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"Negative dysphotopsia" is the term used to describe the "dark shadows" that a few intraocular lens (IOL) patients see in their far peripheral vision. Scientific and healthcare publications indicate that there is no consensus yet about what causes this visual phenomenon, but 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.
This phenomenon is now being evaluated systematically in a series of scientific papers. The papers themselves contain references to earlier work, and the new publications are listed below. The work so far indicates that this visual phenomenon is an expected characteristic of the use of an intraocular lens. This has also led to additional questions about far peripheral vision.
ARVO 2017 Poster (View Abstract)
Simpson MJ, Muzyka-Wozniak M. Iris characteristics affecting far peripheral vision and negative dysphotopsia. Wed. May 10, 8:30-10:15, Baltimore, MD. Poster B0688.
Holladay JT, Simpson MJ, "Negative dysphotopsia: Causes and rationale for prevention and treatment". J. Cataract Refract. Surg. 2017; 43:263-275. View Abstract
M. J. Simpson, “Managing and understanding negative dysphotopsia (Letter)” View Abstract
M. J. Simpson, “Double image in far-peripheral vision of pseudophakic eye as source of negative dysphotopsia,” J. Opt. Soc. Am. A. 31, 2642-2649 (2014). View Abstract
A review paper on the topic, which includes references to many other papers, is: Henderson BA, Geneva II. Negative Dysphotopsia: A perfect storm. J. Cataract Refract. Surg. 2015; 41:2291-2312. View Abstract