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Intraocular pressure, blood pressure and the optic nerve
392
ABSTRACTS
various planes of transition, and a part that behaves the thickness of the vascular layer. Using differential beginning of the experiment-a higher sensitivity of recording directly the intensity of the returning light. qualitative measurements of oxygen saturation of the
as if passed recording-the the sys;em Changes in blood in the
through a blood film of twice difference made zero at the may be employed than when oxygenation gave reproducible vascular layer.
REFEREXCE Broadfoot,
K. D. Gloster,
Photocoagulation J.
J. and
Greaves,
D. P. (1961).
in Retinal Vein Thrombosis
Brit.
J. Ophthalmol.
45, 161.
*
A. OOSTERHUIS AND S. C. SEDNEY, Leiden
Xenon-arc photocoagulation has been carried out in patients with either central or branch occlusion of a retinal vein. Indications for treatment were: (a) diminishing or low visual acuity, in some of the patients associated with development or presence of cystoid macular degeneration; (b) neovascular proliferation. Fluorographic pictures of the fundus of the eye were a guide on photocoagulation, as they clearly outline (a) the area and intensity of vessel wall leakage; (b) the pattern of retinal vessels to be spared; (c) the areas of new vessel formation. Results were favourable in seven patients with branch occlusion as regards the clearance of haemorrhages and oedema and decrease of vessel leakage. Central vision improved considerably except when cystoid macular degeneration had made recovery of good macular function impossible. In four patients with central venous occlusion the increase of vision was not such as might be expected, in view of the improvement of the fundus aspect after photocoagulation, due to the rather intense irreversible macular degeneration. The results obtained indicate that hypoxia is a major factor in the pathogenesis of the clinical picture in so-called retinal vein thrombosis.
Blood Pressure, Blood Flow and Intraocular D.
Pressure
KASPEL, W. BAUMGARTAND H.Jkv~,Bonn
An experimental series was carried out in order to analyse the influence of blood pressure and blood flow volume on the intraocular pressure in the perfused rabbit’s head. During perfusion of a rabbit’s head, using the blood of a donor-animal (first experimenta. series) there were certain influences of the blood pressure and blood volume on the intraocular pressure to be observed, which were, however, not significant. Perfusion with oxygenated suspension of erythrocytes (2) showed an extremely high coefficient of determination with regard to the influence of blood pressure and blood flow volume. During perfusion with non-oxygenated suspensions of erythrocytes (3), no relationship between blood pressure and intraocular pressure was observed. The findings are discussed with special regard to the interaction between blood pressure and intraocular pressure.
Intraocular K.HEILMANN,
Pressure, Blood Pressure and the Optic Nerve Munich
Clonidine is a new agent for reducing the intraocular pressure. Presumably it exerts a double effect-peripheral and central-although the mode of action is unknown. Clonidine lowers the intraocular pressure in all forms of glaucoma, does not cause contraction of the pupils but unfortunately has some striking systemic effects which may occur after local application: these are sedation, lowering of blood pressure and bradycardia. The effectiveness of a drug introduced into the treatment of glaucoma cannot be measured exclusively by the pressure reducing action. Because the vascular effects in the eye due to Clonidine are largely unknown, ophthalmo-dynamographic investigations were made in a double-blind study. In an acute trial the significant reduction of all the parameters investigated indicated that circulation is altered in a vascular region which is of decisive importance for the influx to the vessels supplying the optic nerve. * With
exhibit.
393
ABSTRACTS
In a further series of tests on the visual field damage due to glaucoma, the effects ofreducing the intraocular pressure alone (with acetazolamide) and of simultaneously lowering the intraocular pressure and systemic blood pressure (with Clonidine) were investigated by individual perimetric comparisons. Whilst the perimetric value was significantly altered by acetazolamide, with Clonidine it remained unaltered within the limits of error. In general, therefore, the perimetric result is imunchanged when the blood proved by lowering the intraocular pressure alone, but it remains pressure is simultaneously decreased. Care is therefore necessary to guard against the possibility that Clonidine therapy may convert glaucoma t,o low-tension glaucoma.
Intraocular D.
COLE
F.
Pressure Responses to Administration AXD
S.?~'AGASUBRAMANIAN,
of Nicotine
London
The effect of intravenous infusion of 250 /*g/min nicotine bitartarate on intraocular pressure was followed by means of applanation tonometry in rabbits given %5:/, ethanol by intragastric tube 35 min previously. Comparison of responses in the same animals with and without nicotine infusion showed that the ocular tension in the nicotine-treated series was significantly increased over that in the control series (ethanol loading only). Administration of nicotine without previous ethanol loading tended to depress ocular tension although there was ocasionally a brief initial increase. In acute experiments in which direct recordings were made of arterial B.P.. anterior chamber temperature and IOP, the response to nicotine consisted of a brief rise of ocular tension followed by a fall associated with comparable changes in blood flow and arterial pressure. It is already known that ethanol loadin, 0 in rabbits suppresses endogenous vasopressin production and causes a fall of ocular tension which may be counteracted or reversed by intravenous infusion of exogenous vasopressin (Pitressin) at a physiological rate (Cole and Nagasubramanian. 1973a, b) and it is suggested that the ocular hypertension observed in the ethanol pretreated animals is due to stimulation of endogenous vasopressin production by the nicotine infusion. (Part Support
of this work was carried out under a Lister from the Fight for Sight Fund, Institute
Research Fellowship of Ophthalmology,
of Moorfields is gratefully
Eye Hospital. acknowledged.)
REFERENCES Cole, D. F. and Nagasubramanian, Cole, D. F. and Nagasubramanian,
The Influence of Adrenergic A.
KEETENS,
S. (1973s). S. (1973b).
Int. Res. Commun. (73), Exp. Eye Res. 16, 251.
Drugs on Intraocular
24-l-l.
Pressure in the Anaesthetized
Dog
Antwcrp
Experiments were performed on mongrel dogs anaesthetized either with morphine (1 mg/kg s.c.) and alpha-chloralose (80 mg/kg i.v.) or with pentobarbital (30 mg/kg i.v.). Parameters measured were: arterial blood pressure (femoral artery), recipient venous pressure (ipsilateral jugular vein) and intraocular pressure. The effects of carotid artery and jugular vein occlusion were checked. Noradrenaline, not administered topically, lowered the intraocular pressure, whilst adrenaline produced inconsistent responses. Isoproterenol, also not administered topically, had an intraocular pressure raising effect. Unless extremely low doses are used, these effects tend to be masked by opposite changes of arterial perfusing pressure.
The Mechanism Study
of Aqueous Outflow in Primates,
RANESH C.TRIPATHIAND
Lower Mammals
and Birds: a Comparative
BRENDA J. TREATHI, London
The channel immediately concerned with the drainage of the aqueous from the angular (trabecuiar) meshwork in primates is known as the canal of Schlemm. Although controversy exists as to the presence of a comparable structure in lower mammals and birds, our light- and electron-microscopical studies have shown that analogous aqueous drainage channels, which we prefer to term “angular a.queous plexus/sinus”, indeed exist in non-primates. It was further shown that although in gross morphology (location, limit and general shape), the angular aqueous plexus/sinus in primates, lower mammals and birds differ from species to species, they have certain common features. H
ABSTRACTS
various planes of transition, and a part that behaves the thickness of the vascular layer. Using differential beginning of the experiment-a higher sensitivity of recording directly the intensity of the returning light. qualitative measurements of oxygen saturation of the
as if passed recording-the the sys;em Changes in blood in the
through a blood film of twice difference made zero at the may be employed than when oxygenation gave reproducible vascular layer.
REFEREXCE Broadfoot,
K. D. Gloster,
Photocoagulation J.
J. and
Greaves,
D. P. (1961).
in Retinal Vein Thrombosis
Brit.
J. Ophthalmol.
45, 161.
*
A. OOSTERHUIS AND S. C. SEDNEY, Leiden
Xenon-arc photocoagulation has been carried out in patients with either central or branch occlusion of a retinal vein. Indications for treatment were: (a) diminishing or low visual acuity, in some of the patients associated with development or presence of cystoid macular degeneration; (b) neovascular proliferation. Fluorographic pictures of the fundus of the eye were a guide on photocoagulation, as they clearly outline (a) the area and intensity of vessel wall leakage; (b) the pattern of retinal vessels to be spared; (c) the areas of new vessel formation. Results were favourable in seven patients with branch occlusion as regards the clearance of haemorrhages and oedema and decrease of vessel leakage. Central vision improved considerably except when cystoid macular degeneration had made recovery of good macular function impossible. In four patients with central venous occlusion the increase of vision was not such as might be expected, in view of the improvement of the fundus aspect after photocoagulation, due to the rather intense irreversible macular degeneration. The results obtained indicate that hypoxia is a major factor in the pathogenesis of the clinical picture in so-called retinal vein thrombosis.
Blood Pressure, Blood Flow and Intraocular D.
Pressure
KASPEL, W. BAUMGARTAND H.Jkv~,Bonn
An experimental series was carried out in order to analyse the influence of blood pressure and blood flow volume on the intraocular pressure in the perfused rabbit’s head. During perfusion of a rabbit’s head, using the blood of a donor-animal (first experimenta. series) there were certain influences of the blood pressure and blood volume on the intraocular pressure to be observed, which were, however, not significant. Perfusion with oxygenated suspension of erythrocytes (2) showed an extremely high coefficient of determination with regard to the influence of blood pressure and blood flow volume. During perfusion with non-oxygenated suspensions of erythrocytes (3), no relationship between blood pressure and intraocular pressure was observed. The findings are discussed with special regard to the interaction between blood pressure and intraocular pressure.
Intraocular K.HEILMANN,
Pressure, Blood Pressure and the Optic Nerve Munich
Clonidine is a new agent for reducing the intraocular pressure. Presumably it exerts a double effect-peripheral and central-although the mode of action is unknown. Clonidine lowers the intraocular pressure in all forms of glaucoma, does not cause contraction of the pupils but unfortunately has some striking systemic effects which may occur after local application: these are sedation, lowering of blood pressure and bradycardia. The effectiveness of a drug introduced into the treatment of glaucoma cannot be measured exclusively by the pressure reducing action. Because the vascular effects in the eye due to Clonidine are largely unknown, ophthalmo-dynamographic investigations were made in a double-blind study. In an acute trial the significant reduction of all the parameters investigated indicated that circulation is altered in a vascular region which is of decisive importance for the influx to the vessels supplying the optic nerve. * With
exhibit.
393
ABSTRACTS
In a further series of tests on the visual field damage due to glaucoma, the effects ofreducing the intraocular pressure alone (with acetazolamide) and of simultaneously lowering the intraocular pressure and systemic blood pressure (with Clonidine) were investigated by individual perimetric comparisons. Whilst the perimetric value was significantly altered by acetazolamide, with Clonidine it remained unaltered within the limits of error. In general, therefore, the perimetric result is imunchanged when the blood proved by lowering the intraocular pressure alone, but it remains pressure is simultaneously decreased. Care is therefore necessary to guard against the possibility that Clonidine therapy may convert glaucoma t,o low-tension glaucoma.
Intraocular D.
COLE
F.
Pressure Responses to Administration AXD
S.?~'AGASUBRAMANIAN,
of Nicotine
London
The effect of intravenous infusion of 250 /*g/min nicotine bitartarate on intraocular pressure was followed by means of applanation tonometry in rabbits given %5:/, ethanol by intragastric tube 35 min previously. Comparison of responses in the same animals with and without nicotine infusion showed that the ocular tension in the nicotine-treated series was significantly increased over that in the control series (ethanol loading only). Administration of nicotine without previous ethanol loading tended to depress ocular tension although there was ocasionally a brief initial increase. In acute experiments in which direct recordings were made of arterial B.P.. anterior chamber temperature and IOP, the response to nicotine consisted of a brief rise of ocular tension followed by a fall associated with comparable changes in blood flow and arterial pressure. It is already known that ethanol loadin, 0 in rabbits suppresses endogenous vasopressin production and causes a fall of ocular tension which may be counteracted or reversed by intravenous infusion of exogenous vasopressin (Pitressin) at a physiological rate (Cole and Nagasubramanian. 1973a, b) and it is suggested that the ocular hypertension observed in the ethanol pretreated animals is due to stimulation of endogenous vasopressin production by the nicotine infusion. (Part Support
of this work was carried out under a Lister from the Fight for Sight Fund, Institute
Research Fellowship of Ophthalmology,
of Moorfields is gratefully
Eye Hospital. acknowledged.)
REFERENCES Cole, D. F. and Nagasubramanian, Cole, D. F. and Nagasubramanian,
The Influence of Adrenergic A.
KEETENS,
S. (1973s). S. (1973b).
Int. Res. Commun. (73), Exp. Eye Res. 16, 251.
Drugs on Intraocular
24-l-l.
Pressure in the Anaesthetized
Dog
Antwcrp
Experiments were performed on mongrel dogs anaesthetized either with morphine (1 mg/kg s.c.) and alpha-chloralose (80 mg/kg i.v.) or with pentobarbital (30 mg/kg i.v.). Parameters measured were: arterial blood pressure (femoral artery), recipient venous pressure (ipsilateral jugular vein) and intraocular pressure. The effects of carotid artery and jugular vein occlusion were checked. Noradrenaline, not administered topically, lowered the intraocular pressure, whilst adrenaline produced inconsistent responses. Isoproterenol, also not administered topically, had an intraocular pressure raising effect. Unless extremely low doses are used, these effects tend to be masked by opposite changes of arterial perfusing pressure.
The Mechanism Study
of Aqueous Outflow in Primates,
RANESH C.TRIPATHIAND
Lower Mammals
and Birds: a Comparative
BRENDA J. TREATHI, London
The channel immediately concerned with the drainage of the aqueous from the angular (trabecuiar) meshwork in primates is known as the canal of Schlemm. Although controversy exists as to the presence of a comparable structure in lower mammals and birds, our light- and electron-microscopical studies have shown that analogous aqueous drainage channels, which we prefer to term “angular a.queous plexus/sinus”, indeed exist in non-primates. It was further shown that although in gross morphology (location, limit and general shape), the angular aqueous plexus/sinus in primates, lower mammals and birds differ from species to species, they have certain common features. H