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Davi Marques, Monica Alves, Carolina Modulo, Leonardo Malki, Peter Reinach, Eduardo Rocha; Benzalkonium chloride-induced rat dry eye model mimics hyperosmolarity in tear volume deficient dry eye disease. Invest. Ophthalmol. Vis. Sci. 2013;54(15):6016.
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Chronic use of antiglaucomatous eye drops with benzalkonium chloride (BAK) leads to ocular surface disease and tear film hyperosmolarity. In rodent BAK dry eye disease (DED) models, it is unclear if BAK induces hyperosmolarity. We show in rats that the BAK DED model also entails development of tear film hyperosmolarity since tear volume collection is sufficient to monitor osmolarity changes.
Unanesthesized male rats (n=10) were treated twice daily with PBS containing 0.2% BAK in the right eye, whereas the left eye served as a control. After 7 days, tear film osmolarity was measured with the TearLab Osmolarity System (Ocusense). Phenol Red Thread test (PRT) evaluated tear fluid rates in 15 sec whereas vital staining monitored ocular surface integrity. Observers evaluated staining magnitude by assigning arbitrary values of from 1-to 18. Light microscopy evaluated corneal epithelial thickness.
Tear flows were 7.6 ± 2.01 mm in controls and 3.40 ± 0.67 mm in BAK treated eyes (p=0.03). Lissamine staining was 1.0 ± 0.77 in control and 8.40 ± 1.36 in BAK group (p=0.01); and fluorescein was 2.20 ±0.96 in control and 9.80 ±1.49 in BAK group. Control osmolarity was 284.0 ± 3.29 mOsm and with BAK 306 ±4.09 mOsm (p=0.01). Corneal epithelial thickness decreased by day 7 relative to that in the control group. Seven days after suspending BAK application, all changes recovered to their control values.
The rat BAK DED model is novel since increases in tear film osmolarity were measurable. This model is relevant since these rises mimic those identified in tear volume deficient patients afflicted with DED.
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