Delayed visual recovery after returning indoors
Ever feel like your eyes take too long to adjust when going from a brightly-lit room to a darker space, or from transitioning from outdoors to indoors on a bright, sunny day? There is a good reason for that. While this might be annoying, it could actually signal something amiss with your eye health. This delay in recovering vision is caused by photoreceptors being “bleached” by the high luminance levels. When photoreceptors, the light-sensing cells in the retina become bleached, photopigments used to detect light are temporarily ‘out of stock.’ The good news is that these photopigments regenerate quickly, and in most folks, this occurs within 15 to 30 seconds. The time it takes your vision to return to its baseline level after this bleaching or photostress event is used by clinicians to distinguish visual pathway disorders from each other, a test called the photostress recovery test.
The visual pigment regeneration cycle is paramount to visual function. It also subserves the dynamic range of the retina, which can detect anything from a single photon of light, to the billions of photons the eye is bombarded with every second in normal luminance settings.
No tissue in the body works in isolation, however. The star of this process is not only the photoreceptor cell in the retina (the rods and cones), but the retinal pigment epithelium (RPE). The RPE plays the part of major supporting actor. The RPE is the garbage disposal of the retina. When the RPE is sick or withered, the retina does not function, and oftentimes the photoreceptors degenerate (which unfortunately is a permanent event). A sign of a sick RPE that is not working properly can manifest as a delay in photostress recovery. While some researchers have found there is some slight delay in photostress recovery time with normal aging, a significant delay may signify an eye disease. A problem with photopigment recycling can occur with age-related macular degeneration. It can also occur when there is poor circulation in the eye due to a retinal vessel problem as is common with diabetic retinopathy, or a choroidal vessel problem that is common with ocular ischemic syndrome. Ocular ischemic syndrome describes the complex signs the eye demonstrates when it is starved of blood, typically from reduced blood flow through the arteries that supply the brain and the eye (the internal carotid artery). Detecting ocular ischemia before a stroke occurs can save someone’s life. Ocular ischemia, age-related macular degeneration, and diabetic retinopathy can be diagnosed using a combination of dilated retinal examination, in combination with diagnostic tests assessing the structure and circulation of the retina. If you have had these comprehensive tests, and nothing has been uncovered, then ways to reduce the hindrance that this photoreceptor bleaching has on day-to-day function are to wear a wide-brimmed hat outdoors with sunglasses, and to improve indoor lighting so that the difference between outdoor and indoor light levels is reduced.
If you have questions, or are interested in being tested for any of the conditions discussed in this article, call our office for an appointment at 214-501-3310, and make sure you reference this article on Seniorific.com