While modern contact lenses are designed for high stability, the answer to whether one can fall out without your knowledge is yes, though it is uncommon. A contact lens is a thin, curved piece of plastic material placed directly on the cornea to correct vision. The design and the natural anatomy of the eye work together to keep the lens precisely centered, making an unnoticed loss a relatively rare occurrence.
How Contact Lenses Are Secured on the Eye
The primary force holding a soft contact lens in place is the surface tension created by the tear film, which acts like a biological suction cup. This fluid adheres the lens to the surface of the cornea. The lens material is hydrophilic, which helps it integrate seamlessly with the eye’s natural moisture.
Beyond the adhesion of the tear film, the physical fit of the lens is important for retention. An eye care professional determines the correct base curve and diameter to ensure the lens rests appropriately on the corneal and scleral surfaces. A lens that is either too flat or too steep will not be able to maintain this stable relationship with the eye.
The eyelids also play a role, providing a gentle pressure during the blink that re-centers the lens and refreshes the tear film beneath it. When the lens is correctly fitted, the forces of the tear film and eyelid mechanics cooperate to keep the lens stationary on the eye’s surface.
Primary Causes of Lens Dislodgement
The most frequent cause of a lens falling out involves a breakdown of the tear film’s stabilizing grip. Severe eye dryness, often caused by environmental factors like wind, air conditioning, or reduced blinking during screen time, can lead to the tear film thinning or evaporating too quickly. When the pre-lens tear film destabilizes, the lens surface loses its adhesion and becomes susceptible to movement.
Physical actions that interfere with the lens-eye boundary are a common factor. Excessive rubbing of the eyes, especially when debris is present, can easily push the lens out of position. Once the lens moves off the cornea and onto the sclera, it can fold and slip out completely.
High-impact physical activity or a sudden blow to the eye can also overcome the lens’s grip. The type of lens matters, as smaller, less flexible rigid gas permeable lenses dislodge more easily than larger, softer lenses.
How to Detect a Missing Contact Lens
The most definitive indication that a lens is missing is the immediate onset of blurred or poor vision in one eye. If you rely on the lens for vision correction, the clarity of sight will diminish instantly. For many people, the feeling of the lens itself is so subtle that the change in vision becomes the primary clue.
Sometimes, the sensation of loss is preceded by a brief period of discomfort or a foreign body sensation, which occurs when the lens moves or folds before exiting the eye. If the lens has merely moved, you might feel a scratchy or gritty irritation as the lens edge rubs against the inside of the eyelid. This feeling is a sign the lens is still present but is dislocated, often tucked up under the upper lid.
To verify a suspected loss, immediately check your vision by covering the other eye. If the vision in the affected eye is poor, you should then examine the eye in a bright mirror. Gently pull down the lower lid and look up, then pull up the upper lid and look down to check the entire front surface of the eye. If the lens is not visible on the eye or in the surrounding area, it is safe to assume it has fallen out, as the natural anatomy of the eye prevents a lens from traveling “behind” the eyeball.