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Subjective refraction final
The document outlines the processes involved in subjective refraction, including the determination of refractive status and the use of various instruments like the phoropter and Jackson cross cylinder. It explains techniques for ensuring that accommodation is relaxed and provides step-by-step instructions for conducting subjective refraction, including methods for addressing astigmatism and near addition for presbyopic patients. The document also highlights the importance of visual acuity during the refraction process and how to adjust lens prescriptions accordingly.
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Subjective refraction final
- 1.
- 3. What is Refraction? ■Determination of the refractive status (prescription) of the eye. OBJECTIVE Retinoscopy Autorefraction SUBJECTIVE Subjective Refraction Phoropter Epic
- 4. Subjective Refraction ■ Todetermine by subjective means the combination of spherical and cylindrical lenses necessary to to provide best visual acuity. ■ (with accommodation relaxed)
- 5. Principles of Refraction 1.Accommodation-relaxed state 2. Maximum PLUS, minimum minus
- 6. Principles of Refraction Whencan we ignore accommodation?
- 7. How can webe sure accommodation is relaxed? ■ Use PLUS lens to FOG ■ Ensure image is located in front of retina ■ This causes image / VA to become worse if eye attempts to accommodate (Image point becomes further away from the fovea)
- 8. Two sets ofcommonly used instruments
- 9. Start from Auto-RefResults (OD) 1. Best Vision Sphere 2. Jackson Cross Cylinder 3. Best Vision Sphere Repeat 1-3 on OS 4. Binocular Balancing 5. Binocular Best Sphere OU Steps in Subjective Refraction
- 10. Fogging ■ Place enoughPLUS lenses to FOG vision to 20/40 line ■ Pointer: every line is about 0.25 diopter ■ Slowly reduce the plus power until best vision ■ Remember: “Maximum plus power for best visual acuity”
- 11.
- 12. Step 2:JacksonCrossCylinder ■ JCCused to find used to determine the cylindrical axis and the cylindrical power for the patient. Yes, we have these!
- 13. Step 2: JCC ■JCC used to find used to determine the cylindrical axis and the cylindrical power for the patient.
- 16. How can webe sure accommodation is relaxed? ■ Use PLUS lens to FOG ■ Ensure image is located in front of retina ■ This causes image / VA to become worse if eye attempts to accommodate (Image point becomes further away from the fovea)
- 20. Cylinder Power ■ Patientdirected to observe a round target ■ Align red lines OR white lines to trial lens axis
- 23. Cylinder Power ■ Ifview one is clearer, ADD +0.25 cylinder power
- 24. Steps in SubjectiveRefraction Start from Auto-Ref Results (OD) 1. Best Vision Sphere 2. Jackson Cross Cylinder 3. Best Vision Sphere Repeat 1-3 on OS 4. Binocular Balancing 5. Binocular Best Sphere OU
- 25. Fogging like before... ■Use PLUS lens to FOG ■ Ensure image is located in front of retina ■ This causes image / VA to become worse if eye attempts to accommodate (Image point becomes further away from the fovea)
- 26. What about forreading? I'm over 40 years old and I can't read my phone. What's that from?
- 27. Near Addition ■ Presbyopic patientswould require a near addition for their reading.
- 28. Finding the NearAddition ■ Step 1: Estimation from patient’s age + 1.00 + 1.50 + 2.00 + 2.25 + 2.50 40 - 45 46 - 50 51 - 55 56 - 65 65+ Age Estimated Add
- 29. Finding the NearAddition ■ Step 2: Place the estimated near addition on top of the distance prescription ■ Step 3: Put near chart at 40 cm or 16” on near point rod and attach to phoropter.
- 30. Finding the NearAddition ■ Optional stuff after this!
- 31. Range of clearvision 20CM 60CM 40CM ■ Patient’s habitual reading distance in the middle of the range of clear vision.
- 32. Range of clearvision 10CM 50CM 40CM ■ If range is too close to patient: Add -0.25DS in steps
- 33. Range of clearvision 30CM 70CM 40CM ■ If range is too far to patient: Add +0.25DS in steps