Objective, subjective and cyclopegic refraction

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  • The 3-Click Blur Out Technique for monocular sphere check
  • The 3-Click Blur Out Technique for monocular sphere check
  • Objective, subjective and cyclopegic refraction

    1. 1. Objective, Subjective andObjective, Subjective and Cyclopegic refraction Cyclopegic refraction Gauri S Shrestha, M.Optom, FIACLE Lecturer and Optometrist
    2. 2. Objective refraction Objective refraction• Examiner determines the refractive state of the eye on the basis of the Optical Principles of refraction.• Purpose: To obtain an objective measurement of the patient’s refractive state.• Example – Keratometry – Retinoscopy – Optometers – Auto refractometer Gauri S Shrestha, M.Optom, FIACLE
    3. 3. Retinoscopy Retinoscopy• Static retinoscopy – To determine refractive state by patient fixating at distance so that accommodation is at rest• Dynamic retinoscopy – To determine refractive state by patient fixating at near, accommodation is active.• Principle: – Estimate the patients refractive state by bringing patient’s far point at the entrance pupil of examiner with the help of appropriate lens. – The state of refraction at this particular point is called as neutralization. neutralization Gauri S Shrestha, M.Optom, FIACLE
    4. 4. Gauri S Shrestha, M.Optom, FIACLE
    5. 5. Gauri S Shrestha, M.Optom, FIACLE
    6. 6. Procedure Procedure• Working distance• Fixation target• Patient instructions• Starting point• Locating principal meridian• Procedure for spherical ametropia• Procedure for astigmatism Gauri S Shrestha, M.Optom, FIACLE
    7. 7. Principle of subjective refractionPrinciple of subjective refraction• Subjective determination of the combination of sphere and cylindrical lenses that artificially places the far point of Each Eye of patient at infinity• This is the combination of lenses that provides best VA with accommodation relaxed Gauri S Shrestha, M.Optom, FIACLE
    8. 8. Purpose Purpose• To find the strongest plus lens or the weakest minus lens which allows the patient to obtain the best possible visual acuity Gauri S Shrestha, M.Optom, FIACLE
    9. 9. When to start subjective refraction?When to start subjective refraction?• After objective retinoscopy/Auto refraction• Accurate refining when objective retinoscopy is inaccurate – Media opacities, keratoconus, oblique and irregular astigmatism• Post mydriatic cycloplegic refraction• When retinoscope or auto-refractor is absent Gauri S Shrestha, M.Optom, FIACLE
    10. 10. Subjective refraction techniquesSubjective refraction techniques• Fogging• Stenopaic slit• Jackson’s cross- cylinder Gauri S Shrestha, M.Optom, FIACLE
    11. 11. Subjective refraction techniquesSubjective refraction techniques• Astigmatic fan/ Clock dial/ Sunburst dial• Phoropter Gauri S Shrestha, M.Optom, FIACLE
    12. 12. The sequence of the subjective The sequence of the subjective refraction refraction• Monocular sphere check – The Step-Down Technique (Visual acuity method) for monocular sphere check – The Red-Green Technique for monocular sphere check Gauri S Shrestha, M.Optom, FIACLE
    13. 13. The sequence of the subjective The sequence of the subjective refraction refraction• Astigmatism power and axis – Jackson Cross Cylinder – power→axis→power – If the power of cylinder is 1.00 diopter or more • Axis check • Power check • Note: Add constant spherical equivalent Gauri S Shrestha, M.Optom, FIACLE
    14. 14. The sequence of the subjectiveThe sequence of the subjective refraction refraction Fan chart Clock Dial Gauri S Shrestha, M.Optom, FIACLE
    15. 15. The sequence of the subjective The sequence of the subjective refraction refraction• Monocular sphere endpoint – The Step-Down Technique for monocular sphere check – The Red-Green Technique for monocular sphere check – Note: Perform monocular visual acuity test Gauri S Shrestha, M.Optom, FIACLE
    16. 16. Binocular Balancing Binocular Balancing• Purpose: – Equalize accommodation between the 2 eyes• Method – Prism dissociation technique – Prism dissociation bichrome balance – Alternate occlusion technique Final Fused Binocular Shrestha, M.Optom, Determination Gauri S Final Fused Binocular Sphere Power Determination Sphere Power FIACLE
    17. 17. Difficulties with Subjective Difficulties with Subjective Refractive Testing Refractive Testing• Intelligence• Cooperation• Past experience• Poor JND ability• Language barrier Gauri S Shrestha, M.Optom, FIACLE
    18. 18. Principle of cycloplegic refraction Principle of cycloplegic refraction• Determination of total refractive error during Total Hyperopia temporary paralysis of cilliary muscles as an Latent Manifest instillation of hyperopia hyperopia cycloplegic drugs which otherwise doesn’t manifest on subjective non-cycloplegic facultative Absolute hyperopia hyperopia refraction Gauri S Shrestha, M.Optom, FIACLE
    19. 19. Indication for cycloplegic refractionIndication for cycloplegic refraction• Accommodative esotropia• All children younger than 3 yrs• Suspected latent hyperopia• Suspected pseudomyopia• Uncooperative/noncommunicative patients• Variable and inconsistent end point of refraction Gauri S Shrestha, M.Optom, FIACLE
    20. 20. Indication for cycloplegic refractionIndication for cycloplegic refraction• Visual acuity not corrected to a predicted level• Strabismic children• Amblyopic children• Suspected malingering and hysterical patients Gauri S Shrestha, M.Optom, FIACLE
    21. 21. Selection and use of specific Selection and use of specific cycloplegic agents cycloplegic agents• Variable degree of pupil dilatation and cycloplegia• Instill cycloplegic alone or with mydriatricsAgent [C%] Dosage Max Duration Residual cyclople of effect accomAtropine 1, 2 1D TID 3-6 hrs 10-18 Ngblesulfate 3 days daysSco-mine 0.25% 1D TID 60 mins 5-7 days ngbleHBRCyclo- 0.5, 1, 2 1D TID 30-45 24 hrs minimallate HCL minsTro-mide 0.5, 1 1D TID 20-30 4-8 hrs moderateHCL mins Gauri S Shrestha, M.Optom, FIACLE
    22. 22. Cyclopentolate HCl is the drug of Cyclopentolate HCl is the drug of choice in most of the time choice in most of the time• Use 1% [C] in children and adult,• Use 0.5% [C] in infants in combination with 2.5% phenylephrineAge (Yrs) Amount deduced0-6 1.00 DS10 0.75 DS15 0.50 DS20 0.25 DS30 0-0.25 DS40 0 DS Gauri S Shrestha, M.Optom, FIACLE
    23. 23. What does our practice say? What does our practice say?• Advise atropine cycloplegic refraction invariably in the children younger than 2 years• Advise atropine cycloplegic refraction in esotropic children (accommodative type) up to 4 years• After 4 years, advise cyclopentolate cycloplegic refraction up 25-30 years• Above 30 years, check amplitude and lag of accommodation, then advise cycloplegic refraction Gauri S Shrestha, M.Optom, FIACLE
    24. 24. Spectacle prescribing Spectacle prescribing• Prescribing spectacle from cycloplegic finding is an art rather precise science• How to prescribe spectacle? – Concept of emmetropization is necessary – Esotropic children younger than 4 years, full refractive correction is prescribed – With older children, amount of plus can be reduced till fusion is maintained Gauri S Shrestha, M.Optom, FIACLE
    25. 25. Gauri S Shrestha, M.Optom, FIACLE

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