Pilot study: Image-based, Diabetic macular Edema, Adjustment of Laser treatment - trial.

Diabetic macular edema (DME) is a common cause of visual loss in patients with
diabetic retinopathy. In The Netherlands approximately 500 -1000 persons yearly
become legally blind from DME. These numbers are expected to grow substantially
in the coming years, because the number of diabetic patients in the population
is expected to rise from currently about 500000 to 800000 by 2010, according to
the Dutch Health Counsil (RVZ). DME is characterized by retinal thickening,
exudates and capillary microaneurysms. Diabetic macular edema, if present for
more than a few months, causes destruction of photoreceptor cells and leads to
visual loss and eventually blindness. Management and treatment of DME is
evidence based on the results of large randomized clinical trials in the 70*s
and 80*s, such as the Diabetic Retinopathy Study and the Early Treatment for
Diabetic Retinopathy Study (ETDRS). These trials have shown that careful
patient selection and timely treatment by laser photocoagulation of macular
edema prevents visual loss from DME.
The ETDRS defined DME as clinically significant if: (1) retinal
thickening is localized within 500um of the fovea or (2) hard exudates
associated with thickening are localized within 500um of the fovea or (3) a
zone of retinal thickening larger than 1500um in size is localized within
1500um of the fovea. According to the ETDRS the gold standard technique for the
diagnosis of clinically significant macular edema (CSME) is stereo fundus
photography (SFP). In clinical practice slit-lamp biomicropsy (SLB) is used for
detection of CSME.
Currently, laser photocoagulation of CSME is the only treatment of DME
that has been shown effective. In the ETDRS and in current clinical practice
the decision which patients and which lesions in the macula to treat is based
on SLB examination, and SFP to detect clinically significant macular edema, and
fluorescein angiography (FA) to detect treatable lesions. Treatable lesions are
discrete points of retinal hyper fluorescence or leakage, areas of diffuse
leakage within the retina and retinal a-vascular zones. These lesions are
believed to be the cause of the retinal thickening.
New retinal imaging techniques, that allow objective measurement of retinal
thickening, have recently become available. One of the most important new
techniques is the Optical Coherence Tomography (OCT). OCT is a very sensitive
method to measure retinal thickness and is capable of generating topographic
thickness maps of the macula. It is a safe, non-invasive and non-contact
procedure. OCT is used increasingly for the diagnosis and follow-up of CSME.
Different OCT studies show that OCT is more sensitive in detecting retinal
thickening than regular SLB and SFP. Therefore it is to be expected that
retinal thickening that can only be detected by OCT is currently not diagnosed
and therefore not treated. However, it is still unknown whether earlier and
more precise diagnosis of CSME, and treatment based on this more accurate
diagnosis will actually result in less blindness and visual loss.

The aim of this proposal is twofold. Our first objective is to verify if indeed
the OCT is more accurate in diagnosing CSME than SLB. Will more patients be
diagnosed with CSME when examined with OCT compared to SLB? Our second
objective is to determine the differences between the laser treatment strategy
of diabetic macular edema based on SLB and FA versus OCT and FA.

Patients with a suspicion of CSME from the outpatient clinic of The department
of Ophthalmology at the Academic Medical Center (University Hospital,
Amsterdam, The Netherlands) will undergo a standard ophthalmologic examination,
including best corrected visual acuity on an ETDRS chart, slitlamp examination,
fundoscopy, SLB examination and OCT. The SLB results will be documented in
detail by the ophthalmologist. First a comparison is made between the diagnosis
of CSME established on the basis of OCT on the one hand and SLB on the other
hand. In each patient diagnosed with CSME, by OCT or SLB, a FA will be made.
Two laser photocoagulation treatment plans will be composed, and compared; one
based on OCT and FA and one based on SLB and FA (= standard of care). All
patients diagnosed with CSME on SLB will be treated with laser photocoagulation
following the standard procedures. Directly following the laser
photocoagulation treatment a color fundusphotograph will be made to document
the laser treatment.

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