Sphere Power Refinement

Sphere Power Refinement
Ok, we’re almost done. Now we need to simply make sure the sphere power is where we want it to be. If we did a good job of maintaining the spherical equivalent in the last step we should be pretty close to our endpoint.
This step is essentially the same as the very first thing we did, the “establish the sphere”step. We’ll start by fogging the patient by adding a small amount of plus power. Then we’ll check the patient’s vision to see where we are.

“Joe, please read the lowest line you’re able to”

..And he’s reading 20/25 minus.

Now, we’ll progressively click in more minus (or less plus) one step at a time.
“Which is better, one
…or two?”
As we would predict, Joe likes choice two better.
To make sure each increase in power yields about one line of improvement on the chart we’ll continue to monitor our patient’s vision.
“Please read the lowest line you can, Joe”

And now he’s reading about 20/20-, ..so he’s gained the expected one line of vision with a .25 increase in sphere power.

And we’ll just repeat this process of adding minus in .25 steps.
Within one or two steps we should get to a point where adding more minus power does not make an appreciable improvement. When that happens, we’re done with this eye.

After learning the first three steps this one should be pretty easy. In fact, because this step is so simple and so similar to the first step we won’t watch a video of this being done.

To summarize, the sphere refinement step starts with again fogging the patient …and then adding minus (or removing plus), one step at a time. With each step, make sure the vision has objectively improved on the eye chart.

These four steps you’ve learned should work well for many situations, but we still need to learn one more thing, the cylinder power search.