Choroidal microvasculature dropout correlates with visual field loss
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Choroidal microvasculature dropout angular circumference increases were significantly associated with visual field progression among patients with open-angle glaucoma, according to results published in the American Journal of Ophthalmology.
“[T]here is a need for an alternative metric to monitor eyes with advanced glaucoma,” researchers wrote. “In this regard, [OCT angiography (OCT-A)] may play an adjunctive role in detecting disease progression, as it has shown good reproducibility in both healthy and glaucomatous eyes.
“In addition, progressive microvasculature loss has been detected in the superficial retina using serial OCT-A examinations in an eye with advanced glaucoma.”
Researchers enrolled 101 consecutive patients into a retrospective cohort study. Patients had open-angle glaucoma with visual field defects and localized choroidal microvasculature dropout (CMvD) at baseline and received treatment from November 2016 to March 2018. Researchers measured CMvD with OCT-A at baseline and after 2 years.
Researchers observed CMvD angular circumference enlargement in 21.8% of patients and visual field progression in 26.7% of patients with open-angle glaucoma and CMvD over a mean follow-up period of 2.52 years. Of patients with CMvD angular circumference increases, the mean difference from baseline to final follow-up was 4.59 degrees (95% CI, 3.71-5.47), compared with a mean difference of 0.18 (95% CI, –1.45 to 1.81) among 79 patients with stable CMvD angle circumference progression. Each patient in the CMvD angle circumference increase group had visual field progression, compared with five patients in the stable group (P < .001).
Researchers wrote that the results showed “a larger CMvD angular enlargement is significantly associated with subsequent [visual field] progression as well as a higher rate of [visual field] loss during follow-up.”
Perspective
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The longer I manage patients with glaucoma, the more I find myself appreciating the center of the glaucoma continuum: a patient with subtle but detectable structural change and perhaps a hint of manifest visual field loss — definitive early to moderate glaucoma, not an enigmatic “suspect” or an individual with advanced disease.
The left side of the continuum has benefited from the evolution of OCT, which allows accurate and precise quantification of retinal ganglion cell and retinal nerve fiber layer thinning in the absence of detectable visual field loss. More recently, OCT-A has facilitated the identification of decreased vessel density that appears to precede discernable structural damage.
On the right side of the continuum, both the degree of difficulty and the stakes are elevated. Clinical examination is challenging, automated visual field testing is variable, and conventional OCT may reach its measurement floor, yet the consequences of disease progression can be catastrophic. Corroborating contemporary research suggesting that macular vessel density may not have a measurement floor, Lee and colleagues now demonstrate that parapapillary choroidal vessel density loss is also detectable in advanced disease.
Although the extremes of the glaucoma spectrum remain exigent, ancillary tools like OCT and OCT-A are beginning to make them a little less so.
Editor's note: This perspective was updated to correct "arteriovenous fistula testing" to "automated visual field testing."
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