**Background:** Diabetic retinopathy (DR) is a leading cause of blindness in working-age adults. Early detection and treatment of proliferative diabetic retinopathy (PDR) can reduce blindness risk, yet many patients present late. In China, the annual incidence of DR-related blindness rose from 0.06 to 0.23 per million population between 1999 and 2019. This study aimed to investigate the reasons for delayed presentation in PDR patients, including knowledge, attitudes, difficulties, and medical care factors.
**Methods:** A cross-sectional survey was conducted among consecutive PDR patients with delayed presentation (defined as diagnosed with PDR but not treated at initial visit, or treated but not followed up timely) at Beijing Tongren Hospital from January to December 2021. Inclusion criteria: age 18–70 years, PDR requiring photocoagulation or vitrectomy in at least one eye, completed laboratory tests and questionnaire. Exclusion criteria: severe vitreous hemorrhage of unclear cause, both eyes already vitrectomized, no need for treatment, inability to complete survey, comorbidities causing irreversible vision loss, COVID-19 lockdown restrictions, pregnancy. A 4-section questionnaire assessed: (1) knowledge about DR, (2) attitude toward DR treatment, (3) difficulties in real life (social, economic, systemic factors), and (4) medical processes (interactions with internal medicine physicians and ophthalmologists). Clinical data included HbA1c, renal function, ocular examination (visual acuity, intraocular pressure, slit-lamp, indirect ophthalmoscopy). Patients were grouped into: undiagnosed diabetes mellitus (DM) at PDR diagnosis, and known DM (further divided into those who refused DR screening/treatment and those who completed screening/treatment as required, including underdiagnosed PDR and progression after PRP). Logistic regression identified factors associated with refusing DR treatment.
**Key Results:** 157 patients (mean age 50.0±11.6 years, 53.5% male) were included. Median HbA1c was 7.8% (IQR 2.5%). Most eyes (144/157, 91.7%) required vitrectomy; 17 had neovascular glaucoma (NVG); only 13 required additional photocoagulation. Among 36 patients with undiagnosed DM, 100% were unaware of their DM status. Among 121 patients with known DM: only 24.0% knew that diabetes requires regular DR screening; 27.3% knew untreated DR can cause blindness; 81.0% believed good visual acuity meant screening was unnecessary; 93.3% reported regular diabetes medication use but glycemic control was poor (only 18.2% had HbA1c <6.5%). Logistic regression identified three factors significantly associated with refusing DR treatment: inability to receive regular diabetes treatment in internal medicine clinics (OR 6.78, 95% CI 1.73–26.59, p=0.006), inability to tolerate discomfort during ophthalmic examination and treatment (OR 15.15, 95% CI 2.70–83.33, p<0.001), and not being informed about the need for regular screening after a negative DR screening (OR 2.05, 95% CI 1.36–3.09, p<0.001). Deficiencies in healthcare were noted: only 14.9% of known DM patients received DR education from internal medicine physicians; among 30 patients with negative screening within 6 months, 29 developed PDR requiring surgery; internal medicine-initiated screening had a 20/21 missed diagnosis rate vs. 10/45 for ophthalmologists (p<0.001).
**Clinical Implications:** This study highlights that a substantial proportion of PDR patients present late due to undiagnosed diabetes, poor knowledge about DR, and misconceptions that good vision negates the need for eye exams. Key modifiable factors include improving diabetes screening in the general population, enhancing DR education by both internal medicine and ophthalmology providers, addressing patient fear of discomfort during exams/treatment, and ensuring that patients with negative screening results are informed about the need for regular follow-up. The high rate of missed diagnosis by internal medicine physicians underscores the need for better training or use of fundus photography and telemedicine. Patients with poor glycemic control, long diabetes duration, irregular internal medicine visits, and those undergoing cataract surgery or traditional Chinese medicine without conventional diabetes management require targeted attention. Strengthening the chain of care from DM diagnosis to DR screening and treatment is essential to reduce DR-related blindness.