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Photostress recovery time
Photostress testing determines how quickly the photoreceptor cells in the retina recover after being bleached by a bright light. The test involves exposing one eye to a light for 10 seconds to bleach the photoreceptors, then timing how long it takes for the patient to read letters at a certain size after the light is removed. Recovery times longer than 50 seconds are considered abnormal and may indicate a macular disease. The test provides a measure of macular function by assessing how quickly the visual pigment can be resynthesized after being bleached.
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Photostress recovery time
- 1. PHOTOSTRESS RECOVERY TIME OPTOMFASLU MUHAMMED
- 2. Photostress testingdetermines the rate of photoreceptor visual pigment resynthesis by bleaching the foveal cone photopigments and causing a temporary state of retinal sensitivity preceived by the patient as scotoma. The time required to regain visual acuity after this bleaching provides an index of macular functioning.
- 4. procedure 1)Measure distance visualacuity. 2)Ask the patient to remove their spectacles but keep them in their lap so that they can be quickly put back on again. 3) Occlude one eye hold your direct ophthalmoscope about 2-3 cm away from the patient’s eye . 4)Turn on the light and ask the patient to look directly at the light for exactly 10 seconds.
- 5. 5) After 10seconds remove ophthalmoscope ,ask the patient to put their glasses back on and point on to the letters one line larger than the patients original visual acuity , ask the patient to read those possible letters as quickly as possible after the after image has disappeared . 6)Time how long it takes after removal of the bleaching light for the patient to read at least two –thirds of the relevant letters. 7) Repeat the measurement for the other eye if necessary.
- 6. RECORDING Record thetime taken in seconds to recover to within one line of prebleached visual acuity in seconds.
- 7. INTERPRETATION Its generallysuggested that any photostress recovery time longer than 50 seconds is abnormal, and suggests a macular disease rather than optic nerve abnormally. Of course , a normal photostress recovery time depends on the brightness of the light used , and it is best to obtain your own normal values with your own particular technique and instrumentation.
- 8. MOST COMMON ERRORS Allowing a patient to lose fixation of the bleaching light Usually direct ophthalmoscope with batteries that are not fully charged. Having the patient wait until the letters are clearly visible rather than just visible. Timing inaccurately.
- 9.