Today, onabotulinumtoxinA is widely known for its cosmetic use to prevent wrinkles or unwanted aging, but the first uses of Botox – as it’s commonly called – are rooted in ophthalmology and strabismus treatment.
“When people reference Botox, or botulinum toxin, they aren’t typically thinking about eye alignment or double vision, but its purpose is to paralyze muscles, and that can be an effective strategy for returning an eye to its proper position,” explains Lauren Mehner, MD, MPH, assistant professor of ophthalmology at the University of Colorado School of Medicine.
With strabismus, a condition in which one eye is turned in a different direction from the other eye, a botulinum toxin injection can weaken the extraocular eye muscles and help straighten the eyes. These injections have remained a popular treatment among pediatric and adult cases since its use became more widespread in the late 1980s after FDA approval, even as strabismus surgery has improved over the years.
Alan Scott, MD, the doctor credited with formulating botulinum toxin for use in ocular muscles in the 1970s, later explained that his investigation into using the injection was due to the poor outcomes of strabismus surgery, recalling decades later that “as many as 40% of patients needed reoperation.”
Scott, who died in 2021, developed the injection and forever changed the treatment of strabismus and the world of cosmetic procedures. Botulinum toxin continues to be a popular treatment option among ophthalmologists.
“Botox remains an important tool for strabismus surgeons, and it’s being used in different ways,” Mehner says. “It’s much less invasive than surgery and doesn’t have the same kind of risks.”
Still, each case is unique. Mehner stresses the importance of reviewing treatment options with an ophthalmologist and finding the best fit for improving binocularity and quality of life.
Weighing treatment options
Today, some patients wear prism glasses to treat double vision symptoms of strabismus, but eye muscle surgery and botulinum toxin, or a combination of the two, remain the two most common approaches to strabismus management, Mehner says.
The goal of the procedure is to adjust the ocular muscles to treat misaligned eyes. A surgeon may shorten or tighten the muscles or make them looser depending on what the alignment requires.
While surgery outcomes have improved since Scott’s venture into botulinum toxin research more than 50 years ago, Mehner estimates that about 10-20% of her patients need a “touch-up” at some point throughout their life.
“In medicine, there’s never a 100% guarantee that there’s a permanent fix,” she says. “With strabismus we’re dealing with eye muscles, which are controlled by the brain. We aren’t brain surgeons, but we are trying to help the brain.”
One perk of using botulinum toxin in strabismus is that it doesn’t last forever. The toxin eventually wears off. This can buy patients some time before a surgery is necessary. In some situations, such as cranial nerve palsies resulting from head injuries, a patient’s condition may change or improve as they recover from the injury, Mehner explains.
This may prove to be particularly helpful for children whose eyes are still developing, but more research is needed.
“Interestingly, in some forms of strabismus in young children, treatment with botulinum toxin can have similar success rates to surgery in terms of longevity, despite the fact that the effect of the actual toxin is temporary,” she says. “This has to do with the neuroplasticity of the brain in young children, but we are continually studying this to learn more.”
Studying effectiveness
Despite steady popularity, there are still questions about whether a less invasive muscle injection is a better treatment option than surgery for strabismus patients.
In 2023, Mehner and a group of researchers published a review of studies focused on comparing effectiveness between botulinum toxin injections and surgery. Their findings call for more rigorous studies focused on the topic.
“Previous studies have shown that Botox is more effective in certain types of strabismus compared to others, but more data is needed on why that's the case,” Mehner says. “Botox is less invasive, poses less risk, and allows for shorter time under anesthesia – if any – so if we can expand its use, that could be beneficial to patients and the overall healthcare system.”
Mehner says the more research that is done on botulinum toxin’s role in strabismus treatment, the more they can guide treatment standards for different types of strabismus and optimize outcomes for patients.
“We know that strabismus surgery is effective, and it’s easy to keep doing what we know works, but if there’s an alternative method or supplemental procedure that may be equal to or superior to the status quo, you have to be open to it,” she says. “With more research, we can make better decisions suited for each patient. That’s how medicine keeps moving forward.”
May 23, 2024