+2.00D will be the principal meridian with the higher absolute BVP, so as that is less than 3.00D, the tolerance is [+ or -] 0.12D in each principal meridian (see Table 1).
Therefore, the user must be aware of the importance of considering both principal meridian powers.
Dorsher concluded that, The marked degree of correspondence noted in this qualitative study between the distributions of the anatomically derived myofascial meridians to those of acupuncture
Principal Meridians is unlikely to be coincidental'.
Corneal factors include the difference in the radii of curvature of the principal meridians. The non-corneal factors include the lenticular errors, including the difference in the curvature, refractive index or position of the lens.1
Astigmatism is also classified on the relationship between the two principal meridians as regular (when two principal meridians are perpendicular to each other) and irregular (when the two principal meridians are not perpendicular to each other).
The base lines running north and south are known as "
Principal Meridians" while the east and west base lines are called simply "Base Lines." The township numbers east or west of the
Principal Meridians are designated as ranges, whereas the numbers north and south of the Base Line are tiers.
* Patients who have difference in
principal meridians from keratometer readings greater than 0.6mm
Pre-regs should, if using a keratometer, ensure they find the
principal meridians, but also ensure that they know the theory on both one and two-step design keratometers.