Abstract
Glaucoma is a chronic neurodegeneration characterized functionally by initial loss of peripheral vision that may progress to blindness and structurally by loss of retinal ganglion cells (RGCs) and optic nerve axons. Clinical measurement of function is performed by subjective perimetry (visual fields), and measurement of structure loss is performed by direct optic nerve examination and assessment of longitudinal changes in color fundus photographs. Major risk factors for glaucoma include age, race, and intraocular pressure (IOP). IOP is the only FDA-approved factor amenable to modification with topical or oral medications, laser or surgery.
Current research efforts are directed at earlier diagnosis and improved therapy. Standard automated perimetry does not detect functional damage until up to 50% of RGCs are lost, so newer tests target specific RGC subsystems such as magnocellular, parvocellular and motion-sensitive pathways. Wide variation in the appearance of optic nerves makes clinical evaluation highly subjective, so efforts have focused on objective measurements of retinal and optic nerve damage. Loss of RGC axons in the retina can be detected by scanning laser polarimetry and optical coherence tomography (OCT), and changes in optic nerve head topography can be detected by confocal scanning laser. Improvements in imaging involve the combination of adaptive optics and spectral-domain OCT, and polarization-sensitive OCT. Improvements in therapy involve drugs targeting extracellular matrix in the aqueous outflow system and novel surgical devices, and neuroprotective and regenerative strategies unrelated to IOP lowering. With these advances we hope to delay or prevent glaucoma, a leading causes of vision loss world-wide.