The nasal step in normal and glaucomatous visual fields.

We used an original method of kinetic and static analysis to examine the nasal visual field. When the nasal step is less than 4 degrees wide and its depth is less than 0.5 log units it may be merely a physiological sign of the anatomic and functional asymmetry of the retina. Sometimes it is an artifact. The nasal step can also be a glaucomatous defect. In this case it is often an early sign and it is wider than 4 degrees and its depth is greater than 0.5 log units. Because of its typical shape and invariable location it is easy to discover by kinetic perimetry and easy to check by static perimetry. If it is an early glaucomatous defect, it can be reversed. In practice the nasal step is an early and characteristic glaucomatous field defect like the isolated scotomas in the Bjerrum area, and it is easily detected and can be used as a sensitive marker in the follow up of glaucomatous damage.