**Conflict of interest**

*Intraocular Lens*

tions [7, 34, 38].

chamber depth, axial length, and intraocular lens power, can be particularly vulnerable, also be sensitive to aberration, and produce dysphotopsia. This peculiar

Of all these studies, the design of the intraocular lens, specifically the edge, proved to be the source of negative pseudophakic dysphotopsia. The explanation of this enigmatic phenomenon has not been elucidated despite so many investiga-

In 2014, the author reported that the negative dysphotopsia was caused by a stimulation of the unpaired temporary crescent or "half moon" because the incidence of rays on the edge of the intraocular lenses refracts on the peripheral nasal retina outside 30° (location area of the temporary flood). The fact that some patients have it at 30° and others between 60 and 90° would explain why some patients may present them and others not, as well as unilateral or bilateral [39]. The disappearance or transientness of the negative dysphotopsia was explained by the opacification or translucency of the nasal sector of the capsule, later acting as a diffuser of the rays, in the first week or months following the surgery. The opacity of the posterior capsule causes diffusion of light and reduces contrast and retinal sensitivity. The anterior axial movement of the intraocular lens by contraction of the capsular bag maybe is another explanation that decreases the occurrence over time, since it reduces the axial space under the iris to 0.06 mm or less, causing a myopic change that

is extremely rare. However, this has not made dysphotopsia disappear [38].

field, with the disappearance of symptoms [39].

haptic junction minimizes negative dysphotopsia.

In relation to a persistent visual phenomenon, possible therapeutics arise such as the use of miotics [6, 21, 23, 29] but, contrary to expectations, it increases the problem and the pharmacological dilation seems to reduce it [34], anterior and posterior capsulotomies [6, 24, 34, 39, 40], smaller capsulorhexis [6, 31, 37], modifications of the intraocular lens [11, 30, 32, 34], change of intraocular lens [6, 13, 37, 40] do not solve the problem. The placement of another intraocular lens on the primary or "piggy bag" [29, 38] and reverse optical capture of the lens [34, 38] had partial or complete resolution of symptoms. The suture of the IOL-capsule complex iris bag [38] can decrease the visual phenomenon. The author used prism in the eye of dysphotopsia causing a displacement of the temporal crescent outside the visual

Henderson et al. [40] reported a 2.3-fold decrease in negative dysphotopsia symptoms early after cataract surgery when the nasal optic–haptic junction was oriented slightly super nasally (30° from horizontal) when compared with the haptic junction being oriented vertically. Henderson hypothesized that when the haptic junction was placed vertically, it exposed the nasal optic edge to reflections from temporal light. By placing the haptic junction relatively horizontal, the junction would then "block the light," and the intraocular lens edge reflections and the

Erie et al. [41] with a ray-tracing software demonstrated how the horizontal

The incidence of dysphotopsia phenomena in pseudophakic patients after uncomplicated cataract surgery varies, ranging from 20 to 77.7%, since there are only isolated reports as can be seen in the literature [6, 11, 30, 39, 42–49]; however, the prevalence does not seem to be altered with the type of intraocular lens [28].

Pseudophakic dysphotopsia is an entoptic phenomenon induced by intraocular

lenses that cause discomfort to patients. Positive dysphotopsia manifested as glare is well tolerated by patients, and negative dysphotopsia reported from the

resultant temporal negative dysphotopsia shadow would be avoided.

interaction seems to vary from patient to patient [16, 33, 38].

**58**

**4. Conclusions**

The author declares no conflict of interest.
