Effect of Modified Panretinal Photocoagulation on Neurovascular Unit Coupling Remodeling and Visual Function Preservation in Diabetic Retinopathy

INTERVENTION: Standard Panretinal Photocoagulation Group:532 nm multi?spot laser, 300 µm spot, 0.02 s, grade II–III burns, 1–2 spot intervals, 3–4 sessions over 2 weeks, macular?sparing, total 1200–1600 spots, nasal margin =500 µm from optic disc.;Modified Panretinal Photocoagulation Group: Same laser settings as Group A, but with nasal sparing enlarged to 2–3 optic disc diameters (PD, 3000–4500 µm), and the spared nasal spots equally redistributed to temporal, superior, and inferior peripheral zones to maintain identical total spot count.; CONDITION: Diabetic Retinopathy PRIMARY OUTCOME: Superficial capillary plexus vessel density;Deep capillary plexus vessel density;Full retinal capillary plexus vessel density;Choriocapillaris flow density;Choroidal vascular volume;Choroidal vascularity index;Central subfield thickness;Incidence of vitreous hemorrhage; SECONDARY OUTCOME: Best corrected visual acuity;Static perimetry mean deviation;Contrast sensitivity;Multifocal electroretinography;Retinal nerve fiber layer thickness; INCLUSION CRITERIA: 1. Aged 18 to 80 years with treatment‐naïve severe nonproliferative diabetic retinopathy or early proliferative diabetic retinopathy who required panretinal photocoagulation (PRP); 2. Clear ocular media sufficient for high‐quality fundus imaging; 3. Provided written informed consent.