Detecting optic nerve head deformation and retinal nerve fiber layer thinning in glaucoma progression

The application of digital imaging technologies including confocal scanning laser ophthalmoscopy (CSLO), optical coherence tomography (OCT), and scanning laser polarimetry (SLP) has significantly improved the detection of optic nerve head (ONH) deformation and progressive retinal nerve fiber layer (RNFL) thinning for assessment of glaucoma progression. Algorithms for change analysis such as topographic change analysis and guided progression analysis perform event analysis of serial ONH surface height topology maps and RNFL thickness/RNFL retardance maps, respectively, providing a topographical display of the location of significant change. With spectral-domain OCT, it is feasible to delineate and measure the lamina cribrosa surface depth in addition to ONH surface depth and RNFL thickness. Growing evidence from experimental and clinical studies indicates that ONH and lamina cribrosa deformation can be observed prior to detectable RNFL thinning and functional loss in glaucoma. These findings lend support to the notion that upon detection of ONH/lamina cribrosa deformation, a time window for therapeutic intervention for better outcomes may exist. The ONH and the lamina cribrosa are therefore important targets for monitoring glaucoma progression. This review summarizes the latest findings comparing the performance of OCT, CSLO, and SLP for detection of progressive ONH and RNFL damages in glaucoma patients and the clinical implication and limitations of studying the morphological alteration of the ONH, lamina cribrosa, and RNFL in the assessment of glaucoma progression.