The practice of wearing a contact lens in only one eye, known as unilateral wear, involves deliberately correcting the vision in one eye while leaving the other uncorrected or corrected for a different focal distance. Understanding the implications requires considering how the eyes and brain work together to create a cohesive image. Because the visual system is sensitive to any imbalance in focus, this approach requires professional guidance.
The Direct Answer: Is Unilateral Wear Safe?
Wearing a contact lens in only one eye is not inherently dangerous to the health of the eye itself when done under the supervision of an eye care professional (ECP). The uncorrected eye does not sustain harm from the lack of a lens, provided it is otherwise healthy. However, wearing a single lens without professional guidance can lead to significant discomfort and visual problems.
The primary concern is not physical safety but visual efficiency and comfort, as the brain must manage two very different images. An ECP conducts a comprehensive examination to determine if the uncorrected eye requires correction, such as for high astigmatism or a severe refractive error. The eye doctor ensures that the vision difference between the eyes is manageable for the patient’s visual system and lifestyle.
Visual Adjustments When Using a Single Lens
When one eye is corrected and the other is not, the brain receives two images with different levels of clarity, significantly affecting binocular vision. This imbalance forces the visual system to work harder to reconcile the sharp image from the corrected eye with the blurred image from the uncorrected eye, leading to noticeable visual strain.
One of the most immediate consequences of this visual imbalance is a reduction in depth perception, or stereopsis. Accurate depth perception relies on the brain receiving two slightly different, clear images from both eyes to calculate distance. When one image is blurred, the quality of stereopsis is compromised, which is problematic for activities requiring precise spatial judgment, such as driving or sports. This constant visual compensation can result in asthenopia, manifesting as eye fatigue, headaches, or general discomfort.
Specific Scenarios for Wearing One Contact
There are specific, intentional situations where an eye care professional may recommend the use of a single contact lens as a permanent vision solution. The most common scenario is monovision correction, a specialized technique used to manage presbyopia, the age-related loss of near focusing ability. In monovision, the dominant eye is fitted with a lens for distance vision, while the non-dominant eye is corrected for near vision, allowing the patient to see clearly at multiple ranges.
Another medically appropriate use is when a person has a large difference in prescription between their eyes, known as anisometropia, and only one eye requires correction. If the uncorrected eye has naturally sharp vision, the ECP may prescribe a lens only for the eye with the refractive error. Unilateral wear can also be a temporary measure following certain ocular surgeries, such as cataract removal in one eye, where a lens may be needed to balance the vision until the second eye is stabilized.