Ocular Hypotony Induced Change in Corneal Thickness and Its Correlation With Corneal Capacity as a Reservoir for Topically Applied Gentamicin

Abstract

Abstract: : Purpose: To study the effect of simulated ocular hypotony on corneal thickness and on corneal function as a reservoir for topically applied gentamicin sulfate. . Methods: A transcorneal pressure–controlled ex–vivo drug penetration apparatus was used. Eight albino rabbits (2.3–2.7 kg) were sacrificed and their eyes enucleated. Each of the freshly excised corneas (n=16) was mounted horizontally beneath a humidity controlled donor chamber with the endothelial side facing balanced salt solution (BSS–plus, Alcon Labs. Inc., Fort Worth, TX, USA) filled acceptor chamber in beneath. Eight corneas were used for corneal thickness measurements (DGH–2000 ultrasonic pachymeter, DGH technology Inc., Frazer, PA, USA) at two pressure levels of acceptor chamber (5 and 20 mm Hg; 4 corneas for each pressure level). The other eight corneas were used for gentamicin penetration experiment. Four microliters of 4% gentamicin as sulphate (Rafa Labs. Ltd., Jerusalem, Israel) were applied on the epithelial surface of the mounted cornea at two pressure levels of acceptor chamber (5 and 20 mm Hg; 4 corneas for each pressure level). After 60 minutes, the concentration of gentamicin in the mounted corneal button and in the donor and acceptor chambers were measured by fluorescence polarization immunoassay using a TDx System Analyzer (Abbott labs., Irving, TX, USA). Corneal and acceptor chamber gentamicin fractions from the administered dose were calculated. . Results: Both of corneal thickness measurements and corneal fraction of gentamicine sulfate were higher at 5 mm Hg compared to 20 mm Hg acceptor chamber pressure level. . Conclusions:A correlation was found between corneal thickness change and corneal capacity as a reservoir for a topically applied drug in ex–vivo simulated ocular hypotony. .

Keywords: pharmacology • intraocular pressure • cornea: basic science