The controlled-environment chamber: A new mouse model of dry eye

PURPOSE. To develop a controlled-environment chamber (CEC) for mice and verily the effects of a low-humidity setting on ocular surface signs in normal mice. METHODS. Eight- to 12-week-old BALB/c mice were used in a controlled-environment chamber (CEC) where relative humidity (RH), temperature (T), and airflow (AF) are regulated and monitored. Mice were placed into the CEC and exposed to specific environmentally controlled conditions (RH = 18.5% ± 5.1%, AF = 15 L/min, T = 21-23°C) for 3, 7, 14, and 28 days. Control mice were kept in a normal environment (RH = 50%-80%, no AF, T = 21-23°C) for the same duration. Aqueous tear production by means of the cotton thread test, corneal fluorescein staining (score, 0-15), and goblet cell density in the superior and inferior conjunctiva were measured by a masked observer. RESULTS. No statistically significant differences between the groups were found at baseline. Decreased tear secretion and increased corneal fluorescein staining were significantly present on day 3, 7, 14, and 28 in animals kept in the CEC. Goblet cell density was significantly decreased in the superior conjunctiva on day 7, and on day 3, 7, and 14 in the inferior conjunctiva in the CEC-kept mice compared with control animals. CONCLUSIONS. This study indicates that exposure of normal mice to a low-humidity environment in a CEC can lead to significant alterations in tear secretion, goblet cell density, and acquisition of dry eye-related ocular surface signs.