A common side effect of medications is dry eyes. Any medication that impacts the parasympathetic nervous system can reduce tear production and lead to dry eyes.
Among these medications are dilating eye drops, antihistamines, antidepressants, and anti-anxiety or anti-psychotic medications. Another common medication that results in significant dryness is Accutane (isotretinoin). If using any of these medications regularly, dry eyes may get worse or become bothersome. To combat this side effect, many eye doctors will prescribe artificial tears or prescription eye drops to reduce dryness.
Symptoms of Dry Eye
The most common symptoms of dry eye include irritation of the front of the eyes, feeling like there is something in the eye, and blurry vision that comes and goes.
As the tear film evaporates, it exposes the cornea to the air and eyelid which can cause discomfort and a sensation of pain or irritation.
When there is an insufficient tear film, the eye is not covered entirely by the tears, and it may lead to areas becoming rough or scratched which can cause a sensation similar to having an eyelash in the eye.
Since the tear film is not smooth or even, vision can become blurred when the tears evaporate. This happens between blinks and may lead to vision that is blurry but clear right after a blink.
Mechanism of Causing Dry Eye
The tears are produced by the lacrimal gland and secreted onto the surface of the eyes.
The lacrimal gland is controlled by the autonomic nervous system which controls all nonvoluntary bodily processes – like breathing, heart rate, and digestion.
The two aspects of the autonomic nervous system are the sympathetic (fight or flight) and parasympathetic (rest and digest) systems.
Tearing is increased by parasympathetic input along with other secretions like saliva.
Anything that causes a decrease in the parasympathetic innervation or stimulation will reduce the amount of tears produced.
While the parasympathetic system can be naturally suppressed, like when exercising or before giving an important speech, it is more common that the system is suppressed as a result of medication.
Medications that Impact the Parasympathetic Nervous System
There are many medications that impact the parasympathetic nervous system and reduce the overall output of the system.
Medications include classes such as antihistamines, anti-depressants, anti-psychotics, and dilating eye drops.
Each of these medications is intended to work on a different area of the body that is controlled by the parasympathetic nervous system.
However, when taking these medications, the impact of the medication is felt in all areas of the body including the eyes and lacrimal gland.
Dry Eye as a Side Effect of Medication
It is common that after beginning a medication that reduces the parasympathetic nervous system function in the body dry eyes will develop.
This is seen as a manageable side effect and in most cases is not sufficient reason to stop taking the medication.
The symptoms of dry eye can be treated either with a prescription or over-the-counter treatments and will return to baseline following the end of taking the medication.