Photophobia, otherwise known as light sensitivity, is a symptom in which the eyes become sensitive and intolerant to light.
Incandescent light and fluorescent light are the major sources of photophobia. These lights, starting from streetlights, interior lights, and the bright rays of sunlight cause severe irritation or pain in the eye. These types of sensations are collectively known as photophobia, which often requires medication.
If one has signs of itching, wincing, burning, and squinting when exposed to sunlight, it is likely that the individual has photophobia. Another major sign of this condition is the production of excessive tears in the eyes. Photophobia can be neither a temporary nor a permanent side effect. It is purely dependent on the particular health condition due to which it is caused.
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Associated health conditions
The frequent and common diseases that are accompanied by light sensitivity or that serve as the root cause include migraines, anterior segment disease, intracranial conditions, dry eyes, and blepharospasm.
- Migraine: A migraine is an intense headache that triggers sensitivity to light. Chronic and sporadic migraines are two types of migraines that are most likely to induce light sensitivity. People who suffer from chronic migraines often experience more light sensitivity than people with sporadic migraines. It is estimated that up to 80% of people with migraines have photophobia.
- Anterior segment disease: Conditions such as cyclitis, iritis, and blepharitis have a long-term association with photophobia. Each of these disorders is due to direct irritation of the trigeminal afferents that innervate both the cornea and the eye.
- Dry eyes: The condition in which tears fail to provide adequate moisture is called dry eyes. This is caused by the rapid decrease of moisture and lubrication on the surface of the eye, thus paving the way for photophobia. If dry eyes are left untreated, it can result in ulcers and scars on the cornea, and can even reach the extent of vision loss.
- Blepharospasm: Blepharospasm, which is also known as eye dystonia, is an unbearable pain of muscle contraction around the eye. This condition often occurs due to the improper delivery of messages from the brain to the muscles that surround the eye. Blepharospasm is said to be a neurological movement disorder that requires compulsory medication. The symptoms of this disorder are frequent blinking and irritation in the eye. One study found that four out of five blepharospasm patients suffer from photophobia.
- Intracranial Conditions: Meningeal irritation from meningitis, pituitary tumors, as well as several other conditions, has the potential to cause photophobia. Meningitis is an inflammation of the meninges that is caused by a bacterial infection or virus.
Even though the exact spot in the brain that is responsible for photophobia is unknown, recent researches have helped in illuminating the causes of this symptom. The light that enters the retina is carried through the visual path to reach the brain. The cells in the retina, which are known as cones, detect light and creates vision.
A second system known as the melanopsin system specifically senses light without playing any role in visual creation. There are very few amounts of melanopsin cells in the retina. These cells do not turn off once they are on.
It is believed that both cones and melanopsin set up a sense of brightness, which may cause the issues associated with photophobia.
It has been identified that the intrinsically photosensitive retinal ganglion cells (ipRGCs) contain the photopigment melanopsin. Moreover, ipRGCs detect light and transform the photosignal into the suprachiasmatic and olivary pretectal nuclei.
The suprachiasmatic nucleus helps in the sleep and wake cycle, while the olivary pretectal nucleus helps by providing information for the entertainment of the circadian rhythms and simulates the pupillary light reflex.
These cells are found in both the retina and iris, thus making the eye photosensitive. In deep brain centers, these cells connect with the trigeminal system and cause pain to the eye.
Anyone with a sensitive eye can be easily affected with photophobia. The eye color of a person has great influence in causing this sensitivity. People with light-colored eyes are at greater risk of being affected, as they may have a lower pigment quantity that leads to inefficient scattering of the light beams. This inability makes the eyes more sensitive to light and causes intense pain.
Once affected by photophobia, the particular person has a chance of getting albinism (low pigment level), conjunctivitis, iritis, and total color deficiency, the latter of which causes visuals to only be seen in gray shades. In some cases, it is natural for people to be born with light sensitivity. People who are blind can also experience some kind of photophobia.
Photophobia is not to be considered as a disease but a sign of conditions like infection or inflammation that can irritate the eyes. Treating the underlying causes is the best solution to get rid of photophobia. Once affected by light sensitivity, it is advisable to consult an eye care professional such as an optometrist or ophthalmologist and make a grass-root eye examination.