Crying out of one eye, or unilateral epiphora, is a common experience. While often benign, it can signal an underlying issue with the eye’s tear production or drainage system. Understanding the reasons behind this phenomenon helps identify when it’s a temporary irritation and when professional guidance is needed.
How Tears Work
The eye’s tear system, or lacrimal apparatus, continuously produces and drains tears to maintain eye health. Tears are created in the lacrimal glands, located above the outer corner of each eye. These glands release fluid that spreads across the eye’s surface with each blink, lubricating and protecting the cornea and conjunctiva.
Tears are composed of three types: basal, reflex, and emotional. Basal tears provide constant lubrication, while reflex tears respond to irritants like dust or smoke, flushing them away. Emotional tears are triggered by strong feelings. After serving their purpose, tears drain through tiny openings called puncta, located in the inner corner of the eyelids. From the puncta, tears travel through small tubes called canaliculi into the lacrimal sac, eventually draining into the nasal cavity through the nasolacrimal duct. This system ensures tears are efficiently managed, but disruptions can lead to excessive tearing.
Common Reasons for Unilateral Tearing
Direct irritation to the eye is a frequent cause of one-sided tearing. Foreign bodies like dust, an eyelash, or a small speck of dirt stimulate reflex tear production in the affected eye to flush out the irritant. Environmental factors, including strong winds, cold air, or exposure to smoke or chemicals, can also trigger this protective tearing response.
Allergies can also lead to unilateral tearing, especially if an allergen primarily affects one eye. Allergic conjunctivitis, for instance, causes itching, redness, and excessive watering in one eye. This localized reaction results from the body’s immune response to specific substances.
Partial or temporary blockages within the tear drainage system are another common reason for one-sided tearing. A minor obstruction, such as a small particle, mucus, or mild swelling, can prevent tears from draining properly. This leads to tears pooling and overflowing onto the cheek. Such blockages are often temporary and may resolve on their own.
Paradoxically, dry eye syndrome can also manifest as excessive tearing, known as reflex tearing or epiphora. When the eye’s surface becomes too dry, it signals the lacrimal glands to produce a flood of tears to compensate. These reflex tears are often watery and lack the balance of oils and mucus needed to effectively lubricate the eye, leading to a cycle of dryness and overproduction, which can be more pronounced in one eye.
When It’s More Than Just an Irritant
While often benign, one-sided tearing can indicate more serious medical conditions. Infections like conjunctivitis (pink eye) or blepharitis (eyelid inflammation) can affect a single eye and cause tearing. These conditions often come with additional symptoms such as redness, discharge, itching, or a gritty sensation. Viral conjunctivitis may start in one eye and then spread to the other within 24-48 hours.
Inflammatory conditions, such as dacryocystitis (infection and inflammation of the tear sac), can also lead to unilateral tearing. This condition typically presents with pain, swelling, and redness near the inner corner of the eye, often with discharge. Another inflammatory condition, keratitis (inflammation of the cornea), can cause excessive tearing along with eye pain, redness, blurred vision, and light sensitivity.
Eyelid abnormalities can also disrupt tear distribution and drainage in one eye. Conditions like ectropion (eyelid turns outward) or entropion (eyelid turns inward) can prevent tears from properly spreading across the eye or directing them into the drainage system. Ectropion can cause tears to pool and overflow, while entropion can lead to eyelashes rubbing against the eye, causing irritation and reflex tearing.
In rare instances, neurological conditions affecting facial nerves can impact tear production or drainage in one eye. For example, some forms of facial paralysis may lead to issues with eyelid function or tear gland control, resulting in unilateral tearing. Tumors in the orbit or near the tear drainage system are also rare but serious causes of one-sided tearing by obstructing tear ducts or affecting nerve function.
Seeking Professional Guidance
Seek professional guidance if one-sided tearing persists or is accompanied by other concerning symptoms. If tearing does not resolve on its own within a short period or worsens, an eye care professional should be consulted. Persistent tearing can interfere with daily activities and vision.
Additional symptoms warranting immediate medical attention include eye pain, redness, swelling around the eye, changes in vision, discharge (pus or mucus), or increased sensitivity to light. If tearing began after an eye injury or trauma, or if something feels constantly stuck in the eye, prompt evaluation is advisable. These symptoms could indicate a more serious underlying issue requiring timely diagnosis and treatment.
Managing and Preventing One-Sided Tearing
For common causes of one-sided tearing, several self-care measures can provide relief. Gently cleaning the eye to remove any visible irritants or discharge is helpful. Applying a warm compress to the affected eye can soothe irritation and help alleviate blockages or inflammation, particularly in cases of blepharitis or minor tear duct issues. Avoiding rubbing the eye is also important to prevent further irritation.
Using artificial tears can help lubricate the eye and wash away irritants, especially if dry eye contributes to tearing. When outdoors or in dusty environments, wearing protective eyewear, such as sunglasses or safety glasses, can shield the eyes from wind, dust, and other environmental irritants that trigger reflex tearing. If allergies are suspected, over-the-counter allergy eye drops containing antihistamines can help manage symptoms.
When medical intervention is necessary, treatment approaches vary depending on the underlying cause. For infections, a doctor might prescribe medicated eye drops or oral antibiotics. In cases of tear duct blockages, particularly in adults, procedures such as probing or surgical intervention might be recommended to restore drainage. Conditions like ectropion or entropion often require surgical correction to reposition the eyelid. Addressing the specific cause with professional medical advice is essential for effective management.