The experience of blurred vision in a single eye while wearing contact lenses is common and unsettling. This unilateral blurriness signals a problem specific to that eye, ranging from simple issues with the lens itself to more complex changes in eye health. Understanding the potential causes is the first step toward correcting the problem and maintaining clear vision. The reasons for this blur can be divided into immediate lens concerns, problems with the lens prescription or fit, and underlying medical conditions.
Immediate Causes Related to the Lens
Often, blurriness is caused by a straightforward issue with the contact lens that can be resolved without professional intervention. Deposits on the lens surface are a frequent culprit, as proteins, lipids, and makeup can accumulate and create a hazy film that scatters light. The lens should be removed, cleaned thoroughly with the recommended solution, and then reinserted to troubleshoot.
Another simple cause is the lens being inside out, which prevents it from conforming correctly to the cornea’s natural curve. This improper fit often leads to mild blurriness and discomfort, as the edge of the lens may rub against the eye. A quick check involves placing the lens on a fingertip; if the edges flare outward like a bowl with a rim, it is inside out. A correctly oriented lens forms a smooth, perfect bowl shape.
Dryness or dehydration of the lens material can also cause vision to fluctuate or blur in one eye. If the tear film on one eye is less stable, the lens may lose moisture and clarity faster. A foreign body, such as a tiny speck of dust or an eyelash trapped underneath the lens, will create immediate blurriness and a sharp, irritating sensation. Removing and rinsing the lens is typically enough to flush out the particle and restore clear vision.
Issues with Prescription and Lens Fit
If simple cleaning does not correct the blur, the issue may relate to how the lens interacts with the eye’s unique shape, requiring professional adjustment. An incorrect lens power is a possibility, especially if a patient accidentally places lenses with different prescriptions in the wrong eyes. Even if the lenses are correct, a subtle change in the refractive error of only one eye since the last examination can cause blurriness.
For individuals with astigmatism who wear specialized toric contact lenses, blurriness often results from lens rotation or misalignment. Toric lenses have specific stabilizing zones and must remain precisely aligned on the cornea’s irregular curvature to correct vision. If the lens rotates slightly off its intended axis, the corrective power is misdirected, leading to immediate blur.
The base curve dictates how tightly or loosely the lens sits on the cornea and is a factor in fit. If the lens is too loose, it may shift excessively across the eye, causing fluctuating vision. Conversely, a lens that fits too tightly can restrict tear flow and oxygen exchange, leading to discomfort and blurriness. These fit-related problems require an eye care professional to measure the corneal topography and select a lens with the appropriate diameter and curvature.
Underlying Ocular Health Conditions
A persistent unilateral blur can be a symptom of a localized health condition affecting the eye. Corneal edema, or swelling of the clear front surface of the eye, occurs when fluid builds up within the cornea’s structure. This swelling is often caused by insufficient oxygen, which can happen with extended or overnight wear of contact lenses, and it compromises clarity.
An ocular infection, such as keratitis, is a more serious cause where bacteria, fungi, or parasites contaminate the cornea, often due to poor lens hygiene. Keratitis causes significant blurriness, often accompanied by severe redness, pain, and increased sensitivity to light. A corneal abrasion, caused by improper lens removal or a foreign object trapped beneath the lens, can also lead to sudden blur and acute pain.
Unilateral ocular dryness, where one eye experiences tear film instability more severely than the other, can cause fluctuating blur. This happens because the contact lens relies on a healthy tear film to remain clear and moisturized. These health issues demand immediate attention, as wearing a contact lens over a compromised or infected eye significantly increases the risk of permanent damage or vision loss.
When to Seek Professional Help
Any blurriness that does not clear up after removing, cleaning, and reinserting the contact lens warrants professional consultation. An eye care specialist should be seen immediately if the blur is accompanied by specific warning signs, known as red flags:
- Severe or persistent eye pain
- Discharge from the eye
- Noticeable and sustained redness
- Sudden, dramatic reduction in vision
These symptoms indicate an infection, corneal injury, or other serious complication requiring prompt medical treatment. During an examination, the doctor uses a specialized instrument called a slit lamp to inspect the cornea and the lens fit. They assess lens positioning, check for inflammation or infection, and determine if the problem is a simple fit issue or a developing medical condition. Never wear a contact lens if the eye is painful or appears infected, as this can worsen the condition and increase the risk of long-term visual impairment.