Cocaine is a powerful central nervous system stimulant that blocks the reuptake of neurotransmitters like norepinephrine, dopamine, and serotonin. This triggers a widespread sympathetic nervous system response, leading to potent and rapid systemic vasoconstriction. While the drug is frequently discussed for its effects on the brain and heart, this intense physiological reaction has significant consequences for the ocular system, affecting the outer surface and deep vascular structures of the eye.
Acute Physiological Responses
The immediate effects of cocaine use are driven by the sudden surge of catecholamines, mimicking an extreme “fight-or-flight” response. The most visible sign is mydriasis, or pupil dilation, which occurs because increased norepinephrine stimulates the iris dilator muscle to contract. This dilation can last for hours and often results in photophobia, or increased sensitivity to light, because the pupils cannot constrict normally.
The drug’s potent vasoconstrictive properties cause an immediate narrowing of blood vessels, leading to conjunctival blanching, where the visible blood vessels on the white of the eye temporarily become less prominent. Cocaine use can also cause a transient increase in intraocular pressure (IOP). In individuals with pre-existing narrow-angle glaucoma, this spike in IOP poses a serious risk for acute angle-closure glaucoma, an ocular emergency that can lead to rapid vision loss.
Damage to the Cornea and Eye Surface
The anterior surface of the eye, particularly the cornea, is vulnerable to damage from cocaine use, often leading to a condition referred to as “crack eye.” Smoking crack cocaine exposes the eye to high heat and chemical vapors, which can cause direct superficial keratitis, an inflammation of the cornea. This chemical exposure, combined with impaired corneal nerve sensation and a reduced blink reflex, can rapidly lead to dry eye syndrome and epithelial defects.
Corneal abrasions and ulceration are frequent complications, often initiated by mechanical trauma. Users frequently rub their eyes vigorously while under the influence, transferring cocaine residue or adulterants from their fingers to the eye surface. These defects create openings for opportunistic bacterial or fungal organisms, leading to infectious keratitis, a painful and sight-threatening corneal infection. The damage can range from minor scratches to severe ulcers that leave permanent corneal scarring and vision impairment.
Impact on Retinal Blood Flow and Vision
The most permanent ocular damage results from cocaine’s systemic effects on the cardiovascular system, particularly its ability to induce hypertension and prothrombotic states. The spike in blood pressure and generalized vasospasm can trigger acute ischemic events within the eye’s vascular network. This manifests as a “stroke” in the eye, known as retinal vascular occlusion, where blood flow is blocked to the retina.
Blockages can occur in the main blood vessels, resulting in central retinal artery occlusion (CRAO) or central retinal vein occlusion (CRVO), or in smaller branches (BRAO/BRVO). CRAO is an ocular emergency, causing sudden, painless, and often irreversible vision loss because the retina is quickly starved of oxygen. Cocaine’s tendency to increase platelet aggregation and cause vascular wall damage facilitates the formation of these obstructive clots.
Ischemia can also damage the optic nerve, the bundle of fibers transmitting visual information to the brain, leading to ischemic optic neuropathy. Reduced blood supply causes the nerve tissue to die, resulting in permanent blind spots or complete vision loss. Furthermore, the sudden elevation in blood pressure can cause fragile blood vessels in the retina to rupture. This can result in retinal hemorrhages or Valsalva retinopathy, where bleeding occurs just in front of the retina, severely obscuring central vision.
Severe Ocular Emergencies and Infections
Cocaine use is associated with several ocular emergencies linked to the route of administration or secondary complications. For individuals who inject the drug intravenously, there is a serious risk of endophthalmitis, a sight-threatening infection of the internal eye fluids. This occurs when contaminants, such as bacteria or fungi, are introduced into the bloodstream and travel to the eye.
A complication for intravenous users is talc retinopathy, where micro-emboli, typically talc or cornstarch used to dilute the drug, enter the circulation. These particles travel to the retina and become permanently lodged in the smallest vessels, causing chronic obstruction and damage. For those who use intranasal cocaine, chronic inflammation and tissue death can extend from the nasal cavity into the adjacent orbit, potentially causing orbital cellulitis. This deep infection of the tissue surrounding the eye can compress the optic nerve or spread to the brain, representing a life-threatening complication.