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Challenges in Refraction

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Obstacles in Refraction

Publicado en: Salud y medicina
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Challenges in Refraction

  1. 1. Challenges in Refraction Presented by: Md Riyaj Ali MSc Optometry
  2. 2. Background • Refraction: The process of determining refractive error of the patients • Retinoscopy: The process of determining refractive error of the patient objectively 18-06-2019 Challenges_in_Retionscopy_Riyaj 2
  3. 3. Common Problems in Retinoscopy 1. Dim reflex • Causes: media opacities, small pupil or high ametropia • Solution: – Try retinoscopy on dilated pupil – Off-axis retinoscopy – Reduce working distance (radical retinoscopy) – Add mod-high powered plus or minus lens 18-06-2019 Challenges_in_Retionscopy_Riyaj 3
  4. 4. Examiner performing off-axis retinoscopy 18-06-2019 Challenges_in_Retionscopy_Riyaj 4
  5. 5. Examiner performing Radical retinoscopy 18-06-2019 Challenges_in_Retionscopy_Riyaj 5
  6. 6. 2. Media opacities and/or small pupil • Dim reflex is seen as reduced amount of light reaches the retina and even less returns to your retinoscope • Solution: – Use large aperture sight hole – Use smaller number of lenses in the trail frame – Do not use working distance lens – Reduce working distance 18-06-2019 Challenges_in_Retionscopy_Riyaj 6
  7. 7. 3. Scissor reflex • This reflex moves like the action of a pair of scissors, moving simultaneously in opposite direction from the centre of pupil • Causes: optical aberration , abnormalites in the media like keratoconus or corneal scarring • Solution: – The examiner should neutralize the bright central band rather than the darker peripheral band – Increase room light level→ reduces pupil size, cuts down peripheral aberration 18-06-2019 Challenges_in_Retionscopy_Riyaj 7
  8. 8. 4. Large pupil: • Spherical aberration can provide a more against movement in the periphery of the lens compared to the centre • Solution – Concentrate on the central reflex and ignore the remainder – Increase room light level→ reduces pupil size, cuts down peripheral aberration 18-06-2019 Challenges_in_Retionscopy_Riyaj 8
  9. 9. 5. Accommodative fluctuations: • The pupil will be seen to vary in size and the reflex movement and brightness will rapidly change • seen with young children who change fixation (typically to look at the retinoscope light or their parent/guardian) • Keep reminding the patient to look at distance target 18-06-2019 Challenges_in_Retionscopy_Riyaj 9
  10. 10. • If reflex fluctuations do not appear related to change in fixation ↓ Latent hyperopia or psedomyopia should b suspected ↓ Cycloplegic refraction and assessment of accommodation should be performed 18-06-2019 Challenges_in_Retionscopy_Riyaj 10
  11. 11. 6. Patients with strabismus: • Retinoscopy is ideally performed along the patient’s visual axis • Retinoscopy on the ‘good’ eye must be performed slightly off-axis • For the strabismic eye, change the fixation point for the ‘good’ eye, so that retinoscopy along the visual axis of the strabismic eye is easier • Alternatively, occlude the ‘good’ eye and perform retinoscopy slightly off axis 18-06-2019 Challenges_in_Retionscopy_Riyaj 11
  12. 12. 18-06-2019 Challenges_in_Retionscopy_Riyaj 12
  13. 13. Retinoscopy in patient with strabismus 18-06-2019 Challenges_in_Retionscopy_Riyaj 13
  14. 14. 7. Patients with nystagmus: • Fog the fellow eye of patients with a high plus lens • Complete occlusion makes the nystagmus worse and lowers uniocular activity 18-06-2019 Challenges_in_Retionscopy_Riyaj 14
  15. 15. 8. Patients with Low vision • Large dioptric changes in sphere and a high-powered Jackson cross-cylinder (0.75 or 1.00 D) are required • Static Retinoscopy is preferably performed with a wide aperture trial lens • The examiner should use radical and off-axis retinoscopy • Allow unusual head and eye positions (ecentric fixation) 18-06-2019 Challenges_in_Retionscopy_Riyaj 15
  16. 16. • To verify your endpoint see the point of reversal by varying your working distance (move forward to observe ‘with’ movement and move backward to observe ‘against’ movement) • In case of media irregularities, opacities and miotic pupils retinoscopy should be repeated post dilatation • In case of children below 15 years of age with good amount of accommodation, it is recommended to perform refraction under cycloplegia 18-06-2019 Challenges_in_Retionscopy_Riyaj 16
  17. 17. Possible causes of inaccurate retinoscopy findings 1. Incorrect working distance→ spherical error 2. Scoping off the patient’s visual axis→ astigmatic error 3. Failure of the patients to fixate the distant target 4. Failure to obtain reversal 5. Failure to locate principal meridian 6. Failure to recognize scissor reflex 18-06-2019 Challenges_in_Retionscopy_Riyaj 17