Læknablaðið - 15.06.1997, Page 80

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LÆKNABLAÐIÐ 1997; 83
A-15. Changes in choroidal circulation at
the macula following panretinal photo-
coagulation
Rhatigan MC, Roxburgh STD, Sutton D, Suchi A
From The Department of Ophthalmology, The De-
partment of Medical Physics, Ninewells Hospital
and Medical School, Dundee DDl 9SY, Scotland
Introduction: Argon laser photocoagulation
has been shown to cause permanent closure of the
choriocapillaris and animal studies have demon-
strated increased blood flow in the sub-macular
choroid following panretinal photocoagulation.
In this study the changes in choroidal blood flow
in the human submacular choroidal circulation in
response to panretinal argon laser photocoagula-
tion were quantified using image processing com-
puter softwear to analyse indocyanine green an-
giograms (ICGA).
Material and methods: Three patients with pro-
liferative diabetic retinopathy had ICGA with a
scanning laser ophthalmoscope using a standard
protocol before and 48 hours after treatment (av-
erage nurnber of argon laser burns 1454). ICGA
images were recorded on S-VHS videotape and
sequences for analysis were digitised using a
frame grabber interfaced to a SUN SPARC 20
computer. A sequence of frames between dye
entry and the end of dye filling was analysed and
the indocyanine fluorescence of selected submac-
ular choroid for each frame was determined. The
mean dye-filling rate was calculated and the data
capture and analysis procedures were repeated for
each angiogram. The respective grey level ratio
versus time curves were plotted and compared.
Results: The results show an increase in choroi-
dal blood flow at the macula following panretinal
photocoagulation in the three cases studied (14-
36% increase).
Discussion: Argon laser obliteration of periph-
eral choriocapillaris is likely to cause redistribution
of blood in the choroidal vascular network. This
study supports this and the authors propose that the
resulting increase in the submacular choroidal
blood flow may be a factor in the pathogenesis of
macular oedema following such treatment.
A-16. Retinal vessel dilatation and elon-
gation: a role in the pathophysiology of
diabetic macular edema
Einar Stefánsson, Jóhannes Kári Kristinsson,
Man'a Soffía Gottfreðsdóttir
From The Department of Ophthalmology, Uni-
versity of Iceland, Reykjavík, Iceland
Purpose: We have developed a hypothesis
based on Starling’s law to explain the formation
of diabetic macular edema and its disappearance
following laser photocoagulation. It predicts that
during the development of diabetic macular ede-
ma we should see a dilation and elongation of the
retinal arterioles and venules involved. This study
is undertaken to test the hypothesis by measuring
the diameter and segment length of retinal arte-
rioles, venules and their macular branches before
the development of diabetic macular edema and
at time of diagnosis of diabetic macular edema.
Material and methods: From a group of diabetics
who have been followed in our clinic with annual
fundus photographs we selected three groups (12
each) of patients with (1) no diabetic retinopathy
(NDR), (2) background diabetic retinopathy
(BDR) that was stable throughout the observation
period and (3) those who developed diabetic mac-
ular edema (DME). The diameter and segment
length of retinal vessels was measured at the begin-
ning of an approximately four year follow-up peri-
od and at the end, which was the time of diagnosis
of diabetic macular edema in the DME group.
Results: A statistically significant dilatation
and elongation of retinal arterioles, venules and
their macular branches was seen in the DME
group and no significant changes were found in
the NDR and BDR groups.
Conclusion: Our measurements demonstrate
dilatation and elongation of arterioles and ven-
ules serving the macula preceding the formation
of diabetic macular edema. This suggest that Star-
ling’s law plays a role in the pathophysiology of
retinal edema, just as it does in most, if not all
tissues in the body.
A-17. Optic nerve sheath meningioma
management
Scott CM, Cullen JF
From The Princess Alexandra Eye Pavillion,
Edinburgh, Scotland
A series of six patients with optic nerve sheath
meningioma is presented, comparing modes of
presentation and treatment with visual outcome.
The rationale for proceeding to surgery in five
patients is explained with emphasis on the case of
one patient who regained and who has retained
visual function after microsurgical resection of
the meningioma with preservation of the optic
nerve. Case histories, clinical photographs, oper-
ative drawings and pathological macroscopic
specimens and histology are presented, followed
by a discussion of the current thinking in the
management of this condition, which is frequent-
ly not straightforward.