Posture-Dependent Intraocular Pressure Difference As A Screening Marker Of Early Zonular Weakness In Age-Related Cataract

To assess whether the difference in intraocular pressure (IOP) between sitting and supine positions can identify early (grade I) capsular–zonular instability in patients with age-related cataract lacking obvious clinical signs of zonular weakness.

Patients with immature or mature age-related cataract and anterior chamber depth of 2.4–3.0 mm were included. Exclusion criteria were glaucoma, high myopia, grade II–III lens subluxation, prior ocular surgery, and systemic conditions affecting aqueous dynamics. IOP was measured with a portable non-contact pneumotonometer in the sitting position and after 5 min supine. A sitting–supine IOP difference ≥4 mmHg indicated grade I zonular weakness. Anterior segment OCT and UBM were used when indicated

In the control group, IOP increased in the supine position relative to sitting (mean difference 1.7 ± 0.8 mmHg, p<0.001), consistent with physiological expectations. In contrast, eyes classified as grade I zonular weakness showed a reversed pattern, with higher IOP in the sitting position; the mean difference reached 5.7 ± 1.2 mmHg (p<0.001). In 48% of these eyes, the difference exceeded 6 mmHg. Imaging supported the functional marker: OCT demonstrated iris–lens diaphragm position changes in 84%, and UBM revealed zonular defects/thinning in 88%.

Comparative IOP measurement in sitting versus supine positions appears to be a simple, reproducible, and low-cost screening approach for detecting early zonular instability in cataract patients. This may improve preoperative risk stratification and surgical planning, particularly when conventional slit-lamp findings are equivocal.