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Giulio Ferrari, Paolo Rama; Trigeminal Stereotactic Electrolysis Induces Dry Eye In Mice. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2333.
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The purpose of this study was to detect and quantify the development of dry eye in a novel, murine model of corneal denervation. Corneal sensory nerves contribute to the maintenance of the cornea surface integrity by providing the afferent loop of the blink reflex. However, it has been shown that the role of corneal nerves goes beyond mere sensory detection. They secrete a number of peptide mediators such as Nerve Growth Factor, Calcitonine Gene Related Peptide, and others which have profound effects on corneal surface homeostasis.
Seven eyes of seven C57/Bl6 mice were used for this experiment. We used a recently published method to induce corneal denervation by inactivating the ophthalmic branch of the trigeminal nerve (Trigeminal Stereotactic Electrolysis, TSE). At the end of the procedure tarsorrhaphy was performed. The effectiveness of the procedure was confirmed by the absence of blink reflex. Animals were examined before and 7 days after TSE to detect any change induced by denervation. The animals were examined using a biomicroscope, corneas were stained with fluorescein, and scored according to the National Eye Institute Grading System. Finally, tear production was quantified with phenol red thread test.
Before TSE was performed, biomicroscopy revealed a normal cornea. Cornea fluorescein staining was negative before TSE (score: 0), and phenol test was 2.7±0.5mm. Corneal reflex was present in all the eyes.Following TSE, cornea fluorescein staining score was 10.4±2.2, phenol test decreased to 0.5±0.3mm; corneal reflex was absent in all the eyes. We found a significant difference in both fluorescein score ( P<0.001) and phenol test ( P<0.001) before and after TSE (t test).
Sensory corneal denervation induces dry eye in the TSE murine model. This occurred despite tarsorrhaphy was performed, suggesting a role for corneal trigeminal nerves beyond sensory perception. These findings are supported by existing literature in other animal models of corneal denervation.
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