Something is off. Re-test, possibly using ±0.125 or ±0.50 lenses for comparison.
(Note: Prescriptions are always in 0.25 diopter increments.)
If -0.25 improves vision and +0.25 worsens it:
Subtract 0.25 from the current sphere. Replace the lens in the back of the frame with one that is 0.25 more negative. Then repeat the test by going back to "Refining the Sphere".
If +0.25 improves vision and -0.25 worsens it:
Add 0.25 to the current sphere. Replace the lens in the back of the frame with one that is 0.25 more positive. Then repeat the test by going back to "Refining the Sphere".
If -0.25 improves vision and +0.25 makes no difference:
This is interesting. It does not happen very often. You might test again, and if the results are the same, experiment by subtracting 0.25 from the current sphere and replacing the rear sphere lens accordingly. Then re-test by going back to Part 06 - Refining the sphere and Astigmatism.
If +0.25 improves vision and -0.25 makes no difference:
This is interesting. It does not happen very often. You might test again, and if the results are the same, experiment by adding 0.25 to the current sphere and updating the rear lens. Then re-test by going back to Part 06 - Refining the sphere and Astigmatism.
