Blurry vision that comes and goes is most often caused by dry eye, especially when it clears after you blink. Blur that stays the same all day, or that only affects distance or reading, is more likely a prescription change. A comprehensive eye exam at Lucent Family Eye Care in Vancouver can tell the difference by checking both your prescription and your tear film. Sudden or severe blur should be checked the same day.
Why Dry Eye Makes Vision Blur On and Off
Your tear film is the first surface light passes through when it enters your eye. When that film is smooth, vision is sharp. When it breaks up too quickly, the surface becomes uneven, and vision blurs until your next blink spreads the tears again.
This is why dry eye blur tends to:
- Clear for a moment when you blink, then return
- Get worse during long screen sessions, reading or driving, when you blink less
- Build toward the end of the day
- Feel worse in heated rooms, air conditioning, wind or on flights
- Come with burning, grittiness, redness or watery eyes
Most dry eye is caused by blocked oil glands in the eyelids rather than a lack of tears. Learn more about dry eye treatment in Vancouver.
Signs Your Prescription Has Changed
A prescription change usually causes blur that is more constant. You may notice:
- Distant signs or the TV look soft, even after blinking
- Reading or phone text is harder to focus on, often after age 40
- Squinting, headaches or eye strain at the end of the day
- One eye seeing noticeably less clearly than the other
- Glare or halos around lights at night
Changes in near vision after 40 are often caused by presbyopia, the natural loss of focusing flexibility. In children, blur at a distance can be a sign of progressing myopia, which our myopia management program can help slow.
Dry Eye or Prescription? A Quick Comparison
Dry eye
Comes and goes during the day
Prescription change
Fairly constant
| Item | Dry eye | Prescription change |
|---|---|---|
| Pattern | Comes and goes during the day | Fairly constant |
| Blinking | Often clears vision briefly | Little or no change |
| Worse with | Screens, wind, heating, end of day | Distance or near tasks, depending on the change |
| Other signs | Burning, grittiness, redness, watering | Squinting, headaches, eye strain |
| Usual solution | Treating the tear film and oil glands | Updated glasses or contact lenses |
Many people have both. A new prescription can make vision sharper, but if dry eye is not treated, the blur can still come and go.
Other Causes of Fluctuating Vision
Not all on-and-off blur comes from dry eye or your glasses. Other possible causes include:
- Changes in blood sugar in people with diabetes, which can temporarily alter focus
- Digital eye strain from long periods of close work. See our tips on digital eye strain
- Contact lenses that fit poorly, are worn too long or have deposits
- Allergies that irritate the eye surface
- Certain medications that reduce tear production
If you have diabetes, regular diabetic eye exams help protect your vision.
When Blurry Vision Is an Emergency
Some types of blur need same-day care. Call us or seek urgent eye care right away if you notice:
- Sudden blurred or lost vision in one or both eyes
- New flashes of light or a shower of floaters
- A curtain or shadow across part of your vision
- Severe eye pain, a very red eye or light sensitivity
- Blur after an eye injury
Sudden vision changes together with weakness, numbness, facial drooping or trouble speaking need emergency medical care immediately.
How an Eye Exam Finds the Cause
At Lucent Family Eye Care, Dr. Linda Yee and our associate doctors look at every part of the visual system that can affect clarity:
- Refraction to check whether your prescription has changed
- Tear film testing to see how quickly your tears break up
- Digital meibography to image the oil glands in your eyelids, when dry eye is suspected
- Optomap and OCT imaging to check the retina, macula and optic nerve. Learn about Optomap retinal imaging
- A review of your screen habits, health and medications
Because the exam covers both your prescription and your eye surface, you leave with a clear answer and a plan, whether that means new lenses, dry eye care or both.
Book an Eye Exam in Vancouver
If your vision keeps blurring on and off, it is worth getting checked. Visit us at 612 West 58th Avenue in Marpole, minutes from Oakridge, Kerrisdale, South Vancouver and Richmond. Book an eye exam online, or call or text 604-777-7579.
Frequently Asked Questions
What can cause blurry vision to come and go?
The most common cause is dry eye, where an unstable tear film blurs vision until you blink. Other causes include digital eye strain, contact lens problems, allergies, medications and blood sugar changes in people with diabetes.
Can dry eye cause blurry vision?
Yes. When tears evaporate too quickly, the eye surface becomes uneven and vision blurs. This blur often clears briefly when you blink.
How can I tell if blurry vision is serious?
Blurry vision is more urgent when it is sudden, affects one eye, comes with flashes, floaters, a shadow, pain or redness, or follows an injury. These symptoms should be checked the same day.
Why is my vision blurry at the end of the day?
End-of-day blur is often caused by dry eye or eye strain, since you blink less during screen work and reading. An outdated prescription can also make your eyes work harder by evening.
Will new glasses fix blurry vision that comes and goes?
Only if the blur is caused by a prescription change. If dry eye is the cause, new glasses alone will not stop the fluctuation. An eye exam can identify which applies to you.