Several common habits can throw off your eye exam results, from drinking coffee that morning to wearing eye makeup. Most of these are easy to avoid once you know about them, and skipping them helps your eye doctor get the most accurate picture of your vision and eye health.
Skip the Coffee and Caffeine
Caffeine can raise the pressure inside your eyes, which matters because your doctor will likely measure that pressure to screen for glaucoma. In a large population study called the Blue Mountains Eye Study, people with open-angle glaucoma who drank coffee regularly had significantly higher eye pressure readings (19.63 mm Hg) compared to non-coffee drinkers (16.84 mm Hg). Those consuming 200 mg or more of caffeine daily, roughly two cups of coffee, showed higher readings as well.
Even if you don’t have glaucoma, artificially elevated pressure could trigger unnecessary follow-up testing. Avoid coffee, energy drinks, and strong tea for at least a few hours before your appointment.
Don’t Drink Alcohol the Night Before
Alcohol disrupts your tear film in ways that persist well into the next day. Research published in Investigative Ophthalmology & Visual Science found that 12 hours after drinking, tear film break-up time dropped from about 14 seconds to just 6 seconds. Tear evaporation nearly doubled, the protective lipid layer thinned significantly, and tear production measured by the Schirmer test fell by 40% in many eyes. Blink rates also jumped from about 12 blinks per minute to nearly 15.
All of this means your eyes will appear drier and more irritated than they normally are. If your doctor is evaluating you for dry eye disease or fitting you for contact lenses, alcohol the night before can distort the results. It can also make your vision slightly less stable during refraction testing, the part where you read letters through different lenses.
Leave Your Contacts Out
Contact lenses reshape your cornea slightly while you wear them. If your doctor needs to measure your corneal curvature, check your natural prescription, or fit you for new lenses, that temporary reshaping can skew the numbers. Remove soft contact lenses at least two hours before your appointment. If you wear rigid gas permeable lenses, check with your doctor’s office, as they may want you to leave them out for several days or longer before certain measurements.
Bring your glasses and your contact lens case so you have a backup way to see. Also bring the boxes or packaging from your current contacts if you have them, since the brand, power, and base curve are printed there and save time during the exam.
Don’t Wear Eye Makeup
Mascara, eyeliner, and eyeshadow can all interfere with your exam. Mascara clumps on your lashes and gets in the way during slit lamp examination, retinal photography, and contact lens fittings. Eyeliner and shadow can flake or smudge into your eyes, obscuring what your doctor sees when examining the surface of your eye and potentially causing irritation during the visit. Your makeup will also likely get smeared or ruined during testing anyway, so it’s best to skip it entirely or plan to apply it afterward.
Avoid Intense Exercise Right Before
Vigorous physical activity temporarily lowers eye pressure. In one study, eye pressure dropped from an average of 16.4 mm Hg before exercise to 13.2 mm Hg just five minutes after finishing, a change of about 3 mm Hg. This happened in roughly 74% of eyes tested. The good news is that pressure returned close to baseline within 20 minutes of stopping exercise.
If you normally work out in the morning and have a morning appointment, either reschedule your workout or arrive at least 20 to 30 minutes early to let your body settle. A brisk walk to the office won’t cause problems, but a hard run, cycling session, or heavy lifting could temporarily mask elevated pressure that your doctor needs to detect.
Get a Decent Night’s Sleep
Sleep deprivation affects how your eyes track and focus. Research on even a single night of lost sleep shows measurable changes in eye movement speed, with slower tracking responses and a tendency for the eyes to drift outward. Some people experience double vision after significant sleep loss. While the impact on visual acuity itself appears modest (the visual system is fairly resilient), fatigue can make subjective refraction less reliable. That’s the “which is better, one or two?” portion of your exam where your answers guide the prescription. Being exhausted makes those judgments harder and less consistent, which could mean a less accurate prescription.
Don’t Forget Your Medication List
Certain everyday medications change your pupil size or eye pressure, and your doctor needs to know about them to interpret results correctly. Antihistamines like diphenhydramine can dilate your pupils and, in rare cases, raise eye pressure in people with narrow drainage angles. Several common antidepressants, including SSRIs like fluoxetine and paroxetine, tricyclics like amitriptyline, and others like venlafaxine and escitalopram, can also cause mild pupil dilation through their effects on brain chemistry.
You don’t need to stop taking these medications before your exam. Just bring a complete list of everything you take, including over-the-counter allergy pills and supplements. Your eye doctor will factor these into their assessment rather than mistaking a medication side effect for an eye problem.
Limit Screen Time Beforehand
Staring at your phone or computer for extended periods right before your exam can temporarily affect how your focusing muscles behave. Prolonged near-focus work causes the muscles inside your eye to lock up slightly, a phenomenon called accommodative spasm. This can make you appear more nearsighted than you actually are during testing. While one session won’t permanently change your prescription, it can bias the results enough to matter. Try to give your eyes a break from screens for at least 30 minutes before your appointment, or at minimum, look at distant objects periodically during the drive or walk over.
Plan for Dilation Afterward
This isn’t about what to avoid before the exam, but it’s something to prepare for. If your doctor uses dilating drops, your pupils will stay wide for several hours, making you sensitive to light and blurring your near vision. In one study, 20 patients experienced noticeable glare after dilation, and three found it severe enough to make driving difficult. Bring sunglasses, and if possible, arrange for someone else to drive you home. If you have to drive yourself, stick to familiar roads, avoid peak sunlight, and give yourself time to adjust before getting behind the wheel.