Fluorescein angiography during induced ocular hypertension in man

Development and clinical application of an quantitative head-band formed ocular compressor

In order to investigate the efficiency of a new quantitative head-band formed ocular compressor to reduce intraocular pressure (IOP), ocular compression by this new reducer with 40 mmHg for 10 min was performed on 87 cataractous eyes of 78 cases. The changes of IOP (87 eyes) and anterior chamber depth (ACD) were observed. There was a significant decrease of IOP and increase of ACD within 30 min after decompression (P < 0.001). The mean decrease of IOP was 5.62 +/- 2.41 mmHg and the mean increase of ACD was 0.18 +/- 0.09 mm within 5 min after decompression. The IOP 5 min after decompression had no significant difference with that 10 min after decompression (P > 0.05). IOP below 10 mmHg could last for about 15 min. This apparatus had been successfully applied to 80 eyes for extracapsular cataract extraction. It was suggested that this device had the advantages of safety, accurate quantification, reliable effect, casually adjusting pressure according to various demands and time-saving.

The blood supply of the optic nerve head and the evaluation of it - myth and reality

Evidence has gradually emerged that there is vascular insufficiency in the optic nerve head (ONH) in both anterior ischemic optic neuropathy (AION) and glaucomatous optic neuropathy (GON); thus both represent ischemic disorders of the ONH. Together these diseases constitute a major cause of blindness or seriously impaired vision in man. Consequently there has recently been great interest in the ONH circulation in health and disease and in how to evaluate it. Many studies of the subject have been published, with conflicting interpretations and claims. The basis of the inconsistent information seems to be confusion on some fundamental issues concerning the ONH circulation itself. The objective of this paper is to differentiate myths and misconceptions from reality about the ONH blood supply; to elucidate the reasons for disagreement on the blood supply of the ONH; and to evaluate the reliability and validity of various methods currently used to measure ONH blood flow.

Diagnosis and pathogenesis of glaucomatous optic neuropathy: morphological aspects

Glaucomatous optic neuropathy is classified by morphologic changes in the intrapapillary and parapapillary region of the optic nerve head and the retinal nerve fibre layer. These changes can be evaluated using descriptive optic nerve head variables which are the size and shape of the optic disc; size, shape and pallor of the neuroretinal rim; size of the optic cup in relation to the area of the disc; configuration and depth of the optic cup; cup-to-disc diameter ratio and cup-to-disc area ratio; position of the exit of the central retinal vessel trunk on the lamina cribrosa surface; presence and location of splinter-shaped haemorrhages; occurrence, size, configuration and location of parapapillary chorioretinal atrophy; diffuse and/or focal decrease of the diameter of the retinal arterioles; and visibility of the retinal nerve fibre layer. Assessment of these variables is useful for the early detection of glaucomatous optic nerve damage, to follow-up patients with glaucoma, to differentiate various types of the chronic open-angle glaucomas, and to get hints for the pathogenesis of glaucomatous optic nerve fibre loss.

Optic disk morphology in experimental central retinal artery occlusion in rhesus monkeys

PURPOSE

To evaluate longitudinally the optic disk morphology of nonglaucomatous optic nerve damage secondary to retinal nerve fiber damage, using experimental central retinal artery occlusion in rhesus monkey eyes as a model.

METHODS

This prospective study included 24 eyes of 16 monkeys. In eight eyes of eight animals, central retinal artery occlusion was produced by clamping the central retinal artery in the retrobulbar space. Occlusion was verified by fluorescein fundus angiography. The same eyes at baseline as well as the eight contralateral healthy eyes and eight monkey eyes with experimental high-pressure glaucoma served as control groups. Serially taken optic disk photographs were morphometrically evaluated.

RESULTS

The area and shape of the neuroretinal rim and alpha zone and beta zone of parapapillary chorioretinal atrophy of eyes after central retinal artery occlusion did not vary significantly (P > .30) from the same eyes before central retinal artery occlusion nor from the normal contralateral eyes. In the glaucomatous eyes, the neuroretinal rim was significantly (P < .001) smaller and parapapillary atrophy significantly (P = .01) larger than in the eyes after central retinal artery occlusion.

CONCLUSIONS

Experimental central retinal artery occlusion, in contrast to glaucoma, does not markedly change the size and shape of parapapillary atrophy and neuroretinal rim; this confirms previous clinical studies. Thus, assessment of parapapillary atrophy and neuroretinal rim may be helpful to differentiate between glaucomatous optic neuropathy and nonglaucomatous optic neuropathy secondary to retinal nerve fiber damage. Parapapillary atrophy is independent of decreased retinal blood perfusion and development of nonglaucomatous optic nerve atrophy following experimental central retinal artery occlusion.

Hemodynamic parameter estimation from ocular fluorescein angiograms

BACKGROUND

A method is proposed for parameterizing choroidal blood flow from fluorescein angiograms.

METHODS

After digitizing and aligning the angiographic sequence, the intensity build-up curves of fluorescence are analysed per pixel (approx. 10 microns in fundo). Two models are compared. A one-compartment model predicts an exponential build-up curve, from which the following parameters are estimated: maximum fluorescence, dye appearance time and local perfusion rate (reciprocal of the time constant of the exponential). To account for the contribution of the systemic circulation to the shape of the build-up curve, a two-compartment model is used which predicts a bi-exponential curve.

RESULTS

Introduction of the second (systemic) compartment resulted in a significant improvement of fit in 37 of 48 patients studied. The rate constants of the systemic compartment found were mainly in the range of 0.30-1.00 s-1.

CONCLUSION

For the individual patient, the local perfusion rates may vary strongly, with lower perfusion rates possibly being of prognostic value for ocular diseases such as glaucoma or diabetic retinopathy.

The effect of arterial pressure on the ocular pressure-volume relationship in the rabbit

The purpose of this study was to quantify the effect of mean arterial pressure (MAP) on the ocular pressure-volume relationship. The experiments were performed in pentobarbital anesthetized rabbits instrumented with occluders on the thoracic aorta and inferior vena cava to control MAP which was measured via a cannula in the central ear artery. To vary the ocular volume and measure the intraocular pressure (IOP), two 23 gauge needles were inserted through the pars plana into the vitreous: one needle was connected to a saline-filled syringe and the other needle was connected to a pressure transducer. In one group of animals (n = 5), pressure-volume curves were determined at MAPs of 100, 80, 60, 40 and 20 mmHg and post mortem by cumulative saline injections (2 microliters) every 1-1.5 sec. In a second group (n = 7), pressure-volume curves were obtained at MAPs of 80, 60 and 40 mmHg and post mortem by saline infusion at 0.5 microliter sec-1 until the IOP reached 100 mmHg. The infusion protocol was repeated in a third group (n = 11) where the choroidal flux and the concentration of moving blood cells (CMBC) were measured by a laser Doppler flowmeter as indices of choroidal blood flow and the blood volume, respectively. MAP had three primary effects on the ocular pressure-volume relationship: (1) the baseline IOP varied exponentially with MAP, (2) the steepness of the initial portion of the pressure-volume curves was MAP-dependent and (3) the curves exhibited a 'plateau' as the IOP approached the prevailing MAP at MAPs > or = 40 mmHg. All of the curves in the living eye intersected and became indistinguishable from the post mortem curve when the IOP exceeded the prevailing MAP. The flux and CMBC measurements indicated that the MAP-dependence of the initial portion of the curves was due to failure of choroidal autoregulation and diminished increases in choroidal blood volume at the lower MAPs, and that the plateau portion of the curves was due to expulsion of blood from the eye. It is concluded that MAP has a significant effect on the ocular pressure-volume relationship.

Trabeculectomy is associated with retrobulbar hemodynamic changes. A color Doppler analysis

PURPOSE

To determine whether color Doppler hemodynamic changes occur in the retrobulbar circulation after trabeculectomy.

METHODS

The authors prospectively enrolled 20 patients undergoing trabeculectomy and performed color Doppler imaging of both eyes before surgery and then at approximately 2-, 5-, and 14-week intervals after surgery. The systolic maximum velocity, mean velocity, end-diastolic velocity, and vascular resistance (resistance index) of the central retinal artery, nasal and temporal short posterior ciliary arteries, and ophthalmic arteries were determined. Statistical comparison of the preoperative and postoperative measures were performed on both the operative and nonoperative eye using the paired Student's t test.

RESULTS

A statistically significant increase was observed in the mean and end-diastolic velocity and a significant decrease in the vascular resistance of the central retinal artery and both short posterior ciliary arteries at nearly all postoperative intervals (25 of 27 preoperative and postoperative comparisons; P < 0.05) The ophthalmic artery, while showing an increased velocity at all intervals, only attained a statistically significant increase in one of three postoperative intervals for mean velocity and two of three intervals for end-diastolic velocity (P < 0.05). There were no notable changes in resistance. The nonoperative eye did not show a statistically significant change in velocity or in resistance in the central retinal artery or either nasal or temporal short posterior ciliary artery at any interval (0 of 27 preoperative and postoperative comparisons for mean velocity, end-diastolic velocity, and resistance index.)

CONCLUSION

Sustained increases in mean velocity and end-diastolic velocity and decreases in resistance index were observed in the central retinal artery and the short posterior arteries with clinically attainable reductions in intraocular pressure after trabeculectomy in patients with chronic glaucoma. These findings are consistent with, but not diagnostic of, increased blood flow through these vessels.

Anterior ischaemic optic neuropathy and intraocular pressure

Anterior ischaemic optic neuropathy is a stroke syndrome of the distal optic nerve, characterised by disc oedema and optic nerve dysfunction--loss of central vision, loss of colour vision, a relative afferent pupillary defect, and nerve fibre layer field loss. We prospectively evaluated the changes of intraocular pressure throughout the day in 16 patients with non-arteritic anterior ischaemic optic neuropathy and 15 normal control subjects of similar age and race. The peak intraocular pressure exceeded 21 mm Hg in five of the ischaemic optic neuropathy patients but none of the controls. The mean peak intraocular pressure was 19.9 mm Hg for the ischaemic optic neuropathy group versus 17.6 mm Hg for controls (p = 0.034). The range of intraocular pressure was also greater for the ischaemic optic neuropathy group (p = 0.030). Eight of 16 ischaemic optic neuropathy patients had a range of intraocular pressure of 6 mm Hg or more, compared with three of 15 control subjects. The intraocular pressure exceeded 21 mm Hg during a subsequent visit in two additional patients in whom the hourly determined intraocular pressure peaked at less than 21 mm Hg. Thus, seven of 16 of our ischaemic optic neuropathy group had an intraocular pressure exceeding 21 mm Hg during the study period. Raised intraocular pressure may be a predisposing factor in some patients who develop anterior ischaemic optic neuropathy.

Main posterior watershed zone of the choroid. Variations of its position in normal subjects

The main posterior watershed zone of the choroid is located between the nasal edge of the optic disc and the fovea and represents the area situated between the territories supplied by the temporal and nasal posterior ciliary arteries. In the fluorescein angiographies of 800 normal subjects a watershed zone was not observed in 33.1% due to technical reasons and in 22.3% due to the simultaneous filling of the peripapillar and macular choriocapillaris. In the remaining 44.6% the watershed zone was well outlined: it was straddling the optic disc in about half of these cases and involved the temporal half of the optic disc and the close choroid in the other half. Very rarely the watershed zone involved the nasal half of the optic disc or the papillo-macular area. The position of the watershed zone could be important to explain the visual field defect in anterior ischemic optic neuropathy and glaucoma.

Anterior ischaemic optic neuropathy secondary to cluster headache

This report describes a patient with cluster headache who developed anterior ischaemic optic neuropathy during an attack of headache, an association not previously described. A possible pathophysiologic mechanism based upon the understanding of optic disc physiology and ocular vascular pathology in headache syndromes is proposed.

[The electroretinogram and the visual evoked potential in normal and glaucomatous eyes (author's transl)]

The functional changes of the intraocular nerve structures caused by glaucoma were examined electro-ophthalmologically. The OPs, the photopic and scotopic ERG to examine the receptor and bipolar layers, as well as the EPs, elicited by luminance and pattern-reversal stimuli, for evaluation of the signal conduction in the optic nerve, were recorded. The problem was approached by way of three investigations: first was the question of which nerve structures are affected by glaucoma and exactly how the loss of visual field due to glaucoma can be determined. For this reason, 55 glaucomatous eyes with regulated intraocular pressure and different visual field losses were examined. The results show a functional diminution of all intraocular nerve structures in which the prelaminary part of the optic nerve is most affected. Differences in the visual field loss of both eyes can be well determined by the EPs. Second, the electro-ophthalmologic behavior in seven normal and eight pressure-regulated glaucomatous eyes was studied by gradually elevated intraocular pressure in order to obtain better insight into the functional pathology of glaucoma. The elevation of intraocular pressure was performed with a Müller spring dynamometer in five steps, depending on the ophthalmic blood pressure. The pressure behavior of the ERG components and the EPs is different. The amplitudes of the ERG components show a gradual decrease in normal as well as in glaucomatous eyes when intraocular pressure is increased, and are maintained when intraocular pressure reaches ophthalmic blood pressure. On the other hand, the EPs show a strong decrease in amplitude when intraocular pressure exceeds the mean ophthalmic blood pressure, particularly in the case of glaucomatous eyes. This behavior can be explained by a high pressure sensitivity of the preliminary part of the optic nerve, even greater in glaucomatous eyes. Third, the influence of pressure decrease on the electrical response was examined in glaucomatous eyes with chronic and acute pressure increase before and after pressure regulation. A mean pressure decrease of 37-13.6 mm Hg in ten eyes with chronic pressure increase led to no change in electrical responses other than a phase shift on the pattern-reversal EPs. In five cases with acute pressure increase, an amplitude increase on the luminance EPs was noticed after pressure regulation, with unchanged systemic blood pressure and almost unchanged ERG components. However, in one case an amplitude decrease on luminance EPs and ERG components was found with simultaneous blood pressure decrease. The increase of the amplitudes of the luminance EPs and the phase shifts of the pattern-reversal EPs can be explained as the functional improvement of the prelaminary part of the optic nerve caused by pressure decrease due to improved blood circulation in the prelaminary part of the optic nerve...

Low-tension glaucoma

A retrospective study of 45 patients with low-tension glaucoma revealed the mean age at diagnosis to be 66 years. Seventeen patients had follow-up visual field examinations, the average follow-up period being 6.4 years. There was no significant difference in prognosis of the ocular course between patients with Po/C equal to or greater than 100 and those with Po/C less than 100. The presence of splinter hemorrhages at the optic disk (10% of affected eyes) or of systemic arterial hypertension (diastolic blood pressure greater than 100 mm Hg) was associated with progression of visual field defects. Patients with sudden visual loss or associated hemodynamic events (33% of the total patients) had a more favorable prognosis regarding stability (lack of progression) of visual field defects than those without such an event. Extension of visual field defects across the macula was a common finding (25% of affected eyes). No firm evidence was obtained to indicate that treatment of the low-tension glaucoma improved the prognosis of the ocular course.

Ischaemic papillopathy. Clinical and fluorescein aniographic review of forty cases

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Ischaemic optic neuropathy in chronic simple glaucoma

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