Wearing contact lenses while smoking cannabis is a common concern for many lens wearers. The interaction involves both the direct effects of smoke on the ocular surface and the systemic physiological changes caused by cannabis compounds. While physically possible, wearing contacts during cannabis use introduces factors that can rapidly lead to significant eye discomfort and potential health risks. These risks stem from external irritation and internal changes in tear film composition.
How Smoke Irritation Affects Contact Lenses
Inhaling cannabis smoke creates a cloud of fine particulate matter that directly irritates the eyes. These microscopic particles can land on the exposed surface and become trapped between the contact lens and the cornea. This deposition often causes immediate discomfort, causing a gritty sensation and blurred vision.
Soft contact lenses contain a significant percentage of water, acting like a sponge on the eye. The heat and dryness from smoke rapidly accelerate lens dehydration. As the lens loses moisture, it tightens against the cornea, reducing oxygen exchange and leading to irritation and adhesion.
Physiological Changes and Dry Eye
Beyond direct smoke irritation, the systemic effects of tetrahydrocannabinol (THC) significantly impact the eye’s natural lubrication system. THC is a known vasorelaxant, which lowers blood pressure and causes the visible dilation of blood vessels associated with “red eyes.” This systemic change also affects the delicate balance of the tear film.
THC interacts with CB1 cannabinoid receptors located in the lacrimal gland, which produces the aqueous layer of tears. Activation of these receptors inhibits the gland’s normal function, resulting in a measurable reduction in tear secretion and volume. This drug-induced dry eye condition is compounded by a documented decrease in the natural blink rate while impaired.
A thin or unstable tear film is detrimental to contact lens wear, as it increases friction between the lens and the eyelid. This lack of lubrication makes the lens feel dry, scratchy, and prone to adherence to the eye’s surface. This raises the potential for corneal micro-abrasions.
Safety When Handling Lenses
The practical risks associated with wearing contacts while impaired often revolve around hygiene and dexterity. Cannabis consumption can temporarily impair motor coordination and judgment, making the precise act of inserting or removing a contact lens more challenging. This impairment increases the risk of touching the eye with unwashed hands, which introduces bacteria and can cause a serious eye infection.
When the eyes are severely dry from THC’s effects, the lens can become tightly adhered to the cornea. Attempting to remove a dry, adhered lens without adequate rewetting solution or proper technique can cause mechanical damage to the corneal surface. Reduced attention to hygiene, such as dropping a lens or improperly cleaning it, significantly elevates the risk of corneal abrasion or microbial keratitis. Taking out contact lenses before consumption or ensuring hands are thoroughly cleaned are important steps to mitigate these risks.