Question: I am constantly sensitive to light, but I can normally watch a little TV, go online, etc. However, when I’m having a flare-up in my photophobia symptoms, I can’t bare any lights in my house when it’s dark outside. I also can’t look at a phone or TV (my mum is typing this for me). Do people have a flare in photophobia symptoms or are they generally constant? What causes the increase in light sensitivity, and what helps you to get out of it?

Answer: That is an excellent question and very difficult to answer because although science is making great progress, to this day it doesn’t have all the answers those of us who suffer from photophobia – an abnormal intolerance to light, or light sensitivity – would need [Diagnosis, pathophysiology, and treatment of photophobia (2016)].

Disclaimer: My interest in photophobia symptoms is due to my problems with light sensitivity (photophobia), discomfort glare, and computer eye strain. I am not a vision scientist.

The second part of your question (the causes for increased sensitivity to light) is particularly difficult. For one thing, it is frequently not clear whether photophobia is a symptom, cause or effect. Subsequently, scientists prefer to speak about the conditions that are associated with photophobia. Moreover, it appears that photophobia may frequently be caused by a constellation of conditions which may differ from person to person [idem., Shedding light on photophobia (2012)].

It is very complex to understand the signals that are sent from our eyes to the brain, because they include signals from non-image-forming photoreceptors, and it is not yet clear how [Measuring and using light in the melanopsin age (2014)]. These photoreceptors appear to be the principal receptors and transmitters of glare related pain signal to our brain. Interestingly, even blind patients show light aversion responses as long as they still have their non-image forming photoreceptors [Intrinsically photosensitive retinal ganglion cells are the primary but not exclusive circuit for light aversion (2012)].

If identifying the causes of photophobia symptom fluctuation is difficult, knowing what to do to decrease the symptoms is even more so.

Therefore, this answer suggests some possible causes of photophobia and of the fluctuation in photophobia symptoms. Among them you can, hopefully, find some that might apply to you.

Unfortunately, there are no one-size-fits-all treatments or solutions to photophobia. Moreover, it seems that one very rarely finds a physician who is able to help. Ultimately, you have to discover yourself why you are having your flares in photophobia symptoms and based on that information seek your solutions (a good place to start may be here).

Also, you are invited to add the causes of increases in intensity of your photophobia symptoms but are not listed below. You can do so either in the comments or by writing to me. You’ll help others in a similar situation get over the rough spots faster.


Photophobia symptoms do vary in intensity due to different causes

Our vision is not always equally sensitive to light, i.e. our threshold for light-induced pain may be higher or lower at different points in time. This is a quote from [Shedding light on photophobia (2012); bold added for emphasis]:

It is clear that there are individual “thresholds” of light sensitivity even in normal people. (…) Light sensitivity may also vary by season. Vanagaite and colleagues found that migraine patients, and to a lesser extent controls, had lower pain thresholds to light in the winter months (November through January) than in the summer months (May through July). There also appears to be a ‘summation’ or ‘integration’ involved in photophobia. Wirtschafter et al. () showed that binocular viewing lowered the threshold of light whereas uniocular viewing raised the threshold. Finally, the perception of light brightness is dependent on the state of retinal adaptation (e.g. dark adaptation), as is readily appreciated when stepping from a darkened movie theater into the sunshine (, ).

The wavelength of light may also affect the photophobia percept. Main et al. () found that shorter wavelength (blue) light was more uncomfortable for subjects with migraine than for those with tension-type headache or controls. These investigators also reported that longer wavelength (red) light was also less comfortable for subjects with migraine (). (…) The reasons for this difference, and the noxious nature of both blue and red light to migraineurs, are unclear.

More from research [Diagnosis, pathophysiology, and treatment of photophobia (2016)]:

Some patients will recognize that they are especially sensitive to artificial indoor lighting. The perspicacious patient will recognize that they’re specifically sensitive to non-incandescent artificial indoor light. Computer monitors are another common source of discomfort for the photophobic patient. Anecdotally, patients tend to have less trouble with natural light from the sun, unless they are faced with glare from snow or other highly reflective surfaces.

Inflammations in the head (sinus infection, flu, etc.), stress, and lack of sleep may also be sources of increases in light sensitivity. I noticed this happens even in people who normally don’t experience greater sensitivity to light. Some visitors to this site have also experienced that dehydration or too much coffee contributed to greater light sensitivity.

It is, therefore, clear that as light sensitivity threshold increases or decreases, the symptoms fluctuate in intensity. Personally, I can identify with several of the above-mentioned causes of this fluctuation: artificial lighting; digital screens; summation/integration; dark adaptation; low light wavelengths (blue light) – red light, however, is not a problem at all for me; intense glare from roads, snow or water; and season.


Example: Seasonal changes and increase in light sensitivity

In a poll, carried out last December on this site, 79% of over 1500 respondents agreed that their photophobia symptoms and other computer eye strain symptoms worsen in winter months when days are shorter.

I tend to struggle with an increase in the intensity of my photophobia symptoms from late August until Spring-time. It seems to be connected to the position of the Sun. In Fall/Winter, it is much lower and it feels as if it reflects more intensely from the ground than in Spring/Summer when it is higher.

I’ve also noticed that after the first frosts, as grass turns brown and less shiny, the glare is more bearable (green grass reflects more blue light, brown absorbs much/all of it).

I am lucky to live in a place that hardly ever gets snow. Being on the snow on a sunny day gives me a terrible headache in a matter of minutes (even with a wide-brimmed hat and two pairs of dark, polarized, blue blocking sunglasses one on top of the others).

Moreover, when the Sun is low, it is more likely to sneak into my field of vision, thus causing intense glare (even if I am wearing a wide-brimmed hat).

A related issue might be that, as the days get shorter, we are more and more exposed to artificial lights at the cost of natural sunlight!?


Chronic photophobia: Caution with low-dosage causes!

Sometimes photophobia symptoms can get worse and you cannot identify why. This is because the causes of photophobia symptoms getting worse may sneak up on you over a longer period of time without you realizing it.

It is very easy to identify that being on snow or water on a sunny day causes a flare-up in light sensitivity symptoms. That is because the dose is so high that its effects are almost immediate and acute. So, you immediately know what to do.

Unfortunately, light sensitivity may get worse due to far gentler abuse – low dosage over a longer period of time – as with other types of chronic pain. It may be just one of the above-identified causes or several of them. This is far more dangerous because it may go unnoticed for a long period of time. Then, suddenly, when your photophobia symptoms get really bad, you don’t know what caused it. In such a scenario, it is also much more difficult to figure out what to do to raise your light sensitivity threshold thus improving its symptoms.

Moreover, as if not knowing what to do were not bad enough, the recovery in light sensitivity symptoms also tends to be much slower. You may try different things and not one of them might result in an immediate improvement. So you must be patient. You might try to remove one or several possible causes at the same time, but then you have to wait a few days (sometimes weeks) to notice improvement – or no improvement. And, again, unfortunately, patience is very difficult to exercise when you are in pain.


There could be many other causes: What are yours?

If you’ve identified other causes of fluctuation in the intensity of photophobia symptoms, do help complete this list either by adding a comment below or by writing to me for the benefit of others who might find themselves in a similar, terrible situation.