Subjective Refraction JCC PDF

Preview

Summary

Clinical Procedures used from first year to fourth year and in practice....

Description

Subjective Refraction – Jackson Cross Cylinder (JCC) Purpose  

Refining the Cylinder component found during Ret. If Cylinder component was not found during Ret.

Instructions “I am going to show you 2 lenses, and I want you to tell me when the target is rounder, it will be blurry, (Axis refinement) and when it is clearer (Power refinement)” Target   

Circle of dots O Line above best VA

Procedure No Cyl found during Ret: 1. Bracketing 2. Insert Cyl in bracket and refine axis 3. Determine Cyl power Cyl found during Ret: 1. Refine axis 2. Determine power Trial Frame 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

“Is the circle rounder with lens 1 or 2? JCC red lines at 90⁰ (1) or 180⁰ (2) Px picks (1): Bracket is between 90⁰ or 135⁰ Px picks (2): Bracket is between 45⁰ and 180⁰ After bracketing, insert -0.25 DC halfway between the bracket Refine the axis: align handle with red markings on lens Twirl JCC: “Is it more round with (1) Above red markings or (2) Below red markings? Above: Change axis with 15⁰ clockwise or anti-clockwise. Move with 15⁰, 10⁰ and 5⁰ Repeat process until “same” or reversal Refining cyl power: Align lens markings with JCC markings “Is the target clearer with (1) (+) or (2) (-) Keep adding cyls until reversal or same Stop at reversal or same: “Is it clearer with the lens or without?”

Phoropter 1. JCC unit in front of eye

2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

Rotate dial until flipping wheel parallels axis markings Red dots at 90⁰ “Is the circle getting rounder with (1) (Red dots at 90⁰) or (2) (red dots at 180⁰) Px picks (1): Rotate dial until clicks. Bracket: between 90⁰ and 135⁰ Rotate Cyl axis to 100⁰ Insert -0.25 Cyl “Is the circle now clearer with (1) (red dot above) or (2) (red dot below)?” Above: change axis upwards Below: Change axis downwards Change with 15⁰, 10⁰ and 5⁰ Stop at same or reversal Rotate JCC unit until wheels parallel the cyl axis Rotate flip wheels until white markings correspond with P “Is the circle clearer with (1) (+Cyl) or with (2) (-Cyl)?” Change cyls until reversal or same Change sphere power every 0.50 DC change, with 0.25DS

Possible Cyl Rx VA after BS ⁶⁄₆ ⁶⁄₉ ⁶⁄₁₂ ⁶⁄₁₈ ⁶⁄₂₄

Possible Cyl Rx 0.25-0.75 0.75-1.25 1.25-1.75 1.75-2.25 2.25-3.00...