First Line of Defense (Optometry in Glaucoma)

Optometrists play a crucial role in reducing undiagnosed glaucoma cases globally—bridging the gap between primary and specialized eye care

As the primary gatekeepers for eye care, optometrists often shoulder the responsibility of detecting glaucoma. Dr. Michael Chaglasian, the executive vice president of the Optometric Glaucoma Society, sheds light on the pivotal role optometrists play in glaucoma screening, the challenges they face, the emerging tools at their disposal and why their expertise is more important than ever.

Glaucoma, the leading cause of irreversible blindness worldwide, presents a major public health challenge. In 2020, around 52.7 million people were diagnosed with glaucoma, while a staggering 43.8 million went undetected. By 2040, these numbers will rise to 79.8 million detected and 67.1 million undetected cases.1

Optometrists, often the first line of defense against glaucoma, play a critical part in detecting the disease. Despite their essential role, the capacity for accurate diagnosis can vary significantly among practitioners.

Fortunately, new tools—such as home testing, wearable devices and artificial intelligence (AI), can help optometrists quickly and consistently identify high-risk changes, easing the challenges of traditional screening methods. These advancements make early and accurate detection more accessible, bolstering optometrists’ ability to fight glaucoma effectively.

A tag-team approach

According to an Oxford Eye Hospital study, for decades, optometrists have played a fundamental role in screening for glaucoma, initiating over 90% of glaucoma-related referrals to hospital eye services. Despite the heavy reliance on primary care eye providers in early glaucoma detection, the relationship between optometrists and ophthalmologists has historically been complex.2

Back in the 1940s, it was unlawful for U.S. optometrists to use diagnostic and therapeutic drugs. This changed in 1971 when Rhode Island passed a bill allowing optometrists to use drugs for diagnostic purposes, blurring the lines between optometry and ophthalmology.

Since then, debates about expanding optometrists’ roles have persisted, with inconsistent collaboration between the two fields. In the United States, this is further complicated by varying state laws governing the scope of optometry practice.

Adding to the challenge is the dwindling number of ophthalmologists. One study projected a 12% decline in ophthalmologists and a 24% increase in demand between 2020 and 2035, revealing a significant 30% gap in workforce adequacy.3

To address the rising number of glaucoma patients amidst a growing shortage of ophthalmologists, optometrists must take on more responsibilities, such as screening and early detection.

“Baby boomers in the United States are aging and have a greater likelihood of having glaucoma. Many will become glaucoma suspects and that’s going to overwhelm ophthalmologists,” said Dr. Chaglasian. “Optometry has a huge role as the primary contact point to identify those at risk for glaucoma,” helping to reduce the burden on ophthalmologists.

Collaboration between optometrists and ophthalmologists enhances coordination and efficiency in eye care services, ultimately improving the quality of care for patients. “Communication between the two providers is essential for optimal patient care,” noted Dr. Chaglasian. “They should share data about the patient and communicate about what’s in the patient’s best interest. That’s what we should focus on.”

This integrated approach allows each professional to focus on strengths, resulting in a more effective treatment plan. “Optometry excels at many things, and ophthalmology excels at others,” Dr. Chaglasian said.

Optometrists can identify potential cases early and manage nonthreatening conditions. They can refer patients to ophthalmologists for further evaluation and treatment for more serious cases. This referral system ensures that patients receive appropriate care based on the severity of their condition, effectively bridging the gap between primary and specialized eye care.

Slipped between the cracks

Typically, a comprehensive eye exam includes several diagnostic procedures to identify early signs of glaucoma. “It starts with a family history and includes a microscopic examination of the front of the eye and the back of the eye, focusing on the optic nerve head for early glaucoma changes,” Dr. Chaglasian explained. “It also involves measuring intraocular pressure (IOP).”

Optometrists will conduct additional tests if any risk factors are identified during the exam. “A follow-up visit will cover scanning of the optic nerve head and retina with an OCT device, measuring the visual field with a perimeter, further investigation into the intraocular pressure, and various other tests used in glaucoma diagnosis,” said Dr. Chaglasian.

“Optometry excels at many things, and ophthalmology excels at others.”

Despite these thorough examinations and significant improvements in the field of glaucoma screening, a 2021 study revealed that the proportion of undetected glaucoma has remained high over the past five decades. “Glaucoma diagnosis isn’t always clear-cut. Patients can be suspects for years without evident changes that confirm glaucoma.” Dr. Chaglasian explained.¹

“A true diagnosis of glaucoma generally means evidence of histological changes to the optic nerve head and retinal nerve fiber layer consistent with glaucoma pathology,” he said.

Integration of OCT technology in optometry practices also has challenges. While OCT devices are now more available to optometrists, interpreting the images can be problematic. “Reading the results is a hurdle for some optometrists because they’re not black and white. There could be subtle signs of early disease, it could be random noise, or it could be an erroneous piece of information that comes back in the test results,” noted Dr. Chaglasian.

A study by Wong et al. found that 66% of missed glaucoma cases involved patients with an enlarged cup-to-disc ratio on OCT images, often overlooked due to the difficulty of assessing the optic nerve head. A New Zealand study comparing glaucoma-accredited optometrists and glaucoma specialists showed agreement in most areas assessed but less so in interpreting OCT images. ^4,5

Continuous training, as shown in a study by Patel et al. significantly boosted community glaucoma detection rates. Similarly, research in Scotland suggested that additional training, more clinical experience, and clearer guidelines could improve diagnostic accuracy for accredited glaucoma optometrists. ^6,7

Standardized guidelines exist, like the American Optometric Association (AOA) Care of the Patient with Primary Angle Closure Glaucoma, written in a consensus, evidencebased manner by optometrists. A 2018 study showed that retailbased optometry clinics followed guidelines for glaucoma care well, but there were gaps in performing certain tests including dilated fundus exams, central corneal thickness measurements, visual fields (VF) tests, gonioscopy, and setting target IOP. ⁸

VF testing is a crucial tool for spotting glaucoma and should ideally be done more than twice a year, with experts suggesting a minimum of three times annually to catch any variability in test results. The Wong et al. study also underscored the importance of regular testing, showing that nearly half of the glaucoma cases were undiagnosed due to missed VF screenings. These findings highlight a critical point: Infrequent testing can lead to missed diagnoses, allowing glaucoma to progress unchecked. ^4,9

Glaucoma care: Beyond the clinic

Traditional in-clinic testing often falls short, offering only a snapshot of a patient’s condition and consuming significant time and resources. Additionally, the challenges brought on by the COVID-19 pandemic, combined with the increasing number of glaucoma patients, have pushed the eye care community to prioritize telemedicine and improve practice efficiency.

Inspired by home monitoring advancements in other fields, like portable blood pressure cuffs and glucose meters, glaucoma care is evolving beyond the clinic. Portable testing is changing the way optometrists think about glaucoma detection, offering effective screening that rivals traditional methods.

“Home tonometry is now available, and it’s quite good.”

Home testing

Home tonometry, with devices like the iCare Home tonometer (iCare; Vantaa, Finland), lets patients monitor IOP outside clinic hours. It is quick, comfortable, and closely matches the accuracy of traditional Goldmann applanation tonometry. Since IOP fluctuations often occur when clinics are closed, home monitoring provides essential data, helping practitioners to monitor IOP accurately.¹⁰

“Home tonometry is now available, and it’s quite good,” noted Dr. Chaglasian. “The patient can use it at home, five or six times a day for a twoweek period, giving us much more information about their fluctuation in intraocular pressure.”

Home visual acuity tests have also become a promising tool for monitoring glaucoma. A systematic review of more than 1,000 studies highlighted three standout remote visual acuity tests—DigiVis® (Cambridge Medical Innovation; Cambridge, UK), iSight Test Professional (Kay Pictures; Tring, UK), and Peek Acuity (Peek Vision; London, UK)—comparable to in-clinic assessments. These apps offer an accessible and efficient way to keep tabs on vision health without frequent clinic visits.¹¹

Portable perimeters are now allowing frequent at-home visual field testing. The Melbourne Rapid Fields (tabletbased, GLANCE Optical; Melbourne, Australia), the IMOvifa™ (VR-based, CREWT; Tokyo, Japan), the VisuALL (VR-based, Olleyes; Summit, NJ, USA), and the re:Vive 2.0 (VRbased, Heru; Miami, FL, USA) are four notable options. Studies show these portable tests provide reliable results, often matching the traditional Humphrey Field Analyzer used in clinics.^12,13

Smartphone adapters and dedicated self-imaging systems, like the SCANLY® Home OCT (Notal Vision; Manassas, VA, USA), are paving the way for at-home optic nerve imaging. While nondilated eyes captured by smartphones may not always match the precision of conventional fundus photography, they still show strong agreement in optic disc cup assessment compared to professional graders.^14,15

Wearable tech

One promising approach to making glaucoma screening easier and more effective is the use of wearable devices. These nifty gadgets offer continuous monitoring, addressing the challenge of getting patients into the office to take their IOP measurements.

Take the FDA-approved Triggerfish® (SENSIMED; Lausanne, Switzerland), for instance. This innovative device is a contact lens with a built-in microsensor that measures tiny, spontaneous changes in the eye’s shape to estimate IOP. The data collected by the lens is sent wirelessly to an adhesive antenna placed around the eye, which then transmits it to a portable recorder worn by the patient. From there, the information is transferred via Bluetooth to the practitioner’s device, making the whole process smooth and convenient. Studies show that Triggerfish is safe, well-tolerated, and eliminates user error and the need for self-testing.¹⁶

However, at-home testing and wearable devices have yet to be fully implemented in most optometry practices due to their high cost. “They’re not fully implemented yet. We’re making headway, but it’s slow,” said Dr. Chaglasian. “Most devices can be thousands of dollars, so it’s somewhat impractical at this point.”

A glimpse into the future

Artificial intelligence is making significant strides in glaucoma detection, offering promising advancements for diagnosing this sight-threatening condition. These algorithms can identify progression risk and disease stage, and recommend referrals.

Perimetry

Since as early as 1994, researchers have used AI to diagnose glaucoma using VF testing datasets. Noteworthy algorithms have outperformed glaucoma experts, distinguishing between normal and glaucomatous visual fields. When trained with both OCT images and standard automated perimetry (SAP) VF results, these algorithms achieve even greater accuracy making them excellent tools for identifying patients with glaucoma. ¹⁷

Fundus photographs

AI reduces variability in the assessment of optic nerve head and retinal nerve fiber layer changes. Using segmentation and structured learning, AI models achieve impressive accuracy (94% to 98%) in diagnosing glaucoma from fundus photos. One exciting study showed how an OCT-trained deep learning model applied to fundus photographs can track glaucomatous changes over time. Given the complexity of OCT imaging, this technology could be deployed in community settings, such as kiosks, to make glaucoma screening more accessible.¹⁸

OCT

Since 2005, studies have demonstrated the effectiveness of deep learning models in analyzing OCT imaging data to detect glaucoma optic neuropathy. These models offer a quick and objective way to manage glaucoma.¹⁹

Despite these advancements, significant barriers remain before AI can be widely adopted in primary healthcare. Poor image quality can lead to false positives and increased healthcare costs, while privacy concerns may deter patients from participating.²⁰

AI also needs to prove its efficacy in the real world. “There’s still a lot of testing that needs to be done, and we’re still in the early days,” said Dr. Chaglasian. “We’ll see what happens in the next couple of years.”

By providing more accurate and consistent diagnoses, AI has the potential to significantly reduce the burden of glaucoma, ensuring early detection and better management of this chronic eye disease. “If it works, it’s only going to enhance my ability to take care of patients and hopefully make things more efficient so I can spend more time face-to-face with them,” said Dr. Chaglasian.

Jump in but proceed with caution

Optometrists play a crucial role as the first line of defense against glaucoma. Dr. Chaglasian noted, “Because glaucoma can lead to vision loss, optometrists naturally approach it with caution, which is wise. But I also think caution prevents them from jumping in and taking care of these patients, which is what we really need to do,” said Dr. Chaglasian. “We have to get optometry on board, and we need to do the right thing for our patients.”

As glaucoma screening technologies continue to develop and become more accessible, optometrists have increased potential to reduce the global prevalence of undiagnosed glaucoma, preserving the vision of millions worldwide.

Editor’s Note: A version of this article was first published on COOKIE Issue 16.

References

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