The SA Journal Diabetes & Vascular Disease Vol 7 No 3 (September 2010) - page 31

"
VOLUME 7 NUMBER 3 • SEPTEMBER 2010
117
SA JOURNAL OF DIABETES & VASCULAR DISEASE
Patient
information
leaflet
Keep and Copy Series
LASER TREATMENT FOR DIABETIC
RETINOPATHY
WHAT IS LASER?
Laser is the acronym for Light Amplification by
Stimulated Emission of Radiation. The laser machine
generates a powerful light beam consisting of a sin-
gle wavelength of light.
WHAT IS DIABETIC RETINOPATHY?
Over time, high blood glucose will cause damage to
retinal blood vessels, leading to diabetic retinopathy.
The damaged blood vessels might leak onto the
macula at the centre of the retina (often referred to
as diabetic maculopathy or diabetic macular oede-
ma/swelling) or, because of the damage to the blood
vessels, they eventually close off completely, leading
to ischaemia (death) of the peripheral retina.
This ischaemic retina then produces a substance
called vascular endothelial growth factor (VEGF),
which stimulates the growth of abnormal new ves-
sels on the surface of the retina (referred to as pro-
liferative diabetic retinopathy). These vessels often
bleed or are accompanied by scar tissue, which
contracts over time and pulls the retina off (tractional
retinal detachment).
HOW DOES LASER WORK IN DIABETIC
RETINOPATHY?
When a laser is aimed at the eye, there are three
types of tissue reactions that can be seen depending
on the wavelength of the laser light used: photoco-
agulation (burns), photodisruption (small explosion),
or photoablation (precise removal of tissue).
Many people are familiar with the excimer laser,
which utilises light of 193 nm and causes ablation
of the surface of the cornea, thereby changing the
refraction of the eye and allowing patients to see
without spectacles. This is however not the same la-
ser used for the treatment of diabetic retinopathy. In
the case of diabetic retinopathy we need to use a la-
ser with a wavelength of 532 nm to photocoagulate
(burn) the retina. Retinal phototcoagulation is usually
of three types:
Panretinal (scatter) laser photocoagulation
A large number of laser burns (up to 3 000) are made
to the peripheral retina to destroy the ischaemic ar-
eas of retina thereby decreasing the production of
vascular endothelial growth factors and ultimately
leading to regression of the abnormal new vessels
on the surface of the retina.
Focal laser photocoagulation
The laser beam is directed at specific leaking blood
vessels (micro-aneurysms) in a small area at the
centre of the retina (macula) to seal off the leak. The
burns are usually few, small and of low power.
Grid laser photocoagulation
The laser treatment is done for diffuse leakage in the
macular region. The beam is not aimed at specific
blood vessels, but rather is put down in a grid pat-
tern around the central point (fovea) at the back of
the eye, always remaining about 1 mm away from
the fovea.
WHY SHOULD I HAVE LASER TREATMENT?
Laser treatment is done to reduce the risk of vision
loss caused by diabetic retinopathy. It is most often
used to stabilise vision and prevent future loss rather
than improve vision loss that has already occurred.
Linda Visser
Department of Ophthalmology,
Nelson R Mandela School of Medi-
cine, University of KwaZulu-Natal
Tel: +27 (0)31 260-4341
e-mail:
S Afr J Diabetes Vasc Dis 2010;
7
: 117–118
1...,21,22,23,24,25,26,27,28,29,30 32,33,34,35,36,37,38,39,40,41,...48
Powered by FlippingBook