Optical modelling for negative dysphotopsias
Research needed to fill the gaps in data
RESEARCHERS appear to have moved towards a hypothesis that explains negative dysphotopsias perceived by some pseudophakic patients, but more work is needed to fully understand the aetiology of these bothersome dark shadows, said Michael J Simpson, PhD.
Speaking during a Clinical Research Symposium on “Understanding and Dealing With Dysphotopsias”, Dr Simpson discussed work he has been doing with ray-tracing to help characterise the mechanism underlying negative dysphotopsias and the challenges for developing a better understanding.
He explained that with large visual angles, “vignetting” of light at the edge of an IOL is likely to be the primary cause of negative dysphotopsias that are perceived with a small pupil.
“The main image goes dark in the periphery with a small pupil, and light can also miss the IOL. As the pupil opens, the shadow effect rapidly disappears, and this sensitivity to pupil size may explain why patients find the phenomenon bothersome,” said Dr Simpson, an optics expert from Arlington, Texas, USA.
Looking ahead, he noted that elucidating the cause of negative dysphotopsias will require research to fill gaps in data on its related parameters.
Far peripheral vision has been a neglected topic, and information is needed on pupil diameters, visual angles and specific IOL design characteristics associated with the dark shadows, said Dr Simpson.