"Negative dysphotopsia" is the term used to describe the "dark shadows" that a few intraocular lens (IOL) patients see in their far peripheral vision. The primary cause is highly likely to be the limited size of the IOL in comparison to the natural crystalline lens that it replaces. At very large visual angles the light is no longer imaged by the IOL, and a shadowlike phenomena may be visible. This is actually an imaging property related to IOLs, rather than the casting of a shadow, and it has been evaluated systematically in a series of scientific papers. A pdf is included below, along with an initial video simulation of what might make a peripheral dark shadow "bothersome".
This work led to finding that "Far peripheral vision" appears to be a visual region where there has been very little research (above 60 degrees). A review summarizes the information that is readily available: Simpson MJ. Mini-review: Far Peripheral Vision. Vision Research 140C (2017) pp. 96-105 (a version can be downloaded from the Downloads page). One question is how the limit of vision varies with age and refractive error, with a limiting visual angle measurement of about 105 degrees dating from 1915, but modern test equipment only extending to 90 degrees at most. What if there happens to be an unexpected connection to myopia development, for example, but there are no data so nobody has noticed...
"Positive dysphotopsia" is also a potential concern with IOLs, and these are bothersome if there is total internal reflection at the lens edge at night. This is discussed in the 2021 JCRS paper.
This is like the eye rotating to the right then back again, starting with a 2.5 mm pupil, and then increasing to 3, 3.5, 4, and 5mm pupils as it continues to rotate.
Here the pupil starts at 4mm and it does a small rotation to the right, and back to the left. Then the pupil suddenly drops to 2.5mm and it does the same rotations. It repeats this 3 times
Disclaimer. Simpson Optics LLC does not provide medical advice, and neither does this website. If you have concerns about your vision, you should see a specialist, such as an Ophthalmologist or Optometrist.
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