Which of the following does NOT occur in the tear film during sleep?

During sleep, there are several physiological changes that occur in the tear film. One significant change is related to the concentration of immunoglobulins, particularly IgA, which plays a vital role in the immune response of the ocular surface. During sleep, there is typically a reduction in the production of tears, resulting in less dilution of the components found in the tear film. Consequently, this leads to a higher concentration of IgA, as there are fewer tears to distribute and dilute it.

The correct answer pertains to the change in IgA concentration during sleep. The other options reflect accurate physiological changes: the tear film can indeed become more acidic, the concentration of H+ ions can increase, and the overall pH of the tear film tends to decrease. All these changes contribute to the different biochemical environment present in the tear film during sleep, highlighting the adaptive mechanisms associated with the ocular surface physiology. Understanding these changes is crucial for recognizing how tear film composition influences eye health and comfort during different states, such as wakefulness and sleep.