Abstract
Purpose: :
Changes in the biomechanical properties of the lamina cribrosa (LC) are considered a risk factor for the progress of primary open angle glaucoma (POAG).The present study was designed to investigate these changes in the LC induced by POAG in rats and the effect of travoprost (Travatan®) on this process.
Methods: :
POAG was induced in 39 Wistar rats by cannulation of the anterior chamber and increasing intraocular pressure by a water column in one eye with the other eye serving as control.25 matched non-POAG rats were used as controls. Rats received either travatan or vehicle once/day starting four weeks prior to induction of POAG. Eight weeks after POAG induction the rats were killed, the eyes enucleated and processed immediately. 2 strips (width: 1 mm) of each eye containing LC were prepared. The stress-strain relation was measured in the stress range of 0.02 - 6 megapascal (MPa).
Results: :
Stiffness of the LC is reduced in eyes of POAG rats when compared to controls and is further reduced in travoprost treated eyes. At 10 % strain the stress (mean ± SD) of the LC of POAG eyes (5.58±2.45 MPa) is reduced but does not reach statistical significance (P= 0.147) when compared to control LC (6.67±3.10 MPa).When compared to vehicle treated POAG eyes, stiffness of the LC in travoprost treated POAG eyes (4.0±2.3 MPa) was significantly (P= 0.0064) reduced, an effect which was also demonstrated in travoprost treated non-POAG eyes (5.0±1.5 MPa) when compared to vehicle treated non-POAG eyes (6.67±3.10 MPa; P= 0.0027).
Conclusions: :
This study demonstrates reduced stiffness of the LC in rat eyes after 8 weeks of POAG induction and a further reduction of LC stiffness by travoprost.A reduction of LC stiffness results in reduced mechanical stress, a potential protective mechanism for astrocyte and retinal ganglion cell survival in this progressive optic neuropathy enhanced by travoprost.
Keywords: lamina cribrosa • drug toxicity/drug effects • anatomy