The Early Visual Field Defect in Glaucoma and the Significance of Nasal Steps

The earliest field defects in chronic simple glaucoma are important in order to understand the pathogenesis of the disease and develop screening methods for early detection of damage. The nasal step has not been studied and defined in non-glaucomatous people. Patients who had no field defect and then developed one were studied to ascertain the earliest field defects. Normal eyes had the nasal periphery and mid-periphery studied by kinetic and static perimetry. The results show that paracentral scotomata, nasal steps in periphery and centre can be the first signs of damage either alone or in combination. Temporal sector defects occasionally also occur initially. More than one nerve fibre bundle can be affected from the outset. Nasal steps greater than 4° occur very rarely in normals, particularly if all points are tested more than once.