INTRODUCTION

When you watch a good refractionist perform a monocular subjective refraction it looks like a complicated flurry of hand motions and spinning dials. We?re going to try to slow things down a little and show you that refracting isn?t as difficult as it may look. In fact, we can break it down into a simple, step-wise process that will allow you to refract nearly anyone.

As you watch this tutorial, you may find it helpful to stop and rewind some sections. We?ve included pause and play buttons to help you do that. In addition, I?d recommend taking notes. You?ll probably want to refer back to them when you start practicing.

I?d like to start by addressing our goals for doing a monocular subjective refraction. It?s actually pretty simple - we want to make our patients see well. I?ll take this one step further, however. We want to get the best vision through the prescription that has the least amount of minus power (..or the most amount of plus power).

Let?s look at this another way. If we have an eye looking at an image, ..we want to find the spectacle lens that focuses the image on the retina as well as possible. ?

You might be wondering why it?s such a big deal to find the most plus or least minus lens. Well, if we add too much minus power or too little plus power the light will begin to focus behind the retina. A young patient, however, may see quite clearly in this situation because they?re able to use their accommodative muscles to change the shape of the physiologic lens and just focus through it. The problem is, if you prescribe glasses with this much power the muscles will need to maintain this tension to maintain stable vision, which will likely result in headaches and eyestrain, especially with reading.


Now that we have established our goals, let?s start thinking about how to accomplish them.
First we?ll need a patient. This is our patient, Joe. Hi Joe! ...We?ll get him behind the instrument.
Before starting a refraction, we?ll need to get everything set up. We?ll want to make sure the patient is comfortable. ?We?ll make sure the oculars are centered over the patient?s eyes, that the patient is about 12mm behind the lenses, and that the instrument is level.

We?d rather not have to start from zero power so it?s nice to be able to dial in a place to start from. Typically we use a prescription from the patient?s retinoscopy measurements, ?their autorefractor readings, ..or the prescription from their old glasses?well, make that old spectacles..

Now, let?s talk about the steps we?ll take to refract our patient.

At it?s simplest, refracting follows a path with four steps.

The four steps are
Number 1.. Establish the sphere power .
Number 2 .. Refine the Cylinder Axis .
Number 3 .. Refine the Cylinder power .
..and Number 4 .. Refine the sphere power.

There?s one more thing. If our starting point doesn?t include any significant astigmatism, sometimes there is a short detour in the process of refracting called the ?cylinder power search?.

The rest of this tutorial is dedicated to discussing each of these steps in detail.

We?ll stop here so you can take a minute to look over these steps. Like I said, you might even want to write them down. When think you?ve got a handle on everything so far, click the ?next step? button to start learning about the ?sphere power establishment? step.