To perform its primary function of light refraction, the cornea must be relatively thin & dehydrated, with a smooth anterior surface.
In a normal cornea, optical transparency is directly related to the state of hydration of the tissue: If the cornea swells, it increases in thickness and its surface becomes irregular, impairing its optic properties.
Corneal oedema refers to the retention of excess fluid within one or multiple layers of the cornea. The over-hydration of the cornea can have different etiologies including mechanical, dystrophic, inflammatory and toxic causes.
Therefore the use of a hypertonic solution such as sodium chloride 5% :
♦ Reduces the oedema by drawing water out of the cornea,
♦ Improves vision and alleviates symptoms of discomfort.