Zonular instability is a known cause of increased complications during cataract surgery with a risk for vitreous prolapse, capsule rupture, retained lens, and intraocular lens (IOL) dislocation. Novel surgical techniques and devices, when used appropriately, enable surgeons to plan for successful small-incision phacoemulsification with endocapsular posterior chamber IOL (PC IOL) fixation in these cases.1 Preoperative and intraoperative recognition of zonular weakness is essential, requiring appropriate modifications in technique and the use of capsular tension devices. We report a new sign of intraoperative anterior zonular dehiscence.
A 95-year-old woman was referred with decreased vision in both eyes. The ocular history was positive for pseudoexfoliation glaucoma (PXG) managed with topical medications. The corrected distance visual acuity was 20/80+1 in the right eye and 20/200−1 in the left eye. Biomicroscopy revealed appositional narrow angles with high lens rise and no peripheral anterior synechiae. Pseudoexfoliative deposits, brunescent nuclear sclerotic cataracts, and phacodonesis were noted in both eyes. Both corneas were clear with trace endothelial guttata. Ophthalmoscopy revealed a normal macula in the right eye with a glaucomatous optic nerve and a cup-to-disc ratio of 0.7. There was no view of the posterior pole in the left eye, and B-scan ultrasound was normal. Ancillary test results included mean keratometry of 44.25 diopters (D) and 45.00 D in the right eye and left eye respectively; axial lengths of 23.88 mm and 23.74 mm, respectively; anterior chamber depths of 2.51 mm and 2.61 mm, respectively; and lens thicknesses of 5.47 mm and 5.26 mm, respectively.
Small-incision coaxial phacoemulsification in the left eye was performed with a near-clear incision. A continuous curvilinear capsulorhexis was completed, followed by successful hydrodissection. A suggestion of zonular instability occurred during the first crack of the nucleus using a modified stop-and-chop technique: During lateral separation, a localized anterior capsular dehiscence occurred with a visible snapping of the anterior capsule over the capsulorhexis edge (Figures 1 and 2) (Videos 1 and 2, available at http://jcrsjournal.org).
The surgeon (I.I.K.A.) recognized this event as a potential sign of zonular instability and carefully inspected the area. The eye was filled with an ophthalmic viscosurgical device (OVD), preventing anterior chamber collapse, and 5 iris hooks were placed to support the capsule, hooking the capsulorhexis margin. Lens removal was uneventful, followed by gentle cortical aspiration. A capsular tension ring (CTR) was inserted, followed by implantation of an acrylic foldable single-piece IOL in the capsular bag. Care was taken to maintain the anterior chamber with balanced salt solution during manual removal of the OVD. The PC IOL was well centered at the end of the case.
At the first postoperative week, the uncorrected distance visual acuity (UDVA) improved to 20/40−2 and the PC IOL was centered in the capsular bag. The intraocular pressure was 12 mm Hg.
The recognition of zonular instability both preoperatively and intraoperatively is essential to successful cataract extraction and PC IOL insertion. In this case, zonular weakness was diagnosed preoperatively by the presence of phacodonesis. Other preoperative signs of zonular weakness or dialysis include iridodonesis, visibility of the lens equator, decentration of the nucleus, and vitreous prolapse in the anterior chamber.
Zonular weakness should also be considered in the presence of several predisposing conditions such as trauma,2 high myopia, vitreoretinal surgery, connective tissue disorders,3 retinitis pigmentosa,4 and pseudoexfoliation.5 Our patient had a history of PXG.
To our knowledge, this is the first report of intraoperative anterior zonular dehiscence. The mechanism likely relates to the zonulopathy known to occur in patients with PXG. Zonular fibers are anterior, equatorial, and posterior (Figure 3). Localized anterior zonular dehiscence may occur from disproportionate stress to the anterior zonular fibers during cataract surgery. The dehiscence occurred before removal of the dense nuclear fragments, and the nucleus may provide support for the equatorial and posterior zonular fibers, preventing a localized dialysis. The concept that cataract surgery may preferentially stress anterior capsule zonular fibers is novel.
Several modalities can be used in cases of zonular instability including high-viscosity OVDs, flexible iris retractors to hook the area of capsule instability, CTRs, modified CTRs, and capsular tension segments for suture scleral fixation. An OVD, iris retractors, and a CTR were used in this case. A CTR was chosen due to the presence of mild zonular weakness (<4 clock hours) and the underlying progressive zonulopathy (PXG). A CTR prevents marked capsular bag shrinkage. This theoretically leads to the prevention of decentration and tilt of the PC IOL in the long term by avoiding asymmetric capsule contraction.6
An intraoperative anterior capsular snap sign (Figure 1) should alert the surgeon to the presence of an anterior capsule dehiscence with zonular instability. Recognition with appropriate modification of surgical technique and use of ancillary devices will increase the likelihood of successful small-incision phacoemulsification with endocapsular PC IOL fixation.
1. Hasanee K, Ahmed IIK. Capsular tension rings: update on endocapsular support devices. Ophthalmol Clin North Am. 2006;19(4):507-519.
2. Méndez Marín I, Traspas Tejero R, Fernández Dominguez M, Mencía Gutiérrez E. Ocular injuries in mid-face fractures. Orbit
3. Groessl SA, Anderson CJ. Capsular tension ring in a patient with Weill-Marchesani syndrome. J Cataract Refract Surg
4. Hayashi K, Hayashi H, Matsuo K, Nakao F, Hayashi F. Anterior capsule contraction and intraocular lens dislocation after implant surgery in eyes with retinitis pigmentosa. Ophthalmology
5. Naumann GOH, Schlötzer-Schrehardt U, Küchle M. Pseudoexfoliation syndrome for the comprehensive ophthalmologist; intraocular and systemic manifestations. Ophthalmology
6. Lee D-H, Shin S-C, Joo C-K. Effect of a capsular tension ring on intraocular lens decentration and tilting after cataract surgery. J Cataract Refract Surg
Video 1 Initial splitting of the nucleus into 2 fragments results in localized nasal zonular dehiscence and a loss of anterior capsule support. Central bowing of the capsule edge is seen at 14 seconds.
Video 2 Slow-motion replay of the localized zonular dehiscence with central bowing of the capsule edge over the capsulorhexis margin.