Is cannabis harmful to the eyes?

One of the side effects of cannabis use is the potential occurrence of the famous red eyes. This reddening is perceived as the clearest evidence of cannabis use. This effect is simply due to tetrahydrocannabinol (THC), which reduces blood pressure, dilating blood vessels and increasing blood circulation throughout the body.

Even if the red eyes are visible almost instantly after smoking cannabis, the effects do not last over the long term. What are the potential long-term effects of cannabis on the eyes? 

Cannabis against glaucoma

Glaucoma is an eye disease that affects the optic nerve. With age (from 45 onwards), vision deteriorates. Many patients use cannabidiol for therapeutic purposes to treat their glaucoma, the best known being certainly Whoopi Goldberg.

On the front, an American medical journal, Jama Ophthalmology a conducted a study and explains that regular use of cannabis could delay the information transmitted by the retina and ultimately deteriorate eyesight.

Study author Dr. Vincent Laprevote explains, «Such an abnormality might be imperceptible in cannabis users. However, it is important because it could reflect changes in communication between neuronal cells implied by regular cannabis use.»

Subconjunctival hemorrhages

Subconjunctival hemorrhages are discharges of blood into the white part of the eye and the sclera. Laser surgery, sneeze or cough are natural causes. They generally last longer than simple «red eyes», but can also be caused by regular cannabis consumption.

Hemorrhage can cause pupil dilation and take longer than expected to heal. However, it tends to disappear after 2 to 3 weeks. Don't hesitate to talk to your doctor if this happens to you, in order to limit the damage.