There's a reason why so many people rely on a morning cup of coffee: It can help you feel awake and alert. But sometimes it may cause less desirable side effects like caffeine-induced vision disturbances.
Caffeine is a substance naturally found in cacao beans, coffee beans and tea and is synthetically produced for use in certain medications, foods and drinks, according to the U.S. National Library of Medicine (NLM).
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Caffeine stimulates your central nervous system, which is what gives you that jolt of energy you associate with coffee, per the NLM. The other effects of caffeine on the body include:
- More frequent urination
- Increased stomach acid production, which can cause heartburn
- Increased blood pressure
And those aren't the only ways the substance influences your body — caffeine can also cause blurry vision.
Here are the reasons why caffeine can affect vision, plus how to prevent these eyesight issues.
1. You Drank Too Much
Can too much caffeine cause blurry vision? The short answer is yes.
Eating or drinking a moderate amount of caffeine (which, according to the Mayo Clinic, is up to 400 milligrams per day, or the caffeine in about four cups of coffee) can help you feel more awake with little to no additional symptoms, per the University of Michigan.
And while moderate caffeine intake isn't bad for your eyes, consuming large amounts of caffeine may lead to side effects like — you guessed it — blurred vision.
Per the Mayo Clinic, other symptoms of too much caffeine include:
- Frequent urination
- Fast heartbeat
- Muscle tremors
- Digestive issues
The fix: Stick to moderate or low doses to avoid a caffeine vision disturbance, according to the University of Michigan.
Caffeine overdose symptoms (beyond vision) may include nausea, vomiting, breathing trouble, convulsions or hallucinations, per Mount Sinai. If you experience these issues, get medical treatment.
2. It Can Affect Your Blood Sugar
Even moderate doses of caffeine can cause your blood sugar to rise or fall, particularly if you have diabetes, according to the Mayo Clinic. And shaky eyesight can be a side effect of these blood sugar fluctuations, per the Cleveland Clinic.
Besides caffeine-induced blurry vision, high blood sugar may also cause the following symptoms:
- Increased hunger or thirst
- Frequent urination
- An irregular or fast heartbeat
- Pale skin
- Tingling or numbness of your lips, tongue or cheeks
The fix: If caffeine regularly causes blood sugar swings and resulting vision disturbances, limit how much of the substance you drink, according to the Mayo Clinic. If you have diabetes, talk to your doctor about the best sources and dose of caffeine for you.
Can You Get Blurred Vision With Anxiety?
Anxiety alone doesn't typically cause blurred vision. But while anxiety and blurry vision don't typically go hand-in-hand, dizziness is a symptom of anxiety and panic disorders, per the University of Michigan, which may contribute to temporary changes in eyesight.
And can anxiety cause kaleidoscope vision? This visual symptom is usually the result of an ocular migraine rather than anxiety alone, according to the Ohio State University Wexner Medical Center. That said, stress can trigger these migraines for some, per the National Health Service.
3. Heavy Caffeine Use May Contribute to Glaucoma
Research suggests long-term, heavy caffeine usage may contribute to blurry vision down the line. For instance, consuming large amounts of caffeine every day may increase your risk for glaucoma — a group of eye conditions that causes gradual vision loss — if you're genetically predisposed to higher eye pressure, according to a December 2020 study in Ophthalmology.
Per the Mayo Clinic, this eye condition doesn't always cause noticeable symptoms until later stages. When there are warning signs besides blurry vision, these can include:
- Eye pain
- Eye redness
- Halos around lights
- Severe headaches
The fix: Get regular eye exams to take care of your vision, according to the Mayo Clinic. You can also talk to your eye doctor about whether to limit caffeine based on your eye pressure.
- Mayo Clinic: "Caffeine"
- University of Michigan: "Caffeine"
- Mount Sinai: "Caffeine Overdose"
- Mayo Clinic: "Does caffeine affect blood sugar?"
- Mayo Clinic: "Hypoglycemia"
- Cleveland Clinic: "Hyperglycemia (High Blood Sugar)"
- University of Michigan: "Anxiety Disorders and Panic Attacks"
- Ohio State University Wexner Medical Center: "What you should know about ocular migraines"
- National Health Service: "Retinal migraine"
- Ophthalmology: "Intraocular Pressure, Glaucoma, and Dietary Caffeine Consumption"
- Mayo Clinic: "Glaucoma"
- U.S. National Library of Medicine: "Caffeine"