How much do you trust your chiropractor? Because recent research shows that the forceful pressure applied during a neck session at the chiropractor may just be enough to cause vision problems and bleeding inside the eye. This is exactly what happened in one case published last month in the American Journal of Ophthalmology Case Reports.

A 59-year-old woman was on her journey home from the chiropractor, when she noticed a "tadpole"-shaped spot (or floater) creep across her vision. The next day, her vision worsened and two more "tadpole" spots appeared. She was referred to the Kellogg Eye Center, where she was seen by Yannis Paulus, MD, a retina specialist.

Researchers at the University of Michigan have since linked the spots to the cervical spinal manipulation technique used by her chiropractor to help soothe her headaches, which involves "velocity, low-amplitude thrusts on the cervical spine." 

"Chiropractic manipulation has been associated with numerous eye conditions, primarily due to harm of the carotid artery [an important artery in the neck responsible for transporting blood to the brain]," Paulus said in a statement.

That is, the rough and erratic movements of the technique can result in small tears to the neck's artery walls, which can cause blood clots. If a blood clot breaks free and obstructs blood vessels in the neck, it can lead to strokes and then eye problems like double vision and central retinal artery occlusion (when the flow of blood to the retina's nerve cells are blocked). 

This is not good, so Paulus recommends reporting any alternative medicine you use to your regular physician. They can advise best practices and warn against any potential negative health effects. 

However, the researchers think the 59-year-old woman suffered a different complication – direct damage to the eye caused by forceful movements to her neck.

The adjustments may have triggered posterior vitreous detachment (PVD), i.e. the break-away of the vitreous humor (which fills the space between the retina and lens) from the retina. In most cases, there are few complications, but more serious scenarios may require surgery or laser treatment. 

Fortunately for the woman involved, her vision did eventually return to normal. After two months, she had recovered without any treatment. 

Americans make more visits to the chiropractor than primary care physicians, the study authors say. What's more, 72 percent of those that do, do not tell their doctor. 

While it's worth pointing out that cases like these are very rare (hence the treatment's continued popularity), medics say it is worth being mindful and weighing up your options. After all, it is not the first time the potential dangers of chiropractic treatments have made headlines.