13986876
| Pregunta | Respuesta |
| When and why to perform retinoscopy | When: * For objective first measure of refractive * Non-communicative patients * Intellectually disabled patients * infants/pre-verbal children * low vision patients * uncooperative or poorly discriminating patients Why: Objective refraction minimises patient cooperation required, thus allows practitioner to make judgement of the most appropriate optical correction without aid of patient's judgement or response. While subjective refraction depends on Px cooperation and depends on their ability to discern changes in clarity with trial lens |
| Set up Px for retinoscopy | Objective is to find the patient's far point 1. Align phoropter + trial frame 2. With both eyes open ask patient to look at target in the distance 2. Sweep beam of light across patient's eye close to their visual axis at working distance of 50/67cm from patient * View LE with LE and RE with RE 3. Astigmatism or Spherical (find meridia if astigmatism - by aligning streak with beam) |
| Difference between with and against movement in retinoscopy | With movement: The streak reflex within the pupil relative to the movement of the beam indicated the far point location is behind the optom. At a working distance of 50cm (+2.00DS) - far point should be at 50cm from the patient. * Refractive error: suggest hyperopic * Correction: require -ve lens Against movement: The streak reflex within the pupil relative to the movement of beam indicates far point is located between the retinoscope and the patient's eye. * Refractive error: suggest myopic * Correction: require +ve lens |
| Factors that help to determine patient end point with retinoscopy | Factors: * Direction: With or against movement (gives information about refractive error, provided that working distance lens is in place) * Brightness: At neutrality - brightest, reflex gets dimmer the further away it is from neutrality (but could be dim due to media opacity) * Speed: At neutrality - infinite speed (looks like no movement), reflex is slower the further away from neutrality it is * Width: At neutrality - fills pupil entirely, reflex becomes thin close to neutrality but becomes wider the further away it is from neutrality |
| Potential problems when performing retinoscopy | 1. Undetectable initial reflex * as ametropia increase, speed of reflex decrease (might mimic neutralisation) - but dull so not at neutralisation 2. Undetected cylinder * Common in large spherical components - have to alternative axes as approaching neutralisation 3. Small pupils and media opacities * shorter working distance increases speed and visibility (radical retinoscopy) - but also increases error 4. Failure to allow for working distance lens when recording result 5. Split reflex * occurs with cycloplegia, spherical aberration * concentrate on centre of beam 5. Scissors reflex - irregular cornea (keratoconus) 6. Excessive reflection |
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