Which main ions contribute to tear film osmolarity? (Choose 2)

The correct choice regarding the main ions that contribute to tear film osmolarity includes sodium (Na+) and bicarbonate (HCO3-).

Sodium ions play a significant role in maintaining the osmotic balance of the tear film. They contribute to the regulation of fluid movement across the ocular surface, helping to maintain the appropriate level of hydration and osmolarity necessary for healthy tear film stability. The osmotic pressure created by sodium ions also influences tear film thickness and overall tear function.

Bicarbonate ions, on the other hand, are vital for buffering the tear film and maintaining pH balance. They help to counteract acidity that could arise from various metabolic processes or from exposure to environmental factors. The presence of bicarbonate also aids in the stability of the tear film, allowing it to maintain its osmotic properties and function effectively.

While chloride ions (Cl-) do participate in the ionic composition of tears, they are not among the primary contributors to osmolarity in comparison with sodium and bicarbonate. Hydroxide ions (OH-) are generally not considered in the context of osmolarity, as they are typically involved in pH balance rather than the ionic osmotic pressure of the tear film. Therefore, the primary contributions to tear film