Dysphotopsias and Surgical Management

12 Dysphotopsias and Surgical Management

Samuel Masket and Nicole R. Fram

Abstract

As dysphotopsia is a subjective phenomenon, it is difficult to predict as to which patients will experience dysphotopsia following an uneventful surgery. Some patients may be particularly vulnerable or particularly sensitive to dysphotopsia and may require additional surgical treatment. Reverse optic capture, piggyback intraocular lens (IOL) implantation, and sulcus placement of an IOL are considered surgical mode for nonabating negative dysphotopsia. Positive dysphotopsias (PDs) are often associated with thick optic-edge IOLs and IOLs with high index of refraction. PD patients who do not respond to medical line of therapy often need an IOL exchange.

Keywords: dysphotopsia, negative dysphotopsia, positive dysphotopsia, reverse optic capture, secondary reverse optic capture, photophobia, glare

12.1 Introduction

Negative dysphotopsia (ND) represents an undesired optical phenomenon following cataract surgery. It is classically described as a dark temporal shadow. Conversely, positive dysphotopsia (PD) is characterized by light streaks, starbursts, or glare. Both photopsias interfere significantly with the quality of vision and perceived success of surgery. The dysphotopsias can result in unrelenting patient dissatisfaction after otherwise uncomplicated cataract surgery. Given that ND and PD differ in etiology and management, techniques for treatment should be considered separately. However, both conditions may exist simultaneously.

12.2 Negative Dysphotopsia

ND, first described by Davison as a dark shadow in the temporal visual field, is an undesired optical phenomenon that may follow otherwise uncomplicated contemporary cataract surgery in which an intraocular lens (IOL) is placed in the capsule bag remnant with an overlying continuous circular anterior capsulotomy.1,2 As noted in the present report and by others, ND has been reported with a variety of IOLs^2,3 and ND was not described prior to capsulorrhexis and has not been associated with malpositioned IOLs. Although the etiology remains uncertain and is likely multifactorial, several mechanisms have been proposed. Holladay et al, in their original report using ray tracing in a nonclinical study, implicated square-edge design IOLs, increased posterior chamber depth, small pupil diameter, and high index of refraction IOLs among other factors as causal of ND.⁴ In a more recent study, Holladay et al, again employing ray-tracing nonclinical studies, revised their original theory to include nasal anterior capsule overlap, IOL optic shape, high IOL power, high angle kappa (chord mu), small pupil, optic asphericity, etc., as theoretically causes of ND; they no longer limit IOL optic-edge character and iris–optic distance as primary factors.⁵ Interestingly, their recent observations are more consistent with our original clinical findings that implicate the overlapped anterior nasal capsule.^2,5

Diagnostic tests to rule out concomitant ocular pathology including visual field testing and a thorough dilated fundus retinal examination are needed prior to attributing symptoms to persistent ND. Unfortunately, medical treatment has not been shown to be useful in treating ND. Initial reports implicated temporal corneal incisions as a causative factor in ND⁶; however, ND has been reported with superior incisions.⁷ Previous publications have implicated posterior chamber depth, pupil size, index of refraction, lens material, and edge design as causative factors in ND.⁴ Vámosi et al concluded that in-the-bag IOL exchange alone did not improve symptoms of ND and posterior chamber depth as examined by ultrasound biomicroscopy (UBM) was not a significant factor in incidence of ND.⁸ However, with sulcus placement of the IOL during exchange, symptoms of ND were improved. Although the etiology of ND is likely multifactorial, we do know that it can occur with any lens material, is persistent despite collapse of the posterior chamber with an “in-the-bag” IOL, and does not typically improve with in-the-bag IOL exchange. This constellation of findings implicates the anterior capsule–IOL interaction as a possible factor in the etiology of ND.^2,4

Surgical methods to address ND include secondary “piggyback” IOL, reverse optic capture (ROC), and/or sulcus placement of a secondary posterior chamber IOL (PCIOL), which have all been devised and proven useful in reducing visual symptoms of ND. Although ND rarely induces visual disability sufficient to require an operative approach, some patients are very disturbed and can be very vocal in their complaints. To our understanding, ND has never been reported with sulcus placed PCIOLs or anterior chamber IOLs (ACIOLs). In our investigation, we found that ND occurs only with “in-the-bag” PCIOLs with overlap of the anterior capsulorrhexis onto the anterior surface of the PCIOL.2 We do not believe that the corneal incision plays a role in persistent ND.⁶

Given the above, and in keeping with our studies, two surgical strategies have emerged as beneficial: ROC and placement of a secondary “piggyback” IOL. Failed surgical strategies include bag-to-bag IOL exchange wherein the original implant is removed and another of different material, shape, or edge design is replaced within the capsule bag. This is in keeping with the work of Vámosi et al.^2,8

One successful surgical method, ROC, may be employed as a secondary surgery for symptomatic patients or as a primary prophylactic strategy. In the case of the latter, the method has been applied to the second eye of patients who were significantly symptomatic following routine uncomplicated surgery in their first eye. It should be noted, however, that ND symptoms are not necessarily bilateral.

Secondary ROC, performed for symptomatic patients, may be applied if the anterior capsulotomy is not too small or too thick or rigid from postoperative fibrosis. At surgery, the anterior capsule is freed from the underlying optic by gentle blunt and viscodissection ( Fig. 12.1). Next, the nasal anterior capsule edge is retracted with one Sinskey hook (or similar device), while the optic edge is elevated and the capsule edge allowed to slip under the optic ( Fig. 12.2). This maneuver is repeated 180 degrees away temporally, leaving the haptics undisturbed in the bag ( Fig. 12.3, Fig. 12.4, Fig. 12.5, Fig. 12.6). Primary or prophylactic ROC is performed at the time of initial cataract surgery for the symptomatic patient’s second eye. It should be recognized that surgical success in achieving primary or secondary ROC is highly dependent on a properly sized and centered anterior capsulorhexis. There seems to be little optical consequence of ROC, as the haptics remain in the bag; theoretically, however, a modest myopic shift would be induced, varying directly with the power of the IOL. There have been no reported cases of iris chafing with ROC; however, we have had cases of iris chafing associated with piggyback PCIOLs.