EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/1261109
JUNE/JULY 2020 | EYEWORLD | 17 was a wider variety of IOL types in the NDs group, and a more in-depth discussion on vari- ous IOL edge designs would be clinically useful. In fact, the initial reports of NDs began in the early 2000s when square-edge IOLs were taking off, as a means of reducing the incidence of posterior capsular opacification. 6,7 The baseline characteristics between the two groups show almost twice the percentage of females and smaller axial lengths in the NDs group com- pared with pseudophakic controls, both statisti- cally significant differences. These two specific factors may themselves be related and could help explain nasal light ray pathways in patients with persistent NDs. Much larger population studies are needed to make such a conclusion, however. Moreover, it is not entirely clear how the edge of the optic. However, this conclusion was based solely on ray-tracing simulations. Given the currently available evidence, the rela- tive temporal scotoma in NDs likely occurs due to differences in reflected and refracted light rays at the IOL edge. Anatomical conditions that exploit those differences can characterize the types of patients most likely to experience NDs following uncomplicated cataract surgery. A temporally decentered pupil, a small pupil, a tilted iris/IOL complex, or a positive angle kap- pa all change the types of light ray interactions with the IOL at the nasal edge. 2-4 There were several limitations to this study, some of which were addressed in the paper. First, a prospective cohort study with a more even IOL distribution would have been ideal. While all the IOLs seen in pseudophakic con- trols were also present in the NDs group, there continued on page 18 Residents of USC Roski Eye Institute Why is temporal negative dysphotopsia so symptomat- ic in some patients, but not others? I invited the USC residents to review the find- ings from this interesting study published in the July issue of JCRS. —David F. Chang, MD EyeWorld Journal Club Editor