Aim: To identify the presence, and origin, of any “dissociating factors” inherent to the techniques for evaluating progression that mask the relationship between structural and functional progression in open-angle glaucoma (OAG).
Methods: 23 patients (14 with OAG and 9 with ocular hypertension (OHT)) who had received serial Heidelberg Retina Tomograph (HRT II) and Humphrey Field Analyser (HFA) examinations for ⩾5 years (mean 78.4 months (SD 9.5), range 60–101 months) were identified. Evidence of progressive disease was retrospectively evaluated in one eye of each patient using the Topographic Change Analysis (TCA) and Glaucoma Progression Analysis (GPA) for the HRT II and HFA, respectively.
Results: Six patients were stable by both techniques; four exhibited both structural and functional progression; seven exhibited structural progression, only, and six showed functional progression, only. Three types of dissociating factors were identified. TCA failed to identify progressive structural damage in the presence of advanced optic nerve head damage. GPA failed to identify progressive functional damage at stimulus locations, with sensitivities exhibiting test-retest variability beyond the maximum stimulus luminance of the perimeter, and where a perimetric learning effect was apparent.
Conclusion: The three dissociating factors accounted for nine of the 13 patients who exhibited a lack of concordance between structural and functional progressive damage.
- CCT, central corneal thickness
- CD, cup-to-disc
- GPA, Glaucoma Progression Analysis
- HFA, Humphrey Field Analyser
- HRT, Heidelberg Retina Tomograph
- IOP, intraocular pressure
- OAG, open-angle glaucoma
- OHT, ocular hypertension
- ONH, optic nerve head
- SAP, standard automated perimetry
- TCA, Topographic Change Analysis
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