Proliferative diabetic retinopathy: pathophysiology of extraretinal complications and principles of vitreous surgery.

Extraretinal complications of proliferative diabetic retinopathy are caused by neovascular and/or fibrovascular tissue growth and include vitreous hemorrhage, retinal detachment, and other effects damaging the retina and/or optic nerve. Exact features of fibrovascular tissue growth and secondary complications vary widely from case to case. However, the structural pathogenesis of this disease process is consistent because the abnormal tissue nearly always grows along the posterior vitreous surface. Therefore, differing topographic features and secondary complications are dependent on: (1) the places of origin and amount of fibrovascular proliferation, and (2) the location and extent of any posterior vitreous separation. The latter influences the configuration of the fibrovascular tissue growth and determines the effect on the underlying and adjacent retina. Surgical treatment of proliferative diabetic retinopathy is based on this fundamental structural pathophysiology. The -principles of surgery are to minimize damaging effects by reversing the optical and structural complications and preventing recurrence of similar problems. Therefore, the objectives of surgery are to remove any intravitreal opacities and to excise the posterior vitreous surface. To achieve these objectives, various specialized techniques are required, depending on the complexity of the vitreoretinal anatomy in each case. Still, when the objectives are achieved, the operation has similar beneficial immediate and long-term effects in most eyes. This paper discusses and illustrates the structural pathology of proliferative diabetic retinopathy and the principles and methods of surgical therapy, and it presents the results obtained and the complications encountered.