Markus Frentz

Rinsing with isotonic saline solution for eye burns should be avoided

BACKGROUND Recent approaches to emergency treatment of eye burns have given rise to many questions on the effectiveness of traditional rinsing solutions. This led us to study the use of isotonic saline solution and a recently introduced, highly effective solution, Cederroth Eye Wash, in the initial treatment of eye burns. METHODS A central area (Ø 10mm) of the cornea of isolated ex vivo rabbit eyes was burnt for 20s with 25+/-1.4 micro L of 2N NaOH. The anterior chamber pH was measured continuously via microelectrode. The corneas were immediately rinsed for 15 min with flow rates of 50, 100, 200, 300, 400, and 500 mL/min. RESULTS After 20 min measurement, no significant differences in intraocular pH were found between unrinsed eyes and eyes rinsed with isotonic saline solution at any flow rate. At all flow rates, Cederroth Eye Wash brought about a significant decrease (p<0.001; Tukey t-test). CONCLUSIONS Isotonic saline solution was ineffective in the emergency treatment of severe alkali eye burns in this ex vivo rabbit eye model. Cederroth Eye Wash, even at the lowest flow rate, significantly reduced intracameral pH. Thus a small amount of buffer solution effectively decontaminated the eye, whilst large amounts of saline solution did not.

Changing the composition of buffered eye-drops prevents undesired side effects

Purpose The Ex Vivo Eye Irritation Test (EVEIT) is used to analyse the clinical observations of corneal calcification attributed to the presence of phosphate within applied eye-drops used in treating glaucoma, Still–Chauffard syndrome, ocular burns and dry eyes. Method Live corneas from abattoir rabbit eyes were cultured in order to study epithelial healing following mechanical abrasion of the corneal surface combined with repeated exposure to various eye-drops. Results Obvious corneal calcification of the wound area along with a complete epithelial healing covering the calcified area was observed following exposure to phosphate hyaluronate eye-drops. Epithelial healing without calcification was achieved using citrate hyaluronate eye-drops. Conclusion Clinical observations show that topical use of artificial tears containing phosphate on injured eyes may lead to sight-threatening corneal complications. Simulation of such treatment conditions by the EVEIT convincingly demonstrates that changes in the composition of the pharmaceutically used treatments can prevent this undesired side effect. Although considerable healing was achieved during the repeated application of eye-drops, using either a phosphate or citrate buffer, only the drops containing citrate did not develop corneal calcification on the eye. The authors therefore recommend discontinuing the use of phosphate-buffered eye-drops, or other topically applied solutions, to avoid further injury to the patient.

Dynamic analysis of chemical eye burns using high-resolution optical coherence tomography

The use of high-resolution optical coherence tomography (OCT) to visualize penetration kinetics during the initial phase of chemical eye burns is evaluated. The changes in scattering properties and thickness of rabbit cornea ex vivo were monitored after topical application of different corrosives by time-resolved OCT imaging. Eye burn causes changes in the corneal microstructure due to chemical interaction or change in the hydration state as a result of osmotic imbalance. These changes compromise the corneal transparency. The associated increase in light scattering within the cornea is observed with high spatial and temporal resolution. Parameters affecting the severity of pathophysiological damage associated with chemical eye burns like diffusion velocity and depth of penetration are obtained. We demonstrate the potential of high-resolution OCT for the visualization and direct noninvasive measurement of specific interaction of chemicals with the eye. This work opens new horizons in clinical evaluation of chemical eye burns, eye irritation testing, and product testing for chemical and pharmacological products.

Towards a New in vitro Model of Dry Eye: The ex vivo Eye Irritation Test

Understanding of dry eye syndrome (DES) today is driven by in vivo analysis of tear osmolarity, tear film break up time, impression cytology and description of symptoms. Existing in vivo models of DES need severe alterations of tear production or corneal integrity. For a more detailed analysis of DES under particular environmental and treatment conditions a considerable lack of in vitro methods exists. The main disadvantage of current in vitro models is the limited experimental time frame of only several hours and the impossibility to evaluate healing of epithelial defects. In the present study, evidence is given that these restrictions can be overcome by modifying the established Ex Vivo Eye Irritation Test (EVEIT) to realize a model system for DES. This test is based on abattoir rabbit eyes allowing an experimental time frame of up to 21 days using self-healing corneal cultures. In first experiments it is demonstrated that different severity levels of dry eye can be simulated in the EVEIT system. High-resolution optical coherence tomography (OCT) is applied to monitor the initial phase of DES under evaporative stress acting on the cornea. We observed changes in corneal layer thicknesses and in scattering properties of the stroma, which are sensitive indicators of environmental stress leading to irritation of the ocular surface under dry eye conditions. The combination of corneal culture under desiccating conditions and OCT monitoring offers a new perspective in understanding and treating of DES and is expected to allow for significant pharmacological screening tests.