Ivar Hørven

Ophthalmic artery pressure during retrobulbar anaesthesia.

Ophthalmic artery pressure recordings were performed before and after retrobulbar injection of 4.5 ml Xylocain‐Exadrin by the use of Stepanik Arteriotonography. A 50 % reduction in ophthalmic artery pulse pressure was found, which correlates well with the corresponding reduction in corneal indentation pulse amplitudes demonstrated by dynamic tonometry. The results demonstrate a shift from pulsatile towards non‐pulsatile ocular blood flow. In two of the eight patients a pronounced reduction was also found in ocular perfusion pressure, indicating that retrobulbar anaesthesia may be hazardous in certain cases by initiating a major reduction in ocular blood supply. In order to minimize this hazard in eyes especially vulnerable to a reduction in ocular perfusion pressure, such as glaucomatous eyes, it is probably safest to perform retrobulbar anaesthesia with 2–3 ml of Xylocain 1 % without the use of Exadrin (epinephrine).

Glaucoma treatment with timolol.

Thirty‐two eyes from 19 patients with either capsular glaucoma, pigmentary glaucoma or primary open angle glaucoma were given topical timolol and followed through a 3–6 months period.

STUDIES ON CEREBRAL AND OCULAR CIRCULATION IN A PATIENT WITH CLUSTER HEADACHE

INVESTIGATIONS ON the blood supply to the head have previously been carried out only to a small extent in patients with migraine. Various methods have been used; piezoelectric registration,1-3 spinal fluid pressure measurements, rheography (in principal impedance plethysmography),4 cerebral circulation studies with radioactive inert gases,5 and tissue clearance method with Na24,6 The results seems to be somewhat conflicting.

Ocular and cerebral blood flow measurements in healthy subjects. A comparison of blood flow velocity and dynamic tonometry measurements before and after acetazolamide.

Abstract. The ocular and cerebral blood flow was studied in 15 healthy subjects using transcranial Doppler ultrasonography (2 MHz). The blood flow velocity in the precerebral carotid arteries, in the ophthalmic artery and in the middle cerebral artery was measured under baseline conditions and after i.v. administration of 1 g acetazolamide. To measure the intraocular pressure and the corneal indentation pulse amplitude, a dynamic tonometer was used. Pulsatile ocular blood volume was calculated from these values. After one single dose of acetazolamide a significant decrease in ophthalmic artery flow velocity, and a significant increase both in internal carotid and in middle cerebral artery velocity was found. A significant decrease in intraocular pressure and in pulsatile ocular volume after acetazolamide was also demonstrated. These findings suggest that the acute effect of acetazolamide may be associated with a reduced ocular blood flow, explaining some of the reduction in IOP.

BLOOD CIRCULATION CHANGES IN THE EYE AND LIMBS

Alterations in corneal indentation pulse (CIP) amplitudes and pulse volume recordings (PVR) on the limbs were demonstrated in pregnant women, indicating that significant changes occur in the peripheral blood circulation during pregnancy.

CORNEAL INDENTATION PULSE AND GENERAL ANESTHESIA

Most of the experimental work previously done in animals in order to study the ocular blood supply and hydrodynamics has been performed during general anesthesia. I t is quite possible, however, that the general anesthesia itself to some extent may influence the various factors responsible for the ocular blood supply, such as blood pressure, intraocular pressure and the peripheral vascular resistence. In order to investigate this possibility, dynamic tonometry (Hurrven 1968) was performed during Nembutal (pentobarbital sodium) anesthesia on two rabbits by one of us (I. H.) with a corneal pulse amplitude recorded close to zero as a result. This preliminary finding initiated the present study which offers the results obtained by dynamic tonometry performed before, following premedication and during general anesthesia in human beings.

CONTACT PROBE FOR CORNEAL TEMPERATURE MEASUREMENTS

A thermistor probe for corneal temperature measurements is presented. The temperature‐sensing cartridge is similar in shape to an electronic tonometer, and the procedure of corneal temperature registration is performed just as easily and in a similar manner as for tonography.

Corneal indentation pulse in Sturge-Weber syndrome.

Sturge-Weber syndrome is characterized by nevus of the skin, angiomatous involvement of the meninges and brain, epilepsy, and often glaucoma (Walsh & Hoyt 1969). Congenital glaucoma with bupthalmus is characteristic, but glaucoma with later occurence, without buphthalmus is also seen. Histologic examination has shown angioma of the choroid to be present in a considerable proportion of eyes enucleated for glaucoma (Dunfihy 1935). Most of the angiomas are flat lesions involving the entire choroid. Clinically the angiomas may constitute a choroidal tumor, but in most cases the angioma is not visible by ordinary ophthalmoscopy. It is known that the blood volume of the choroidal system is about 37 times that of the retinal system (Chao, P. & Bettman, /, 1957). Accordingly, hemangiomas of the choroid should be of major importance for the pulse-synchronous changes in intraocular pressure, by yielding an increase in the pulsatile part of the choroidal vascular bed with a corresponding increase in the corneal indentation pulse amplitudes.

A new hereditary syndrome with a bleeding tendency, extreme miosis, spasms, dyslexia, thrombocytopathia etc.: Pupillometric, evaporimetric, and ophthalmological observations

Abstract A recently described familiar syndrome consists of the following components: A bleeding tendency with thrombocytopathia, miosis, muscular weakness and spasms, ichthyosis, asplenia, dyslexia, and headache. Four definite and 2 probable patients have been identified in 4 generations. In the present study, the pupillary behaviour was scrutinized in two ‘definite’ cases with the infrared, binocular pupillometer. The forehead sweating pattern was also investigated with an Evaporimeter. The basal pupillary widths were: 1.25–1.75 mm. Only minor responses were noted upon topical stimulation with an indirectly acting pupillodilating agent (OH‐amphetamine). A directly acting sympathicomimetic drug (phenylephrine) exerted a more marked influence on the pupil, indicating a relative supersensitivity. The evaporimetric pattern in the forehead seemed to be within reference limits, at variance with what is the case in Horners syndrome. Further findings were: the orbit seemed to be smaller than normal; a bilateral VI. cranial nerve palsy was identified, and a marked upward gaze palsy coexisted with pupils with Argyll Robertsons traits. There is no readily acceptable explanation for the ocular abnormalities. The disorder underlying the pupillary abnormality may possibly be located in the upper mesencephalon.

ELECTRONIC TONOMETER CALIBRATION

The Schiartz weight tonometer yields a scale magnification of 20 times, the one mm distance between each scale reading corresponds to a 0.05 mm plunger displacement. When Schietz made his first standard tonometer with a 15 mm radius of curvature of the concave foot plate, his test block had a slightly longer radius of curvature (4). Placed on this poorly fitted test block the zero scale reading was marked, while a certain displacement of the plunger was present. Later on, when the tonometer was placed upon a steel ball with an exact 15 mm radius of curvature, a scale reading of -1.0 was obtained (5). This explains why a 16 mm radius of curvature test block is used today to indicate the zero scale reading in the standardized Schietz weight tonometers; placed on this test block the plunger actually deflects 0.05 mm while the pointer marks zero. This also explains why tonometer readings below zero may be obtained in very hard eyes when using a Schiartz or identical shaped electronic tonometer. When the tonographic technique was introduced in 1950 (3) the advice was given to transfer the panel scale readings to the running paper by adjusting the different levels of plunger deflection by use of a finger tip. Some later models of electronic tonometers have the running paper marked corresponding to each scale reading. In order to use the Friedenwald 1955 tables (2) converting tension readings into m m H g intraocular pressure, it is a demand that not only the scale readings are properly traced, but also that a 50 microns plunger displacement actually exists between each scale reading. Statements and certification tests offered by the manufacturers tell this to be the fact. Figure 1 demonstrate “Part D: Scale indication” of an independent testing laboratory’s certification of Tonographer No. 1574 (see later). The plunger deflection measured on a micrometer in mm from -1.0 scale reading to scale reading 5 is given as 0.25 k 0.009 mm, to scale reading 10 as 0.05 2 0.002 mm