Photostress recovery time (PSRT) is the time taken for

visual acuity Visual acuity (VA) commonly refers to the clarity of vision, but technically rates an examinee's ability to recognize small details with precision. Visual acuity is dependent on optical and neural factors, i.e. (1) the sharpness of the retinal ...

to return to normal levels after the

retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...

has been bleached by a bright light source. Photostress recovery time measurement procedure is known as photostress test. Normal recovery time is about 15–30 seconds. The photostress test is a simple, easy and quick clinical technique that can differentiate between retinal ( macular) and postretinal (e.g.

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived fro ...

) disease.

Clinical significance

The photo stress test is clinically useful in

diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level (hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...

glaucoma Glaucoma is a group of eye diseases that result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple) glaucoma, in which the drainage angle for fluid within the eye re ...

macular degeneration Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Over time, however, som ...

etc.

Diabetic retinopathy Diabetic retinopathy (also known as diabetic eye disease), is a medical condition in which damage occurs to the retina due to diabetes mellitus. It is a leading cause of blindness in developed countries. Diabetic retinopathy affects up to 80 perc ...

affects the microvasculature of the inner retina and causes

neurodegeneration A neurodegenerative disease is caused by the progressive loss of structure or function of neurons, in the process known as neurodegeneration. Such neuronal damage may ultimately involve cell death. Neurodegenerative diseases include amyotrophic ...

. Several studies reported that PSRT is elevated in people with diabetes. Recovery time is more in macular diseases (50 seconds or more) than postretinal (e.g.optic nerve) diseases. Elevated PSRT has also been found in primary open angle glaucoma (POAG) which is characterized by progressive death of the

retinal ganglion cells A retinal ganglion cell (RGC) is a type of neuron located near the inner surface (the ganglion cell layer) of the retina of the eye. It receives visual information from photoreceptors via two intermediate neuron types: bipolar cells and retina ...

. Amblyopic eyes with normal fundus also have normal recovery time.

Materials needed

Ophthalmoscope or alternative source of light (e.g.penlight), stop watch, distance vision charts like a

Snellen chart A Snellen chart is an eye chart that can be used to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen, who developed the chart in 1862. Many ophthalmologists and vision scientists now use an improv ...

Procedure

* Testing is done monocularly. * Patient is asked to sit in front of an illuminated vision chart, at 6 meter distance. * Initial measurement of best corrected visual acuity should be done. * Locate

fovea Fovea () (Latin for "pit"; plural foveae ) is a term in anatomy. It refers to a pit or depression in a structure. Human anatomy * Fovea centralis of the retina * Fovea buccalis or Dimple * Fovea of the femoral head *Trochlear fovea of the f ...

using ophthalmoscope. * Ask the patient to look at the bright light of the ophthalmoscope for 10 seconds. * Time taken to read any three letters of the pre-test visual acuity is noted. * Normal recovery time is 15–30 seconds.

Disadvantages

The main disadvantage of the test is that there is no standardization of the procedure. The effect of aging on recovery time is also thought as a disadvantage, but it is still under discussion since some studies found increased PSRT with age, and others did not find any significant effect.

References

{{reflist Diagnostic ophthalmology