In 2013, the senior author delivered the American Academy of Ophthalmology Robert N. Shaffer Lecture entitled "Glaucoma Changes-Reality Bites." This talk focused on describing the longitudinal structure-function relationships in glaucoma progression. The study was based on a 10-year longitudinal dataset created by calibrated measurements across multiple OCT generations with corresponding visual fields (VFs). The prior held observation was that functional damage follows structural damage. The lecture posited that structure and function change at similar times, but that current measurement technology limits our ability to detect functional abnormalities and change early in glaucoma, as well as to measure structural change late in the disease. The Shaffer lecture provided evidence that structure and function change concordantly and that any apparent discordance in the relationship was due to technologic limitations to measure glaucomatous change. Furthermore, we observed 5 longitudinal relationships of concordance and discordance that can exist with structure-function interactions. Concordance: (1) structure-structure progression, (2) structure-function tipping point, (3) structural floor tipping point. Discordance: (4) functional progression in a "stable" VF with structure-function correlation, (5) functional progression with "normal" structure. In this review article, we will review longitudinal glaucoma progression studies with long-term follow-up and discuss the clinical relevance of relationships of concordance and discordance that can exist with structure-function interactions.
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