A simple method for evaluation of aqueous humor dynamics “A weight on-off test” in patients with glaucom

Purpose:To evaluate aqueous humor (AH) dynamics in patients with glaucoma through a newly developed method termed the “Weight on-off test”

Methods: Patients: primary open angle glaucoma (POAG)(n=124), primary angle closure glaucoma (n=16), Pseudoexfoliation syndrome(n=17), or senile cataract (n=93) without other eye diseases. For evaluation of AH dynamics, a 50 g weight was placed onto the eye of a subject in a supine position for 5 min and then removed. Intraocular pressure (IOP) was measured before and immediately after removal, and thereafter every minute until IOP returned to baseline. Based upon IOP changes (decreases during the weight on and recovery after removal), we defined AH outflow resistance: IOP drop rate (IOP_drop) (%) = (P₀-P_e) – (P₅-P_e) / (P₀-P_e) x 100 (P₀: IOP at baseline, P_e: assumed episcleral venous pressure, P₅: IOP at 5 min) and AH outflow resistance index (R_{aq out})= 100 - IOP _drop, and AH production: IOP recovery time (IOP_rec) (min) reached to baseline IOP, and AH production index (P_aq) was an IOP increase rate during the IOP_rec by least squares method.

Results:AH outflow resistance was significantly higher in glaucoma subjects than the control. AH production in glaucoma subjects was slightly increased compared to that in control. In POAG, prostaglandin-analogues (PG) caused a significant delay of AH production (IOP_rec).

Conclusions: The current data suggests that a “Weight on-off test” may be simple and useful for estimating AH dynamics in patients with glaucoma and provides a better understanding of glaucoma etiology as well as its pharmacology.