Please activate JavaScript!
Please install Adobe Flash Player, click here for download

2013|14 Annual Report Fraunhofer IGB

9 0 Draize test Chemicals, cosmetics and pharmaceutical products must be tested and classified. Currently, the tolerability and irritation potential of substances that come in contact with the eyes are performed with the “Draize test” where the test substance is added to the lid sack of a rabbit eye and the chemical injury is observed for several days or weeks. Partly due to the high pain sensitivity of the cornea, this test is highly controversial. To date, there are no full replacement tests for these animal studies. Culturing corneas The ex-vivo culture of pig corneas’ is a method that may make experiments on living animals unnecessary. The eyes are re- moved after the slaughter of the animal, prepared so the cor- neas retain their natural curvature and then kept in a suitable medium in culture. The condition of the corneas is tested be- fore and after preparation and at regular intervals during the culture time for possible changes such as swelling, turbidity, injury, and the condition of the epithelium and endothelium. The corneas are only used in the cornea model after all criteria are met. Testing of substances on the corneal model We test substances on cultured corneas by adapting the OECD guideline 405. With our model, acute changes from poisons, corrosive substances, and mechanical and physical action can be detected, as well as long-term changes and potential tissue regeneration. The corneal model allows substances to be ap- plied several times, as it is the case with eye drops, to examine the consequences of multiple applications in sequence over a defined period of time while observing the resulting reaction from each sequence. We distinguish between substances that cause irreversible damage – either after single or repeated administration – and substances that cause a reversible or no damage. Since corneas can be cultured past the required time for substance testing, we can also model the typical healing process of the cornea in the laboratory as well as the regres- sion or healing of the damage to the eye. Evaluation Changes in the surface and the deep cornea can be investigat- ed by specific methods. Treatment with sodium fluorescein, which is also used in ophthalmology for diagnostic purposes, shows damages of the epithelium. Histological studies can make the status of the various layers of the cornea clearly vis- ible. For example, damage to the epithelial and endothelial layers or swelling of the stromal region can be identified. Cornea cell viability is examined by means of a 3-(4,5-dimeth- ylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. More complex measurements, such as impedance and OCT measurement (optical coherence tomography, imaging of tis- sue density with lasers) are appropriate procedures to visualize corneal damage. CORNEA ORGAN MODEL-TEST SYSTEM Angela Rossi, Pharmacist PHARMACY 1 2 3

Overview