Primary angle closure glaucoma (PACG) is the leading cause of irreversible blindness worldwide, but there is sparse information on visual morbidity in PACG among the different racial and ethnic populations in the United States. In a new study published in American Journal of Ophthalmology, researchers assessed the prevalence and risk factors of blindness among patients newly diagnosed with PACG in the US and found that blindness affects one out of nine patients with newly diagnosed PACG. They also found many risk factors, including a strong association with Black and Hispanic ethnicities, male sex, age below 40 or over 80 and reliance on Medicaid or Medicare.

These findings highlight the severe ocular morbidity among PACG patients, including Black and Hispanic patients newly diagnosed with PACG at a higher risk for blindness and the need for improved disease awareness and detection methods.
These findings highlight the severe ocular morbidity among PACG patients, including Black and Hispanic patients newly diagnosed with PACG at a higher risk for blindness and the need for improved disease awareness and detection methods. Photo: Michael Cymbor, OD. Click image to enlarge.

A total of 43,901 eligible patients from the American Academy of Ophthalmology IRIS Registry (Intelligent Research in Sight) had newly diagnosed PACG, defined as:

  • observable during a 24-month lookback period from index date of PACG diagnosis
  • no prior history of eye drops, laser or cataract surgery unless preceded by a diagnosis of anatomical narrow angle
  • no prior history of glaucoma surgery

The study found that overall prevalence of any and bilateral blindness were 11.5% and 1.8%, respectively. Black and Hispanic patients were at higher risk of any and bilateral blindness, along with those under the age of 40 and over the age of 80 years, the male sex, those on Medicaid or Medicare, as well as those who live in the Southern or Western practice region.

“Our findings suggest that PACG is a visually devastating disease, even in the US,” the authors explained. “Historical epidemiological studies on PACG have shaped perception that the burden of PACG falls primarily on Asian patients, yet Black and Hispanic patients newly diagnosed with PACG have significantly higher risk of blindness.”

Black (14.2%, one per seven cases) and Hispanic patients (12.5%, one per eight cases) were disproportionately affected compared to non-Hispanic white (11.2%, one per 8.9 cases) and Asian patients (8.9%, one per 11.2 cases). These racial disparities were magnified for bilateral blindness: one in 34.5 Black patients (2.9%) and one in 43.5 Hispanic patients (2.3%) were bilaterally blind compared to one in 64.5 non-Hispanic white patients (1.6%) and one in 81.3 Asian patients (1.2%). Furthermore, these disparities appear to be independent of IOP and ocular comorbidities, the authors noted.

There are several explanations for these findings. It is widely recognized that PACG is most common among Asian individuals, while there’s an assumption that prevalence is low with other races. “Therefore, provider-level biases about racial or ethnic differences in PACG prevalence may contribute to greater vigilance in detecting angle closure among Asian individuals,” the researchers noted in their paper on the study.

Also, there may be racial and ethnic differences in ocular biometry, such as anterior chamber depth, that could influence the likelihood of eye care providers performing gonioscopy to detect angle closure, the team noted.

“Finally, differences in access to eye care services between racial and ethnic groups may influence visual outcomes independent of any effect by PACG. Although our findings do not ascribe causality, they do support the need for additional research on racial and ethnic differences in anatomical mechanisms and clinical outcomes of PACG,” the authors wrote.  Regarding the age risk factors (under 40 years and over 80 years of age), the authors speculate that the anatomical mechanisms underlying PACG differ between younger and older patients.

The authors suggest that male sex being a risk factor for blindness could be attributed to lower utilization of medical care among men. Patients seeking care in western and southern regions were at higher risk for any and bilateral blindness, which could be attributed to differences in regional screening methods. Lastly, those on Medicare or Medicaid at a higher risk may reflect the effects of confounding socioeconomic factors, the authors noted.

“These findings highlight the importance of renewed efforts to increase awareness about PACG and associated ocular morbidity,” concluded the article. “They also call into question the utilization of healthcare resources and the effectiveness of current practice patterns for detecting and managing patients at risk for PACG. We propose the development of more convenient and precise clinical tools for detecting and evaluating patients with angle closure, especially given the projected rise in PACG prevalence worldwide.”

Shah SN, Zhou S, Sanvicente C, et al. Prevalence and risk factors of blindness among primary angle closure glaucoma patients in the United States: an IRIS Registry analysis. Amer J Ophthalmol. November 3, 2023. [Epub ahead of print.]