Dry eye disease is a common condition characterized by insufficient tears or tears of poor quality. This can lead to discomfort, visual disturbances, and potential damage to the eye’s surface. The tear film, which covers the eye, consists of three main layers: an oily outer layer, a watery middle layer, and a mucous inner layer. Problems with any of these layers can disrupt the tear film’s stability, leading to dry eye symptoms.
Dry Eye in One Eye
While dry eye typically affects both eyes, it is possible for symptoms to manifest in only one eye, a condition known as unilateral dry eye. This is not uncommon, and individuals may experience dry eye symptoms in a single eye.
Specific Causes for Unilateral Dryness
Unilateral dry eye can stem from various factors that disproportionately affect one eye. Meibomian gland dysfunction (MGD) is a frequent cause, where the oil-producing glands within the eyelids become blocked or produce poor-quality oil. Since these glands are located in each eyelid, dysfunction can occur in one eye, leading to rapid tear evaporation and dryness on that side.
Incomplete blinking or issues with the eyelids can also contribute to unilateral dryness. Conditions like Bell’s Palsy, which can affect facial nerves, or previous eye surgeries such as LASIK, might impair an eyelid’s ability to spread tears effectively over one eye. Eyelid abnormalities where the lid turns inward (entropion) or outward (ectropion) can similarly expose one eye and cause dryness.
Environmental factors often play a role, as localized exposure can impact a single eye more significantly. For instance, sitting near a fan or a car vent might direct airflow primarily at one eye, accelerating tear evaporation on that side. Exposure to wind, smoke, or very dry air can also disproportionately affect one eye.
Contact lens use can induce unilateral dry eye if a lens in one eye is ill-fitting, worn excessively, or causes localized irritation. A foreign body or injury to one eye, such as a corneal abrasion, can also cause irritation and dry eye symptoms localized to the affected eye.
Neurological issues involving nerve damage affecting one eye can impact tear production or sensation. Damage to corneal nerves, for example, can disrupt tear production and ocular surface health in the affected eye. A lack of nerve supply to the lacrimal gland, which produces tears, has been reported as a cause of unilateral dry eye.
Certain eye drops or medications used unilaterally can also induce dryness in that specific eye. Both systemic and topical medications, including some antidepressants, antihistamines, and blood pressure medications, can reduce tear production or alter tear composition, potentially affecting one eye.
Recognizing Unilateral Symptoms
Individuals might experience a persistent gritty or scratchy sensation, as if something is in the eye. Burning, stinging, or irritation localized to one eye are common complaints.
The affected eye may appear red or feel painful. Paradoxical tearing, where the dry eye waters excessively in response to irritation, can also occur in a single eye. Other symptoms can include sensitivity to light, blurred vision, especially when reading, and difficulty wearing a contact lens in the affected eye. These symptoms may be constant or intermittent, depending on the underlying cause.
Diagnosis and Management
If dry eye symptoms are experienced in one eye, consulting an eye care professional is important for proper diagnosis. Unilateral symptoms can indicate underlying conditions requiring specific attention.
During a visit, common diagnostic tests may include a tear film breakup time (TBUT) test, which measures how long the tear film remains stable on the eye’s surface after a blink. A Schirmer’s test may also be performed, involving the placement of a small paper strip under the lower eyelid to measure tear production over a set period. The doctor may also examine the tear film and ocular surface using a slit lamp microscope.
Management approaches for dry eye often begin with strategies to improve tear film stability and reduce irritation. Over-the-counter artificial tears are a common first step to lubricate the eye. Prescription eye drops, such as those that reduce inflammation or stimulate tear production, may be recommended for more persistent cases. Warm compresses and eyelid hygiene, including gentle cleaning, can help address issues like meibomian gland dysfunction and blepharitis. Lifestyle adjustments, such as modifying environmental exposure or taking breaks from screen time, can also help manage symptoms.