Many Americans visit chiropractors to address pain, often without informing their physicians.

And they might not consider eye complications that could result, says Yannis Paulus, M.D., a retina specialist at the University of Michigan Kellogg Eye Center.

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The energetic thrusts and rotations sometimes performed in high-velocity neck manipulation have been shown to create stress on the eye. Resulting damage to blood vessels in the retina may also cause abnormal bleeding inside the eye and vision loss.

This was the case for a 59-year-old woman who experienced a "tadpole" shaped spot in her vision while driving home from a chiropractor visit — with her sight worsening the next day. She had just received cervical spine manipulation using the high-velocity technique to help with her headaches.

The woman's vision returned to normal in about two weeks without treatment. 

After evaluation by Nicholas Belill, O.D., the patient was referred to a retina specialist at Kellogg Eye Center. Together the eye care providers reported on the rare case in the American Journal of Ophthalmology Case Reports.

Because the cells of the retina are so sensitive, even small injuries to the blood vessels can translate to vision problems.

That's why Paulus encourages patients to report their alternative medicine pursuits — and for physicians to actively listen and inform them of possible related side effects.  

Risks from chiropractic treatment

Cardiovascular experts have been outspoken about health risks of chiropractic treatment.

High-velocity neck manipulation has been associated with a certain type of stroke, or vertebral artery dissection, which led the American Heart Association to issue a warning statement in 2014.   

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The short, rapid movements of neck manipulation may cause a small tear in the artery walls in the neck. The artery wall injury can result in a stroke if a blood clot forms at the site and later breaks free to block a blood vessel in the brain.

Eye problems can follow, including double vision or central retinal artery occlusion, a blockage of the artery carrying oxygen to the nerve cells in the retina at the back of the eye.

"Chiropractic manipulation has been associated with numerous eye conditions, primarily due to harm of the carotid artery," says Paulus, of a major artery in the neck that brings blood to the brain and head.

But the case at Kellogg suggests a new complication: direct damage to structures in the eye due to the force of neck adjustments. 

It's the first case report of chiropractic care leading to multiple preretinal hemorrhages, authors say.

Other complications possible

The journal article notes the potential for rapid neck rotations to disrupt the vitreous humor — the clear, gel-like substance that fills the eye between the lens and the retina.

SEE ALSO: To Provide Better Eye Care, Ask More Questions in Advance

In the patient Paulus studied, the high-velocity technique may have induced a posterior vitreous detachment, or PVD, which occurs when the vitreous humor pulls away from the retina.

No specific treatment is needed for PVD. Most patients no longer notice flashes in their vision after three months and "floaters" tend to improve, according to the American Society of Retina Specialists.

Complications from PVD are rare but can be serious and in some cases require urgent treatment such as laser treatment to seal the retinal tear or surgery for a retinal detachment.

Although the connection to chiropractic care is considered a temporal association, the timing of the patient's eye symptoms following the chiropractic visit is hard to ignore.

Paulus didn't rule out future chiropractic visits for the patient but notes that "her chiropractor may need to modify techniques used during her visits."