Challenges to the common clinical paradigm for diagnosis of glaucomatous damage with OCT and visual fields

Abstract

The most common clinical paradigm (CCP) for diagnosing glaucoma includes a visual field (VF) with a 6° test grid (e.g., the 24-2 or 30-2 test pattern) and an optical coherence tomography (OCT) scan of the optic disc. Furthermore, these tests are assessed based upon quantitative metrics (e.g., the pattern standard deviation [PSD] of the VF and the global retinal nerve fiber thickness of the OCT disc scan). This CCP is facing three challenges. First, the macular region (i.e., ±8° from fixation) is affected early in the glaucomatous process, and the CCP can miss and/or underestimate the damage. Second, use of the typical VF and OCT metrics underestimates the degree of agreement between structural (OCT) and functional (VF) damage. Third, resolution of the OCT scan has improved, and local glaucomatous damage can be visualized like never before. However, the clinician often does not look at the OCT scan image. Together these challenges argue for a modification of the VF test pattern and OCT protocol, replacement of metrics with a comparison of abnormal regions on VF and OCT, and careful inspection of actual OCT scan images. In principle, the CCP could be modified easily. In practice, change is facing a number of impediments.