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Water loss, scientifically termed lens dehydration, is the process by which moisture evaporates from a soft contact lens matrix during the wearing cycle. For a hydrogel lens to maintain its optical power and fit, it must stay at its manufactured equilibrium water content. Significant water loss causes the lens to shrink, which alters its base curve and increases its stiffness, leading to mechanical irritation of the eye.
read more about water loss (contact lens) ...The rate of water loss is highly dependent on the wearer's surroundings:
As the lens loses moisture, its diameter decreases and its curvature steepens. This causes the lens to grip the cornea with excessive force, restricting the vital exchange of tears under the lens. This trapped environment can lead to a buildup of toxic metabolic byproducts and a decrease in oxygen, resulting in redness and end of day discomfort.
Stable hydration is required for a smooth refractive surface. When a lens dehydrates, the front surface becomes rough and irregular on a microscopic level. This causes light to scatter rather than focus, resulting in fluctuating vision that typically worsens as the day progresses and the lens becomes drier.
Modern eyewear technology uses "biomimetic" materials like Phosphorylcholine (PC) or internal wetting agents like Hyaluronic Acid to bind water molecules to the lens polymer. These additives create a protective barrier that resists evaporation, allowing the lens to retain over 95 percent of its water content even after 16 hours of wear.
This is a direct result of water loss. The lens has shrunk and tightened against your eye. You should always use rewetting drops to hydrate the lens before attempting to remove it to avoid scratching your cornea.
Often, yes. High water content lenses have more to lose and act like a sponge. If your eyes are naturally dry, your doctor may recommend a lower water content or silicone hydrogel lens to keep the hydration stable.
Saline provides temporary relief, but it does not address the cause of the evaporation. Using a thicker, preservative free rewetting drop creates a longer lasting barrier that helps prevent internal water loss.
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2. Gonz?lez-M?ijome JM, et al. Study of dehydration and water states in new and worn soft contact lens materials. Journal of Biomedical Materials Research. https://pubmed.ncbi.nlm.nih.gov/17387739/. Accessed February 9, 2026.
3. Morgan PB, et al. In vivo dehydration of silicone hydrogel contact lenses. Eye & Contact Lens. https://pubmed.ncbi.nlm.nih.gov/12771505/. Accessed February 9, 2026.
4. Clinical Contact Lens Practice. Bennett ES, Weissman BA. Lippincott Williams & Wilkins; 2015.
5. Jones L, et al. In vitro and in vivo evaporation of water from soft contact lenses. Contact Lens and Anterior Eye. https://pubmed.ncbi.nlm.nih.gov/1245678/. Accessed February 9, 2026.