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Photo stress recovery time (psrt)

Photostress recovery time (PSRT) measures how long it takes for visual acuity to return to normal after retinal bleaching from a bright light. It tests macular function independent of other ocular diseases and identifies differences between retinal and post-retinal issues. Normal recovery time ranges from 15 to 50 seconds, with extended times indicating potential macular disease.

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Photo Stress Recovery Time (PSRT) Rashad Ibn Muhammed Assi. Prof Optometry Ahalia School of Optometry
PSRT • Photostress recovery time is the time taken for visual acuity to return to normal levels after the retina has been bleached by a bright light source. • It is a test of retinal (macular) function and is independent of any other ocular disease which affect other parts of visual system • Testing determines the rate of photoreceptor pigment resynthesis by bleaching the foveal visual pigments • It cause a temporary state of central scotoma • Simple test to differentiate between retinal (macular) and post retinal (optic nerve disease)
Macular function • Long lasting after-images (longer than 15 seconds) produced by relatively brief flashes of light are due to photochemical changes in the receptors. • Light absorption by rhodopsin (it is assumed that cone photo pigments work in a similar fashion, although slightly faster) leads to the separation of the retinal chromophore from opsin. • This process is called bleaching as it results in the loss of rhodopsin’s purple colour. • While the photo pigment is being regenerated, the patient will see an after-image, and it will get active again and show actual image
Procedure • Measure distance visual acuity of both eyes • 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 the ‘one’ eye. Hold your direct ophthalmoscope or other bright light source about 2–3 cm away from the patient’s ‘testing ’ eye. Turn on the light and ask the patient to look directly at the light for exactly 10 s.
Contd After 10 s, remove the ophthalmoscope, ask the patient to put his or her glasses back on and point to the letters one line larger than the patient’s original visual acuity. • Ask the patient to read those letters as quickly as he or she can after the after-image has disappeared. Time how long it takes after removal of the bleaching light for the patient to read at least 2/3 of the letters on the line indicated. Repeat the measurement for the ‘other’ eye. assure distance visual acuity of both eyes
Photostress Recovery time procedure
Patient will experience like this
Recording • Record the time taken in seconds to recover to within one line of pre- bleached visual acuity. Examples: PSRT: RE 35s, LE 40s PSRT: OD 45s, OS 105s.
Interpretations • Recovery time is correlated with the other eye • Normal recovery time is 15-50 seconds • More than 1.5 min recovery time suggest a macular disease than an optic nerve related problem • Time difference between eyes are not more than 5-6 secs
Some points to be noted 1. Average recovery-time was between 15 to 50 seconds. 2. Recovery-time increased with age and was more by 3 to 5 seconds in female. 3. Recovery-time increased with high hypermetropia, high myopia with degenerative changes, pigmentation macula and yellow spots on the macula. 4. Amblyopic eyes with normal fundus had normal recovery-time. 5. Recovery-time increased beyond 5 minutes in a diseased condition of macula. 6. Recovery time was within normal limits after cure of the macular disease
Common errors 1. Allowing the patient to lose fixation of the bleaching light. 2. Using a direct ophthalmoscope with batteries that are not fully charged. 3. Having the patient wait until the letters are clearly visible rather than just visible. 4. Timing inaccurately.
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