Optic nerve and retinal nerve fiber layer analyzers in glaucoma

There is mounting evidence that retinal nerve fiber layer (RNFL) loss precedes detectable visual field loss in early glaucomatous optic neuropathy. However, examination and photography of the RNFL is a difficult technique in many patients, particularly older individuals, and eyes with small pupils and media opacities. It is subjective, qualitative, variably reproducible, and often unreliable. Furthermore, optic nerve head and RNFL photography is time consuming, operator dependent, has limited sensitivity and specificity, and requires storage space. Imaging technologies have emerged which enable clinicians to perform accurate, objective, and quantitative measurements of the RNFL and optic nerve head topography. There is good agreement between such measurements and clinical estimates of optic nerve head structure and visual function. The reproducibility of these instruments suggests that they have the potential to detect structural change over time. This report will review the technological principles, reproducibility, sensitivity and specificity, capacity to detect glaucomatous progression, and limitations of currently available ocular imaging technologies.