This past November, a patient asked optometrist Kaitlin Soracco to remove a bulge of skin on her eyelid. Such skin tags can be excised right there in the office using procedures Soracco studied and observed in optometry school almost a decade ago. Yet in California, where Soracco works, as well as in 32 other states, non-physician optometrists are not legally permitted to perform these treatments. So when Soracco saw this patient at Peach Tree Live Oak, a federally qualified health center north of Sacramento, she had to refer her to an ophthalmologist, a type of physician who specializes in treating the eyes.

But such referrals can be difficult. Some ophthalmologists have stopped accepting Medicaid, the low-income health insurance program that supports 30 percent of all Californians, said Peach Tree CEO Greg Stone. In California, Medicaid payments for some laser procedures run 16 to 55 percent lower than Medicare reimbursements, which are, in turn, well below commercial insurance fees. For ophthalmology practices already filled with commercially insured patients, Stone said, accepting someone new on Medicaid doesn't make sense financially. Consequently, for Medicaid patients, it can often take six months to be seen by a specialist, Soracco said.

A bill introduced in California last February sought to allow trained optometrists to remove small non-cancerous skin tags and perform several other procedures, including certain laser treatments, that are traditionally restricted to ophthalmologists. Supporters of the bill say that expanding optometrists' scope of practice could help address longstanding challenges with health care access. "There's a runaway demand for health care, and a declining population of providers," Stone said.

Yet in September, California Gov. Gavin Newsom vetoed the bill, citing insufficient optometry education and training for the surgical procedures. After undergraduate studies, ophthalmologists must complete eight or more years of medical school and specialized clinical training, compared with four years of specialized education and training for optometrists.

The California Academy of Eye Physicians and Surgeons hailed the governor's decision as a "major victory for patient safety" — as did the American Medical Association, which called the bill "a radical measure." The American Academy of Ophthalmology had also opposed the legislation.

While the veto closed the book on this particular California bill, a similar bill is now under consideration in South Dakota and debate continues nationwide over whether optometrists should be allowed to perform procedures and make diagnoses that traditionally fall under the purview of ophthalmologists. At stake are questions of patient access and safety, and of financial competition between two overlapping professions.

Already, scientific progress and patient need have propelled the profession of optometry such that its practitioners now provide most primary eye care in the United States, routinely diagnosing and treating conditions that were outside of their scope of practice half a century ago. With continuing advances in a technology-driven field, turf wars in eye care will invariably continue, experts say, with lobbying money playing a key role in determining who is qualified to diagnose and treat a range of common eye conditions.

States determine what optometrists are allowed to do

State legislators have come to play a key role in this debate because any changes to optometrists' scope of practice must be explicitly spelled out in law. Physicians, on the other hand, possess a medical license, which grants broad leeway to diagnose patients, prescribe medications, and — in the case of ophthalmologists and other surgeons — remove or repair tissues and organs.

Optometry's pioneers initially embraced the idea that their work meaningfully differed from that of their medical colleagues. Some noted that a key job of optometrists — dispensing spectacles — benefitted from specialized training in engineering, mathematics, and optical physics, which many physicians lack. Until the 1970s, "we were a drugless profession, and many people were proud of that," said John Amos, a retired optometrist and former dean of the School of Optometry at the University of Alabama at Birmingham.

In practice, however, the profession had begun dipping into medicine decades earlier. During World War I, the United States Army swelled its ranks to include, for the first time, nearsighted men. The dramatic rise in eye care demand spurred a transformation: Optometry evolved in the 1920s from apprenticeships with variable quality and format to a profession shaped by a standardized curriculum offered at schools across the country. That decade, all states passed laws acknowledging optometry as a licensed profession.

Expanded medical needs in wartime reshaped optometry

World War II and the Vietnam War pushed the field further, enlisting optometrists to serve in the Army and work at Veterans Administration hospitals — examining patients and, in some cases, performing duties virtually indistinguishable from physicians. During a yearlong stint as an optometry officer in Vietnam, Amos saw patients with pink eye and a wide range of other inflammatory conditions and eye injuries. "I treated everything," he said.

Yet in civilian settings, diagnosing those conditions, let alone treating them, was off limits. When optometrists examined a patient and found signs of disease, they had to refer the patient to an ophthalmologist for the actual diagnosis.

In the 1970s, several noteworthy advances in eye care served as the impetus for scope expansion. Soft contact lenses were first approved by the Food and Drug Administration in 1971. Compared to hard lenses, which optometrists were already prescribing, soft contacts more often caused complications such as ulcers and eye infections. The conditions were generally treatable — using antibiotic drops and anti-inflammatories that had just hit the scene — but optometrists were not allowed to prescribe medication. This restriction meant that optometrists were similarly unable to offer their patients recently approved eye drops to prevent vision loss associated with glaucoma, a group of conditions — often caused by increased pressure in the eye — that is more common in older adults and can lead to loss of vision by damaging the optic nerve.

To stay competitive, optometrists decided to mobilize. Broadening their scope of practice would require optometrists to "go through the legislative process and change the law," said Richard Castillo, who trained in optometry and ophthalmology decades ago and now teaches at Oklahoma College of Optometry at Northeastern State University.

Who's best to treat glaucoma?

Scope expansion required multiple waves of state legislation spanning several decades. During this time, optometrists were given some leeway to use diagnostic drugs, to make diagnoses, and to prescribe treatments. Often the initial laws were limited, and many states saw further rounds of legislation to expand them. In California, for example, optometrists gained some therapeutic privileges in 1996 but could not fully treat glaucoma until 2008. Glaucoma has no cure, but if caught early, medication can help reduce eye pressure and prevent vision loss.

Over time, with advances in medical equipment, ophthalmologists started seeing similar benefits treating some glaucoma patients with laser light, which lowers eye pressure promoting drainage of excess fluids. One such procedure, selective laser trabeculoplasty, has been studied for about three decades. When compared head-to-head with eye drops in a trial in the U.K. of patients with the most common type of glaucoma, laser treatment relieved eye pressure as safely and effectively as drops — and at lower cost to patients and providers.

This outpatient laser procedure is now considered a first-line therapy not only in ophthalmology but also, increasingly over time, in optometry. Before the recent California veto, similar bills extended laser authority to optometrists in 10 states, four since 2021. In total, some 225 state laws have been enacted since the 1970s to broaden the scope of optometric practice.

Expensive lobbyists helped get optometry-friendly legislation passed

These legislative changes have come at significant financial cost. To secure therapeutic prescribing privileges in Alabama, for example, the state's optometric association paid a top lobbying firm $100,000 per year and asked each member to donate, on top of their usual association dues, around $5,000 toward legislative efforts over a four-year period in the 1990s. Those contributions, totaling nearly $1 million, went to political candidates who the polls projected would win or had a reasonable shot, according to an article Amos wrote for Hindsight: Journal of Optometry History. Other states have applied similar strategies.

Though it's hard to determine how much directly goes toward scope expansion efforts, total lobbying expenditures of California's optometry and ophthalmology associations last year exceeded $1 million. During that period, the California Optometric Association spent more than $777,000 while the California Academy of Eye Physicians & Surgeons paid just under $300,000.

Effects on patients are still open to debate

Experts disagree on what the new scope expansion laws mean for patients. To some, the statutes are troubling because they appear to undercut the science-backed foundation of mainstream medicine. "It's not necessarily a training or an educational system that ends up defining what is safe and not safe," said Stephen McLeod, CEO of the American Academy of Ophthalmology and former chair of ophthalmology at the University of California at San Francisco. "It really is legislative — a stroke of the pen."

Others see the situation differently. "The law has to catch up with the training," said Kristine Shultz, executive director of the California Optometric Association. Optometrists are no longer trained in loosely regulated apprenticeships. Instead, their four years of post-undergraduate training increasingly incorporate diagnosis and treatment of medical conditions.

Just as optometrists' scope of practice has expanded over the past 50 years, so has the nature of their curriculum. By the time Soracco completed her four-year doctor of optometry degree in 2016, she and her classmates had learned to recognize and manage a range of eye conditions, including infections, inflammation, and diseases such as glaucoma. They learned which medications to prescribe. They learned how to determine if a skin tag might be cancerous. And by shadowing ophthalmologists in clinical rotations, they have observed firsthand how to use lasers and remove skin tags. "Every optometry school in America right now teaches these office procedures," said Castillo.

A closer comparison of success rates after laser eye surgery

What Soracco's training did not offer was a chance to perform these methods on live human patients — a key point of contention from opponents of the scope expansion bill. "Treating a plastic eye is not the same thing as treating a real eye," said Craig Kliger, executive vice president of the California Academy of Eye Physicians and Surgeons. "The tissue reacts totally differently."

Furthermore, offering laser eye treatments requires much more than mastering the instrument. "The bigger issue is not the mechanics of the procedure itself in a particularly well-chosen patient," said McLeod, "but choosing the right procedure for the right patient and managing any complications that happen afterward." With such delicate tissue layers packed into a tiny organ, stakes are high. Often "you get one chance," he said. "To try and reverse something you've done is incredibly difficult to do without some compromise to eye health."

The National Institutes of Health considers laser surgeries a safe and effective first-line glaucoma treatment, yet case reports document examples of retinal damage resulting from accidental misuse. Researchers have tried to determine, on a broader level, whether optometrists have worse outcomes than ophthalmologists when performing the same laser procedures.

One analysis, published in 2016 in JAMA Ophthalmology, looked specifically at laser trabeculoplasty — one of the procedures on California's recent scope expansion bill. The researchers analyzed Medicare claims data on 891 patients with glaucoma who received laser trabeculoplasty between 2008 and 2013 in Oklahoma, where optometrists have been offering this treatment for more than two decades. The study found that patients who saw an optometrist for the laser treatment were about twice as likely to undergo additional laser procedures in the same eye, compared with patients who had the initial procedure done by an ophthalmologist.

And in a 2021 analysis, optometrists had worse scores than ophthalmologists in Medicare's payment incentive program, which rewards physicians based on quality metrics — reduction of eye pressure, for example.

Comparing outcomes can be tricky

On the surface, both studies would seem to urge caution about extending laser privileges to optometrists. Yet the data can be challenging to interpret. The laser trabeculoplasty study used Medicare billing data, which reports procedure rates but not patient outcomes. Lacking information about eye pressure changes or complications after treatment, some experts suggest it is hard to conclude that a higher volume of care translates to lower-quality procedures.

The payment incentive study is also hard to parse, in part because it is a generalized comparison — data on specific procedures are not available. Plus, performance metrics could be skewed by low-income patients, who are more likely to see an optometrist than an ophthalmologist, said study co-author Dustin French, a health economist in the ophthalmology department at Northwestern University Feinberg School of Medicine.

Aggregate data on health outcomes are notoriously difficult to track in the United States' fragmented health care system. "There's almost never a central repository," said McLeod.

"We have incomplete data now," he added, "and I don't see the data getting any better anytime soon."

This makes it challenging to produce solid data to support scope expansion, or to refute it. It's "all speculation and a matter of opinion and position," French said.

What about depth and breadth of training?

It's also tricky to compare professional training. Although ophthalmologists spend more total years in post-undergraduate training, the first segment covers medicine more broadly; whereas, the optometry curriculum focuses entirely on eye care — a point that optometrists highlight when advocating for scope expansion. Furthermore, for those wanting laser privilege, the vetoed California bill called for additional training that included 43 procedures on live humans. That would have gone "above and beyond" other states where optometrists got laser authority with very little live patient experience or even none at all, Shultz said.

On the whole, however, optometrists have much less experience treating disease. They mainly see healthy patients for routine eye exams, said Kliger. Ophthalmologists "see more pathology," which gives them a broader, more nuanced understanding of eye diseases and how to treat them.

At first blush, each side of the scope debate puts the focus on patients. Optometry highlights the need to expand health care access while medicine stresses safety and quality of care.

'It is, at some level, always financial'

Both sides also acknowledge that conversations on the ground center around different agendas. "I've been to enough department of ophthalmology meetings at enough hospitals where I can tell you the discussion is rarely about patient care when it comes to these scope battles," said Castillo, a practicing ophthalmologist who teaches optometry students. More often, he added, those conversations revolved around market share, competition, reimbursements — the business of eye care.

Amos, the retired optometrist, agreed. "It is, at some level, always financial," he said.

Up until the early 1990s, Castillo said, ophthalmologists who performed cataract surgeries earned more than $2,000 per eye. Nowadays, he continued, each procedure reimburses about $600. What happened? Over the years, the surgery became safer, faster, and more effective, which drove up demand in the aging U.S. population, and, in turn, prompted a steep drop in reimbursement rates. "If Medicare was still paying $2,000 per cataract surgery, Medicare would be broke — more broke than it is," Castillo said. Ophthalmology, he added, "was a victim of their own success."

Compensation is also a key concern for optometry. When Medicare was enacted in 1965, optometrists were not eligible for payment because the federal health insurance program only reimbursed physicians. It took two decades for optometry to gain inclusion — a historic legislative feat, in the view of leading professional bodies.

Given the steady march of scientific advancements in a technology-heavy specialty, friction over scope of practice in eye care is unlikely to subside. "It may not go on with the same rapidity," said Amos, "but I suspect it will continue in one form or the other."

Esther Landhuis (@elandhuis) is a California-based science journalist who writes about biomedicine and STEM diversity. Among other publications, Landhuis' has written for NPR, Nature, Scientific American and UNDARK, where this story first appeared.