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Photocoagulation and the electroretinogram
The Influence of Epinephrine, Tolazoline (Priscoline) and Corticosteroids through Capillaries at the Cornea1 Limbus in Man B. JIEISSNER
11. brEDBURG.
AXD
li.
MIE,
on the Blood Flovv
~ii~.wkt~llf
The influence of various locally applied drugs was studied by means of fluorescein angiography of capillaries at the cornea1 limbus. Epinephrine caused a definite reduction of blood flow and t,olazoline produced hyperaemia. Dexamethasone had a slight inhibitory effect on the blood flow. In ocular inflammat,ion due to cornea1 grafting (rejection reactions) the influence of local and systemic corticosteroid treatment on limbal capillaries was also demonstrated. In these cases the question arises as to whether the reduction of hyperaemia is a primary effect on the vessel3 or nlerely secondary to the reduction of the innnunologirnl reaction.
Photocoagulation
and the Electroretinogram
Retinal function can objectively be assessed by means of the electroretinogram (EM:). Such assessment is difficult in disturbances of the retinal circulation, when photocoagulat,ion has been carried out, since the influence of the coagulation itself on the ERG is not exactly known. \Ve approached this problem by examining the ER,(+ in a group of rabbits before and after coagulation. comparing the decrease in height of the electrical responses with the extent anti localization of the coagulated area. The decrease in height of the responses after phot,ocoagulation applied in a checkerboard pattern is more than one would expect considering the ophthalmoscopic aspect Histologically, it, appeared that this discrepancy may be ascribed to a degeneration of the retina between the coagulations. After serried coagulations eliminating less than 30°, of the retinal surface, the ERG is reduced proportionally to the destroyed area. When more t.hsn 3W,, of the retinal surface is eliminatcti. the decrease in response becomes greater than t,he enlargement of t,hc coagulated area. C’ongulation of the retinal periphery will be performed in order to investigate whether these findings are to be attributed to a relatively high contribrrtion of the retinal prriphery to the ER( I.
Retinal Blood Flow after Experimental 11. \\'.
HILL
.\XD
S. POUYG.
Photocoagulation
London
Photocoagulation has been applied by xenon arc, to close the capillary bed in the lower temporal quadrant of one eye in four cats, after preliminary tine-angiography. Three weeks later the flo\\ rate has been reassessed and the animal sacrificed to allow post mortem examinat’ion of the injrctctl flattened retina. Flow in the major arteriole supplying the coagulated area was reduced in proportion to the extent of the coagulated area. Flow in the branches supplying t.he coagulated area was greatly reduced, but that into branches supplying untreated retina depended upon the flow rate of t.bc parent major arteriole. Reduction to 75O ;1 pretreatment vallle was accompanied b,v an increase. &Au&ion to 5Oo,, by a decrease in branch vessel flolv. The exnlanation of this behaviour is likelv to lie with the rhcologv U” of the blood. The results roaltl be if importance in clinical phot,ocoagnlat’ion and in the pathogcnesis of occlusive PRSWI:II rctinopathp. Y
Evolution of Optic Disc Oedema in Raised Intracranial S. S. HAYREH
AND
31. S. HAYREH,
Ioun
City,
Pressure. Experimental
Study
U.S.A.
Progressively growing intracranial space-taking lesions \vero simulated in 33 monkeys by balloons introduced into the subarachnoid space. The fundi were examined ophthalmoscopically, bv stereoscopic colour fundus photography and by fluoresccin angiography serially to’ study the evolut.ion and resolution of optic oedema (ODO) and the patt.erns revealed by each technique at different stages of ODO. These studies revealed that ODO first appears at the lower pole, then the upper pole. then the nasal part and lastly the temporal part of the disc, and that the severity of the swelling generally follows suit: most marked at t,he lower pole, etc. (I’ < 0~005). Except in very early ODO, striation of the nerve fibres (best seen in the peripapillary retina) was a constant ophthalmoscopic finding and seems to represent axoplasmic flow stasis.
11. brEDBURG.
AXD
li.
MIE,
on the Blood Flovv
~ii~.wkt~llf
The influence of various locally applied drugs was studied by means of fluorescein angiography of capillaries at the cornea1 limbus. Epinephrine caused a definite reduction of blood flow and t,olazoline produced hyperaemia. Dexamethasone had a slight inhibitory effect on the blood flow. In ocular inflammat,ion due to cornea1 grafting (rejection reactions) the influence of local and systemic corticosteroid treatment on limbal capillaries was also demonstrated. In these cases the question arises as to whether the reduction of hyperaemia is a primary effect on the vessel3 or nlerely secondary to the reduction of the innnunologirnl reaction.
Photocoagulation
and the Electroretinogram
Retinal function can objectively be assessed by means of the electroretinogram (EM:). Such assessment is difficult in disturbances of the retinal circulation, when photocoagulat,ion has been carried out, since the influence of the coagulation itself on the ERG is not exactly known. \Ve approached this problem by examining the ER,(+ in a group of rabbits before and after coagulation. comparing the decrease in height of the electrical responses with the extent anti localization of the coagulated area. The decrease in height of the responses after phot,ocoagulation applied in a checkerboard pattern is more than one would expect considering the ophthalmoscopic aspect Histologically, it, appeared that this discrepancy may be ascribed to a degeneration of the retina between the coagulations. After serried coagulations eliminating less than 30°, of the retinal surface, the ERG is reduced proportionally to the destroyed area. When more t.hsn 3W,, of the retinal surface is eliminatcti. the decrease in response becomes greater than t,he enlargement of t,hc coagulated area. C’ongulation of the retinal periphery will be performed in order to investigate whether these findings are to be attributed to a relatively high contribrrtion of the retinal prriphery to the ER( I.
Retinal Blood Flow after Experimental 11. \\'.
HILL
.\XD
S. POUYG.
Photocoagulation
London
Photocoagulation has been applied by xenon arc, to close the capillary bed in the lower temporal quadrant of one eye in four cats, after preliminary tine-angiography. Three weeks later the flo\\ rate has been reassessed and the animal sacrificed to allow post mortem examinat’ion of the injrctctl flattened retina. Flow in the major arteriole supplying the coagulated area was reduced in proportion to the extent of the coagulated area. Flow in the branches supplying t.he coagulated area was greatly reduced, but that into branches supplying untreated retina depended upon the flow rate of t.bc parent major arteriole. Reduction to 75O ;1 pretreatment vallle was accompanied b,v an increase. &Au&ion to 5Oo,, by a decrease in branch vessel flolv. The exnlanation of this behaviour is likelv to lie with the rhcologv U” of the blood. The results roaltl be if importance in clinical phot,ocoagnlat’ion and in the pathogcnesis of occlusive PRSWI:II rctinopathp. Y
Evolution of Optic Disc Oedema in Raised Intracranial S. S. HAYREH
AND
31. S. HAYREH,
Ioun
City,
Pressure. Experimental
Study
U.S.A.
Progressively growing intracranial space-taking lesions \vero simulated in 33 monkeys by balloons introduced into the subarachnoid space. The fundi were examined ophthalmoscopically, bv stereoscopic colour fundus photography and by fluoresccin angiography serially to’ study the evolut.ion and resolution of optic oedema (ODO) and the patt.erns revealed by each technique at different stages of ODO. These studies revealed that ODO first appears at the lower pole, then the upper pole. then the nasal part and lastly the temporal part of the disc, and that the severity of the swelling generally follows suit: most marked at t,he lower pole, etc. (I’ < 0~005). Except in very early ODO, striation of the nerve fibres (best seen in the peripapillary retina) was a constant ophthalmoscopic finding and seems to represent axoplasmic flow stasis.