Subjective Refraction & JCC Simulator

1. Start from an approximate refraction

   Begin with an approximate prescription from retinoscopy or autorefraction, then refine it subjectively.

2. Refine the best sphere

   Refine sphere while avoiding unnecessary over-minus. Aim for the clearest vision with the maximum plus or minimum minus accepted by the patient.

3. Use the duochrome test

   If red is clearer, move in the minus direction. If green is clearer, move in the plus direction. Equal clarity suggests you are near the spherical endpoint.

4. Refine cylinder axis first

   Flip the Jackson cross-cylinder and ask which view is clearer. Move the cylinder axis in small steps toward the preferred position until the two choices are approximately equal.

5. Then refine cylinder power

   After refining axis, compare cylinder power. When cylinder power changes, maintain the spherical equivalent with the appropriate spherical compensation.

6. Perform the final check

   Recheck clarity and spherical balance after axis and power refinement. Repeat duochrome if needed before accepting the final prescription.

Exact sequencing can vary between clinics, phoropters, trial frames and teaching methods. This simulator is for education only and does not replace supervised clinical training.