Proliferative diabetic retinopathy

Fig. 41.1 Management of proliferative diabetic retinopathy.

41 Proliferative and pre-proliferative retinopathy ment, and if severe, glaucoma should be excluded. The risks of these complications are reduced by using low-energy levels and by applying the treatment over several sessions. ETDRS showed that aspirin did not affect the progression of retinopathy, risk of visual loss or the risk of vitreous haemorrhage among patients with proliferative retinopathy, although aspirin did reduce the risk of morbidity and death from cardiovascular disease by 17%. Patients with persistent vitreous haemorrhage, persistent severe proliferative retinopathy or macular retinal detachment will benefit from pars plana vitrectomy. The Diabetic Retinopathy Vitrectomy Study showed that patients with type 1 diabetes benefit from early rather than late vitrectomy,4 whilst deferment of vitrectomy did not appear to affect visual outcomes in patients with type 2 diabetes. Unfortunately, vitrectomy is associated with a variety of complications and rates of no light perception have been reported to be more than 20%.

For practical purposes, clinically significant macular oedema (CSMO) is defined as any retinopathy lesion within half a disc diameter of the centre of the macula. Diagnosis of macular oedema is made clinically and sometimes with the aid of fluorescein angiography. Macular disease should be suspected in patients with reduced visual acuity, reduced colour vision and/or reduced contrast sensitivity. Whilst patients with ischaemic maculopathy are not responsive to treatments, laser treatment is often effective in patients with focal and diffuse exudative maculopathy. In focal maculopathy, treatment is applied directly at the area of leakage (e.g. microaneurysms at the centre of a circinate exudate), whilst diffuse macular oedema is often treated with grid macular treatment, commencing 500 mm from the centre of the macula with sparing of the fovea. Patients should be reviewed about 2-4 months after treatment. Data from ETDRS suggest that a combination of focal and grid photocoagulation reduced the risk of moderate loss of visual acuity in patients with CSMO by about 50%. Immediate photocoagulation is beneficial if oedema involves the centre of the macular, but treatment may be deferred if this is not the case. Where CSMO exists with proliferative retinopathy, ETDRS recommended that the macula should be treated first, as panretinal photocoagulation may lead to a worsening of the maculopathy. Similarly, cataract extraction may also worsen maculopathy and thus macular laser treatment should be applied first, prior to cataract surgery.

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