25 The Rise of the Femto-Intraocular Lens
Negative Dysphotopsia (ND) is an enigmatic and annoying postoperative complication that occurs only in what is considered to be “perfect” contemporary cataract surgery with an IOL in the capsule bag overlapped by a continuous curvilinear anterior capsulotomy. ND is improved, relieved, or prevented when the optic overlies the anterior capsule; this arrangement may have some downsides with current IOL design and surgical methods. However, a newly designed IOL fixates the anterior capsule in a groove in the optic. The Morcher 90S (Masket) IOL accomplishes this goal while bringing other advantages: Capsulotomy fixation improves optic centration, reduces optic tilt, enables better prediction of effective lens position (ELP), and reduce higher order optical aberrations with multifocal IOLs. No cases of ND have been observed with capsulotomy supported IOLs.
Keywords: Negative dysphotopsia (ND), reverse optic capture (ROC), capsulotomy fixated IOL
Negative dysphotopsia (ND) represents an undesired optical consequence of contemporary cataract surgery. 1 Typically, patients complain of a temporal dark crescent that may simulate wearing “horse blinders.” However, temporal light flickering may accompany the blind spot, suggesting a concurrent element of positive dysphotopsia (PD). Although patients complain of a temporal blocking of their vision, automated perimetry most often proves normal in these cases. 2 Although the true incidence of the condition has not been widely studied, evidence from Osher suggests that the condition may affect 12 to 15% of cases early after surgery, with chronic incidence of roughly 3% at 1 year. 3 Given approximately 3 million cataract surgeries are performed annually in the United States, the condition may impact nearly 100,000 cases annually. Dysphotopsia represents the single greatest source of patient complaints following uncomplicated cataract surgery. 4 Although the etiology of ND is debated, certain features are consistent: it is associated only with what is considered to be anatomically “perfect” or “near-perfect” surgery (▶ Fig. 25.1), it is associated with any “in-the-bag” posterior chamber intraocular lens (IOL), symptoms improve with pupil dilation and may worsen with pupil constriction, and it is not associated with sulcus placed or anterior chamber IOLs. Moreover, other than ND occurring in one eye, there are no meaningful identifying factors that might indicate those patients would be at risk for the condition.
Fig. 25.1 A 360-degree overlap of anterior capsule atop an “in-the-bag” intraocular lens appears to be the final common pathway for negative dysphotopsia.
Fortunately, the majority of affected patients note improvement with time, suggesting neuroadaptation. However, when patients experience the symptoms beyond 6 months, spontaneous resolution is unlikely, and nonsurgical strategies have proven to be of no value. Alternatively, eyeglass frames with thick temple pieces may bring symptomatic relief given they block temporal light rays that appear to be the stimulus for ND. Otherwise patients may benefit from surgery. As previously reported, beneficial surgical strategies include elevation of the optic edge anterior to the anterior capsulotomy (referred to as “reverse or anterior optic capture;” ▶ Fig. 25.2), exchange of a bag fixation for sulcus placement of the IOL, or piggyback lens implantation. 2, 5, 6, 7 As has been noted, in-the-bag exchange for an IOL of varied material and design has not proven to be universally beneficial. 2, 5 Although ciliary sulcus placement appears to preclude ND, there are disadvantages of this strategy with respect to iris chafing syndrome IOL decentration, capsule bag contraction, and fibrotic posterior capsule opacification. 2 In our clinical practice, we have applied surgical management of ND to 47 cases. ▶ Table 25.1 indicates the degree of success for varied surgical strategies (▶ Fig. 25.3). With regard to reverse optic capture, it may be considered as either therapeutic for established cases or preventative for second eyes of symptomatic patients or for patients in general. As can be noted, reverse optic capture proved successful in 27 of 29 cases. However, primary reverse optic capture may also be associated with rapid-onset fibrotic posterior capsule opacification (PCO; ▶ Fig. 25.4). One strategy with some degree of success that we have not attempted is laser relaxation of the nasal anterior capsulotomy. 8, 9
Fig. 25.2 Ultrasound biomicroscopic (UBM) view of a single-piece acrylic posterior chamber lens with the optic prolapsed anterior to the capsulotomy and the haptics remaining in the capsule bag after secondary reverse optic capture (ROC).
Fig. 25.3 Success of various surgical strategies against negative dysphotopsia (ND), noted in tabular form.
Fig. 25.4 Fibrotic posterior capsule opacification noted shortly after cataract surgery with primary reverse optic capture.