Tell me what you know about Diabetic Retinopathy Study (DRS). Answer This is a multi-centre clinical trial looking at the effect of panretinal photocoagulation in patients with proliferative diabetic retinopathy. About 1700 patients were enrolled in the study. All patients have proliferative diabetic retinopathy in both eyes. In the study, one eye received panretinal photocagulation and the other receive no treatment. Significant visual loss was defined as visual acuity of less than 5/200 on 2 follow-up visits. The results showed a 50% reduction in significant visual loss in treated eyes compared to controls at 5 years. Eyes that benefited most from panretinal photocoagulation were those with high risk proliferative diabetic retinopathy. The conclusion of the study recommends early panretinal photocoagulation for high risk proliferative diabetic retinopathy. What is high risk diabetic retinopathy? Answer Disc neovascularization (NVD) covering more than one-quarter of the disc area. Any disc neovascularization (NVD) with retinal or vitreous haemorrhage Neovascularization elsewhere (NVE) which is at least half the disc diameter and associated with retinal or vitreous haemorrhage. What would you say to this patient before carrying out panretinal photocoagulation? Answer I will inform the patient about the following points: Purpose of treatment: It is important that the patient understands that the treatment is to prevent visual loss and not to improve vision. In addition, it is essential to inform the patient that the neovascularization takes a few weeks to regress following treatment. Bleeding may sometimes occur while waiting for the vessels to regress. In about 1/3 of patients, regression may not occur and further filled in laser may be required. Complications: The patient should be told of the visual field loss following treatment and the possible development of cystoid macular oedema. However, the benefit of treatment outweigh these complications. How would you perform panretinal photocoagulation? Answer The procedure should be explained so that the patient does not make sudden eye movement during the treatment which can result in burns to the optic disc or macula. Topical anaesthesia is applied such as benoxenate and the patient is positioned comfortably. The fixation target is pointed out to the patient to avoid unnecessary eye movement. The lens used may be panfundoscopy or Mainster wide field lens. The standard laser used is argon blue-green laser. Begin the setting at 200 um size, 0.15s and 200mW. The power is adjusted according to response (the alternative setting may be 500um size, 0.15s and 500mW. Note: set the ratio of size to power at 1:1 and then adjust according to response) Mark the vascular arcades with 2 rows of laser. During the laser, avoid the blood vessels which can lead to haemorrhage. Adjust the power to give the retina a greyish white burn. Begin the laser inferiorly so that if haemorrhage were to occur before the next laser session, the superior retina will be clear for treatment. Would you ever apply laser directly on retina neovascularization? Answer Scatter laser may be applied to flat neovascularization elsewhere (NVD). Laser should not be applied to elevated NVD or disc neovascularization (NVD). Summary of the Diabetic Retinopathy Study can be downloaded from the e-book entitled "Studies you need to know for MRCOphth/MRCS/FRCS" Click to download the book. More questions
Tell me what you know about Diabetic Retinopathy Study (DRS).
What is high risk diabetic retinopathy?
What would you say to this patient before carrying out panretinal photocoagulation?
How would you perform panretinal photocoagulation?
Would you ever apply laser directly on retina neovascularization?
Summary of the Diabetic Retinopathy Study can be downloaded from the e-book entitled "Studies you need to know for MRCOphth/MRCS/FRCS" Click to download the book.
