subjective refraction sphere check

Question 1

what is the fogging technique?

Answer 1

1. occlude eye not being tested
2. measure unaided vision
3. estimate refractive error
4. Blur eye under test by sufficient plus sphere spherical power to reduce VA to 6/30 or worse
5. Then the plus power is reduced or minus power is increased in steps of 0.25DS to arrive at most plus/least minus spherical lens component that results in max VA

Question 2

what is the bracketing procedure?

Answer 2

1. occlude one eye
2. check unaided VA
3. estimate spherical refractive error
4. add +1.00DS , is the vision worse?
5. NO= add more positive lenses until vision blurs and from the blur point reduce by +0.25DS. The BVS should be the maximum plus that the eye can tolerate without causing blur on the letter chart
6. YES? add minus spherical power until the best line can be resolved. Ensure each addition actually increases VA and does not just make the letter smaller.

Question 3

describe the PLUS/MINUS sphere test to refine spheres?

Answer 3

1. Hold up plus/ minus spheres but always try plus before minus
2. Add +0.25DS and ask are the letters clearer, more blurred or the same? use the letter chart as the target and ask the patient to look at one line bigger than current vision, user a larger lens power is vision is poor (like +0.50 or 1.00 DS)