Photostress test: testing is done monocularly. Slight changes in the retinal pigment epithelium (RPE), choroid, choriocapillaris and outer retinal layers can result in reduced acuities. One of the complaints a patient may present with is difficulty with night vision. Examples, small serous detachments of the RPE or retina and macular degeneration. These conditions are not always easy to determine nor to what extent a patient's visual acuity will be reduced when viewed ophthalmoscopically.

The photostress test is a very simple test to run and is intended to differentiate between optic nerve and macular (retinal) problems. There is a difference in the recovery time for those patients over 40 years of age and younger patients. The acceptable recovery times of 50 to 60 seconds are more in line with patients over 40 years. Recovery time for young healthy individuals with no macular problems can be markedly less.

The test should always be run before either Goldmann tonometry or dilation. Specifically patients having reduced vision in one eye that cannot be explained nor improve with the use of a pinhole. The patient's best correction is first determined and their acuities are measured monocularly. The patient is asked to cover or occlude the eye with the worst vision while the good eye is subjected to a bright light from your ophthalmoscope directed onto the macula for 10 seconds. Some authors feel having the patient look at a bright penlight or transilluminator will cause adequate bleaching of the retina. The problem with this technique is you cannot be sure the patient is looking directly at the light with their macula foveal area. With the patient wearing their best correction they are asked to read backwards the line of letters just above their best line of acuity. The projector and acuity chart should already be set up containing the line of best acuity and the line just above. The timing starts when the ophthalmoscope or penlight is removed. Photostress recovery time (PSRT) is the time it takes for the patient to read the line just above its pre-test best acuity line backwards. The same procedure is then repeated for the fellow eye.

Patients with normal healthy macular function should be able to read the line in 50 to 60 seconds. Patients with a macular problem may have recovery times lasting 1.5 to 3 minutes or longer. Those patients with visual acuities of 20/80 or worse are not good subjects for this test.

If the cause for the reduce visual acuity is optic nerve, the bleaching of the retina will have no effect on the recovery time. Recovery time will be normally 50 to 60 seconds or basically equal for both eyes.