Contact lenses are thin devices placed directly on the eye’s surface. Many new wearers wonder if they are secure enough to stay in place, but the fear of a lens frequently “falling out” is largely unfounded, especially with modern soft contact lenses. When properly fitted, a contact lens is designed to remain centered and stable on the eye throughout the day.
The Likelihood of Lenses Dislodging
A well-fitted contact lens is secured to the cornea primarily through surface tension. The natural tear film coating the eye acts like a thin adhesive, creating a strong bond that keeps the lens flush against the ocular surface. Research indicates that it takes an external force of about 11 grams to dislodge a correctly centered lens. The curvature of the cornea also plays a significant role in lens security. Modern soft lenses are flexible and conform closely to the eye’s shape, making them highly resistant to falling out. Minor movement (0.5 to 1 millimeter with a blink) is normal and necessary for tear exchange and eye health.
Common Causes for Contact Displacement
When a lens does shift or dislodge entirely, the most common reason is an improper physical fit. Contact lenses are prescribed with a specific base curve designed to match the individual corneal shape. If the base curve is too flat, the lens will move excessively, while a curve that is too steep can result in a tight fit that limits the necessary tear flow.
Another frequent cause of instability is eye dryness or dehydration. If the aqueous layer is insufficient, the lens loses the surface tension that holds it firmly in place. This lack of moisture can cause the lens to shift position, especially in dry environments or during periods of reduced blinking.
The introduction of a foreign body, such as dust or debris, can instantly lift the lens off the cornea. Even a microscopic particle can disrupt the lens-cornea relationship, causing irritation and forcing the lens to move.
Excessive eye rubbing or trauma is also a direct cause of displacement. Applying pressure or friction to the eyelid can easily push the lens to the side or fold it under the eyelid. While the lens cannot physically roll to the back of the eye, it can become lodged beneath the upper or lower eyelid until it is retrieved.
Practical Methods for Lens Security
Ensuring the correct fit is the single most important preventative measure for lens security. An annual visit to an eye care professional for a fit check confirms that the base curve and overall lens diameter are still appropriate. A professional fitting optimizes the lens movement and centration, helping to prevent uncomfortable shifting.
Maintaining adequate moisture is also a practical step to keep lenses stable. Using rewetting or lubricating drops helps to replenish the tear film, especially in low-humidity or air-conditioned settings. This consistent hydration ensures the surface tension remains strong enough to keep the lens centered.
Good hygiene and careful handling further contribute to lens security. Always wash hands thoroughly before touching the eyes to avoid transferring debris. Patients should also avoid rubbing their eyes, which instantly destabilizes even a perfectly fitted lens. Adhering to the prescribed wearing schedule is important, as overwearing can lead to discomfort and instability.