Intraocular lens exchange in patients with negative dysphotopsia symptoms

Abstract

The iris-optic distance was not statistically significantly different between eyes with severe negative dysphotopsia symptoms and nonsymptomatic eyes. However, when IOL exchange reduced the iris-IOL distance, the severe negative dysphotopsia symptoms resolved.

Negative dysphotopsia: The enigmatic penumbra

“…In short, optical defects in the lens plane (cornea) are not visible at the image plane (retina) but do cause reduction in contrast and image quality from the light scatter. Also, additional clinical studies comparing temporal clear corneal incisions with nasal, 5 superior, 6,9 and scleral tunnel 6 incisions found no difference in the incidence of negative dysphotopsia acutely (transient) or long term (permanent).…”

“…This extreme depth of the IOL behind the iris would be very apparent to a clinician at the slitlamp and is far deeper than that reported for negative dysphotopsia (w0.4 to 0.5 mm). 8,9 Therefore, this type 2 shadow is not what has been referred to as negative dysphotopsia over the past 10 years, either. Figure 4 shows the third type of shadow that occurs in the extreme temporal field (near 90 degrees).…”

“…The mechanism of this disorder has remained a clinical enigma, with proposed explanations that include IOL material with a high index of refraction, 4-6 optics with a sharp or truncated edge, 4,6 idiosyncratic predisposition, 7 a cataract incision located temporally in clear cornea, 8 brown irides, 8 a prominent globe, 9 a shallow orbit, 9 an IOL anterior surface that is more than 0.46 mm from the plane of the posterior iris, 9 a negative afterimage, 10 neural adaptation, 10 and reflection of the anterior capsulotomy edge projected onto the nasal peripheral retina. 11 Several additional articles and letters with case reports showing the absence of some of these suggested mechanisms have also been published.…”

Reply: Etiology of negative dysphotopsia

“…It was not until Davison's original article 2 that heightened awareness of ND was universally recognized and reports flourished. Narvaez et al, 7 Trattler et al, 8 Osher, 9 V amosi et al, 10 Mamalis, 11 Cooke, 12 Wei et al, 13 and Masket 14 all followed Davison, 2 suggesting the same mechanism of the truncated sharp edge as the cause. Our work provides the optical explanation for ND and proves their suspicions were correct.…”

Dysphotopsia-Unraveling the Enigma

“…24,25 Causative factors of ND could be primary or secondary. Primary factors are small pupil 5,26 larger distance between the back of the iris and IOL 27,28 sharp-edged design (edge radii ≤ 0.05 mm), anteriorly extending functional nasal retina 26,29 and reflection of the anterior capsulotomy edge projected onto the nasal peripheral retina as suggested by Masket and Fram. 25 This theory is supported by ray tracing model by Hong et al 30 ND shadow is easier to perceive with constricted pupils as pupillary constriction leads to increased contrast between the shadow and the rays adjacent to it, similar to the pinhole.…”