Retinopathy

Despite advances made in improving the outcome of patients with proliferative diabetic retinopathy, many patients still require surgery for the condition owing to poor access to care, inadequate treatment and a host of other factors, said Dr Peter Scanlon MD, MRCOphth, Gloucestershire and Oxford Eye Units, at the 11th EURETINA Congress.

A leading cause of delayed treatment is poor screening attendance, which can result from socioeconomic factors and poor attendance even at free screening programmes. For example, a study carried out in Iceland, showed that blind diabetic patients had only a 27 per cent level of compliance with their regular screening programmes, compared to a 77 per cent level of compliance among non-blind diabetic patients (Zoega et al, Acta Ophthalmologica Scandinavica 2005; 83: 687–690).

Another study, conducted in Somerset UK, showed a correlation between a patient's grade of retinopathy and the number of reminders they had required for attendance in the screening programme (Gray et al. Eur J Ophthalmol 2009; 19: 510). In another study, which he and his associates conducted in Gloucestershire UK, sight-threatening diabetic retinopathy appeared to occur most frequently among the most socio-economically deprived patients, who were also the least likely to attend for screening (Scanlon et al, J Med Screen 2008; 15(3): 118–121).

Poor screening attendance leads to late presentation, which in turn diminishes the efficacy of treatment. According to the results of the Early Treatment of Diabetic Retinopathy Study (ETDRS), four per cent of eyes not treated until they had reached the stage of high risk proliferative diabetic retinopathy required vitrectomy, under the ETDRS protocol within five years, compared to only 2.1 per cent of eyes treated with early full scatter photocoagulation (Flynn et al. Ophthalmology 1992; 99(9): 1351–1357).

Prevention better than cure

As with many diseases, in eyes with diabetic retinopathy an ounce of prevention is worth a pound of cure, Dr Scanlon noted. Patients can delay the onset and slow the progression of retinal disease through the adoption of lifestyle and dietary habits that will keep their blood sugar pressure and blood lipids levels at the recommended levels. Smoking cessation may also reduce the risk in people with Type 1 diabetes although the evidence in Type 2 diabetes remains controversial.

'When I reviewed patients at our clinics who had gone blind, I found that they had had high HbA1c's and high blood pressure for years which I had only vaguely been aware of. And although they had been turning up regularly at my clinic they had not been attending the diabetic clinic. So I was doing patchwork but the underlying blood sugar and blood pressure had been pretty poor for years,' Dr Scanlon said.

There is also a range of psychological factors that could be addressed to ensure diabetic patients manage their condition more effectively. Self-efficacy and active coping behaviour influences maintaining blood glucose levels close to normal whereas depressive illness can cause patients in turn in to neglect their glycaemic and blood-pressure control regimes. In addition, as is the case in the general population, some diabetic patients have eating disorders that can cause problems with metabolic control and cause progression to very severe diabetic retinopathy particularly in young women.

'Eating disorders in Type 1 diabetes are a nightmare, some run their blood sugars high in order to keep a certain body shape and that has a disastrous effect on their eyes,' Dr Scanlon said.

Some diabetic patients are in denial of their condition. Dr Scanlon described the case of a woman with Type 1 diabetes who hid her condition from her partner for 11 years. Needle phobia is another condition that can have a negative bearing on a patient's management of their disease and can lead to serious retinopathies.

However, a number of non-modifiable risk factors remain, such as genetic predisposition to more advanced disease, duration of diabetes, and the age at diagnosis and at subsequent examinations. Ethnicity may also play a role, though it is often difficult to deduce an ethnicity factor independent of the other risk factors.

Treat sooner rather than later

Delayed treatment appears to increase a patient's risk of developing more severe disease (Flynn et al. Ophthalmology 1992; 99:1351-1357). 'Most ophthalmologists in the UK now treat patients when they develop neovascularisation (either NVE or NVD) and they do not wait until high risk characteristics have developed [RCOphth Guidelines 2005]. This is because the risks of laser treatment are considered to be less than when the original ETDRS studies were performed,' Dr Scanlon said.

However, there is no universal consensus as to what constitutes adequate laser treatment. For example, whereas the Diabetic Retinopathy Study (DRS) group recommended treating an area equivalent to 157mm to 314 mm2 of the retina, the ETDRS recommended an area equivalent from 236 mm2 to 314 mm2. Another study conducted around that time indicated that more treatment may be necessary for regression of the proliferation among patients with a high number of risk factors (Reddy et al. Am J Ophthalmol. 1995 Jun; 119(6):760-766). The general view amongst ophthalmologists is that the amount of pan- retinal laser treatment needs to be tailored to individual patients.

He noted that even with optimum laser treatment there will still be some patients who will require vitrectomy. They include patients with non-clearing vitreous haemorrhage, those with a large subhyaloid haemorrhage on or adjacent to the macula, tractional retinal detachment, and taut posterior hyaloid in diabetic macular oedema.

Another condition that will not respond to laser treatment is progressive severe fibrovascular proliferation. This is a problem that may become more common with the increased use of anti-VEGF agents, Dr Scanlon said. On the other hand, the use of anti-VEGF agents appear to be a useful treatment for neovascular glaucoma associated with diabetic retinopathy because they enable regression of the neovascularisation that occurs in the angle of the anterior chamber, reducing the intraocular pressure and enabling a clearing of the corneal oedema so that adequate laser treatment can be applied Dr Scanlon said.