Retinal vascular alteration following surgical intraocular pressure reduction in primary angle closure disease

Aims To investigate retinal vascular geometric alterations following intraocular pressure (IOP)-lowering surgery in patients with primary angle closure disease (PACD) and determine associations between IOP reduction magnitude and retinal vascular parameters.Methods This retrospective, self-controlled study included patients with PACD who underwent IOP-lowering surgery at Beijing Tongren Hospital. Retinal vascular parameters were quantitatively measured from fundus photographs before and after surgery using a validated deep learning-based analysis system. Main outcomes included retinal arteriolar and venular calibre, tortuosity, fractal dimension (FD), segment number (N_seg) and vascular density. Linear mixed-effects models, adjusted for age, follow-up interval and PACD subtype, assessed associations between IOP reduction magnitude and vascular parameter changes.Results Among 126 eyes (112 patients), surgery decreased IOP from 35.0±9.9 to 16.7±5.7 mm Hg (p<0.001). Venous FD increased from 1.52±0.06 to 1.53±0.05 (p=0.003), N_seg from 123.50 (IQR: 61.75–182.50) to 153.00 (88.50–185.00) (p=0.007), vessel area density (VAD) from 6.13±1.56 to 6.50±1.34 (p=0.006) and vessel skeleton density (VSD) from 1.24±0.35 to 1.35±0.31 (p=0.003). Vessel calibre and tortuosity showed no significant changes. IOP reduction magnitude was independently associated with changes in venous FD (p=0.023), N_seg (p=0.031), VAD (p=0.012) and VSD (p=0.030).Conclusions Surgical IOP reduction in PACD patients produces selective retinal venous alterations with increased complexity and density. These pressure-responsive changes may provide complementary, non-invasive information regarding vascular response after surgery.