Examination of the conjunctival microbiota after 8 hours of eye closure

We investigated the effect of overnight eye closure on the levels and types of microbiota in the external eye, the conjunctiva, and lid margins of 40 normal subjects during the day and immediately after eye opening following 8 hours of sleep over 3 consecutive days. Overall, clinically important levels of gram-positive bacteria were isolated from 22.1% of samples; 2.3% of samples yielded gram-negative bacterial growth. The incidence of clinically important levels of gram-positive bacteria was greater in closed-eye compared with open-eye samples. There was no significant increase in the incidence of gram-negative bacteria or fungi with eye closure. There was no difference between the open- and closed- eye samples with regard to types of microorganisms isolated. Our results suggest that eye closure may promote the growth of normal external ocular microbiota. These findings have implications for extended contact lens wear and ocular surgery.