The experience of a contact lens suddenly feeling irritating or uncomfortable in only one eye is a common issue for lens wearers. This unilateral discomfort often points to a specific, identifiable problem, ranging from a simple mechanical error to a subtle physiological change in the eye itself. Since contact lenses rest directly on the highly sensitive corneal and conjunctival tissue, even a minor disruption can cause a significant foreign body sensation. Understanding the potential causes for this difference in comfort is the first step toward finding relief.
Immediate Mechanical Issues
The most frequent causes of sudden discomfort are often simple mechanical issues that require immediate physical inspection and correction of the lens. The presence of a foreign body, such as a tiny piece of dust, lint, or an eyelash, can become trapped underneath the lens, causing intense, localized irritation upon blinking. Removing the lens, rinsing it thoroughly with fresh solution, and then carefully reinserting it will usually clear this issue.
Another common source of one-sided discomfort is an inverted lens, meaning it has been placed inside out on the eye. An inverted soft lens does not conform properly to the eye’s curvature, causing its edges to lift and rub against the sensitive conjunctiva, leading to noticeable irritation and movement. You can check for inversion by placing the lens on your fingertip and looking at it from the side; if the edges flare out like a rimmed bowl, it is inverted, but if it forms a perfect, smooth cup shape, it is correctly oriented.
A lens that has been compromised by minor damage, such as a tiny chip or tear along its edge, can also cause localized discomfort. Even a small imperfection along the lens perimeter will repeatedly scrape the delicate eye surface during the blink cycle. If inspection reveals any nicks, tears, or damage, the lens must be immediately disposed of, as continued wear risks scratching the cornea.
Lens Quality and Maintenance Problems
Discomfort that develops slowly over hours or days is often linked to the lens material, its fit, or insufficient maintenance. Proteins, lipids, and calcium from your natural tear film can accumulate on the lens surface over time, forming deposits. This deposit buildup changes the lens’s surface smoothness, leading to increased friction and a gritty sensation, especially with bi-weekly or monthly replacement lenses.
To counteract this, proper cleaning technique, including gently rubbing the lens in the palm of your hand with solution for 5 to 10 seconds, is necessary to mechanically remove these deposits, even with “no-rub” solutions. Furthermore, wearing a lens beyond its prescribed lifespan allows these deposits to accumulate to a degree that significantly reduces comfort and breathability. Using an expired or defective lens from a new box can also result in discomfort if there is a manufacturing irregularity in that single lens.
A persistent, non-debris-related discomfort may also indicate an incorrect fit, which can affect one eye more than the other because the curvature of each cornea is often slightly different. The base curve (BC) of the lens, which determines how tightly or loosely it rests on the cornea, is a specific measurement that must be customized.
A lens with a BC that is too flat will move excessively, while one that is too steep will fit too tightly, restricting tear exchange and oxygen flow, both causing irritation. An incorrect lens diameter can also cause constant rubbing or instability, leading to chronic discomfort in the eye with the less compatible measurements.
Physiological Factors and Eye Irritation
Beyond the lens itself, the physical state of your eye can be the origin of the unilateral discomfort. Unilateral dry eye occurs when one eye is not producing sufficient tears or the tears evaporate too quickly, causing the lens to lose hydration and create friction against the cornea. This dryness can be caused by environmental factors, such as sleeping directly under an air conditioning vent, or by localized issues like an uneven tear film distribution in one eye.
An allergic reaction, known as allergic conjunctivitis, can also be localized to a single eye, perhaps due to rubbing one eye after touching an allergen, making the lens feel rough or gritty. This condition often involves inflammation of the conjunctiva, which causes the lens to feel less stable and more abrasive.
Any mild inflammation or irritation can make the lens feel intolerable, as the eye surface becomes hypersensitive to the lens material and movement. This increased sensitivity can be an early sign of a developing issue, such as a localized reaction to preservatives in a cleaning solution.
Recognizing Urgent Symptoms
While most contact lens discomfort is temporary and easily resolved, certain symptoms warrant immediate professional medical attention. Seek care if you experience severe, sharp, or sudden pain that does not resolve immediately upon removing the lens.
Other urgent signs include:
- A rapid change in vision, such as significant blurriness or a cloudy appearance.
- Intense, persistent redness covering the entire white of the eye.
- Any discharge, especially if sticky or purulent.
- Extreme, unusual sensitivity to light (photophobia).
If any of these symptoms occur, immediately remove the lens and contact an eye care professional, such as an optometrist or ophthalmologist. Do not attempt to self-diagnose or treat a severe eye problem, as a serious condition can rapidly escalate and cause permanent vision damage.