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Dysphotopsias require separate management strategies
Reverse optic capture or placement of a piggyback IOL is ideal for negative dysphotopsia, while first-line treatment for positive dysphotopsia is miotic therapy.
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Negative dysphotopsia, or ND, represents an undesired optical phenomenon after cataract surgery. It is classically described as a dark temporal shadow. Conversely, positive dysphotopsia, or PD, is characterized by light streaks, star bursts or glare. Both symptoms interfere significantly with quality of vision and perceived success of surgery.
My special guests in this column are Samuel Masket, MD, and Nicole R. Fram, MD. Masket gave the Charles D. Kelman Lecture at the 2013 American Academy of Ophthalmology meeting.
Amar Agarwal, MS, FRCS, FRCOphth
OSN Complications Consult Editor
Dysphotopsias can result in unrelenting patient dissatisfaction after an 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.
Negative dysphotopsia
Davison originally described ND in 2000 as complaints of a dark temporal shadow, similar to “horse blinders.” What is most frustrating to the surgeon and patient alike is that ND is mainly reported in cases in which the posterior chamber IOL, of any design, is well centered within the confines of the capsular bag.
Surgical methods to address ND, including a secondary “piggyback” IOL, reverse optic capture and/or sulcus placement of a secondary posterior chamber IOL, have been devised and proven useful in reducing visual symptoms. Although ND rarely induces visual disability sufficient to require an operative approach, some patients are disturbed and can be vocal in their complaints. To our understanding, ND has never been reported with sulcus-placed posterior chamber IOLs or anterior chamber IOLs. In our investigation, we found that ND occurs only with in-the-bag posterior chamber IOLs with overlap of the anterior capsulorrhexis onto the anterior surface of the IOL. We do not believe that the corneal incision plays a role in persistent ND.
Given the above, and in keeping with our studies, two surgical strategies have emerged as beneficial: reverse optic capture and placement of a secondary piggyback IOL. Failed surgical strategies include within-the-bag IOL exchange wherein the original implant is removed and another of different material, shape or edge design is replaced within the capsule bag.
Reverse optic capture may be employed in a secondary surgery for symptomatic patients or as a primary prophylactic strategy. In cases of the latter, the method has been applied to the second eye of patients who were significantly symptomatic after routine uncomplicated surgery in their first eye. It should be noted, however, that ND symptoms are not necessarily bilateral.
Secondary reverse optic capture, 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 viscodissection (Figure 1). Next, the nasal anterior capsule edge is retracted with one Sinskey hook, or a similar device, while the optic edge is elevated and the capsule edge allowed to slip under the optic (Figure 2). This maneuver is repeated 180° away temporally, leaving the haptics undisturbed in the bag (Figures 3 to 5). Primary or prophylactic reverse optic capture 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 reverse optic capture is highly dependent on a properly sized and centered anterior capsulorrhexis. There seems to be little optical consequence of reverse optic capture because the haptics remain in the bag; theoretically, however, a modest myopic shift would be induced, varying directly with the power of the IOL.
Figure 1. A Sinskey hook is fed underneath the anterior capsule after viscodissection in an attempt to free the optic from the capsule.
Figure 2. The Sinskey hook and blunt spatula are used to elevate the optic edge over the capsule.
Images: Reprinted with permission from SLACK Incorporated.
Figure 3.Once the nasal edge has been captured (see arrow), the opposite temporal edge of the optic is elevated over the anterior capsule edge.
Figure 4. Optic capture has been completed. The nasal and temporal edges of the implant are anterior to the anterior capsule (note arrows), whereas the haptics remain fully within the capsular bag.
Figure 5. Ultrasound biomicroscopy demonstrating reverse optic capture with the optic edge anterior to the capsular edge.
The other surgical method that has proven successful for patients with symptomatic ND is a piggyback IOL. In this method, a second IOL is implanted in the ciliary sulcus atop the IOL-capsular bag complex. It appears that covering the primary optic/capsule junction reduces ND symptoms, although the original concept was that a piggyback lens was effective because it collapsed the posterior chamber by reducing the distance between the posterior iris and the anterior surface of the IOL. We prefer use of a three-piece silicone IOL. Regarding ametropia, for hyperopic errors, multiply the spectacle error by 1.5 to determine IOL power, while for myopic errors, multiply by 1.2. So, as an example, in the case of a 2 D hyperope, implant a +3 D IOL in the ciliary sulcus.
Positive dysphotopsia
PD is reported by patients as light streaks, halos and star bursts. It may be induced by internal reflections from either the optic edge or optic surfaces. Therefore, PD appears to be related directly to IOL material, optic size index of refraction, radius of curvature, surface reflectivity and edge design. Typically, PD is associated with thick square-edge design, high index of refraction, low radius of curvature and high surface reflectivity. Unlike ND, patients may perceive benefit from use of miotic agents, particularly under dim-light conditions. Medical management of PD includes brimonidine tartrate 0.15%; also useful is a dilute solution of pilocarpine, typically 0.5%. While topical miotics may be helpful, they are associated with the potential for allergies and side effects.
Should miotic therapy prove unsuccessful and the symptoms mandate further treatment, IOL exchange may be highly successful. In this situation, opt for a lens with a low index of refraction, a large optic diameter and a thin round-edge design.