Read this before you download
Version 1.0 · In effect from 22 August 2026
This page tells you what the light does, who it is not for, and what to do if something goes wrong. It is written to be read in full by anyone who wants to, including people reading it because it is their job.
No medicines or medical devices regulator has assessed this product. The limits in the limits section are self-imposed and enforced by us alone. No clinician has reviewed them as of the date above.
This page cannot tell you whether you are photosensitive. Nothing short of a doctor and an EEG can. If anything here describes you, or you are not sure whether it does, the answer is to ask a healthcare professional rather than to guess.
Eidovelle is not a medical device and does not diagnose, treat, cure, or prevent any medical condition. It does not monitor or alleviate any condition, and it is not a test for any condition. For medical advice, diagnosis, or treatment, speak to a healthcare professional.
1. The short version
Eidovelle pulses the LED torch on the back of a phone, at rates between 0.5 and 13.0 Hz, at a person's closed eyelids, for five to thirty minutes, with music and narration.
Rhythmic light of this kind can bring on a seizure in people who are photosensitive. That is the principal hazard and no design removes it. About half the people whose brains respond to flicker have never been told they are photosensitive, so "it has never happened to me" is not an all-clear.
Eidovelle never operates between 13.5 and 25 Hz, holds modulation depth at 0.85 of full and torch level at 0.6 of maximum, caps unbroken flicker at twenty minutes, and screens every user before the light runs once. Those things lower the risk. They do not remove it, and the top of the range Eidovelle uses sits inside the wider range published sources treat as capable of provoking a seizure.
Section 6 states which limits rest on published sources and which are judgements with no evidence behind them. Half of them are judgements. Read section 5 and decide honestly whether this is for you.
2. What the light actually is
The light source is the camera flash LED, run as a torch rather than a flash, at a level capped at 0.6 of the maximum the phone can produce. It is a broadly white LED. There is no saturated red anywhere in the product, at any point, because transitions to and from saturated red are separately hazardous irrespective of brightness.
The phone is propped facing you, usually 30 to 60 cm away, in a dim room, and your eyes are closed for the whole voyage.
That geometry is unfavourable. Light at that distance fills essentially the whole visual field, so the lever television guidance relies on, how much of your vision the flashing area covers, is not available here. What is left is frequency, contrast, modulation depth and duration.
3. Closed eyes are not protection
Light passes through an eyelid. The eyelid then acts as a diffuser and spreads that light across a larger area of the retina than open eyes would. The published measurements agree: the range of frequencies a photosensitive person reacts to is wider with the eyes closed than with the eyes open, and wider still with a diffuser in the way (Leijten et al. 1998). A closed eyelid is a diffuser.
Separately, eye closure is recognised as a trigger in its own right for some people, with no light involved at all.
Keeping your eyes closed is how a voyage works. It is not a precaution and it does not make the light gentler.
If you need to reduce what is reaching you, the thing that works is covering one eye with your palm. See section 8.
4. What can happen
A seizure. This is the reason for everything else on this page. Light flashing at certain rates can provoke a seizure in a photosensitive person, whether or not they know they are one.
Here is why screening cannot be one question about epilepsy. Of the 103 people who had seizures during one Japanese television broadcast in December 1997, 78 had never had an unprovoked seizure before it. Around half of all people with an abnormal response to flicker are unaware of the trait. A first seizure has to happen somewhere, and it should not happen here.
Short of that, and far more commonly: headache, eye strain, dizziness, nausea, disorientation. These occur in people who are not photosensitive at all, and they are common enough to be an ordinary reason to end a voyage early. No incidence figure exists for unsupervised solo home use of a product like this one. The figures that exist come from supervised laboratory sessions with pre-screened participants and somebody else in the room, and they do not transfer.
Distress and dissociation. Flickering light can produce experiences that are distressing for people already prone to them, including people experiencing psychosis, people who dissociate, and people with post-traumatic flashbacks. This is not a seizure risk, and it is a real one.
Migraine. Flicker is a recognised migraine trigger, and photosensitivity and migraine can each make the other more likely. Among children examined for migraine, abnormal responses to flicker were most frequent in those with migraine with aura.
Dizziness from the sound alone. One layer of the score is a tone built to seem to fall without ever arriving. It can be felt in the body as motion or falling, and it can become dizziness or nausea. It does this with the light off as well. If you feel it, stop.
5. Who must not use Eidovelle
5a. The app asks about these, and a yes closes the light on that phone
Unsure is counted as a yes. There is no button that says you accept the risk. The audio worlds stay open.
These questions are not a test for epilepsy or for photosensitivity, and getting through them is not a finding that you have neither.
- Under 18. Photosensitivity most often appears before 20, most commonly between 7 and 19. This is an adults-only product and there is no version of it suitable for a child
- Epilepsy, or any seizure ever. Any type, any age, however long ago, provoked or not
- Known photosensitivity, or a bad reaction to flickering light. Strobes at a gig, club lighting, sunlight through railings or a line of trees, striped patterns on a screen
- Proxy symptoms of undiagnosed epilepsy. An unexplained blackout. A lapse in awareness you could not account for. Jerking of the arms or head in the first hour after waking. Morning absences that leave you unable to concentrate. One episode is enough to answer yes. These are the signs that most often go unrecognised, and they are why the questions do not stop at "do you have epilepsy"
- Eye-closure symptoms. Fluttering or jerking of the eyelids on closing your eyes, or a visual sensation on closure that was not the ordinary dark
Family history is asked separately, and the follow-up decides. If a parent, brother, sister or child of yours has epilepsy, the app asks whether its cause is known. If the cause was never established, the light closes. If it has a known cause with nothing to do with light, such as a head injury or a stroke, the light does not close on that answer alone. Photosensitivity is strongly heritable: identical twins show near-total concordance, and first-degree relatives carry several times the population risk.
What this lock is and is not. The decision is held on that phone. It is not held on an account, because the app has no account, and the decision itself is never sent anywhere. That means it does not follow you to a second handset, and it does not survive deleting and reinstalling the app. Answering the questions again from Settings starts them from the first question, and we have no way to stop somebody answering differently the second time. We are not going to pretend otherwise. The screening works on people who answer it honestly.
5b. The app asks about these before every voyage, because they change
States rather than traits. They pass, so the app re-asks rather than assuming.
- Short sleep, or just up from a nap. Sleep deprivation lowers the seizure threshold
- Alcohol today
- Cutting back on alcohol, or recently stopped a regular drink or a sedative. Withdrawal is itself a seizure trigger, and the first 48 hours are the sharp end of it
One more belongs in this group and the app does not ask about it, so it is yours: recreational drugs in the last 24 hours. Do not run a voyage on them.
5c. Do not use Eidovelle if any of these apply. The app does not ask, so these are yours to check
A contraindication that cannot be screened for is listed rather than left out, so that the screening is not read as covering everything.
- Pregnancy. The exclusion is precautionary rather than measured
- Brain injury, or a recent head injury
- A heart condition, or an implanted cardiac device
- Psychosis, or a history of it. Flickering light can produce hallucinatory experiences that are distressing to someone already experiencing psychosis
- Dissociative disorders, post-traumatic stress disorder, or panic attacks. Flicker can bring on dissociation and anxiety in people prone to them
- Active thoughts of harming yourself. This is not a product to be alone with that in
- Migraine with aura, or marked light sensitivity
- Medication or substances that lower the seizure threshold. See 5d
5d. Medicines and substances that lower the seizure threshold
Read this before the list. This is not advice about your medicine, and it is not a reason to stop taking anything. Do not alter a prescription because you read a web page. This is not a complete list, and a medicine being on it does not mean it is unsafe for you. It means ask your prescriber or a pharmacist whether this light is a bad idea for you.
Grouped, with examples.
- Airway medicines: aminophylline, theophylline
- Antibiotics and antimalarials: ciprofloxacin, metronidazole, isoniazid, nalidixic acid, high-dose penicillins, mefloquine, chloroquine
- Antidepressants: bupropion, clomipramine
- Antihistamines: diphenhydramine, promethazine
- Opioids: tramadol, morphine, codeine, fentanyl, pethidine, pentazocine
- Stimulants: amphetamines, methylphenidate, cocaine, phenylpropanolamine
- Antipsychotics: clozapine, phenothiazines, butyrophenones
- Anti-sickness medicines: prochlorperazine, cyclizine, domperidone
- Anti-inflammatories: mefenamic acid, diclofenac, indometacin, high-dose aspirin
- Others: baclofen, oxybutynin, ciclosporin, chlorambucil, triptans, sildenafil, tadalafil, and the dementia medicines donepezil, rivastigmine, galantamine and memantine
Again, because it matters more than the list does: this is not advice about your medicine, and it is not a reason to stop taking anything. Do not alter a prescription because you read a web page. Ask whoever prescribed it, or a pharmacist.
5e. Why conditions are named on this page
Every condition above appears here for one reason: it is a reason not to use the light.
Eidovelle makes no claim about any of them, does nothing about any of them, and is not offered as having anything to do with any of them. Naming a condition as an exclusion is the opposite of claiming to act on it.
6. The limits built into the app
These are compiled into the application itself, not into the content. No world, no update, no signed package and no authoring error can ask a phone for a value outside them. If something tries, the light goes out.
The Basis column says where each limit comes from. Sourced means published guidance gives the number or the boundary. Judgement means it is ours, arrived at without a number in the literature to derive it from. Half of this table is judgement, and pretending otherwise would be the more dangerous choice.
| What | Limit | Basis | Why |
|---|---|---|---|
| Excluded band | Nothing between 13.5 and 25.0 Hz, ever, including during ramps | Sourced, then narrowed by judgement | This was 10 to 25 Hz, the union of every published peak-provocation window we could find: 10 to 20, 15 to 20, 15 to 25, 16 to 25 and 10 to 25. It is now that union minus its lowest 3.5 Hz, which is a loosening rather than a restatement. What survives whole is every window that describes the maximum: 15 to 20, 15 to 25 and 16 to 25 all sit inside the band that is still excluded |
| Energy inside that band | At most 0.35 of a region's alternating energy | Judgement | A pulse of light is not a sine wave, so a rate below the band still puts some energy above it, in the harmonics. Excluding the band as a rate and saying nothing about the harmonics would be a claim the light cannot keep. This is the bound on how much may land in there: it is applied to every region of every voyage before any of it is emitted, using the closed form for a rectangular pulse train, and a region over the bound is refused rather than trimmed. The dirtiest single region in the catalogue measures 0.17, so nothing shipping sits near the bound |
| Frequency | 0.5 to 13.0 Hz | Judgement | The ceiling was 9.5 Hz until 22 August 2026 and is now 13.0, half a hertz below the excluded band. It is inside the wider range published sources treat as capable of provoking a seizure, and it stops 2.0 Hz below the lowest published estimate of where the risk peaks. It was not derived from evidence we hold. It is the limit in this table most in need of an independent view, and no clinician has given one. At the floor, 0.5 Hz is a wide margin below the roughly 3 Hz at which a following response becomes common |
| Modulation depth | Capped at 0.85 of full | Sourced lever, judged number | Reducing modulation depth is the most effective single lever in the published guidance. 0.85 is a 15% reduction from full, which is a modest one, and we say so |
| Duty cycle | 0.15 to 0.50 | Judgement | No dose-response data relates duty cycle to risk. The bounds keep the light off for at least half of each cycle and keep pulses long enough for the LED to render them faithfully |
| Torch level | Capped at 0.6 of maximum | Judgement | No photometric measurement at the eyelid exists. The cap is conservative in the absence of one, and the absence is the honest part: luminance is the one term of the published area rule this product cannot state a number for |
| Unbroken flicker | 1,200 seconds, which is 20 minutes | Judgement, with one precedent | This was two minutes, and two minutes was reasoned from broadcast guidance about a flashing sequence, which is a different thing from a continuous exposure. 1,200 seconds is taken from the published protocol this product's session lengths are built on, which used twenty minutes of unbroken flicker at 3 Hz and 10 Hz. It is the largest continuous exposure with a published precedent at frequencies this product reaches. It is not a comfortable number and it should not be read as a safe one: beyond it there is no evidence either way |
| Rest between bursts | At least 1.5 seconds | Judgement, unsourced | Photic stimulation as it is done in a hospital uses pauses of about four seconds. This is shorter. It was chosen for the pacing of the experience, not for safety, and there is no evidence that it is sufficient |
| Total flicker in one session | 2,400 seconds, which is 40 minutes | Backstop, not a design limit | Published broadcast guidance states that the cumulative risk from prolonged flashing is unknown, so there is no mechanism to derive a number from. What this value honestly does is catch a malformed or tampered package. It does not shape content, and it is set from what the heaviest voyage in the catalogue actually delivers rather than from evidence about dose |
| Colour | No saturated red anywhere, at any point | Sourced | Transitions to or from saturated red are separately hazardous regardless of brightness |
| Timing faults | A missed pulse is dropped, never fired late and never caught up | Judgement, following from the excluded band | Firing a backlog of pulses back to back would produce transitions at a far higher effective rate, potentially straight through the excluded band. That is the fault that matters, and it is forbidden absolutely |
About the 13.0 Hz ceiling, and what moved
On 22 August 2026 the ceiling was raised from 9.5 Hz to 13.0 Hz and the excluded band was narrowed from 10 to 25 Hz down to 13.5 to 25 Hz. Both changes make the light more permissive than it was, and both are stated here rather than left to be discovered.
What is given up is the bottom of the published trigger range, the part furthest from where the risk peaks. What is kept is the whole of the peak. There is a second, smaller property that pushed the same way: at a 13.0 Hz fundamental the second harmonic lands at 26 Hz, clear of the excluded band entirely, where at the old 9.5 Hz ceiling it landed at 19 Hz, inside it, and was tolerable only because the duty cycle nulls even harmonics.
None of that makes 13.0 Hz a measured limit. It is a judgement, it is more permissive than the judgement it replaced, and the sentence at the top of this page still holds: no clinician has reviewed it.
What the twenty worlds actually deliver
The table above is the ceiling. This is the traffic underneath it, measured across all 120 built timelines rather than asserted.
| Parameter | What the content delivers | What the app permits |
|---|---|---|
| Frequency | 2.01 to 13.00 Hz | 0.5 to 13.0 Hz |
| Inside the excluded band | No world, at any point | Refused |
| Torch level | 0.130 to 0.480 | up to 0.6 |
| Modulation depth | 0.34 to 0.68 | up to 0.85 |
| Duty cycle | 0.33 and 0.50 | 0.15 to 0.50 |
| Longest unbroken run of light | 1,020 s | 1,200 s |
| Most flicker in one voyage | 1,612 s | 2,400 s |
One world of the twenty reaches the 13.0 Hz ceiling. None enter the excluded band. The light runs continuously through a voyage rather than in bursts, and a rest is inserted at 1,020 seconds of unbroken light, which is why the longest run and the cap are different numbers.
What the app does when something goes wrong
Backgrounding the app, an incoming call, a thermal warning, a torch that does not report the state it was commanded into, or timing the phone cannot hold: all of these end the voyage and put the light out. Not pause. End. The iOS Dim Flashing Lights setting is a hard gate, and turning it on mid-voyage stops the voyage.
7. Which phones
The light needs a camera flash and iOS 17 or later. The App Store will not offer Eidovelle to a device without a flash, so if you can install it, the hardware is there.
Torch timing is not the same on every handset, and iOS updates have changed it under phones that behaved differently a month earlier. Version 1.0 does not measure the torch timing of your particular handset, and no handset is refused the light on timing grounds. What the app does instead is watch the timing while a voyage runs and end the voyage if the phone cannot hold it. Per-handset qualification before the first voyage is being built, and when it ships it will name any model or iOS version found to fail consistently. Nothing is named today, and that is because the measurement is not running yet rather than because every phone has passed.
The full device compatibility statement is on the support page.
8. If something happens during a voyage
Cover one eye with your palm. Turn the phone face down.
Do that first, before you look for a button. Covering one eye halves the light reaching your visual system, and published guidance says that substantially reduces the risk of a light-provoked seizure. Turning the phone over takes the light off your face. Closing both eyes does not work: the light still comes through the lids, and spreads further when it does.
Then end the voyage. Touching the lower half of the screen ends it at once. Sit up slowly afterwards.
Stop, do not start another, and speak to a doctor before you use the light again if you have any of these:
- Twitching or involuntary movement
- Muscle spasms
- A convulsion
- An absence, or a lapse in consciousness
- Confusion
- A strong feeling of déjà vu
- Strong dizziness or faintness
If someone has a seizure, do what you would do for any seizure. Keep them from harm, put nothing in their mouth, turn them on their side once the movements stop, and call emergency services if it lasts more than five minutes, if a second one follows, or if they are injured or do not come round.
9. After something happens
Logging a voyage as anything other than comfortable holds the light closed on that phone. The audio worlds stay open.
The hold does not lift on a timer. It lifts only when you tell the app you are all right, by tapping I am fine now on the library screen, which is a decision you make rather than one that happens to you. The app takes your word for it and verifies nothing. Do not tell it that until you have spoken to a doctor about what happened.
The hold only exists if you logged the voyage. If you left without answering the comfort question, nothing is held, and if something happened you should not use the light again until you have spoken to a doctor.
10. Telling us something happened
If you need help now, contact emergency services or your doctor. Do not wait for us.
That address is read by a person, every day, and a person replies to it, usually within a day. It is not an emergency line and it is not watched overnight.
It works whether or not you still have the app, whether or not you ever paid us anything, and whether or not you want anything from us. Deleting the app does not close the door.
There is no form on this website that asks you for symptoms, and that is deliberate. Health details typed into a web page travel through infrastructure they should not travel through, so the route is a plain message to a person and you send exactly as much as you want to send. Email is not private either: what you write will sit on your mail provider's servers and on ours.
You are entitled to tell somebody other than us and you do not need our agreement to do it. Your own doctor is the person to start with, and they are the only person who can tell you what happened to you. For a problem with the app itself, Apple takes reports through the App Store. There is no consumer reporting scheme in the United States that covers a product like this one, because Eidovelle is not a medical device and is not sold as one. We would rather say that plainly than point you at a route that does not apply.
11. Where the numbers come from
Some of what is above traces to published sources. Some of it is our own judgement, because no published number exists for the case. Section 6 marks each limit as one or the other, row by row.
The published sources:
- Fisher RS et al., "Visually sensitive seizures: an updated review by the Epilepsy Foundation", Epilepsia 2022;63:739 to 768
- Fisher RS, Wilkins A, Takahashi Y, Thio LL, Acharya J et al., "Visually-provoked seizures: consensus of the Epilepsy Foundation Working Group", Epilepsia 2026;67(2):565 to 581
- Kasteleijn-Nolst Trenité D et al., "Frequently asked questions and answers on visually-provoked (photosensitive) epilepsy", Epilepsy & Behavior Reports 2025;30:100753
- Leijten FS et al., "Light diffusion in photosensitive epilepsy", Electroencephalography and Clinical Neurophysiology 1998;106(5):387 to 391
- Ishiguro Y et al., Epilepsia 2004;45:377 to 383, on the December 1997 broadcast
- ITU-R Recommendation BT.1702-3 (2023), guidance for the reduction of photosensitive epileptic seizures caused by television
- Bartossek et al., on twenty minute continuous flicker sessions at 3 Hz and 10 Hz, which is where this product's session lengths and its unbroken-flicker limit come from
- W3C, Web Content Accessibility Guidelines 2.2, Success Criterion 2.3.1
- Epilepsy Action and Epilepsy Society, public information on photosensitive epilepsy
Nothing is cited on this page that is not in that list. Where a figure was available only from a preprint or from a summary of an abstract, it was left out rather than quoted.
Three honest notes about the list.
The authorities disagree with each other about where the peak-risk band sits. 10 to 20 Hz, 15 to 20, 15 to 25, 16 to 25 and 10 to 25 all appear in current sources. Until 22 August 2026 the union of all of them was excluded. Now the part of that union furthest from the peak is not.
The numbers were written for television. The guidance that exists was designed for a screen across a room, viewed with open eyes, and the thresholds that depend on how much of your vision the screen fills do not transfer to a torch at arm's length through a closed eyelid.
Half the envelope is judgement. Where the established guidance does not reach this case, the more conservative reading was taken where we could take one, and where a limit is a judgement rather than a measurement, section 6 and the source code both say so in those words.
12. What this page is not
Eidovelle is not a medical device and does not diagnose, treat, cure, or prevent any medical condition. It does not monitor or alleviate any condition, and it is not a test for any condition. For medical advice, diagnosis, or treatment, speak to a healthcare professional.
Nothing on this page is a diagnosis, a treatment recommendation, or advice about your own medicines. The first-aid steps in section 8 are the standard public guidance for any seizure and are reproduced here because you may need them in a hurry. Nothing on this page is a promise about what a voyage will do for you or to you. It is a description of a hazard, and of what has been built against that hazard.
If you are not sure whether this is for you, the answer is not to try it and see. It is to ask a doctor, or to leave it.
There is no light on this website
Nothing here flashes, pulses or strobes. There is no motion anywhere on this site, no animation in any stylesheet, and no script on any page at all.
A web page has nobody screened in front of it. Anyone can arrive at one, at any age, in any state, by accident. So the light lives behind the screening, inside the app, or it does not run at all.