Limitations and Sources of Error: Area of the Cornea Measured
The clinician must realize that many of the instruments are limited to measuring the central 8 mm or so of the cornea. This limits the usefulness with respect to fitting of contact lenses or evaluating why a lens may move more or less on a particular cornea. Some of the instruments make assumptions about the corneal shape beyond the points actually measured when displaying the data or calculating a contact lens design or fluorescein pattern.
