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Study finds SD-OCT most reliable test
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Researchers found that spectral-domain optical coherence tomography, when used alone, had better expert agreement when comparing its diagnostic performance with stereoscopic disc photographs and automated perimetry in differentiating individuals with early glaucoma from suspects.
The study from Investigative Ophthalmology & Visual Science compared 46 eyes from 46 patients with suspicious optic nerves who had previously underwent spectral-domain optical coherence tomography scans, 24-2 visual fields and optic disc photographs. Four glaucoma specialists studied the 138 diagnostic tests and classified the patient as likely glaucomatous or nonglaucomatous based on the results of a single test.
Interobserver agreement for the glaucoma specialists across the three diagnostic tests was poor for visual field and photos, according to the researchers.
The percentage of eyes rated by experts as “likely not glaucoma” varied widely, from 39% to 78% using visual fields and from 33% to 61% using stereo photos.
Spectral-domain optical coherence tomography (SD-OCT) had the highest sensitivity among the glaucoma specialists, with a value of 0.81, compared to sensitivities for both visual fields and photos at about 0.64.
The average specificity was also the highest for SD-OCT, at 0.87, while visual fields and photos were approximately 0.73, according to researchers.
The researchers concluded that SD-OCT is more objective and less subject to patient reliability than a visual field test. They added that it is possible the SD-OCT changes developed before visual field changes. – by Abigail Sutton
Disclosure: Blumberg reported no relevant financial disclosures. For all remaining authors’ financial disclosures, please see the full study.
Perspective
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Carl H. Jacobsen, OD, FAAO
Early glaucoma diagnosis is a difficult task. With numerous risk factors, disease presentations and variations in normal, it is often more art than science. In this study, Blumberg and colleagues set out to determine which of three tests (disc photos, visual field or retinal nerve fiber layer optical coherence tomography), when considered in isolation, offers the best diagnostic value.
Not surprisingly, they found that the subjective interpretation of an objective test (OCT) is more diagnostically accurate than subjective interpretations of subjective tests (photos and visual field).
What does this mean for the glaucoma doctor? The fact that a single OCT test has the best diagnostic value when taken in isolation (something you would never do) is interesting, but it is hard to imagine this finding changing your practice. The most challenging part of early glaucoma diagnosis is accurately identifying and characterizing suspects. Change over time is proof positive for glaucoma.
This study does validate the use of OCT in glaucoma diagnosis, but please continue doing history, clinical exam, photographs, visual fields, gonioscopy and pachymetry. Analysis of all data over time is certainly the best practice, and to do less or rely on a single test would be a disservice to your patients.
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