METHODS: The model exploits the principle of dynamic and geometric similarity, so while dimensions were up to 30× greater than actual, the flow had similar properties. Scleral flaps were represented by transparent 0.8- and 1.6-mm-thick silicone sheets on an acrylic plate. Dyed 98% glycerin, representing the aqueous humor was pumped between the sheet and plate, and the equilibrium pressure measured with a pressure transducer. Image analysis based on the principle of dye dilution was performed using MATLAB software.
RESULTS: The pressure drop across the flap was larger with thinner flaps, due to reduced rigidity and resistance. Doubling the surface area of flaps and reducing the number of sutures from 5 to 3 or 2 also resulted in larger pressure drops. Flow direction was affected mainly by suture number and position, it was less toward the sutures and more toward the nearest free edge of the flap. Posterior flow of aqueous humor was promoted by placing sutures along the sides while leaving the posterior edge free.
CONCLUSION: We demonstrate a new physical model which shows how changes in scleral flap thickness and shape, and suture number and position affect pressure and flow in a trabeculectomy.
METHODS: Seventeen POAG patients with suboptimal IOP control despite pre-existing topical medications were subjected to adjunct SLT (50 applications 180 degrees) or second line medical therapy. Current medications were continued, and patients were followed up for 6 months for degree of intraocular pressure (IOP) lowering. HRQoL was assessed using Glaucoma Quality of Life 36-item (GlauQoL-36), Assessment of Quality of Life-7D (AQoL-7D) and Vision related Quality of Life (VisQoL). Costs involved were calculated and compared to the effect (IOP reduction) achieved in each arm.
RESULTS: Ten patients were in the SLT group and 7 in the topical medication (MED) group. Mean baseline intraocular pressure (IOP) was 18.90±3.48mmHg in SLT group and 15.57±2.23mmHg in MED group. Mean reduction of IOP was 4.30±1.64mmHg in SLT group and 2.71±2.56 mmHg in MED group at 6 months which was not statistically significant (p=0.14) between two groups. All the HRQoL questionnaires did not show significant changes in the groups or between groups when compared baseline with 6-month post treatment (p-values ranging from 0.247 to 0.987). For every 1mmHg reduction in IOP, cost involved in MED group (RM53.61) was 165% of the cost involved in SLT group (RM32.56).
DISCUSSION AND CONCLUSION: This study has shown that SLT was as effective clinically and tolerable as topical anti glaucoma medications and was possibly more cost effective in the step-up treatment of patients with POAG at 6 months follow- up.