The symptoms that do not wait
Start here, because the rest of the page is about comfort and this part is about vision you may not get back. Any of the following is a reason to be seen the same day — by an ophthalmologist, an urgent eye clinic, or an emergency department if nothing else is available.
| What you notice | Where to go |
|---|---|
| Sudden loss of vision in one eye, partial or complete | Same day, urgently. Do not sleep on it |
| A dark curtain or shadow spreading across part of the visual field | Same day, urgently |
| A sudden increase in floaters, especially with flashes of light in the periphery | Same day. A few long-standing floaters are ordinary; a sudden shower of new ones with flashes is not |
| Severe eye pain with nausea, vomiting, or haloes around lights | Emergency care |
| Any chemical splashed into the eye | Irrigate immediately and continuously with clean water while arranging emergency care — do not wait to see whether it settles |
| An eye injury, a penetrating object, or vision change after a blow to the head or face | Emergency care |
| New double vision, or a droopy lid with headache | Urgent assessment |
The distinction that matters most in that list is sudden and many versus gradual and few. Floaters accumulate slowly for most people over a lifetime and are unremarkable. A distinct new shower of them, particularly with flashes, is the presentation that gets looked at today.
Why screens make eyes uncomfortable
Concentrating on a screen cuts the blink rate substantially — people blink far less while reading or working than in conversation — and each missed blink is a missed resurfacing of the tear film. The result is a set of symptoms that feel unrelated but come from the same place: grittiness, stinging, a sense of something in the eye, and, confusingly, watering. The watering is a reflex response to the surface being dry and irritated, which is why people describe eyes that are dry and streaming at the same time.
Alongside that runs focusing fatigue. Holding accommodation at one near distance for hours is muscular work, and the blurred, heavy feeling at the end of a long day is that work showing. It resolves with rest and with distance, which is the entire logic behind the 20-20-20 habit: about every twenty minutes, look at something roughly twenty feet away for about twenty seconds, and blink deliberately while you do it. There is nothing magical about the numbers. The mechanism is the break and the change of distance, not the arithmetic. A repeating prompt makes it happen — the eye rest timer plan lays the intervals out across a working day, and the monitor distance calculator settles the other half of the problem, which is whether the screen is too close to begin with.
| Measure | What it addresses |
|---|---|
| Deliberate breaks with a distance change | Both the blink deficit and accommodative fatigue, which is why it does more than any single purchase |
| Room humidity, and air not blowing at your face | Evaporation from the tear film. Vents and fans aimed at the desk are a common and fixable cause |
| Screen slightly below eye level | A lower gaze angle exposes less of the eye surface to the air |
| Lubricating drops | Symptomatic relief. If you are using them many times a day, preservative-free single-use vials are the usual recommendation, and persistent need is a reason to be examined rather than to buy more |
| Contact lens hours | Lenses worsen dryness. Reducing wear time on heavy screen days is a straightforward lever, and sleeping in lenses not designed for it is a genuine risk |
| An up-to-date prescription | Straining to resolve text through an out-of-date correction produces exactly these symptoms and is frequently the whole answer |
Blue-light glasses and eye supplements, examined
These are the two things people buy for their eyes, and both deserve a straight answer. A 2023 Cochrane review pooling randomised trials of blue-light filtering spectacle lenses did not find that they reduce eye strain from computer use. That is not a claim that they cause harm, and it is not a reason to discard a pair you already own and like. It is a reason not to expect them to solve screen discomfort, whose main drivers are the reduced blink rate and sustained near focus described above.
Supplements marketed for vision usually trace back to research on specific carotenoid and antioxidant formulations studied in people who already had intermediate or advanced age-related macular degeneration, where the question was slowing progression. That is a narrow finding about a specific population. It does not establish that the same ingredients sharpen vision, prevent disease, or relieve eye strain in people without that diagnosis. If you have been diagnosed with macular degeneration, whether to take anything is a conversation with your ophthalmologist, and this page does not name a product or a dose for anyone.
Fatigue versus a change in vision
A useful thing to notice, and to be able to report accurately, is whether the problem resolves. Eyes that feel tired and blurred by evening and are fine after a night's sleep behave like fatigue. Vision that stays blurred after rest, that is clearly worse when you cover one eye, that distorts straight lines into wavy ones, or that has lost a patch of the visual field is behaving like something else, and something else is examined rather than rested.
Needing more arm's length to read small print from around the mid-forties is an ordinary age change in the lens. It is worth having reading correction measured rather than estimated off a rack, partly because the right power is more comfortable and partly because the examination looks at everything else while you are in the chair.
Examinations, and why they happen without symptoms
Several of the conditions that cost people vision develop without any symptom that the person could notice, because peripheral field loss is filled in perceptually until it is extensive. That is the argument for periodic examination as an adult even when nothing is wrong: not to check whether you need glasses, but so that pressure, optic nerve and retina are looked at by someone who would recognise an early change.
| Who | Typical pattern | Why |
|---|---|---|
| Adults from around 40 | Periodic comprehensive exams, interval set by the clinician | The age at which several silent conditions begin to appear in screening |
| High myopia, family history of glaucoma, or diabetes | More frequent, on a schedule your clinician specifies | Higher retinal and optic nerve risk; diabetic eye screening is its own established pathway |
| Children | Vision checked in early childhood and periodically after | Some childhood vision problems respond to treatment only within a window, which is why they are looked for before a child can report anything |
None of the intervals above are instructions; they are the shape of the schedule, and the actual interval is set by the person examining you. What you can control is showing up for it and describing changes accurately when they happen. If your eye discomfort tracks with late nights and long screen evenings rather than with anything about your eyes, the sleep hygiene guide may be closer to the real subject.
Questions people ask
I suddenly have a lot of new floaters. Is that urgent?
A few floaters that have drifted around for years are ordinary. A sudden noticeable increase in them, particularly alongside flashes of light in the peripheral vision or a shadow or curtain across part of the visual field, is assessed the same day rather than watched. The distinguishing features are sudden and many, not the presence of floaters as such.
Do blue-light glasses reduce eye strain?
A 2023 Cochrane review of randomised trials did not find reliable evidence that blue-light filtering lenses reduce eye strain from computer use. The main drivers of screen discomfort are a sharply reduced blink rate and sustained near focus, which is why breaks with a change of distance, room air that is not blowing at your face, and an up-to-date prescription tend to do more than a lens coating.
Will taking lutein improve my eyesight?
The research behind those products concerns specific formulations studied in people who already had intermediate or advanced age-related macular degeneration, and the question there was slowing progression rather than improving vision. It does not follow that the same ingredients sharpen sight or relieve strain in people without that diagnosis. If you have been diagnosed, whether to take anything is a discussion with your ophthalmologist.
Can I use artificial tears as often as I want?
Frequent use is common, and the usual guidance is that if you are reaching for drops many times a day, preservative-free single-use vials are preferred, because repeated exposure to preservatives can itself irritate the surface. The more important point is that needing them constantly for weeks is a reason to be examined so the underlying cause is identified, rather than a reason to buy a larger box.
How do I know whether my blurred vision is just tiredness?
The pattern to report is whether it resolves. Blur that builds through a long day at a screen and clears after sleep behaves like fatigue. Blur that persists after rest, that is obviously worse in one eye when you cover the other, that makes straight lines look wavy, or that comes with a missing patch of visual field is a reason to be examined rather than rested, and sudden loss of vision in one eye is same-day urgent.