Published in Primary Care

Disease, Damage, and Drugs: Ocular Manifestations of Substance Abuse

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9 min read

When it comes to illicit drugs and their impacts on the eyes, it can feel like an uphill battle. To help, this article provides an overview of how different drugs, including stimulants, depressants, and cannabinoids, affect the eye.

Disease, Damage, and Drugs: Ocular Manifestations of Substance Abuse
My favorite class in college was called “Drugs and Behavior.” It took a look at how all sorts of drugs impact a person's behavior. What was focused on most was the impact of the drugs’ mechanics on blood flow and the nervous system. And even then, we know that the nervous system impacts blood flow and vice versa.
To understand how illicit drugs impact the body (and more specifically the eye), let’s do a quick review of the sympathetic and parasympathetic nervous system to gain a better understanding of what we could see systemically. To identify what parts of the body are impacted by the sympathetic nervous system, I like to think to myself, “I would feel sympathy for someone running from a bear.”
The signs of the sympathetic nervous system being triggered are:
  • Pupils dilating
  • Blood focused in the extremities
  • Release of bladder
  • Increased bronchioles width
  • Increased heart rate
  • Increased adrenaline
  • Increased blood pressure
All of these things occur when someone is in fight or flight mode.
Now almost think of the opposite for the parasympathetic nervous system. To remember the difference, I know para means “protection”, so how would I feel if I had something protecting me from a bear.
The key signs of the parasympathetic nervous system are:
  • Constricted pupils
  • Increased digestion,
  • Blood more focused to internal organs
  • Decreased heart rate
  • Decreased bronchiole width
  • Decreased diaphragm movement
  • Decreased blood pressure
The parasympathetic nervous system is all about resting and digesting.

Knowing what happens when each portion of the nervous system is stimulated makes it easier to see how illicit drugs will impact visual function and the retina.

Let’s have a closer look.


Let’s start with illicit drugs that impact the sympathetic nervous system. The image that comes to my mind when someone has all their sympathetic nervous system stimulated is Leonardo DiCaprio’s character in The Wolf of Wall Street: full of adrenaline and addicted to cocaine.
Cocaine is the first stimulant that comes to mind for many people when they think of illicit drugs. Others to consider are meth amphetamines, MDMA, "poppers," and non-prescription Adderall. During your entrance testing, you may notice mydriasis, increased accommodation, possible esophoria, increased IOP, and narrow angles. Many times you will also find sluggish pupils during the swinging flashlight test.
After these findings, it is important to do a further investigation of the anterior chamber and retina. There are possibilities to find closed angles, talc retinopathy, or glaucomatous changes due to prolonged narrowed or closed angles and increased IOP.
Another aspect of stimulant use can be destructive repetitive behaviors while using the stimulant. People can begin eye rubbing, pulling out eyelashes or eyebrows, or picking at the skin. These repetitive behaviors can cause additional damage to eyes that may already be compromised.
Stimulants may be the most exciting (get it?) illicit drugs, but there are even more to cover.


When you think of depressants, we are going to focus on the parasympathetic nervous system. Heroin slows things down—like thoughts and emotions—but also slows things down, like breathing and heart rate. Most people think of heroin when they think of illicit depressants. Other depressants to consider are morphine, methadone, oxycodone, and fentanyl. A lot of these drugs are prescription narcotics, and with overuse, they will have the same impacts as other illicit depressants.
Since depressants impact the parasympathetic nervous system, you can find several key signs of depressant overuse during entrance testing. You will find miosis, sluggish pupils, crossed diplopia, downbeat nystagmus, and exophoric posture. If you notice a new onset of these signs, make sure you are looking with high magnification at the retina for white specs.2 With heroin or other opioid use, it can be cut with talc or other white powder. This minute white power flows through the bloodstream and gets stuck in the capillaries of the retina, leading to neovascularization.
More recent studies are noticing that due to vasoconstriction from the depressants, there is thinning of the choroid. Simultaneously there is also a thickening of the RPE. There are discussions in the future of using OCT technology to detect opioid/depressant addiction.3 RPE may not only be an important factor in glaucoma but also in diagnosing opioid addiction in new ways. Speaking of glaucoma, have you heard there is another illicit drug that can lower IOP?


Okay, promise no talk about marijuana and glaucoma today. It feels like any time illicit drugs are brought up in the context of optometry, the drugs in question are marijuana, THC, or similar cannabinoids. IOP isn’t the only thing we should be interested in when we discuss cannabinoids. There are several other signs of excessive cannabinoid use to be aware of.
During entrance testing, dilated pupils, decreased accommodation, and other ocular motor dysfunctions can be detected. Retinal findings are not as common with cannabinoid use. Recent studies are finding neuroprotective effects in the retina with the use of marijuana. THC found in marijuana seems to be the main factor in protecting the nerve fiber layer.4
An article about illicit drugs wouldn’t be complete if we didn’t briefly touch on glaucoma and marijuana. While cannabinoids (THC specifically) can have an IOP-lowering impact, it is not significant enough for it to truly be an option we prescribe to patients regularly.5 Even with some of these possible great therapeutic effects of THC in the retina, there can be detrimental impacts to ocular health based on the route of administration of illicit drugs.

How route of administration impacts ocular health

For people using illicit drugs, an important part of the process is how quickly the drug can reach the brain. The top way drugs get to the brain quickly is through the bloodstream. Intravenous use is very effective for drugs to enter the bloodstream efficiently, which then travel quickly to the brain. A consideration when intravenous injection is that anything that is in the needle or syringe also enters the bloodstream. Many times secondary particles, infections, and even air can enter the bloodstream quickly and cause more harm than good.
Another effective way to have drugs enter the bloodstream is through snorting/sniffing. This may seem unconventional, but there is a very large capillary bed lining the inside of the nostrils. Drugs quickly enter the bloodstream and cross the blood-brain barrier for quick access to modify synapses. Over time, blood vessels break down in the nose and cause increased nosebleeds.
Also, the nasolacrimal duct can become compromised or even infected with excessive snorting/sniffing of drugs. The least effective but more common route of administration is through smoke inhalation. The drugs access the bloodstream through the alveoli in the lungs. This route of administration can have the most impact on oxygen levels throughout the body, especially the eye.

When it comes to illicit drug use, it is just as important to be cognizant of the route of administration as it is what drug is being used.


When it comes to illicit drugs and their impacts on the eyes, it can feel overwhelming and like an uphill battle to manage the impacts. The drugs covered here aren’t even an exhaustive list of what is used or what may become available in the future.

The biggest impact that you can make in improving your patient’s life is by counseling them on cessation while also connecting them with other resources for mental health and recovery.

Make sure you know of recovery or rehabilitation programs in your area to refer patients to. Having great partnerships with physicians who specialize in psychiatric and illicit drug recovery will also be great referral resources for your patients. Practice your conversation of illicit drug cessation with a colleague to be prepared when the time comes to have an honest conversation with a patient.
We should all strive to be a provider who can not only treat the impacts of illicit drugs on ocular health but also improve the lives of our patients by connecting them with the help they need to live a healthy life without dependence on illicit substances.

Disclaimer: Kate Hamm works for EssilorLuxottica. The views stated in this article do not necessarily reflect the views of her employer and are her views alone.

Kate Hamm, OD
About Kate Hamm, OD

After graduating from UMSL College of Optometry in 2019, Dr. Kate Hamm, OD began practicing at a private practice in Wichita, KS. Optometry and women’s equality are Kate’s passions. She volunteers with the Kansas Optometric Association, co-hosts a podcast on Defocus media: Lunch Date with Rachel and Kate, is the co-founder of the Optometric Compensation Research Group, and she recently completed an internship with Essilor.

Kate loves to connect with her community, and is involved with her local Lean-In and League of Women Voters chapter. Even though she seems busy, you can usually find her goofing around on her Instagram @dr.instahamm with her cat and husband.

Kate Hamm, OD
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