Disease

Diabetic retinopathy (DR) is the leading cause of preventable blindness. Of working-age Americans diagnosed with Diabetes Mellitus, it is estimated that about 1/3 have diabetic retinopathy (DR) and 4.4% have vision-threatening retinopathy.

Risk Factors

Independent risk factors for DR included diabetes duration, hemoglobin A1c, serum glucose, systolic blood pressure, and Indian ethnicity based on the Singapore Eye Disease Study. Duration of diabetes is a major risk factor, and is the main criteria utilized to decide when to begin DR screening. After 5 years, approximately 25% of type 1 patients will have retinopathy. After 10 years, almost 60% will have retinopathy, and after 15 years, 80% will have retinopathy. Proliferative diabetic retinopathy was present in approximately 50% of type 1 patients who had the disease for 20 years. In the Los Angeles Latino Eye Study (LALES) and in Proyecto VER (Vision, Evaluation and Research), 18% of participants with diabetes of more than 15 years’ duration had PDR, and there was no difference in the percentage with PDR between those with type 1 and type 2 diabetes.

Screening Methods

The most recent guidelines for DR screening were released by the International Council of Ophthalmology (ICO) and American Diabetes Association (ADA) in 2018. This article focuses on DR screening in the United States. Other guidelines may vary by country and availability of resources. The method used to screen for DR is dependent on resource settings. The 2018 ICO/ADA guidelines state that adequate DR screening should include a visual acuity exam and a retinal examination.

Adequate visual acuity screening includes at least one of the following:

(1) Refracted visual acuity examination using 3- or 4-m visual acuity lane and a high-contrast visual acuity chart

(2) Presenting visual acuity examination using a near or distance eye chart and pin-hole option if visual acuity is reduced

(3) Presenting visual acuity examination using a 6/12 (20/40) equivalent handheld chart consisting of at least 5 standard letters or symbols and a pin-hole option if visual acuity is reduced.

Adequate retinal examination includes at least one of the following:

(1) Direct or indirect ophthalmoscopy or slit-lamp biomicroscopic examination of the retina

(2) Retinal (fundus) photography, including any of the following: 30° to wide field, monophotography or stereophotography, and dilated or undilated photography.

The retinal examination can be done with or without optic coherence tomography (OCT). Retinal examination may not need to be performed by individuals with a medical degree, so long as they are trained to perform ophthalmoscopy or retinal photography and can assess disease severity.

Initial Screening and Referral

Based on recent guidelines by the AAO Diabetic Retinopathy Preferred Practice Pattern for the recommended time of first retinal examination for patients with diabetes: (Flaxel et al. 2020, Diabetic Retinopathy Preferred Practice Pattern )

– Type 1 DM: 1^st Retinal exam 3-5 years after diagnosis

– Type 2 DM: 1^st Retinal exam at the time of diagnosis

– Pregnancy (with type 1 or type 2): 1^st Retinal exam soon after conception and early in the 1^st trimester of pregnancy. An eye examination is not required if patients without DM newly develop gestational diabetes during pregnancy.

Screening follow-up depends on the severity of disease as well as the available referral resources in a given geographic location. DM without DR and mild NPDR does not need to be referred to an ophthalmologist. In addition, high-resource settings may employ the use of optical coherence tomography (OCT) to further satisfy patients that have diabetic macular edema to further determine follow-up intervals.