The phrase “coke eyes” describes the visible ocular changes following cocaine use. Cocaine is a potent central nervous system stimulant that profoundly impacts the body’s vascular and nervous systems, leading to noticeable effects on the eyes. This analysis examines the physiological mechanisms behind these changes, focusing on whether cocaine causes eye redness and the associated risks to ocular health.
Cocaine’s Immediate Vascular Impact on the Eyes
Cocaine acts as a powerful vasoconstrictor, narrowing blood vessels by blocking the reuptake of norepinephrine, a neurotransmitter controlling the “fight-or-flight” response. This initial effect on the tiny blood vessels in the conjunctiva—the clear membrane over the white part of the eye—should theoretically make the eyes appear paler. However, the commonly observed symptom of bloodshot eyes arises from secondary mechanisms.
The primary cause of redness is reactive hyperemia, or rebound vasodilation. As the initial drug effect wears off, the constricted blood vessels subsequently over-dilate to compensate for the temporary reduction in blood flow. This vascular response causes the small capillaries across the sclera to become visibly engorged, leading to a pronounced, bloodshot appearance.
Irritation from Method of Use
The method of use also contributes significantly to redness and irritation. Powder or smoke from cocaine can directly irritate the sensitive ocular surface, causing inflammation, burning, and pain. When the drug is snorted, residue can travel through the nasolacrimal duct, which connects the nose to the eye, resulting in conjunctiva irritation. Stimulant use often leads to sleep deprivation and frequent eye rubbing, which physically exacerbates existing redness and dryness.
Other Acute Visual Changes
Beyond the vascular effects, cocaine strongly influences the muscles controlling the pupil, leading to mydriasis, or pupil dilation. Cocaine’s stimulation of the sympathetic nervous system floods the system with norepinephrine, causing the iris dilator muscles to contract. This results in abnormally large pupils that react sluggishly to light, often measuring 6–8 millimeters in diameter.
Light Sensitivity and Focus
This exaggerated dilation causes intense light sensitivity, known as photophobia, because the wide-open pupil allows excessive light to reach the retina. Individuals often find normal lighting uncomfortable and may squint or seek dimly lit areas. Cocaine can also impair the eye’s ability to focus, a condition called cycloplegia, which temporarily paralyzes the ciliary muscle responsible for adjusting focus for near vision.
The stimulant effect also disrupts the natural tear film, leading to dry eye syndrome. This dryness is compounded by a potential reduction in the normal blinking reflex, especially when smoking the drug, which leaves the cornea exposed. Chronic dryness and subsequent irritation contribute to eye strain and discomfort.
Long-Term Effects on Eye Health
Repeated cocaine use can lead to serious, chronic damage that goes beyond temporary redness or dilation. The chronic dry eye and altered blinking patterns increase the risk of severe corneal issues, including abrasions, keratitis (corneal inflammation), and painful ulcers. These surface injuries are prone to infection and can cause permanent scarring, potentially leading to lasting vision impairment.
The drug’s severe vasoconstrictive properties pose a serious threat to the delicate blood supply of the inner eye. Chronic vascular stress can result in retinal vascular occlusions, where blood vessels in the retina become blocked. This can manifest as central retinal artery or vein occlusion, an event that starves the retina of oxygen and often leads to sudden, irreversible vision loss.
Cocaine use is also associated with an increased risk of glaucoma, a condition that damages the optic nerve. The drug’s effect on blood pressure and vascular constriction can alter the pressure of fluid within the eyeball, known as intraocular pressure. Sustained high intraocular pressure slowly damages the optic nerve, which connects the eye to the brain, presenting a long-term risk of blindness.