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Ocular tonometry as routine part of physical examinations.
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[Average values of intraocular pressure in adults in the light of mass ocular tonometry (31.387 eyes)].
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[Findings on the ocular tonometry for indentation in the rabbit].
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Ocular tonometry in the child under general anesthesia with IM ketamine.
In the young child, the ocular tension cannot be taken without general anesthesia. Most of the anesthetic drugs lower the ocular tension which may give false low results in glaucoma. Ketamine is the only practical drug elevating the ocular tension. To determine the amount of the change in ocular tension under ketamine, the ocular tension was measured under I.M. ketamine 5 to 10 mg/kg in 30 children without ocular disease. The ocular tension before the anesthesia has not been measured. As soon as the child fell asleep, the ocular tension was recorded between 15 to 20 minutes. We noticed that the ocular tension remains stable in the beginning, but that it tends to rise after eight minutes of narcosis. So the ocular tension must be measured as soon as possible after induction, as soon as the child does not react to stimuli. Abnormal ocular tensions under ketamine are discussed. The ocular tensions under two different types of anesthesia (ketamine and methohexital + Thalamonal) are compared. Some examples of ocular tensions in glaucoma under ketamine are presented.
[Ocular pressure tonometry--value as a procedure in the diagnosis of glaucoma in comparison with classical tonography].
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[Relevance of ocular pressure tonometry and classical tonometry with reference to prognosis in suspected glaucoma and ocular hypertension].
A total of 44 eyes of patients with suspected glaucoma or ocular hypertension were examined both by ocular pressure tonometry (OPT) according to Ulrich and by tonography according to Leydhecker. The visual fields of these eyes were prospectively followed up for 3 years to compare the prognostic value of the two methods. In 30 of the 44 eyes a worsening visual field loss was observed, while in 14 the visual fields showed no change. Much better correlation was noted between values obtained by OPT and changes in visual field than between values obtained by tonography and visual field loss. Conventional tonography yielded 39% of false-negative values, but only 11% were recorded with OPT. Therefore, according to results of these and further investigations, OPT appears to be a more helpful and reliable method for assessment and decisions on therapy in patients with suspected glaucoma or ocular hypertension.
Central corneal thickness, tonometry, and ocular dimensions in glaucoma and ocular hypertension.
PURPOSE: To assess possible correlations between central corneal thickness, tonometry, and ocular dimensions. PATIENTS AND METHODS: One hundred seventeen eyes of 117 patients who were not taking any intraocular pressure-lowering medications were studied prospectively. Forty-one patients had ocular hypertension; 13 patients had primary open-angle glaucoma; and 10 patients had normal-pressure glaucoma. Twenty-three healthy eyes were included. Thirty glaucoma suspects (10 patients monitored for possible normal-pressure glaucoma and 20 patients with intermittent ocular hypertension) were included for correlation analysis. Tonometry was performed with Goldmann applanation and pneumotonometry, and central corneal thickness, anterior chamber depth, lens thickness, and axial length were measured ultrasonically. RESULTS: Central corneal thickness was lowest in eyes with normal-pressure glaucoma (538 +/- 51 microm), highest in eyes with ocular hypertension (570 +/- 32 microm), and intermediate and similar in eyes with primary open-angle glaucoma and healthy eyes (547 +/- 34 microm and 554 +/- 32 microm, respectively). These differences were significant (P = 0.028). Goldmann applanation tonometry and central corneal thickness were weakly correlated (r = 0.12, P = 0.205), with a 0.2-mm Hg change per 10-microm variation in central corneal thickness. Pneumotonometry measurements were more strongly correlated with central corneal thickness (r = 0.21, P < 0.05). Lens thickness was strongly correlated with age (r = 0.57, P < 0.001). Anterior chamber depth was negatively correlated with lens thickness and age (r = -0.29, P < 0.005 and r = -0.25, P < 0.01). Axial length was correlated with anterior chamber depth and age (r = 0.5, P < .001 and r = -0.19, P < 0.05). CONCLUSION: Eyes diagnosed as having ocular hypertension have thicker corneas and eyes labeled as having normal-pressure glaucoma have thinner corneas, when compared with healthy eyes or eyes with primary open-angle glaucoma. The effect of central corneal thickness on Goldmann applanation tonometry accuracy appears to be small and usually not clinically relevant. When corneal thickness is markedly different from normal, the clinician may need to factor this into diagnosis and management.
[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.
Re: Central corneal thickness, tonometry, and ocular dimensions in glaucoma and ocular hypertension.
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[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.
Vibration tonometry and ocular rigidity.
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Development and modelling of arterial applanation tonometry: a review.
Arterial tonometry allows non-invasive and continuous registration of the arterial pressure waveform, by applanating (flattening) a superficial artery supported by bone with an external transducer. Inspired by ocular tonometry used for eye disease diagnosis, G.L. Pressman and P.M. Newgard built the first arterial tonometer in 1963, and derived a discrete, linear mechanical model. Accuracy remained poor until new sensor production techniques (silicon technology) arrived. G.M. Drzewiecki et al. published a second, more elaborate theoretical model for tonometer positioning in 1983. Few years later, the first modern tonometers were commercialised. Although the problems of sensor positioning, motion artefacts and calibration still exist, the tonometer has proven its usefulness in arterial compliance and hypertension studies. Attention should now go to analysis of the arterial pressure waveforms, and the combination with other signals (e.g. flow wave morphology) to allow a complete non-invasive haemodynamical description of the heart and the arterial tree.
[Use of althesin in general surgery with particular reference to ophthalmic surgery].
Personal experience with Althesin in general surgery, with particular regard to eye surgery, is reported. Ocular tonometry was carried out in all patients. This showed that a diminution is a constant feature of Althesin anaesthesia. In 80% of patients, the diminution in O.T. values was 50% compared to basal levels. The O.T. reduction brought on by Althesin was also significant after administration of succinylcholine which is well known to cause a rise in ocular tension. Results also show a reduction in curare consumption in all anaesthesias carried out with Althesin. It is concluded that the drug is completely reliable in all branches of surgery.
Intraocular pressure during mechanical ventilation with different levels of positive end-expiratory pressure.
OBJECTIVE: To determine the effect of positive end-expiratory pressure (PEEP) on intraocular pressure. DESIGN: Prospective, controlled, longitudinal, dual center study. In one group, patients served as their own control. In the second group, isolated determinations of intraocular pressure were made in mechanically ventilated patients receiving PEEP. SETTING: Adult intensive care units of two university hospitals. PATIENTS: Intraocular pressures were measured serially in eight patients during the recovery phase of different clinical conditions and in 22 patients receiving mechanical ventilation with PEEP > or = 10 cm H2O for > 24 hrs. INTERVENTIONS: Group A) In eight patients, a PEEP dose-response curve was established (PEEP 0, 5, 10, 15, and 0 cm H2O every 15 mins). Intraocular pressures were measured at the end of each period. Group B) In 22 patients, measurement of intraocular pressures were done while the patients received mechanical ventilation with PEEP > or = 10 cm H2O for at least > 24 hrs. MEASUREMENTS AND MAIN RESULTS: In both groups, there was a positive correlation between the PEEP level and the central venous pressure (p < .05 in group A, and p < .03 in group B). No relationships between intraocular pressure and PEEP or central venous pressure were observed. However, there was a correlation between intraocular pressure and length of PEEP therapy (p < .03). We found ocular hypertension in only one patient (right eye intraocular pressure = 26 mm Hg; left eye intraocular pressure = 24 mm Hg). CONCLUSIONS: Short-term therapy with PEEP of < or = 15 cm H2O does not present a clinically important significant risk for intraocular pressure increase in a population with normal basal ocular tonometry. During prolonged mechanical ventilation with PEEP, increments in intraocular pressure may occur, but these increments appear to not be of a clinically relevant magnitude.
An explanation for so-called consensual pressure drop during tonography.
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Research into the pathogenesis of keratoconus. A new syndrome: low ocular rigidity, contact lenses, and keratoconus.
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