compared with matched healthy controls and each other. RESULTS: Neither IOP nor systemic perfusion parameters were significantly (p >0.1) altered, but OPA (mm Hg) in RP patients beginning with stage RP-II (1.6 (0.1), 27.3%, p<0.0001), and RP-III (1.2 (0.1), 45.5%, p<0.0001) was significantly reduced when compared with matched subgroups from a pool of healthy controls (2.2 (0.1), n = 94). CONCLUSIONS: OPA can be used neither for early clinical detection of RP nor to follow the natural course of the disease. However, our data show that in advanced stages of RP not only the retina but also the choroidal circulation is affected.

Adult↗
PubMed2000

[Ultrasound biomicroscopy in pigmentary glaucoma].

PURPOSE: To evaluate the anatomical relationships of the iris in pigmentary glaucoma before and after laser iridotomy and to evaluate the effect on intraocular pressure. METHODS: Ultrasound biomicroscopy (UBM, Humphrey-Zeiss) of the anterior segment was performed in 28 eyes of 28 patients (20 male, 8 female, mean age 43 years, mean untreated IOP 24.3 mmHg) with pigmentary glaucoma before and after laser iridotomy. The slope of intraocular pressure was documented. Mean follow-up was 9 months. For statistical analysis the Wilcoxon test was used. RESULTS: Ten out of 28 eyes showed iridozonular contact and concavity of the midperipheral iris. Laser iridotomy resulted in a significant pressure drop (P < 0.05) in these 10 eyes (24.6 mmHg to 18.3 mmHg). Eighteen eyes, however, did not show iridozonular contact and intraocular pressure did not drop sufficiently (P > 0.05; 25.1 mmHg to 23.1 mmHg) after laser iridotomy. CONCLUSION: The results show that iridozonular contact does not exist in every patient with pigmentary glaucoma. Therefore, it seems possible that more than one pathogenic mechanism is involved in pigmentary glaucoma. In patients with iridozonular contact, however, laser iridotomy significantly reduces intraocular pressure.

Adult↗
PubMed1999

Regional distribution of optic nerve head blood flow.

BACKGROUND: Advanced glaucoma typically results in damage of the temporal neuroretinal rim. As vascular factors are of pathogenic importance in the development of glaucomatous damage, the present study investigated whether regional differences in perfusion might be the reason for the preferential damage of the temporal neuroretinal rim. MATERIAL AND METHODS: Blood flow of the neuroretinal rim was measured with the laser Doppler flowmeter (LDF) Oculix 4000 (continuous measurement of an area of 160 microm diameter) and the Heidelberg retina flowmeter (HRF). Both instruments measure the capillary blood flow (flow), the relative velocity of erythrocytes (velocity) and the relative volume of moving erythrocytes (volume). We examined one randomly chosen eye of 55 healthy subjects without history of glaucoma aged 22-57 years (mean 30 years). Each subject was measured with the LDF and HRF, each time nasally and temporally, away from visible vessels. The intraocular pressure (IOP) was measured with the Goldmann tonometer. Heart rate and systolic and diastolic blood pressure were measured. RESULTS: The LDF measurements of the optic nerve head showed nasal flow of 12.4+/-5.6 AU and temporal flow of 9.8+/-3.6 AU. The HRF showed a nasal flow of 477+/-161 AU and a temporal flow of 368+/-166 AU. The volume measurements done by LDF showed nasally a value of 0.68+/-0.40 AU and temporally a value of 0.46+/-0.21 AU. The HRF volume measurements showed nasal values of 16.1+/-4.3 AU and temporal values of 13.0+/-4.0 AU. The LDF velocity values were nasally 0.22+/-0.05 kHz and temporally 0.26+/-0.05 kHz. HRF measurements showed velocity values of 1.7+/-0.5 kHz nasally and 1.3+/-0.6 kHz temporally. The differences were highly statistically significant for flow (LDF P=0.00007, HRF P=0.0005), volume (LDF P=0.00002, HRF P=0.00004) and velocity (LDF P=0.0002, HRF P=0.00004). The IOP was 12.6 mmHg. Blood pressure was 118/75 mmHg and the heart rate was 73 beats per minute. There was no correlation between age, IOP, BP and HR and the HRF/LDF measurements. CONCLUSION: The measurements with two different methodologies showed a decreased blood flow of the temporal neuroretinal rim compared to the nasal side. These local differences might be one reason for the preferential damage of the temporal neuroretinal rim in advanced glaucoma.

Adult↗
PubMed1999

Effect of topical dorzolamide on optic nerve head blood flow.

PURPOSE: The topical carbonic anhydrase inhibitor dorzolamide has proven effective in lowering intraocular pressure in glaucoma patients. Because an impaired blood supply of the optic nerve has to be regarded as a major pathogenic risk factor it seems important to examine the effect of this new antiglaucomatous drug on capillary optic nerve head blood flow. METHODS: In a double-masked, randomized clinical trial, dorzolamide eye drops were applied to both eyes of 15 healthy subjects (8 female, 7 male, mean age 30.6 years) three times daily for 3 days. The control group (15 healthy volunteers, 9 female, 6 male, mean age 30.8 years) received a placebo preparation according to the same protocol. Intraocular pressure (IOP), blood pressure, heart rate, capillary optic nerve head blood flow and retinal blood flow were measured at baseline (1D0), 90 min after single instillation (1D90), and after 3 days of therapy (3D). Scanning laser Doppler flowmetry (Heidelberg Retina Flowmeter) and laser Doppler flowmetry according to Riva (Oculix 4000) were used to measure optic nerve head blood flow. RESULTS: IOP dropped in dorzolamide-treated subjects from 12.5 mmHg to 11.0/10.5 mmHg (1D0, 1D90, 3DO) and in the control group from 13.0 mmHg to 12.5/12.5 mmHg. Optic nerve blood flow as measured by scanning laser Doppler flowmetry showed no significant changes in dorzolamide-treated volunteers (temporal 310/329/315 AU, nasal 387/402/399 AU) or in the placebo group (temporal 238/306/276 AU, nasal 356/382/379 AU). Also as measured by laser Doppler flowmetry optic nerve head blood flow did not show significant changes in dorzolamide-treated volunteers (temporal 12.98/12.6/11.7 AU, nasal 16.6/16.9/15.7 AU) or in the placebo group (temporal 11.9/12.4/12.4 AU, nasal 16.1/15.8/17.7 AU). The systemic parameters blood pressure and heart rate remained unchanged during the treatment period. CONCLUSION: The results showed the expected drop in IOP. However, capillary optic nerve head blood flow, measured by two different techniques, did not change during therapy. This may be due to the effective autoregulation in human optic nerve head circulation, which seems not to be affected by dorzolamide.

Administration, Topical↗
PubMed1999

[Ocular pulse amplitude, intraocular pressure and beta blocker/carbonic anhydrase inhibition in combined therapy of primary open-angle glaucoma].

BACKGROUND: Beyond intraocular pressure (IOP, German abbreviation: IOD) ocular perfusion is increasingly discussed in the pathogenesis of the glaucomas. The present study was designed to investigate for ocular pulse amplitude (OPA) in primary open angle glaucoma patients with elevated intraocular pressure (POAG, German abbreviation: POWG) following application of timolol, a beta-blocker and dorzolamide a topical carbonic anhydrase inhibitor. METHODS: OPA (Ocular Blood Flow System, OBF Labs U.K.) IOP, heart rate, systolic and diastolic brachial artery pressures were measured before and 4 weeks following application of timolol and additional 4 weeks following application of a timolol/dorzolamide combination in 14 POAG patients. RESULTS: Following administration of timolol, IOP was highly significantly reduced in drug treated POAG eyes; this effect was additively enhanced by dorzolamide. Timolol did not affect OPA, whereas dorzolamide significantly increased OPA in drug treated POAG eyes. Systemic perfusion parameters were unchanged. CONCLUSION: Timolol and dorzolamide drastically reduced IOP, in addition dorzolamide increased OPA in POAG, an ocular microcirculatory effect which may further help to improve prognosis of POAG.

Adrenergic beta-Antagonists↗
PubMed1999

Effect of acute intraocular pressure changes on short posterior ciliary artery haemodynamics.

BACKGROUND/AIMS: Vascular insufficiency due to abnormal autoregulation has been proposed as a major factor in the development of glaucoma. The anterior optic nerve is primarily perfused by the short posterior ciliary arteries. The autoregulatory capacity of these vessels in response to acutely elevated intraocular pressure (IOP) was examined in normal human subjects. METHODS: Colour Doppler imaging was performed on the short posterior ciliary arteries of 10 normal subjects at baseline and during four incremental IOP elevations. Using a scleral suction cup placed temporally, IOP was elevated to approximately 25, 30, 40, and 50 mm Hg. Additional measurements were performed immediately after pressure release. Systolic and diastolic flow velocities were measured and Pourcelot's resistivity index was calculated. RESULTS: Systolic and diastolic flow velocities decreased linearly with each incremental increase in IOP (p < 0.001). Pourcelot's resistivity index increased linearly with each incremental increase in IOP (p < 0.001). Changes in end diastolic velocity, peak systolic velocity, and Pourcelot's resistivity index were linearly related to changes in IOP. CONCLUSION: The normal healthy eye is not able to autoregulate to maintain PCA blood flow velocities in response to acute large elevations in IOP.

Adult↗
PubMed1998

[Ocular pulse amplitude during manipulation of systemic perfusion parameters].

BACKGROUND: The mechanism for the control of choroidal perfusion is unclear. The present study was designed to investigate for the effect of standardized alteration of systemic perfusion parameters on choroidal hemodynamics in healthy volunteers. METHODS: Intraocular pressure (IOP; German abbreviation: IOD), Ocular Pulse Amplitude (OPA), systemic blood pressure, and pulse rate were measured, and ocular perfusion pressure was calculated in 14 otherwise non-smoking, healthy volunteers prior to and following exercise and smoking. RESULTS: Exercise significantly (sig., p < 0.05) increased pulse rate, systolic blood pressure and ocular perfusion pressure, while it sig. (p < 0.05) reduced IOP and diastolic blood pressure. However OPA was not sig. (p > 0.1) affected by changes in these parameters. Smoking sig. (p < 0.05) increased systolic blood pressure, diastolic blood pressure, pulse rate, and ocular perfusion pressure but did not sig. (p > 0.09) alter OPA. CONCLUSION: Despite affecting ocular and systemic perfusion parameters, exercise and smoking did not alter OPA, suggesting functional isolation i.e. autoregulation of the choroidal and/or ophthalmic artery circulation.

Adult↗
PubMed1998

[Peak pulse blood volume in controlled modification of local perfusion parameters].

BACKGROUND: Choroidal autoregulation is discussed controversially. The present study was designed to investigate for the effect of standardized manipulation of local perfusion parameters on choroidal hemodynamics in cynomolgus monkey eyes with lasersurgically induced glaucoma (CMG; German abbreviation: RA-LHDG). METHODS: CMG unilaterally received 2-3 laser treatments so as to develop the lasered-eye glaucoma model. Intraocular pressure (IOP; German abbreviation: IOD) and Ocular Pulse Amplitude (OPA) were measured and Peak Pulse Blood Volume (PPBV; German abbreviation: PGBV) was determined. RESULTS: In CMG PPBV was not significantly (sig., p > 0.05) altered in laser-treated eyes--despite a sig. (p < 0.05) increase in IOP. Untreated contralateral control eyes of monkeys with an IOP-increase > 5 mm Hg in laser-treated eyes showed a sig. (p < 0.05) increase in PPBV. CONCLUSION: Unchanged PPBV in laser-treated eyes of CMG and an increase in PPBV in control eyes point at a bilateral autoregulatory compensatory mechanism, which is more manifest in eyes with IOPs in the normal range.

Animals↗
PubMed1998

Topical carbonic anhydrase inhibition increases ocular pulse amplitude in high tension primary open angle glaucoma.

BACKGROUND: Ocular pulse amplitude (OPA) is reduced in normal tension primary open angle glaucoma (NTP) patients when compared with healthy age matched controls (CTL) while increased OPA appears to protect ocular hypertensive patients from visual field loss. If NTP is accompanied by vasospasm, as in roughly half of the primary open angle glaucoma (POAG) population (independent of intraocular pressure, IOP), calcium channel blockers increase OPA and thus stabilise visual fields in these patients. Current glaucoma drugs reduce IOP but do not activate (compromised) ocular perfusion. METHODS: The influence of dorzolamide, a topical carbonic anhydrase inhibitor in standard dosage (three times daily, one eye) on OPA, IOP, blood pressure, and heart rate was investigated in a randomised, prospective, masked clinical trial assessing the acute effects of dorzolamide v placebo before and 2 days after application in 33 cataract patients with (n = 14) and without (n = 19) high tension POAG (HTP) who provided informed consent. RESULTS: Following application of dorzolamide (D) IOP (mm Hg, mean (SEM)) in HTPD (20.2 (0.5)/16.3 (0.5) and in CTLD (16.0 (0.5)/12.3 (0.5)) was highly significantly (p < 0.001) reduced and was significantly (p < 0.03) reduced in vehicle (V) treated eyes (HTPv: 20.3 (0.4)/19.0 (0.4)) and CTLv: 15.8 (0.4)/14.9 (0.3)) when compared with respective baseline measurements. OPA (mm Hg) in HTPD (2.1 (0.1)/2.5 (0.1)) and CTLD (2.2 (0.1)/2.6 (0.2)) eyes was significantly (p < 0.05) increased and unaffected in vehicle treated eyes when compared with respective baseline measurements. Systemic perfusion variables were also unchanged. CONCLUSION: Dorzolamide increased OPA in HTP and CTL. Drugs stimulating OPA may improve prognosis of POAGs.

Aged↗
PubMed1997

Autoregulation of human optic nerve head circulation in response to increased intraocular pressure.

The following experiments were undertaken to determine if blood flow is maintained by autoregulation in the human optic nerve head when circulation is challenged by elevated intraocular pressure, and to determine if the presence or absence of autoregulation is universal. Laser Doppler flowmetry was used to determine the average velocity, the number of moving erythrocytes, and the volume of flow in the capillary bed of the optic disc. These parameters were measured in 10 subjects at spontaneous levels of intraocular pressure (IOP), and at pressures artificially elevated to 25, 35, 45 and 55 mm Hg with a scleral suction cup. Four subjects (two who showed autoregulation and two who did not) were studied on six additional occasions to determine consistency of the findings. In these same four subjects a second location on the disc was also measured on six occasions to determine if the IOP-effect on blood flow varied by location. Of the 10 subjects initially studied, seven maintained the baseline level of blood flow over the lower part of the range of elevated intraocular pressure (evidence of autoregulation), but showed a decline in flow by the time IOP reached 45 or 55 mm Hg. Two subjects showed a linear decline in blood flow beginning with the smallest increment of elevation of IOP (no autoregulation), and one showed an uninterpretable result. The two individuals who showed the linear decline and two of those who showed efficient autoregulation were remeasured, and each showed consistently the same pattern as before when restudied on six different occasions each. However, at a different location on their discs, autoregulation was manifest in all of these four individuals. When challenged by elevated IOP, the optic nerve head typically maintains a steady-blood flow over a range of IOP, but fails to maintain the same flow by the time IOP reaches 45 or 55 mm Hg. Some disc locations, at least in some individuals, do not show this autoregulation, but exhibit a decline in blood flow linearly related to IOP, even with the modest elevation of IOP.

Adult↗
PubMed1997

[Ocular pulse amplitude and local carbonic anhydrase inhibition].

UNLABELLED: Ocular perfusion is increasingly being discussed in the pathogenesis of glaucoma. The present study was designed to investigate ocular pulse amplitude (OPA) in primary open-angle glaucoma (POAG) patients with elevated intraocular pressure (HTG) and non-glaucomatous controls (CTL) following topical application of the carbonic anhydrase inhibitor dorzolamide. METHODS: OPA (Ocular Blood Flow System, OBF Labs UK) intraocular pressure (IOP), heart rate (HR), and systolic (BPsyst) and diastolic (BPdiast) bronchial artery pressures were measured before and 2 days after initiating treatment in 33 cataract patients with n = 14) and without (n = 19) POAG. RESULTS: Following application of dorzolamide, IOP (mmHg) in drug-treated HTG and CTL eyes was highly significantly reduced (p < 0.001) and in vehicle-treated HTG and CTL eyes significantly reduced (p < 0.03) compared to respective baseline measurements. OPA (mmHg) in drug-treated HTG and CTL eyes was significantly increased (p < 0.05) and in vehicle-treated eyes in affected compared to respective baseline measurements. Systemic perfusion parameters were also unchanged. CONCLUSION: Dorzolamide increased OPA in HTG and CTL eyes. An increase in OPA may improve the prognosis of HTG.

Adult↗
PubMed1997

Reduced ocular pulse amplitude in low tension glaucoma is independent of vasospasm.

PURPOSE: A vascular basis for the pathogenesis of primary open angle glaucoma has been postulated for many years. Defects in the regulation of ocular blood flow may be the initiating factor in this group of multifactorial diseases. This study was designed to evaluate the effect of vasospasm on ocular pulse amplitude (OPA) in low tension glaucoma (LTG) patients. METHODS: OPA, using the Langham Ocular Blood Flow (OBF) System, applanation intraocular pressure (IOP), systemic blood pressure and heart rate were measured and vasospasm was determined by a fingernail capillary blood flow test. RESULTS: OPA (mmHg) in the LTG patients with a vasospastic reaction (LTG-V, 1.4 +/- 0.1, n = 17) was not significantly (p > 0.09) different when compared with non-vasospastic LTG patients (LTG-NV, 1.5 +/- 0.2, n = 15) but was significantly (p < 0.001) reduced in LTG-V and LTG-NV patients when compared with matched healthy control subgroups (2.3 +/- 0.2 and 2.4 +/- 0.3, respectively). IOP (mmHg) in LTG-V (13.3 +/- 0.4) and LTG-NV (13.2 +/- 0.5) patient groups was not significantly (p > 0.05) different when compared with each other, but was significantly (p < 0.05) lower when compared with matched control subgroups (15.0 +/- 0.3 and 15.2 +/- 0.4, respectively). Haemodynamic parameters were not significantly different from controls. CONCLUSION: The abnormality in choroidal perfusion indicated by a reduction in OPA in all LTG patients is unrelated to the presence or absence of vasospasm.

Adult↗
PubMed1997

Reproducibility of laser Doppler flowmetry in the human optic nerve head.

PURPOSE: We sought to demonstrate reproducibility of the noninvasive laser Doppler flowmetry technique for measuring microvascular hemodynamics of the optic nerve head in human subjects. METHODS: Laser Doppler flowmetry was performed by four examiners on four human optic nerve heads during multiple sessions. Intersubject, interexaminer, intersession, and intrasession variabilities were calculated for velocity, blood volume, and blood flow (flux). RESULTS: Initial variability of measurements improved after 3 months' experience. The standard deviation of the intrasession variation for single readings was 18% of the velocity mean value and 24% of the flow (flux) mean value. Based on this, a sample size of 17 (power beta = 0.8, alpha = 0.05, paired t test) will demonstrate a 10% physiologic change in flux within a session if the average of five readings is used before and after the experimental perturbation. The intersession variation was 12% and 32% for velocity and flux, respectively. Because of this, a larger sample size or additional measurement sessions are required for detection of an experimental influence between two sessions. The coefficient of variation among subjects for single readings was 7% and 10% for velocity and flux, respectively. CONCLUSIONS: Reproducibility of velocity measurements is better than reproducibility of flux measurements. After experience with the method, laser Doppler flowmetry is sufficiently precise to permit feasible studies of human optic nerve head microvascular hemodynamics when physiologic perturbations are applied.

Adult↗
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↗