Photophobia term brings different things to mind. One may get the mental image of an awkward teen. Alternatively, a vampire curled in the corner of the room when the slightest slither of light peaks through the blinds. However, photophobia is a very real symptom of a plethora of underlying medical issues. It refers to discomfort or pain in the eyes as a response to a light stimulus, especially bright light. In other words, it is an abnormal sensitivity to light. 

Photophobia can be caused by a range of neurological (brain-related) and ophthalmological (eye-related) conditions such as migraine, dry eye, uveitis and traumatic brain injury amongst others. Currently used treatments of photophobia target the root cause of the symptom and not the symptom itself. 

Introduction

Photophobia (or light sensitivity) is a neurological/ophthalmological symptom that results in eye pain or discomfort as a response to light. It is usually diagnosed in tandem with the disorder that causes it, sometimes being part of the diagnostic criteria for a disorder (for example in migraines). Photophobia may lead to squinting upon light exposure, avoidance of light, decrease in quality of life, and mental health problems such as anxiety and depression. 

Conditions associated with photophobia 

Photophobia has many different causes, ranging from the eyes to the psyche. Below is a list of the conditions that are associated with photophobia. 

Ocular

Photophobia presents as a pain in the eye, hence it is no surprise that it can be caused by eye conditions such as:

• Dry eyes 
• Eye inflammation conditions like uveitis or Cogan syndrome
• Conjunctivitis 
• Diseases of the cornea 
• Damage to the optic nerve for example caused by optic neuritis
• Blepharitis
• Advanced astigmatism 
• Eye tumour

Neurological

Photophobia can also be caused by neurological conditions. This is because the perception of our sensory input is generated by the brain, hence these two are closely linked in medicine. The neurological causes of photophobia include:

• Migraine
• Traumatic brain injury 
• Meningitis 
• Concussion 
• Intracranial hypertension
• Blepharospasm
• Progressive supranuclear palsy
• Attention deficit hyperactivity disorder (ADHD) 
• Chronic fatigue syndrome
• Brain tumour

Systemic

There are also systemic conditions that can result in photophobia. These are typically associated with eye health and inflammation and include:

• Diabetes
• Lupus
• Arthritis 
• Nutritional deficiencies such as deficiencies in vitamin A, vitamin B1, and zinc

Genetic

Genetics often play a big role in ocular and neurological health. The following are some of the genetic conditions associated with photophobia:

• Retinal dystrophies 
• Albinism
• Sjögren–Larsson Syndrome
• Alström syndrome

Psychiatric

As a consequence of photophobia, some mental health disorders can play a part in exacerbating this symptom. These include:

• Anxiety 
• Depression 
• Agoraphobia
• Panic disorder

Pharmaceutical

Finally, photophobia can occur as a pharmaceutical side effect, and taking certain medications has been shown to increase light sensitivity. These medications include:

• Bisphosphonates (used to treat osteoporosis)
• Topiramate (used to treat epilepsy and migraine)
• Certain antihistamines (used to treat allergies)
• Certain antibiotics
• Retinoids
• Certain types of chemotherapy 

It should be noted that prescribed medication use should not be terminated without consulting a healthcare professional even if one suspects that it is the cause of photophobia. 

Mechanisms behind photophobia

 Photophobia has so many linked conditions because it is a term that can be used to describe many different states as long as they fit the criteria of abnormal light sensitivity. The exact mechanism underlying this symptom is still not well defined, however there are some things known regarding the possible biological reasons behind the different thresholds of light that our bodies can tolerate. 

Under normal circumstances, when light hits the eye, it is concentrated and directed to the retina at the back of the eye. This activates the photoreceptors (rods and cones) in the retina, which turn light into electrical signals that stimulate the optic nerve. These signals make it through to the brain where the information is processed. We have many protective mechanisms along the way to make sure we keep our eyes safe. For example, to prevent damage from bright lights and objects in the eye, we have the blink reflex. 

Photophobia occurs when the incoming light signal triggers pain receptors in one way or another, with a greater light input associated with more activation. There are various theories as to where this pain signal is triggered, however it is possible that there are multiple points of origin, and these depend on the underlying condition. 

Diagnosis

Photophobia is a symptom in and of itself. Its presence indicates an underlying issue, hence if someone approaches a healthcare practitioner with this condition, they may advise further neurological/ophthalmological screening depending on his/her medical history. It is important to know the root cause of the photophobia to not only give treatment options but to get proper diagnosis. It has been shown that treatments that are effective in photophobia caused by one disorder can exacerbate it in photophobia caused by another disorder. 

Treatment options

 Photophobia is a symptom observed in many different diseases and disorders, so its treatment usually consists of treating the cause and prevention of episodes. 

Addressing Underlying Causes 

Treatments for common causes of photophobia include:

• Eye drops and ointments for dry eyes and blepharospasm
• Anti inflammatory or dilating drops for conditions associated with eye inflammation
• Botulinum toxin (BOTOX) for blepharospasm
• Medicines for migraine prevention
• Antidepressants when depression is comorbid
• Sedatives to help lengthen sleep and increase time with eyes closed
• Treatments for underlying infections 
• Taking supplements for vitamin and mineral deficiencies 

Lifestyle Modifications

There is no “one size fits all" treatment for photophobia, so it may be challenging for those without a formal diagnosis to get the help for their condition. Alternatively, photophobia can persist even after treatment of an underlying cause. Below are the examples of lifestyle modifications which may aid in alleviating symptoms:

• Limiting screen time and managing indoor lighting
• Avoiding migraine triggers
• Cognitive behavioural therapy to look after mental health 
• Wearing specialised coloured glasses/contact lenses
• Wearing sunglasses when outdoors

Please note: Wearing sunglasses indoors to alleviate photophobia symptoms may work against you. It has been shown that using dark-tinted glasses in lower light may further sensitise the photoreceptors resulting in an increase in light sensitivity. 

Preventative measures

The easiest way to help prevent experiencing photophobia is to take care of general and eye health. One can do this by:

• Limiting screen time
• Maintaining a healthy and balanced diet
• Quit smoking 
• Having a regular eye test
• Taking breaks from contact lenses if they are causing dry eyes
• Getting enough sleep 

When to see a doctor

Photophobia can be a sign of something serious. Please consult with a medical professional if experiencing any of the following:

• Extreme eye pain 
• Changes to eyesight like sudden blurring or blind spots
• Migraine symptoms persist for over 72 hours
• Symptoms of meningitis 
• Symptoms of a severe head injury

Summary

Photophobia is a symptom experienced in many neurological or ocular disorders. It is classified as an abnormal sensitivity to light, in which light exposure leads to discomfort or pain. This symptom is associated with a plethora of ophthalmological, neurological, systemic, genetic and psychiatric disorders. Common causes include migraine, traumatic brain injury, dry eye, and eye infections. Photophobia has also been observed as a side effect of some medicines. 

Photophobia results from an abnormal activation of pain receptors by light input into the eye. Due to the diverse range of associated conditions, this symptom cannot be pinpointed to a specific location, hence, the treatment of it usually involves targeting any diagnosed underlying issues. Those suffering from photophobia may find it additionally helpful to use specialised coloured glasses or contact lenses to block certain wavelengths of light. 

There is no clear cut way to prevent photophobia with certainty. However, taking care of general and ocular health can aid in doing so. Maintaining a balanced diet, quitting smoking and limiting screen time can contribute to protection against photophobia. Those experiencing photophobia as a result of migraine may find it helpful to seek preventative therapies and avoid migraine triggers. It is advised to seek professional help in the case of severe pain that continues, sudden changes in vision or when experiencing symptoms of meningitis or traumatic head injury.