Diabetic
retinopathy is the leading cause of acquired blindness under
the age of 65. The great majority of this blindness can be
prevented with proper examination and treatment by
ophthalmologists
Background
Diabetic Retinopathy (BDR)
may occur at any point in time after the onset of diabetes.
In general, this is the first “stage” of diabetic
retinopathy and, therefore, the least concerning. This
condition is often present without any visual symptoms.
Findings in the retina include dot and blot hemorrhages
(tiny hemorrhages in the retina itself), microaneurysms
(out-pouchings of capillaries), and exudates (retinal
deposits occurring as a result of leaky vessels). The
development of this condition in type I (juvenile-onset)
diabetics is rarely present prior to three or four years
following the onset of diabetes. In type II (adult-onset)
diabetics, background diabetic retinopathy may be present at
the time of diagnosis of the condition.
Red
spots are the haemorrhages/bleeding areasWhite/yellow spots
are the exudates:
In general,
patients are not typically treated with laser
photocoagulation of the retina for background retinopathy.
An exception exists for some patients with an advanced form
of BDR known as pre-proliferative diabetic retinopathy.
Ophthalmologists may recommend treatment at this stage,
especially if the opposite eye has had diabetic related
complications.
Clinically
significant macular edema (CSME) is
a condition of swelling of the macula (central retina)
related to the development of leaky capillaries and
microaneurysms. This condition may or may not be associated
with reduced or distorted vision. Ophthalmologists use
rather strict criteria to determine whether a patient should
be treated with focal laser photocoagulation for this
condition.
Patients
with CSME are generally recommended to undergo focal laser
photocoagulation. This entails a fluorescein angiogram
to guide treatment and utilization of a laser to help “dry
up” the localized swelling (macular edema).
Ophthalmologists apply laser treatment to the macula of the
eye, avoiding the fovea where central acuity resides, in a
grid-pattern or directly to leaking microaneurysms. The risk
of visual loss is reduced by more than 50% for patients with
CSME who undergo focal laser photocoagulation. Even patients
with 6/6 vision who meet guidelines for treatment should be
considered for laser therapy to prevent eventual visual
loss. It is important to realize that laser treatment
does not usually improve vision, but is aimed at prevention
of further visual loss. Most patients with CSME require
3 to 4 different focal laser sessions, two to four months
apart, to resolve the swelling.
Proliferative
Diabetic Retinopathy (PDR) carries
the greatest risk of visual loss of the conditions discussed
thus far. The condition is characterized by the development
of neovascularization on or adjacent to the optic nerve and
vitreous or pre-retinal hemorrhage (hemorrhage in the
vitreous humor or in front of the retina). PDR usually
occurs in eyes with advanced background diabetic. The
neovascular vessels are abnormal and have a tendency to
break and bleed into the vitreous humor of the eye. In
addition to sudden vision loss, this may lead to more
permanent complications, such as tractional retinal
detachment and neovascular glaucoma.
Patients
with PDR should receive scatter laser photocoagulation
(laser treatment of the ischemic peripheral retina) as soon
as possible following diagnosis of the condition. This
treatment is also known as pan-retinal laser
photocoagulation. By causing regression of the
neovascular tissues, the risk of severe vision loss is
substantially reduced. Scatter laser photocoagulation (also
known as PRP, or pan-retinal photocoagulation) is an
in-office or out-patient procedure done with or without an
anesthetic injection adjacent to the eye. Many patients will
experience mild discomfort with the laser treatment,
although this can be resolved with an anesthetic block. The
laser treatment usually takes less than 30 to 45 minutes per
session. A complete laser treatment, however, may require up
to 3 or 4 different sessions, with a total of one to two
thousand laser applications (“spots”).
In some
patients with PDR, the vitreous hemorrhage prevents the
ophthalmologist from performing the laser treatment. Simply
put, the blood is in the way of the laser beam. If the
vitreous hemorrhage fails to clear within a few weeks or
months, a vitrectomy surgery may be performed to
mechanically clear the hemorrhage and laser photocoagulation
is then applied, either at the time of the vitrectomy or
shortly thereafter. Patients who have tractional retinal
detachment are usually scheduled for vitrectomy surgery
promptly.
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