Correlation of Retinal Nerve Fiber Layer Thickness and Visual Fields in Glaucoma: A Broken Stick Model

• Published in: American journal of ophthalmology Vol. 157; no. 5; pp. 953 - 959.e2
• Main Authors: Alasil, Tarek, Wang, Kaidi, Yu, Fei, Field, Matthew G, Lee, Hang, Baniasadi, Neda, de Boer, Johannes F, Coleman, Anne L, Chen, Teresa C
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2014; Elsevier Limited
• Subjects: Aged; Algorithms; Cross-Sectional Studies; Diabetic retinopathy; Dietary fiber; Exfoliation Syndrome - diagnosis; Female; Field study; Glaucoma; Glaucoma, Open-Angle - diagnosis; Glaucoma, Open-Angle - physiopathology; Health Insurance Portability & Accountability Act 1996-US; Humans; Intraocular Pressure; Male; Medical imaging; Middle Aged; Models, Biological; Nerve Fibers - pathology; Ophthalmology; Optic Nerve Diseases - diagnosis; Optic Nerve Diseases - physiopathology; Optics; Retinal Ganglion Cells - pathology; Retrospective Studies; Software; Standard deviation; Statistical methods; Tomography; Tomography, Optical Coherence; Tonometry, Ocular; Vision Disorders - physiopathology; Visual Field Tests; Visual Fields - physiology
• ISSN: 0002-9394; 1879-1891
• DOI: 10.1016/j.ajo.2014.01.014

Purpose To determine the retinal nerve fiber layer (RNFL) thickness at which visual field (VF) damage becomes detectable and associated with structural loss. Design Retrospective cross-sectional study. Methods Eighty-seven healthy and 108 glaucoma subjects (1 eye per subject) were recruited from an academic institution. All patients had VF examinations (Swedish Interactive Threshold Algorithm 24-2 test of the Humphrey Visual Field Analyzer 750i) and spectral-domain optical coherence tomography RNFL scans. Comparison of RNFL thickness values with VF threshold values showed a plateau of VF threshold values at high RNFL thickness values and then a sharp decrease at lower RNFL thickness values. A broken stick statistical analysis was used to estimate the tipping point at which RNFL thickness values are associated with VF defects. The slope for the association between structure and function was computed for data above and below the tipping point. Results The mean RNFL thickness value that was associated with initial VF loss was 89 μm. The superior RNFL thickness value that was associated with initial corresponding inferior VF loss was 100 μm. The inferior RNFL thickness value that was associated with initial corresponding superior VF loss was 73 μm. The differences between all the slopes above and below the aforementioned tipping points were statistically significant ( P  < .001). Conclusions In open-angle glaucoma, substantial RNFL thinning or structural loss appears to be necessary before functional visual field defects become detectable.