31-year-old man with type 2 diabetes presenting with one day of right eye “red floater”
Retinal vein occlusion
Proliferative diabetic retinopathy
Hyperviscosity syndrome (leukemias)
Sickle cell retinopathy
Proliferative diabetic retinopathy
Microvascular diabetic disease causes ischemia of the retina. Hypoxia-induced growth factors, most notably but not limited to VEGF, are secreted. These growth factors stimulate neovascularization out of the retina. These new vessels use the posterior vitreous as a scaffold. There is a high risk of hemorrhage from these vessels causing diabetic hemorrhages into the vitreous and subhyaloid spaces. There is also a proliferation of fibrous tissue along with neovascularization. The regression of the vessels with persistent fibrous proliferation can lead to complications including tractional retinal detachments.
Panretinal photocoagulation (PRP) has been the mainstay of therapy for proliferative diabetic retinopathy for > 35 years. The Diabetic Retinopathy Study (1981) showed that the rate of severe vision loss was reduced by 50% in eyes treated with PRP. There are several side effects of PRP, including post-procedural macular edema, decreased night vision, and loss of peripheral vision.
As shown by the Diabetes Control and Complications Trial and UK Prospective Diabetes Study, intensive blood sugar control reduces microvascular complications including diabetic retinopathy.
Prognosis and Future Directions
Anti-VEGF therapy, widely used for diabetic macular edema, has recently been suggested as a potential alternate treatment to PRP for proliferative diabetic retinopathy. Protocol S of the Diabetic Retinopathy Clinical Research Network compared initial PRP to a series of ranibizumab injections and monthly monitoring with deferred PRP. This study found that the peripheral visual field[CAC1] sensitivity loss was worse, DME more frequent and vitrectomy more often required in the PRP group. The primary outcome-mean visual acuity letter improvement at 2 years-was +2.8 in the ranibizumab group and +0.2 in the PRP group (95% CI of difference – -0.5 to +5.0). Overall, it was determined that ranibizumab with monthly visits was non-inferior to PRP. The use of anti-VEGF agents as primary treatment, with PRP for rescue, remains an exciting new area of development for PDR treatment with appropriate patient selection.
We had an extensive discussion of the risks, benefits and options of anti-VEGF injections with monitoring or prompt PRP. The patient indicated that he may not follow-up as advised and elected prompt PRP therapy. This illustrates one of the greatest practical limitations to Protocol S, the importance of close follow-up. This limitation is especially germane in any patient population where close, reliable follow-up is not possible.
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