Diabetic retinopathy (DR) and age-related macular degeneration (AMD) are the leading causes of irreversible vision loss in adults in the United States, and they share common features of ischemia. Many believe that panretinal photocoagulation (PRP) increases macular choroidal perfusion and may offer a protective effect against neovascular AMD (nAMD). Researchers from Stanford University recently found that there are possible commonalities between the diseases—but that laser treatment for proliferative DR likely does not confer protection against later developing nAMD.

They presented their findings at ARVO 2019 last week.

From a database of health claims, of which 70% are Caucasian, almost six million patients met the inclusion criteria, and the researchers categorized them in 10-year brackets between the ages of 50 and 90. Of these patients, 30.2% had diabetes, 4.9% had nonproliferative DR and 1% had proliferative DR. Also, 6.9% of patients had AMD, with 2% having nAMD. In the youngest age bracket, nAMD’s prevalence was higher in patients with proliferative DR compared with nonproliferative (odds ratio=3.47), but the odds decreased with age (OR=1.45 for the oldest bracket). 

However, the study also found high rates of co-diagnosed diabetic macular edema (DME) in nAMD patients (44% in proliferative DR, 20% in nonproliferative DR), confounding the diagnosis of nAMD. Excluding patients with comorbid DME, the odds decreased slightly to 3.24 in the youngest to 1.36 in the oldest age bracket.

As the main treatment option for proliferative diabetic retinopathy, the researchers used the ICD-9 diagnosis of the disease as a surrogate for PRP, assuming those with the condition underwent PRP.

They concluded that their findings suggest that the microvascular insult and proclivity towards a neovascular response in proliferative DR increases the risk of nAMD, which PRP does not alleviate.