Task force develops classification system for retinopathy screening

By Sean Henahan

ORLANDO, FL - A classification system proposed by an international task force should simplify and improve diabetic retinopathy screening in the real-world office setting, according to retina specialists.
Surgeons at the annual American Academy of Ophthalmology (AAO) meeting said the current gold standard for diabetic retinopathy screening is based on the staging system used in the Early Treatment Diabetic Retinopathy Study (ETDRS).

However, the complicated ETDRS system is a tool best suited to professional screeners participating in clinical trials, rather than the typical practising ophthalmologist, noted member of the Diabetic Retinopathy Task Force, C. Pat Wilkinson MD.

"Our review of the current status of diabetic screening revealed that different modifications of the original ETDRS system had been developed around the world.
"It became clear there was a need for a single, practical classification system which could be used around the world to facilitate communication across groups of practitioners," he explained.

The original ETDRS screening tool utilised photographs of 20 lesions graded on a three to six step scale. Local efforts to simplify the scale produced various systems which tended to have fewer grades and to be based on clinical observation rather than photographic comparison.

The task force compared the different modified systems and, not without some debate, arrived at a consensus.
Using a process developed by the RAND Corporation think tank, the Task Force determined that the new scale should be based on solid scientific evidence and provide a common user-friendly terminology to describe disease severity and risk of progression.

The new system also needed to tie in with the levels of risk described in ETDRS, Paul P. Lee MD, JD explained.
The new system is known as the International Clinical Diabetic Retinopathy (ICDR) severity scale. The new scale includes five levels of disease, ranging from 'none' to 'proliferative diabetic retinopathy'.

Each level includes findings that would be observable with dilated ophthalmoscopy. For example, 'mild non-proliferative diabetic retinopathy' is associated with 'microaneurysms only', while 'severe non-proliferative diabetic retinopathy' may present with a host of findings including 'prominent intraretinal microvascular abnormalities (IRMA) in one or more quadrants'.

The task force took the ETDRS and Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR) guidelines as starting points. The international panel sought to correlate common clinical findings with risk of progression.

For example, data from the ETDRS and the ESDR established a clear link between IRMA and venous beading and higher risk of progression to proliferative retinopathy.
The studies also provided support for creating a separate stage of severe non-proliferative retinopathy, where early treatment is known to benefit type II diabetes patients.

The ICDR scale also includes general management options and recommendations for ongoing screening.

The guidelines suggest that patients with no evidence of retinal disease should be screened every 12 months, since it is known that as many as 10% of that group may go on to develop diabetic retinopathy in that period.
More frequent screening is recommended for those with moderate or more extensive disease.

The new grading system is not intended to be used only by retina specialists. Rather, the guidelines were developed with the needs of general ophthalmologists in mind.
The direct ophthalmoscope is the key, with the goal of the guidelines being that busy clinicians should be able to recognise the important lesions of diabetic retinopathy including microaneurysms, blot haemorrhages, hard exudates, cotton wool spots, IRMA, venous beading, neovascularisation, vitreous/pre-retinal haemorrhages, fibrosis and retinal detachment.

German ophthalmologist Anselm Kampik MD played a key role in developing the new screening guidelines. Dr Kampik was part of the 'Initiativgruppe zur Früherkennung der diabetischen Retinopathie', a German group that developed and initiated a simplified retinopathy grading scale in 1995.

The system is very similar to the one presented by the international task force. The primary difference was that the German system had four levels rather than five, having opted not to include a 'no disease' classification.

"We can say that our system has been a success. It created a standard form of communication between ophthalmologists, referring diabetologists and primary care physicians.

"It has proven to be a significant aid to communication between the different medical providers and the patient," Dr Kampik told an AAO press conference in Orlando.
He credited the success of the programme in part to an extensive and ongoing media campaign.

Even with maximum effort to propagate a new system of guidelines, the German experience has been that it could take four to five years to implement a new scale, he noted.

The international panel also developed a related screening scale for diabetic macular oedema.
Following a similar process to that used to develop the retinopathy screening system, the panel created a system which identifies the factors that determine whether macular oedema is sight-threatening.

These include the location and the area of retinal thickening and hard exudates.
The new guidelines appear at a time when the AAO is making new efforts to prevent or delay diabetes-related vision problems.
Some 16 million people in the US have diabetes and the number is growing rapidly, a trend attributed to the aging population and an epidemic of obesity.

The AAO has initiated a public health campaign to encourage all those with diabetes to have an annual dilated eye examination.

Both of the new classification systems can be viewed in their complete forms free of charge at the AAO website: http://www.aao.org/aao/education/library/international_DR.cfm

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