External diathermy treatment of proliferative diabetic retinopathy with vitreous haemorrhage

Sixty-six cases of advanced proliferative diabetic retinopathy were treated by external diathermy. The eyes had extensive fibrovascular proliferations growing into the vitreous. All had some blood, recent and old, in the vitreous. The vitreous was extremely degenerated and retracted. All the patients had inadequate diabetic control. More than half were hypertensive, with reasonable medical control, while a few had some degree of renal failure, with lower limb oedema. None of the cases were suitable for photocoagulation. Thirty-two control eyes were followed up together with the treated eyes for one to eight years. Of 53 eyes of patients with maturity onset diabetes 28 improved, 12 remained unchanged, and 13 deteriorated. Only two eyes developed neovascular glaucoma, while eight of 13 eyes of patients with juvenile diabetes improved. Of the control eyes, one regressed spontaneously, six remained unchanged, and 25 deteriorated. Of these 25 eyes eight developed traction detachment, 10 suffered relentless attacks of vitreous haemorrhage, and seven developed neovascular glaucoma. External diathermy appears to be a logical approach to cases which could not be treated by either photocoagulation or vitrectomy.