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Aims-Corneal perfusion chambers are important tools in the development and assessment of ophthalmic drugs. The aim of this study was to design and test a modified perfusion chamber suitable for topical application of drugs to isolated corneoscleral preparations, and which allowed continuous monitoring of endothelial cell function. Methods-A polycarbonate and stainless steel perfusion chamber was designed to clamp corneas in a horizontal plane suitable for topical drug delivery. Endothelial cell function was assessed by ultrasonic pachymetry and specular microscopy during perfusion. Epithelial barrier function was assessed by penetration of fluorescein. Leakage was examined by measuring penetration of a large protein, IgG. Tissue architecture after perfusion was examined by conventional histology. Results-Corneas maintained a functionally and morphologically intact endothelial monolayer during perfusion periods of up to 14 hours. The epithelial barrier function was well preserved. The tissue clamp sealed the preparation eVectively against leakage of macromolecules. Conclusion-The new chamber device forms a reliable tool for in vitro drug penetration and toxicity studies in isolated perfused corneoscleral tissue. (Br J Ophthalmol 2001;85:450-453) In vitro drug penetration and endothelial toxicity studies on isolated corneoscleral preparations are important for developing and testing ophthalmic drugs, drug vehicles, and irrigation solutions.

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S U M M A R Y1. Normal subjects performed fatiguing static hand-grip contraction at tensions of 20% and 55% of their maximum voluntary contraction (MVC). Intraocular pressure (IOP) was measured by applanation tonometry before, during and after the isometric exercise. Forearm blood samples were taken from the antecubital vein in both the exercised and non-exercised arm before and 2 min post-exercise for measurement of plasma lactate, osmolality, Pv,oz, Pv,co2 and pH.2. During hand grip the heart rate and blood pressure increased significantly, whereas the IOP remained unchanged from control in both the 20% and 55% MVC experiments.3. In the recovery period heart rate and blood pressure returned to control values within 3 min and the IOP decreased significantly from control in both the 20% and 55% MVC experiments.4. When an occlusion cuff was inflated on the exercising arm just before release of the 55% MVC grip, the decreased IOP could be delayed until the cuff was released. 5. Post-exercise blood samples showed elevated lactate concentrations and Pv,oz and decreased pH in the exercised arm; however, the values remained unchanged in the non-exercised arm. The decreased IOP after exercise may be related to an increased blood lactate concentration.