Photophobia


Photophobia is an extreme sensitivity to any form of light. It is often marked by pain and discomfort, leading to aversion and avoidance of sunlight and well lit places.

Photophobia is the symptom that occurs due to too much light entering the eye. Normally, the amount of light that is able to enter the eye is controlled by the reflex response (meaning it is automatic) of the iris. The iris is controlled by the occulomotor nerve and may constrict and relax in response to different levels of light. When there is a high level of ambient light, the iris constricts, preventing too much light from entering the eye. This is a protective mechanism, preventing any damage to the eye. The opposite of iris constriction is dilation, which occurs in dark places. This is an important mechanism to allow us to see objects in low light, by letting as much light as possible into the eye.

Causes of Photophobia

The retina is the part of the eye that is responsible for detecting light. It is located at the back of the eye and has multiple photoreceptors, which are responsible for sensing light. There are 2 types: rods and cones. The rods are responsible for detecting light, whereas the cones are concerned with detecting colours. When they become activated by rays of light hitting them, they send impulses via the optic nerve to the area of the brain responsible for vision, the occipital cortex. This area is at the back of the brain. It is this pathway that allows us to perceive the environment around us as images.

In some cases this pathway can become damaged, leading to problems with vision. In photophobia, the reflex mechanism to prevent too much light entering the eye is faulty. This can be caused by the iris being constantly dilated, allowing more light into the eye than is necessary. When the retina is exposed to too much light, an excessive number of impulses are sent to the brain (occipital cortex). This over excitation leads to the perception of pain in the eye, causing the affected individual to shy away from the light. This is also known as light aversion. Many people who experience this symptom will often stay indoors in dark rooms, or wear very dark sunglasses when outside.

Many thousands of individuals undergo laser eye surgery every month. The two most common procedures, LASIK and LASEK, are able to correct a wide number of vision problems. Both procedures involve making a flap in the front of the eye, also called the cornea. This then allows ophthalmologists (eye surgeons) to use a special femto-second (emits a pulse of light in 1/15th of a second) laser to remove some of the corneal tissue to correct the patients vision. The procedure is very safe and provides outstanding results, however as with all operations there can be some associated side effects. These can range from seeing halo like structures around light sources, to under correction (when the visual defect is not adequately corrected).

Around 1-5% of individuals having laser eye surgery may be likely to experience photophobia or transient light sensitivity, otherwise known as TLS. It is still unknown as to why this occurs, however some say it is a side effect of producing a flap in the cornea with a laser. It seems to be most evident in the LASIK procedure.  It usually becomes apparent approximately 2 months after the procedure and usually spontaneously resolves after a couple of months. The severity differs between individuals, ranging from severe sensitivity and light aversion to very few problems at all. At its worst, photophobia can lead to headaches, nausea and even migraines.

There are many more causes of photophobia, ranging from cataracts and prescription drug use, through to more serious conditions such as meningitis and bleeding in the brain.

Treatment for Photophobia

Many doctors have begun to treat photophobia in post-operative LASIK patients using a high dose of steroids for a few days. Many patients have reported improvement in their symptoms whilst some have noticed a complete return to normal.

It is important to stress that this symptom is a very rare side effect of the LASIK procedure. Of the people who suffer photophobia or TLS, only the minority have the severe symptoms. Even then, it is likely to resolve spontaneously after a few months and is treatable. If you are worried that you may have photophobia or you are worried about the LASIK procedure, please consult your ophthalmologist or optician.


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