Side Effects of Eye Dilation

Dilating drops permit medical professionals a better view into the eye, make it much easier to carry out eye surgery, and eliminate the pain of some eye diseases, like uveitis, an inflammation of the uvea in the eye. Drops used to dilate eyes are called mydriatics. Cycloplegic drops are a kind of mydriatic drop; cycloplegics disable the ciliary muscles to keep the pupil dilated. Some dilating drops combine mydriatics and cycloplegics. Like any medication, dilating drops can cause side effects. Side effects of cycloplegics are longer lasting and potentially more serious.

Side Effects of Eye Dilation

Mydriatic Effects

Dilating drops can sting and burn when first placed. This impact usually lasts just a minute or more, according to the Mayo Clinic. Eye irritation or reddening might take place. Drops that are strictly mydriatics, with no cycloplegic drug added, like phenylephrine, dilate the eye for several hours. The side effects of pupil dilation are light sensitivity and blurred vision. Headache and pain in the eyebrow can also happen, according to the Mayo Clinic.

See also How to Undilate Eyes

Cycloplegic Effects

Cycloplegic drugs disable the ciliary muscles of the eye and keep the pupil open longer. Atropine, a cycloplegic, is a drug that has long lasting results; if atropine is offered, the pupil may remain dilated for two weeks, inning accordance with the Mayo Clinic. Eyes may water or redden from cycloplegic drops, also inning accordance with Mayo, and eyelids might swell. Cycloplegics can cause a major rise in intra-ocular pressure in people with narrow angle glaucoma, which is fluid buildup behind the colored part of the eye, the iris, according to Aging Eye Times, and must not be given to individuals with this condition. Cycloplegics likewise cause a loss of accommodation in the eye; accommodation is the changing of the curvature of the lens to see things close up.

See also: Best OTC Eye Drops for Infection, Allergy, Dry or Pink Eyes and Other Disorders

Systemic Effects

Any dilating drop can be taken in systemically and cause side effects outside the eye. You might experience and increase in blood pressure, lightheadedness, paleness, headache, a sensation that your heart is pounding, or an irregular heartbeat or quick heart beat, according to the Mayo Clinic. Thirst, dry mouth or skin, or uncommon tiredness may also happen.

Reyus Mammadli/ author of the article

I’m the author and editor of this health blog, active since 2008. With a background in medical and biotechnical devices, I focus on making health and self-care topics—especially in ophthalmology—clear and accessible.

Although I’m not a licensed physician, I’ve spent over 15 years working with medical literature and guidelines, with particular attention to trusted ophthalmic sources such as the American Academy of Ophthalmology, National Eye Institute, and PubMed. I also follow the latest updates in diagnostics and treatment technologies.

My aim is to help readers better understand eye diseases, tests, and treatment options—so they can feel more confident when consulting a doctor.

Note: This blog does not provide medical diagnoses or treatments. It offers clear, reliable health information to support informed conversations with healthcare professionals.