The Likeliness of Diabetic Retinopathy Progressing to Blindness

A cohort study evaluated the relationship between the severity of newly diagnosed diabetic retinopathy in adult patients and the incidence of progression to sustained blindness. 

Diabetes remains the leading cause of adult-onset blindness, as a result of diabetic retinopathy (DR). As DR progresses, abnormal retinal blood vessels grow to increase oxygen supply to the retina’s hypoxic areas. Progression can eventually lead to diabetic macular edema, potentially causing leakage of hyperpermeable capillaries and vision loss. A retrospective cohort study was conducted to evaluate the relationship between DR severity and the incidence of progression to blindness in patients with diabetes. 

Researchers used patient data from the American Academy of Ophthalmology’s Intelligent Research in Sight (IRIS) registry to identify patients with newly diagnosed DR and good vision. Newly diagnosed DR was determined utilizing ICD-9 and ICD-10 codes, and patients had to have data for at least 18 months before the onset of DR to be included. Good vision was defined as a minimum of two visual acuities (V.A.) readings of at least 20/40 in one eye before or up to 3 months after initial DR diagnosis. DR severity was categorized into mild nonproliferative DR (NPDR), moderate NPDR, severe NPDR, proliferative DR, or unspecified DR. The study’s primary outcome was SB, defined as V.A. readings of 20/200 or worse at two separate visits more than three months apart. The statistical analysis method used was the Chi-square or student t-test for patient covariates and SB associations. Similarly, the Kaplan-Meier survival curve was used to determine survival probability associated with DR severity status. A total of 53,535 eyes met eligibility criteria and were analyzed in the primary outcome. At baseline, most of the patients were initially diagnosed with mild NPDR (49.3%) or unspecified DR (29.5%).  

After an average follow-up of 662.5 days, researchers found that 678 eyes developed SB. About 39.5% of the eyes that grew SB had a worse vision at baseline, although they comprised 18% of the population assessed. Furthermore, 26.5% of the eyes developing SB had PDR at baseline, which accounted for 10.5% of the study population. In contrast, among eyes that did not develop SB during follow-up, 98.5% maintained good vision criteria. Altogether, the incidence of SB development increased with DR severity at baseline within the first two years of follow-up. At one year post-diagnosis, mild NPDR at baseline was associated with the lowest risk of SB development. However, moderate NPDR, severe NPDR, and baseline PDR were associated with a 2.0, 2.7, and 3.8 times increase in SB development risk versus mild NPDR eyes. At two years post-DR diagnosis, the SB development risk was 2.6, 3.6, and 4.0 times more likely, respectively, for moderate NPDR, severe NPDR, and PDR at index, compared with eyes with mild NPDR at index. Upon analyzing the baseline characteristics, patients greater than 50 years of age and those without private insurance had a lower SB development incidence. In contrast, females, smokers, and Black and Asian patients had increased SB incidence.  

In conclusion, this study found that patients with severe NPDR and PDR at the time of DR diagnosis had the highest SB onset risk. Researchers also highlighted the importance of early intervention and DR treatment to prevent vision loss with this finding. Current DR management strategies include laser photocoagulation and intravitreal anti-vascular endothelial growth factor injection, with the latter showing improvements in DR severity. Therefore, the impact of DR severity on SB outcomes is emphasized through this study’s results, stressing a need for early recognition and screening. A limitation of this study is its retrospective nature, which limited electronic health record data. Furthermore, the study did not account for HbA1c and comorbid diseases such as hyperlipidemia and hypertension, which may impact the development of vision loss. Overall, among patients with good vision and newly diagnosed DR, eyes with severe NPDR and PDR were associated with a greater likeliness of SB development.  

Practice Pearls 

• Clinicians should implement early strategies to prevent and delay vision loss and impairment in patients with diabetic retinopathy.  
• Patient education and awareness must be increased among patients with diabetes to improve screening.  
• Future studies are needed to evaluate the association of diabetic and diabetic retinopathy medications with blindness development and progression.  

Wykoff CC, Khurana RN, Nguyen QD, et al. Risk of Blindness Among Patients With Diabetes and Newly Diagnosed Diabetic Retinopathy. Diabetes Care. 2021. 

Ciulla TA, Amador AG, Zinman B. Diabetic retinopathy and diabetic macular edema: Pathophysiology, screening, and novel therapies. Diabetes Care. 2003.  

Macrina Ghali, PharmD Candidate 2021, Florida A&M University, College of Pharmacy and Pharmaceutical Sciences