biology

Photophobia

Photophobia is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Photophobia rather than just read about it. In short: Photophobia is a medical symptom of abnormal intolerance to visual perception of light. As a medical symptom, photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of actual physical sensitivity of the eyes, though the term is sometimes additionally applied to abnormal or irrational fear of light, such as heliophobia.

Key takeaways

Photophobia belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Photophobia to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Photophobia from memory before moving on to harder problems.

Reference excerpt

Photophobia is a medical symptom of abnormal intolerance to visual perception of light. As a medical symptom, photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of actual physical sensitivity of the eyes, though the term is sometimes additionally applied to abnormal or irrational fear of light, such as heliophobia. The term photophobia comes from Greek φῶς (phōs) 'light' and φόβος (phóbos) 'fear'.

Causes Patients may develop photophobia as a result of eye disease or injury, neurological or psychiatric disorders, or as a side effect of certain drugs. Photophobia may manifest itself in an increased response to light starting at any step in the visual system, such as:

Too much light entering the eye. Too much light can enter the eye if it is damaged, such as with corneal abrasion and retinal damage, or if its pupil is unable to normally constrict (seen with damage to the oculomotor nerve). Due to albinism, the lack of pigment in the colored part of the eyes (irises) makes them somewhat translucent. This means that the irises cannot completely block light from entering the eye. Overstimulation of the photoreceptors in the retina Excessive electric impulses to the optic nerve Excessive response in the central nervous system Common causes of photophobia include migraine headaches, temporomandibular joint dysfunction, cataracts, Sjögren syndrome, mild traumatic brain injury (MTBI), or severe eye diseases such as uveitis or corneal abrasion. A more extensive list follows:

Eye-related Causes of photophobia relating directly to the eye itself include:

Nervous-system-related Neurological causes for photophobia include:

Other causes

Treatment Treatment for light sensitivity addresses the underlying cause, whether it be an eye, nervous system or other cause. If the triggering factor or underlying cause can be identified and treated, photophobia may disappear. Tinted glasses are sometimes used.

Artificial light People with photophobia may feel eye pain from even moderate levels of artificial light and avert their eyes from artificial light sources. Ambient levels of artificial light may also be intolerable to people afflicted with photophobia such that they dim or remove the light source, or go into a dimmer lit room, such a one lit by refraction of light from outside the room. Alternatively, they may wear dark sunglasses, sunglasses designed to filter peripheral light, precision tinted glasses, and/or wide-brimmed sun hats or baseball caps. Some types of photophobia may be helped with the use of precision tinted lenses which block the green-to-blue end of the light spectrum without blurring or impeding vision. Other strategies for relieving photophobia include the use of tinted contact lenses and/or the use of prescription eye drops that constrict the pupil, thus reducing the amount of light entering the eye. Such strategies may be limited by the amount of light needed for proper vision under given conditions, however. Dilating drops may also help relieve eye pain from muscle spasms or seizures triggered by lighting/migraine, allowing a person to "ride out the migraine" in a dark or dim room. A paper by Stringham and Hammond, published in the Journal of Food Science, reviews studies of effects of consuming lutein and zeaxanthin on visual performance, and notes a decrease in sensitivity to glare.

Disability Photophobia may preclude or limit a person from working in places where lighting is used, unless the person is able to obtain a reasonable accommodation like being allowed to wear tinted glasses. Some people with photophobia may thereby be better able to work at night or be more easily accommodated in the workplace at night. Outdoor night lighting may be equally offensive for persons with photophobia, however, given the wide variety of bright lighting used for illuminating residential, commercial and industrial areas, such as LED (light-emitting diode) lamps. The increasing popularity of "overpoweringly intense" LED headlights being used on "pickups and S.U.V.s" has prompted more frequent reports of photophobia among motorists, cyclists, and pedestrians.

See also Photic sneeze reflex, a medical condition by which people exposed to bright light sneeze Photosensitivity in humans

References

External links

Worked examples

Example 1 — a first encounter with Photophobia

Start with the simplest possible case. Write down what Photophobia claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Photophobia before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Photophobia ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Photophobia

In research: Photophobia appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Photophobia in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Photophobia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Neurological disorders, Phobias, Visual disturbances and blindness, so understanding it makes those chapters shorter.
In everyday life: Look for Photophobia outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Photophobia in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Photophobia means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Photophobia out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Photophobia in simple terms?

Why does Photophobia matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Photophobia?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Photophobia.