Zonulopathy (also called zonular dehiscence or rupture) refers to a condition where the supporting function of the zonular fibers (Zinn’s zonule) that support the lens capsule is insufficient. It may or may not be accompanied by lens position abnormalities (subluxation or dislocation).
The Zinn’s zonule has two main functions: (1) a positioning function that pulls the lens capsule equator in 360 degrees to fix the lens at the center of the visual axis, and (2) a shape-maintaining function that maintains the shape of the lens capsule by uniform tension. Depending on the extent and range of zonular rupture, either or both of these functions may be lost. As the rupture range expands, it progresses from partial rupture to subluxation, complete dislocation, and nucleus drop.
If recognized preoperatively during cataract surgery, countermeasures can be taken, but in many cases it is first discovered during surgery. Worsening during surgery can lead to serious complications such as nucleus drop and vitreous prolapse.
The incidence of general zonular rupture is about 1.1% in low-risk cases and increases to about 6.7% in cases with pseudoexfoliation syndrome1). In a 402-eye objective classification study of zonular weakness, greater weakness was associated with more frequent use of capsular stabilization devices during PEA and more frequent IOL scleral suturing 5). Small series using capsule expanders (CE) have reported that capsular support can be assisted and PEA performed in eyes with weak zonules 6,7). Late dislocation of the IOL-capsule complex occurs on average 8.5 years postoperatively, with pseudoexfoliation syndrome being the most common cause 3).
QCan surgery be performed even with zonulopathy?
A
With appropriate preoperative evaluation and preparation, and using auxiliary devices such as capsular tension rings (CTR) or capsule expanders by an experienced surgeon, phacoemulsification (PEA) can be safely performed in many cases of zonulopathy. However, in cases of severe weakness, extracapsular cataract extraction (ECCE), intracapsular cataract extraction (ICCE), or IOLscleral fixation may be required.
Many patients are asymptomatic and are first identified during preoperative evaluation for cataract surgery. When significant subluxation or dislocation is present, the following symptoms occur.
Blurred vision and fluctuating vision: Varies with dilation/constriction of the pupil and movement of the lens within the eye
Monocular diplopia: Due to refractive changes when the lens is displaced
Visual distortion: When the lens edge crosses the visual axis
Evaluation with slit-lamp microscopy is fundamental.
Phacodonesis: Trembling of the lens during eye movement. A typical sign of zonular weakness.
Iridodonesis: Trembling of the iris accompanying lens movement.
Anterior capsule wrinkles: Wrinkles appear toward the equator when the anterior capsule is punctured.
Asymmetry of anterior chamber depth / shallow anterior chamber: Preoperative anterior chamber depth <2.5 mm is a risk indicator, increasing complication risk nearly fivefold.
Lens displacement / exposure of the equator: The lens equator is visible at the pupillary margin.
Pseudoexfoliation material deposition: White fibrillary material deposits on the anterior capsule margin and pupillary margin (pseudoexfoliation syndrome).
Vitreous prolapse into the anterior chamber: Seen in severe cases.
In patients with systemic sclerosis, zonular dehiscence may occur intraoperatively even in the absence of known risk factors. A case has been reported of a 55-year-old man with scleroderma who experienced intraoperative zonular dehiscence and iris prolapse during separate cataract surgeries in both eyes. Preoperative evaluation showed no pseudoexfoliation material, and the preoperative anterior chamber depth in the left eye was slightly shallow at 2.59 mm, later considered suggestive of zonular instability 1).
In spherophakia, due to severe zonular laxity, the IOL-capsule complex may subluxate downward (in the direction of gravity), and postoperative focal iris synechiae (PAS) and iris bombe may occur 2).
Pseudoexfoliation syndrome: The most common cause. Abnormal accumulation of fibrillin-elastin fibers weakens the zonules. Surgical complication rate is 21.5%, and zonular dehiscence is 6.7% 1)
Trauma: Shearing force to the zonules from blunt ocular trauma
Marfan syndrome: Mutation in fibrillin-1 protein of the FBN1 gene. About 60% naturally develop lens dislocation. Zonular strength and elasticity are reduced.
Homocystinuria: Accumulation of abnormal glycoproteins weakens the zonules
Zonular weakness is assessed by the degree of lens wobble at the start of CCC (Taniguchi et al.’s ZW classification):
Grade 0: No lens wobble, no anterior capsule folds (nearly normal).
Grade 1: Slight wobble, folds present.
Grade 2: Wobble present, anterior capsule puncture and tearing possible under BSS or OVD.
Grade 3: Significant wobble, requires puncture with a thin needle under Healon V®.
Grade 4: Lens tremulousness or dislocation.
The Very Weak group (large wobble) in this subjective classification accounts for about 9% of all cases, and the rate of capsular support device use reaches 96.1%.
QIf preoperative tests are normal, is intraoperative safety guaranteed?
A
Not necessarily. Even for experienced surgeons, it is not uncommon for zonular weakness to become apparent only during surgery. In pseudoexfoliation syndrome, sudden rupture may occur intraoperatively even if there is no wobble during CCC. All anterior segment surgeons must be proficient in intraoperative management techniques.
For cases with zonular rupture, considering long-term prognosis, it is most ideal to complete the procedure with IOL scleral suture fixation. Since a technique for suturing a 7.0mm IOL through a small incision is now established, the challenge is how to perform the preceding total lens extraction through a small incision (a corneoscleral incision of about 3.0mm and two corneal ports of about 2.0mm). Use of a CTR requires a completed continuous curvilinear capsulorhexis.
In cases with fragile zonules, countertraction is reduced, making CCC difficult.
Avoid the zonular defect area and adjust the direction of shear force to obtain counterforce from areas with intact zonules.
Insert a second instrument through a side port to create a fixation point in the central lens capsule.
Little capsulorhexis tear-out rescue maneuver (2006): A powerful tool to prevent outward extension of the capsulorhexis. Use sufficient ophthalmic viscosurgical device and gently counteract.
Alternative techniques that minimize manipulation and rotation of the nucleus may be appropriate.
Cross chop (reported by Dooho Brian Kim): After horizontal chop, create an “X” shape by crossing the phaco handpiece for a second chop, allowing division without rotating the lens.
Double chop: A technique that minimizes stress on the zonules.
Tangential stripping, applying force perpendicular to the radial fibers, minimizes stress on the zonules.
Hurricane cortical aspiration (Nakano et al., 2014): Demonstrated reduction of forces generated by tangential cortical stripping in cadaver eye video analysis.
For severe extensive zonular laxity (e.g., age 90+): “Central cortical cleanup” (Mansour et al., 2016)—a new technique that leaves a central clear visual axis while avoiding excessive stress on the periphery.
Modified nylon iris hooks. The looped support end distributes force over a wide area on the capsule, reducing the risk of anterior capsule rupture. Inserted through a limbal or paracentesis incision parallel to the iris. Easy to insert and remove. In cases of partial zonular dialysis due to trauma, placing two hooks at the dialysis site can stabilize the capsular bag.
An open-ring PMMA device, approximately 12–14.5 mm in diameter (compressed about 2 mm within the capsule). Effective for Zinn zonule breaks up to about 150 degrees. Covered by insurance.
Situations to consider changing the surgical plan: If the capsular bag cannot be stably maintained, or if anterior/posterior capsule rupture, irregular CCC, severe subluxation/dislocation, or dropped nucleus occurs, consider switching to ICCE, vitrectomy, IOLscleral fixation, etc.5,7).
Insertion timing: CTR can be inserted at any point during surgery. Early insertion stabilizes the capsule sooner but can make cortical removal more difficult, whereas later insertion may reduce additional zonular stress. The risks and benefits should be judged case by case8,9).
Note that there is no evidence that CTR placement prevents late IOL-capsule complex dislocation 3). However, if early support is needed, a capsular tension segment (CTS) is an alternative option.
Modified CTRs:
Henderson CTR: Has eight scalloped indentations to facilitate removal of residual lens fragments.
Cionni Ring: Used for extensive Zinn zonule defects requiring scleral fixation. It is directly sutured to the sclera through an angled hook with a fixation eyelet (developed by Robert J. Cionni and Robert Osher).
Introduced by Ike Ahmed (2002). Made of PMMA, covers 120 degrees of the zonular damage area, and the anterior fixation eyelet is sutured to the sclera. Its greatest advantage is that it can be inserted before lens removal.
Composed of a T-shaped pad hook with a total length of 12 mm and a tip width of 2 mm, a 5-0 polypropylene thread body, and a silicone fixation part. It has been reported as a device that supports the capsular rim and equator in eyes with weak zonules, and modified CE has also been reported for scleral fixation of the capsule-IOL complex6,7).
Situations to consider changing the surgical plan: If the capsular bag cannot be stably maintained, or if anterior/posterior capsule rupture, irregular CCC, severe subluxation/dislocation, or dropped nucleus occurs, consider switching to ICCE, vitrectomy, IOLscleral fixation, etc.5,7).
Create scleral pockets at two locations 180 degrees apart posterior to the corneal limbus (Brian Hoffman, 2006), and tie the sutures within the pockets. Advantages include no need for conjunctival incision, improved postoperative comfort, and reduced risk of suture exposure.
QIs caution needed after surgery for microspherophakia?
A
In spherophakia, the zonules are severely lax, and the IOL-capsule complex may continue to subluxate downward (in the direction of gravity) postoperatively. In some cases, localized iris bombe, shallow anterior chamber, and angle synechiae may occur, which can be prevented by performing an additional iridotomy during surgery 2). Postoperative follow-up and intraocular pressure management are important.
Approximately 140 fiber bundles constitute the zonular apparatus, with the main component being fibrillin (FBN1 gene product)
Originates from the basement membrane of the nonpigmented ciliary epithelium and inserts into the equatorial region of the lens capsule
Attaches over a wide area: 1.5 mm anterior and 1.25 mm posterior to the equator
Fiber diameter 5–30 μm. Responsible for lens suspension and transmission of accommodative movements
Mechanisms by major disease:
Pseudoexfoliation syndrome: Abnormal turnover of extracellular matrix leads to accumulation of abnormal fibrillin, elastin fibers, laminin, and glycosaminoglycans, which deposit on and weaken the zonules and ciliary body
Marfan syndrome: FBN1 gene mutation causes abnormalities in fibrillin-1 protein, impairing the function of fibrillin that provides strength and elasticity to the zonules
Homocystinuria: Deficiency of homocysteine metabolism enzymes leads to accumulation of abnormal glycoproteins, weakening the zonules
Systemic sclerosis: Overactivation of fibroblasts causes excessive production of collagen and extracellular matrix, which deposits in connective tissue. It is inferred that the attachment points of the zonules to the ciliary body become weakened 1)
Mechanisms of iatrogenic injury during surgery:
Forced rotation of the nucleus, contact of the ultrasound tip with the anterior capsule edge, and centripetal forces during I/A manipulation can cause rupture of remaining zonular fibers
In cases with fragile zonules, phacoemulsification may cause detachment of the Wieger ligament, allowing irrigation fluid to enter Berger’s space, leading to a shallow anterior chamber (infusion misdirection syndrome)
7. Latest Research and Future Prospects (Investigational Reports)
Femtosecond laser-assisted cataract surgery (FLACS) with capsulotomy and nuclear softening has been reported to achieve over 90% success in preserving the lens capsule and enabling in-the-bag IOL implantation. The role of FLACS in cases with zonular weakness, where standard intraoperative techniques carry high risk, will be studied further.
For extremely elderly patients aged 90 years or older with severe zonular laxity, a technique using bimanual manipulation to lift central cortical fibers and aspirate toward the periphery has been introduced. This approach is noted for ensuring a clear visual axis while avoiding excessive zonular stress on the periphery.
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Gupta S, Mahalingam K, Ramesh P, Gupta V. Need of additional iridotomies despite lens extraction in spherophakes. BMJ case reports. 2021;14(4). doi:10.1136/bcr-2021-242838. PMID:33875515; PMCID:PMC8057550.
American Academy of Ophthalmology Cataract and Anterior Segment PPP Panel. Cataract in the Adult Eye Preferred Practice Pattern. American Academy of Ophthalmology. 2021.
Yaguchi S, Yaguchi S, Yagi-Yaguchi Y, Kozawa T, Bissen-Miyajima H. Objective classification of zonular weakness based on lens movement at the start of capsulorhexis. PLoS One. 2017;12(4):e0176169. doi:10.1371/journal.pone.0176169. PMID:28426745; PMCID:PMC5398681.
Nishimura E, Yaguchi S, Nishihara H, Ayaki M, Kozawa T. Capsular stabilization device to preserve lens capsule integrity during phacoemulsification with a weak zonule. J Cataract Refract Surg. 2006;32(3):392-395. doi:10.1016/j.jcrs.2005.12.097. PMID:16631045.
Asano Y, Yaguchi S, Nishimura E, Soda M, Kozawa T. Modified capsule expander implantation to reposition and fixate the capsular bag in eyes with subluxated cataractous lenses and phacodonesis: intermediate-term results. J Cataract Refract Surg. 2015;41(3):598-606. doi:10.1016/j.jcrs.2014.06.031. PMID:25708209.
Menapace R, Findl O, Georgopoulos M, Rainer G, Vass C, Schmetterer K. The capsular tension ring: designs, applications, and techniques. J Cataract Refract Surg. 2000;26(6):898-912. doi:10.1016/s0886-3350(00)00446-6. PMID:10889438.
Ozturk E, Gunduz A. Optimal timing of capsular tension ring implantation in pseudoexfoliation syndrome. Arq Bras Oftalmol. 2021;84(2):158-162. doi:10.5935/0004-2749.20210024. PMID:33567013; PMCID:PMC12289253.
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