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OCT use improves accuracy of glaucoma diagnoses, researchers find
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In the majority of cases, a visual field test and optic disc evaluation was sufficient in diagnosing glaucoma, according to a study to be published in Optometry & Vision Science.
Bae and colleagues also found that optical coherence tomography was effective in identifying glaucoma missed by optic disc examination and visual field tests.
To specifically evaluate the clinical performance of these tests, researchers had seven ophthalmologists view tests results in three sets: first, the disc photographs and red-free fundus photographs; second, the visual field tests (24-2 SITA Standard algorithm, Humphrey Visual Field Analyzer, Carl Zeiss Meditec); and, third, the OCT images (ONH and RNFL Analysis: Optic Disc Cube 200 by 200, software version 5.1 or 6.0, Cirrus HD-OCT, Carl Zeiss Meditec), according to the study.
The ophthalmologists, four residents and three fellows, repeated the analysis the following day.
Results showed that intraobserver agreement was nearly perfect between the first and second tests, according to the study. There was no significant difference when evaluation tools were added.
They also showed that interobserver agreement increased when visual field tests were added, from 0.54 to 0.61. Interobserver agreement increased again, to 0.63, with OCT.
"The optic nerve head and visual field evaluation, which comprise the current gold standard for the diagnosis of glaucoma, are sufficient to diagnose glaucoma in most cases," the authors concluded. "However, OCT can provide additional information for detecting glaucoma in cases in which glaucoma could not be clearly defined using only the optic nerve head evaluation and visual field test.
"Our investigation has the advantage of showing how visual field and OCT could facilitate detection of glaucoma by ophthalmology trainees, not glaucoma specialists," they also noted. "In addition, this study demonstrated the actual performances of visual field and OCT by using conditions more similar to those in clinical practice."
Disclosures: This study was supported by a grant from the Korea Health Technology R&D Project, Ministry of Health and Welfare, Republic of Korea (A101727). The authors have no relevant financial disclosures.
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Derek MacDonald, OD, FAAO
Bae and colleagues provide an interesting analysis of the value of sequential ancillary testing in the diagnosis of glaucoma by non-specialist clinicians. Although their definition of glaucoma as requiring functional deficits may be open for discussion, they conclusively demonstrate that adding visual field assessment to optic nerve head examination markedly improves diagnostic accuracy as compared to the reference standard of specialist consensus.
Interestingly, optical coherence tomography analysis appeared more helpful in ruling out glaucoma in the face of anomalous optic nerve heads and/or nonspecific visual field loss than in confirming its presence. One wonders whether changing the order of presentation of additional test results (that is, introducing OCT before visual field analysis: evaluating structure before function) would influence their relative diagnostic worth.
In presenting a study in which nearly two-thirds of participants were glaucoma suspects or had early disease, Bae et al. have confirmed the importance of the clinical optic nerve head examination while emphasizing the value of ancillary testing, particularly in those all-too-common “is it or isn’t it?” diagnostic dilemmas that occupy the vast middle ground of the glaucoma continuum.
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