Combined structure-function analysis in glaucoma screening.

Aim To assess the applicability of a structure–function (S-F) analysis combining spectral-domain optical coherence tomography (SD-OCT) and standard automated perimetry (SAP) in glaucoma screening in a middle-aged population. Methods A randomised sample of 3001 Caucasian participants aged 45–49 years of the Northern Finland Birth Cohort Eye Study was examined. We performed an eye examination, including 24–2 SAP, optic nerve head (ONH) and retinal nerve fibre layer (RNFL) photography and SD-OCT of the peripapillary RNFL. The S-F report was generated by Forum Glaucoma Workplace software. OCT, SAP and the S-F analysis were evaluated against clinical glaucoma diagnosis, that is, the positive ‘2 out of 3’ rule based on the clinician’s evaluation of ONH and RNFL photographs and visual fields (VFs). Results At a specificity of 97.5%, the sensitivity for glaucomatous damage was 26% for abnormal OCT, 35% for SAP and 44% for S-F analysis. Estimated areas under the curve were 0.74, 0.85 and 0.76, and the corresponding positive predictive values were 8 %, 10% and 12%, respectively. By applying a classification tree approach combining OCT, SAP and defect localisation data, a sensitivity of 77% was achieved at 90% specificity. In a localisation analysis of glaucomatous structural and functional defects, the correlation with glaucoma increased significantly if the abnormal VF test points were located on borderline or abnormal OCT zones. Conclusion SAP performs slightly better than OCT in glaucoma screening of middle-aged population. However, the diagnostic capability can be improved by S-F analysis.