In contact lens terminology, what does the term 'hydrophilic' relate to?

The term 'hydrophilic' refers to materials that have a strong affinity for water and can absorb it. In the context of contact lenses, hydrophilic materials are essential for ensuring comfort and moisture retention when lenses are worn. These materials can swell when hydrated, allowing for increased oxygen permeability, which is crucial for maintaining eye health during lens wear.

The ability of hydrophilic materials to attract and hold water is what makes them suitable for various types of contact lenses, particularly soft lenses. This property enhances the comfort and safety of the lenses by reducing dryness and irritation that can occur during wear.

In contrast, water-repelling materials, high-density materials, and flexible materials do not specifically relate to the absorption of water, which is the defining characteristic of hydrophilic substances. Understanding this key feature is fundamental for those involved in the fitting and care of contact lenses.