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Laser photocoagulation
photocoagulation causes permanent paracentral scotoma
in cases of juxta and extrafoveal choroidal membranes.
Patients should also be informed that they may continue
to lose vision, even under the best treatment conditions,
and that treatment does not cure AMD but it is only a
means of reducing the risk of marked loss of visual acuity.
A fluorescein angiography (FA) should be performed 72
to 96 hours before photocoagulation in order to select
treatable cases and to guide the ophthalmologist during
treatment. Patients should undergo treatment as quickly
as possible, since neovascular lesions may grow 10 to 18µ
per day
(21)
. Most neovascular lesions are extra or juxtafo-
veal at the onset, becoming subfoveal with rapid growth
towards the fovea.
2.5.2 Treatment technique
The MPS recommends that treatment should be per-
formed so that a white lesion in the retina is obtained.
The neovascular lesion should be surrounded by laser
marks with a diameter of 200µ and duration of 0.2 to
0.5 seconds. After surrounding the perimeter of the
neovascular lesion, its central part is covered with 200µ
burns; the remaining lesion is covered with 200 to 500µ
burns, with duration of 0.5 to 1.0 seconds. In cases of
juxtafoveal lesions, the foveal centre should be preserved,
although it should be ensured that the entire lesion is
treated. If bleeding extends to the area under the fovea,
treatment should include the entire neovascularization
area and stop at the limit of the fovea. Since the emer-
gence of new treatments, namely intravitreal antiangio-
genic treatments, laser photocoagulation of juxtafoveal
lesions has become controversial.
The MPS demonstrated that the wavelength selected
does not affect laser results. Laser treatment should
avoid retinal blood vessels and the optic nerve (treat-
ment should start 10-200 µm from the optic nerve), as
well as preserve at least 1.5 hours of the papillomacular
bundle (no peripapillary treatment). Treatment of serous
pigment epithelial detachment (PED) could be indicated
when photocoagulation is used to treat subfoveal lesions
including serous PED as a component
(1,3,8,10,11)
.
2.5.3 Post-treatment follow-up
Follow-up of treated patients was also recommended and
defined by the MPS. In addition to self-evaluation, it is
necessary to perform medical examinations and control
FA 2 to 3 weeks, 4 to 6 weeks, 3 to 4 months and 6, 8, 9
and 12 months after treatment. Recurrence is rare after 2
years. The greater risks exist 6 weeks to 12 months after
treatment. Detection through biomicroscopy without
FA is sometimes difficult. Angiography allows detection
of approximately 12% of the cases that go unnoticed in
medical examinations. Recurrence and persistence rates
are much greater in cases of choroidal neovascular or dis-
ciform lesions caused by AMD in the non-treated eye.
Other factors that appear to increase recurrence rates
include smoking, hypertension and choroidal neovascu-
larization with reduced pigmentation
(1,2,8,11).
2.5.4 Treatment complications
Laser photocoagulation treatment may also lead to com-
plications, including choroidal haemorrhage (rarer if
spots ≥ 200 microns and time intervals ≥ 0.2 seconds are
used), premacular fibrogliosis, accidental treatment of
the fovea in extrafoveal or juxtafoveal lesions (minimised
by retrobulbar anaesthesia, drawing of lesion limits and
correct identification of the fovea), rupture of the pig-
ment epithelium (more frequent in cases of PED) and
atrophy of the RPE in the area adjoining the laser scar
(immediately after treatment or years later)
(2,3,7,8)
.
2.5.5 Treatment of occult membranes
The MPS also defined guidelines regarding occult mem-
branes. When extrafoveal and juxtafoveal neovascular
lesions caused by AMD started to be studied no distinc-
tion was made between classic and occult membranes.
Subsequent analysis of all angiography results obtained
during study of juxtafoveal lesions revealed that treat-
ment was effective for classic neovascular lesions with no
occult component. In cases where an occult component
(not treated) coexisted with a classic component no ben-
efits were gained from treatment
(15)
. Photocoagulation
may be reasonably considered in cases of well-defined,
symptomatic, occult neovascular lesions with no classic
component, in order to reduce the risk of membrane
growth towards the fovea. However, little knowledge
exists of the natural progression of these occult mem-
branes and it would not be wrong to delay treatment
while examining patients at regular intervals (of months,
albeit varying according to the type of membrane), in
order to wait for the appearance of a classic membrane
that would benefit from laser photocoagulation treat-
ment. Only 25% of occult choroidal membranes main-
tained baseline VA values after 3 years and approximately
50% suffer severe loss of vision within the same time
period
(13)
.
