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Anthony Johnson, Patricia Buttke, Irene Kochevar, Heuy-Ching Wang, Steven Cora, Sheri DeMartelaere; Surgical Model for Evaporative Loss Dry Eye Model in the New Zealand White Rabbit. Invest. Ophthalmol. Vis. Sci. 2013;54(15):6046.
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Patients with severe facial burns often suffer indirect damage to their eyes. Burn wound contracture of the periocular skin causes cicatricial ectropion resulting in ocular exposure. Skin grafts are often required, but may be insufficient if deeper structures, such as the periocular muscles, are injured and the protective blink reflex is lost. With loss of the blink reflex the patient quickly develops exposure keratitis. No current treatment adequately addresses the severe keratitis that these patients develop. We established this evaporative loss dry eye model that simulates exposure keratopathy resulting from cicatricial ectropion to assist in the development of novel therapies for this condition.
Nine white rabbits were included in this study. The right eye of each rabbit was subjected to a 1.5 cm upper and lower lid blepharoplasty, in addition to excision of the nictitating membrane. The left eyes were untreated to serve as controls. Clinical examination included fluorescein staining and serial photography on days 3, 5, 7, 14, 21 and 28. Rabbits were sacrificed on day 28 and the cornea and conjunctiva were evaluated by histopathology.
Compared with untreated controls, surgically treated rabbits showed significant changes in fluorescein scores on days 5, 7, 14, and 28. Clinical examination revealed ocular surface defects ranging from the development of punctate epithelial erosions to corneal abrasion, beginning on day 7, with corneal ulceration developing in the most severe cases by week 3. Histopathological results revealed epithelium infiltrated by heterophilic inflammation with the underlying corneal stroma demonstrating heretophilic, lymphoplasmacytic inflammation, fibrosis and neovascularization.
The findings of this study demonstrate that upper and lower lid blepharoplasty combined with excision of the nictitating membrane is an excellent surgical model of evaporative dry eye. Damage to the cornea and conjunctiva manifesting as punctate epithelial erosions and corneal ulceration is consistent with clinical observations of burn patients with dry eye resulting from cicitricial ectropion. Future studies utilizing this model are planned to test multiple strategies to protect the ocular surface from evaporation due to ocular exposure.
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