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    Surgical manual · Zonular weakness

    Capsular Tension Rings: An Evidence-Based Manual for Zonular Weakness in Cataract Surgery

    When to implant a ring, which device and which size, at what moment and with which technique. A practical guide built on what the literature shows, with the numbers checked against their sources.

    By Bruno Miolo, MD, M.Sc

    Cataract Surgeon

     · 22 min read

    In brief

    1. A standard capsular tension ring holds the capsular bag open and spreads zonular stress around the equator. It is not attached to the eye wall, and its effect on the progression of zonular disease is unknown.
    2. Two questions decide the device: how much of the circumference has lost support, and whether the cause is static or progressive. Up to about one third of the circumference, a standard ring alone kept the lens centred in most series; beyond that, or in progressive disease, sutured segments and modified rings anchor the bag to the sclera.
    3. The labelling sizes the ring by axial length; white-to-white predicted lens diameter poorly in a cadaver study, although other sources use it together with axial length. The bag measures about 10.4 to 10.5 mm during surgery and the first days, and shrinks afterwards, and the largest ring is labelled only for eyes longer than 28 mm, with a safety suture.
    4. Insert the ring late when the bag allows it and early when it must: with the lens still in the bag, a ring displaced the bag by up to 4 mm in cadaver eyes, while in pseudoexfoliation, in a randomised trial, no eye with a ring placed before phacoemulsification had zonular separation, against 12.8% of controls.
    5. In comparative studies the effects are small: less rotation in two meta-analyses but not in a third, about one degree less tilt that one analysis confines to high myopia, a hyperopic shift near 0.2 D, more tilt with an 11 mm plate-haptic lens in a randomised trial, and no 10-year benefit in uncomplicated pseudoexfoliation.

    1. What the Ring Does, and What It Does Not Do

    A capsular tension ring is an open loop of polymethyl methacrylate (PMMA) with an eyelet at each end, placed in the equatorial fornix of the capsular bag. Prototypes tested in cadaver eyes adjusted to bags of different sizes and kept the equator round despite some shrinkage.1 The first rings appeared in the early 1990s, and by 1995 they were being used to stabilise bags with extensive traumatic or congenital zonular dialysis.2,3

    The mechanism is simple. The ring presses outward on the whole equator, so a sector with weak or absent zonules is held by tension carried around the circle to the intact ones. During surgery this keeps the capsular diaphragm extended; after surgery it keeps the equator round and prevents oval distortion of the bag.4,5

    What the ring cannot do matters as much. It is not attached to anything outside the bag, so where too few zonules remain the bag can decentre despite it. The US labelling of the Morcher rings states that the effect of the ring on the progression of zonular instability over time is unknown,6 and in a series of 45 late in-the-bag dislocations a ring was already present in eight and had not prevented the event.7 The ring also needs an intact capsule: the same labelling lists perforated or damaged capsules as a contraindication.6

    Table 1. The capsular bag in numbers.
    MeasurementValueSource
    Bag diameter in vivo, first postoperative days, eyes with a ring (70 eyes)10.37 ± 0.25 mmVass 19998
    Bag diameter during surgery, measuring ring (58 eyes)10.53 mmTehrani 20039
    Same bags at 6 months9.01 mm (shrinkage 14.8%)Tehrani 20039
    Median shrinkage at 3 months, randomised (92 eyes): measuring ring alone, plus tension ring, plus bending ring0.38, 0.23 and 0.15 mmKurz 200510
    Crystalline lens diameter, cadaver eyes9.28 mm horizontal, 9.30 mm verticalKhng 200811
    Ciliary sulcus diameter, cadaver eyes (19 eyes)11.0 ± 0.37 mmDavis 199112

    Measurements from different methods and populations. The bag keeps shrinking for months after surgery, more without a ring.

    White-to-white is a poor guide to the bag. In cadaver eyes the correlation between corneal and lens diameter was weak, and absent for the horizontal dimensions, so the lens could not be predicted from a caliper measurement of the cornea.11 Another anatomical study found stronger correlations (0.71 between corneal and lens diameter in cadaver eyes; 0.79 between corneal diameter and axial length in living eyes) and proposed axial length and corneal diameter as clues to the size of the bag.13 A regression for the pseudophakic bag diameter uses corneal power (P, in dioptres) and axial length (AL, in mm) and explains 31% of its variance:8

    CBDp = 3.44 − 0.056 · P + 0.713 · AL − 0.0135 · AL²

    In the derivation sample it classified all six large bags (above 10.7 mm) and 10 of 13 small bags (below 10.1 mm) correctly. It flags extremes; it does not choose a ring to the tenth of a millimetre.

    aRing in a bag with a zonular dialysisZonular dialysisIntact zonulesCapsulorhexisRing, open, with eyeletsbOpen and compressed diameterBag in vivo: about 10.4 mmRing at rest: 12.3 mm openIn the bag the ring closes: compressible to 10.0 mm
    Figure 1. What the ring does and how it fits the bag. (a) The open PMMA ring sits in the equatorial fornix and pushes the whole equator outward; where zonules are missing (dialysis, dashed), the bag is held by the tension carried to the intact zonules. It is not attached to anything outside the bag. (b) The 12.3 mm ring at rest closes as it enters a bag of about 10.4 mm; the labelling describes it as compressible to 10.0 mm. Schematic, not to scale except in (b), where 1 mm equals 17 units; the size of the gaps is approximate.

    2. The Devices

    Three families solve different problems. The standard ring supports the bag from inside. Sutured devices add a fixation point outside the bag: the modified ring of Cionni and Osher carries a fixation element that reaches the sclera without violating the bag,14 and the capsular tension segment, known as the Ahmed segment, is a partial ring with an eyelet for a scleral suture, placed over the dialysis.5,15,16 Temporary devices, capsular hooks and retractors, hold the capsulorhexis edge during surgery.17,18

    Table 2. Capsular support devices.
    DeviceWhat it addsEvidence base
    Standard ringCircumferential support and a round equator; no fixation outside the bagA randomised trial in pseudoexfoliation, a multicentre device study and case series19,20
    Modified ring (Cionni)Fixation element for a scleral suture, outside the bagCase series, including 90 eyes with congenital subluxation14,21
    Capsular tension segment (Ahmed)Partial ring with an eyelet, sutured to the sclera over the dialysisCase series22,23
    Two-eyelet segment (Ambati)Two close eyelets spread the tension and avoid peaking of the capsulorhexis; two segments could give four pointsFour cases24
    Capsular anchorProngs hold the anterior capsule and a central rod is sutured to the sclera; also used for subluxated in-the-bag lensesSix and ten eyes25,26
    Capsular hooks and retractorsTemporary support of the capsulorhexis edgeReviews17,18
    Ring with indentations (Henderson)Eight 0.15 mm indentations to ease removal of lens materialDevice description27
    Designs under studySinusoidal indentations against toric lens rotation; adhesion-preventing ring against opacification; equator and bending rings against bag shrinkageCadaver eyes, rabbits and randomised measurements of the bag28,29,30,10

    The devices appeared in the order of the problems they solved: rings that could not centre bags with profound dialysis led to rings designed for scleral fixation,14 and broken fixation sutures led to the recommendation of 9-0 sutures;21 Gore-Tex and sutureless flanged techniques came later (Section 8).

    3. Recognising Zonular Weakness

    The best moment to discover weak zonules is before the first incision, because the plan, the devices on the table and the consent all depend on it. Rings are needed in a minority of eyes: in 4,316 consecutive phacoemulsifications at one teaching hospital, about 1% received one (41 eyes).31

    3.1 Who is at risk

    • Pseudoexfoliation. Weak zonules, poor dilation and capsular fibrosis that keeps loosening the zonules after surgery.32
    • Trauma. Often a focal dialysis; vitreous was in the anterior chamber in 41% of one series of traumatic subluxations.33
    • Congenital ectopia lentis. Marfan syndrome, Weill-Marchesani syndrome and idiopathic ectopia lentis,21 and microspherophakia.15
    • The indications of one consecutive series. Weakness with mature cataract (29%), trauma (24%), pseudoexfoliation (20%), retinitis pigmentosa (15%), degenerative myopia (10%) and lens coloboma (2%).31
    • Previous vitrectomy. Listed among the causes of secondary zonular weakness in the US labelling.6
    • Primary angle-closure disease. Zonulopathy in 7.3% of 806 eyes without other risk factors, against 0.46% to 2.6% reported for the general population.34
    • Very advanced age. Reported with pseudoexfoliation and dense nuclei in patients older than 90.35,36

    3.2 At the slit lamp

    Look for phacodonesis, lens decentration and vitreous in the anterior chamber, the findings used to describe subluxated lenses in the congenital and traumatic series.21,33 A shallow or asymmetric anterior chamber is a quieter sign. The US labelling warns that pseudoexfoliation with a shallow chamber carries a greater likelihood of zonular instability at surgery,6 and comparing the measured difference in chamber depth between the two eyes with the difference expected from their lens thickness and axial length detected weak zonules better than chamber depth alone (area under the curve 0.743 against 0.631).37 When the lens is visibly displaced, ultrasound biomicroscopy maps where the zonules are missing; in one traumatic case it showed no fibres from 6 to 12 o'clock.38

    3.3 During surgery

    Inside the eye the signs are mechanical. A floppy capsular bag, visible zonular laxity and frank dehiscence were the intraoperative findings in a large angle-closure cohort.34 A localised snap of the anterior capsule over the capsulorhexis edge during the separation of the nuclear halves has been described as a sign of anterior zonular dehiscence.36 Fluctuation of the posterior capsule is a hazard of delaying the ring: in a series of eyes with pseudoexfoliation it occurred in 8 of 27 patients with late insertion and led to posterior capsule rupture in two.39

    3.4 How to grade it

    Record two things. The first is extent, in clock hours or degrees; one clock hour is 30 degrees. The second is course: a static condition, such as an old injury, or one that keeps loosening the zonules, as in pseudoexfoliation.32 A review of subluxated lenses names the extent, the location and the static or progressive nature of the weakness as the key considerations for planning.18

    aExtent: clock hours and degrees123694 clock hours120 degrees1 clock hour = 30 degrees4 clock hours: about one thirdbDevice by extent and courseUP TO ABOUT ONE THIRDMORE THAN ONE THIRDSTATICe.g. old injuryPROGRESSIVEe.g. pseudoexfoliationStandard ringSutured segmentwith a standard ring,or a modified ringStandard ringconsider sutured fixationSutured devicetwo fixation pointsfor very large lossesTorn capsule: no standard ringtotal zonular loss: fixation without the bagPseudoexfoliation without signs of weaknessno routine ring (no difference at 10 years)
    Figure 2. Extent and course decide the device. (a) The extent of the loss is recorded in clock hours; 4 hours are 120 degrees, about one third of the circumference, the limit of the multicentre study of the standard ring (dialysis below 34% of the circumference). (b) A reading of the literature cited in Sections 4 and 10. No randomised trial compares the devices: the cells show where each one has worked, not cut-offs validated by a trial.

    4. Standard Ring or Sutured Device

    No randomised trial compares the device families with each other, so the decision rests on case series, device studies and the labelling. Read the ranges below as the territory in which each device has been shown to work, not as cut-offs validated by a trial.

    4.1 Where a standard ring is enough

    A standard ring alone has its strongest record in diffuse weakness and in dialysis up to about one third of the circumference. The US multicentre device study enrolled eyes with less than 34% of the circumference affected and placed 255 rings: 98.8% of lenses were centred immediately after surgery and 97.7% at 12 months.20 Smaller series extended the range to about 150 degrees: success in 90% of 21 eyes, with extension of the dialysis during surgery in two;40 no decentration over a mean of 26 months in 17 traumatic eyes with 80 to 160 degrees, except one lens dislocated by a later injury;41 and centred lenses at one year in 36 eyes with less than 150 degrees when the ring went in after the lens was removed.42

    In pseudoexfoliation, a randomised trial with intraoperative outcomes placed the ring after capsulorhexis and hydrodissection in 39 of 78 eyes. No eye with a ring had zonular separation during surgery, against five of 39 controls (12.8%), and the lens was fixated in the bag in 94.9% against 74.3%.19 The ring is not a universal requirement in these eyes, however. In the Aravind Pseudoexfoliation Study, eyes with pseudoexfoliation but without phacodonesis, shallow chambers or small pupils were randomised to receive a ring or not; at 10 years, decentration was similar in eyes with and without pseudoexfoliation (2.4% against 1.7%), and the authors found no difference by lens type or by the use of a ring.43

    4.2 When to anchor the bag

    Beyond about one third the evidence for a ring alone thins, with series reaching about 150 to 160 degrees,40,41,42 and techniques fixing a segment or a modified ring to the sclera are described for dialysis larger than 120 degrees,44 and in a two-centre series of 21 eyes with a mean dialysis of 142 degrees (range 60 to 210), sutured segments kept the bag centred, with 85.7% of eyes at 20/40 or better; two eyes needed two segments.23 Even with at least six clock hours of traumatic zonulysis, fixated devices preserved the bag in 38 of 41 eyes; it was lost only in the three eyes with total zonulysis.45

    The course of the disease can change the choice even when the dialysis is small. Cionni and Osher designed the modified ring for eyes with extreme loss of zonular support or a significant risk of progressive weakness,14 and in a series of rings that decentred and needed repositioning, seven of 11 eyes had pseudoexfoliation; the authors concluded that decentration is a risk in severe or progressive zonulopathy.46

    Table 3. Which device, by situation.
    SituationDeviceBasis
    Diffuse weakness or dialysis up to about one third, static causeStandard ringDevice study and series20,40,41
    Pseudoexfoliation (unselected eyes in the trial)Standard ring before phacoemulsification reduced zonular separationRandomised trial19
    Pseudoexfoliation without phacodonesis, shallow chamber or small pupilNo routine ringRandomised data, 10 years43
    Dialysis beyond about one third, or progressive diseaseSutured segment with a standard ring, or a modified ringSeries14,44,23,22
    Very large lossesTwo fixation points: two segments or a two-eyelet segmentSeries and cases23,24
    Subluxated bag, with the crystalline lens or an IOLCapsular anchorSmall series25,26
    Torn or perforated capsule; total zonular lossNo standard ring; with total loss, fixation without the bag (Section 12)Series and labelling45,6

    No randomised trial compares these options; each row cites the studies in which the choice worked.

    4.3 Contraindication

    The labelling lists two contraindications: a perforated or damaged capsule, and eyes still growing, in children aged 12 or younger.6 Inspect the capsulorhexis and the posterior capsule before the ring goes in.

    5. Choosing the Size

    A ring has two diameters: the open diameter at rest and the diameter to which it can be compressed. Inside the bag it takes the diameter of the equator, about 10.4 to 10.5 mm in vivo (Table 1).8,9,10 The US labelling of the Morcher rings selects the size by axial length (Table 4).6 The largest ring has a thicker cross-section, a rigid design that may help counteract the strong shrinkage of very myopic bags, and for these eyes the labelling recommends a safety suture: after four fifths of the ring are in the bag, a 10-0 nylon suture is threaded through the remaining eyelet so that its end can be controlled with a hook.6

    Table 4. Standard ring sizes in the US labelling and in the US device study.
    RingOpenCompressible toAxial lengthSource
    Morcher type 1412.3 mm10.0 mm< 24 to 28 mmLabelling6
    Morcher type 14C13.0 mm11.0 mm24 to 28 mmLabelling6
    Morcher type 14A (thicker section; safety suture)14.5 mm12.0 mm> 28 mmLabelling6
    Ophtec 275 and 27612 and 13 mmnot reportedweak or partially broken zonulesDevice study20

    Axial length ranges as printed in the 2003 labelling; those of the 12.3 mm and 13.0 mm rings overlap between 24 and 28 mm. Compressed diameters of the Ophtec rings are not given in the study abstract. Check the current labelling of the ring you use: models and ranges change.

    White-to-white alone is a weak guide (Section 1), although some sources use it with axial length.13 Axial length and corneal power predict the bag only weakly, and the Vass regression is better used to flag a very large or very small bag than to select a size.8,11 In long eyes, a randomised comparison of 89 eyes with axial length of 27 mm or more, with a 13 mm ring or without, found that refraction with the ring tended to be stable at one week, against one month without it.47

    6. When to Insert the Ring

    Timing is a trade-off between support and stress. In four cadaver eyes filmed from behind with the Miyake-Apple technique, a 12.3 mm ring inserted after capsulorhexis and hydrodissection, with the lens still in the bag, produced capsular torque, zonular elongation and displacement of the bag of up to 4.0 mm, significantly more than insertion into the empty bag (two eyes in each arm). The authors concluded that the ideal moment, to minimise further zonular stress, is after lens extraction, when the bag is decompressed.48

    Clinical data support both sides. Inserted after emulsification and cortex removal in 36 eyes with dialysis under 150 degrees, the ring caused no extension of the dialysis and the lenses were centred at one year.42 Inserted before emulsification in the pseudoexfoliation trial, it left no eye with zonular separation during phacoemulsification.19 A prospective comparison in pseudoexfoliation measured the price of each choice: early rings made cortex removal harder, while in the late group the posterior capsule fluctuated in eight eyes and ruptured in two.39

    In practice the question is whether the bag can tolerate phacoemulsification without support. If it can, insert the ring after the cortex is out. If it cannot, insert the ring early and accept a harder cortex removal, or use capsular retractors that also support the equator and delay the ring until after the cortex; iris hooks on the capsulorhexis edge alone give little equatorial support.39,49,50

    Table 5. When to insert the ring, by scenario.
    ScenarioMomentBasis
    Weak zonules, bag stable during phacoemulsificationAfter cortex removal, before the lensCadaver study and series48,42
    Pseudoexfoliation, ring wanted during phacoemulsificationAfter hydrodissection, before phacoemulsification; expect a harder cortex removalRandomised trial and comparative series19,39
    Focal dialysis recognised before phacoemulsificationCapsular retractors holding the equator during phacoemulsification, then the ring after the cortex; or the ring as soon as the capsulorhexis is completeReviews and technique report49,50

    7. How to Insert It

    7.1 Prepare the bag

    Fill the bag with an ophthalmic viscosurgical device first. The labelling recommends it to keep the anterior and posterior capsules apart so that the ring slides,6 and adequate fill reduces the risk that the capsule becomes entangled with the leading eyelet.51 Plan where the ring will first touch the bag relative to the dialysis, because the angle and the point of initial contact can damage zonules.51

    Make a good-sized, centred continuous capsulorhexis: hooks, retractors and tension devices all depend on it.18 In subluxated lenses, starting the capsulorhexis away from the dialysis lets the intact zonules provide counter-traction.49,52

    7.2 Four ways to deliver the ring

    • Forceps or injector. The ring can be dialled in with smooth forceps, with a hook in the trailing eyelet for the final placement, or delivered with an injector.6
    • Fish-tail. The ring is folded until the trailing loops overlap, the apex is inserted into the bag and the arms are placed without dialling, which minimises tangential and shearing forces on the capsule.53 A suture line on the leading eyelet forms the fish without over-bending the ring.54
    • Suture-guided. A suture through the leading eyelet lets the surgeon steer the ring centrally with gentle traction and retrieve it if the bag ruptures.51,50 A loop added to the suture also helps to remove residual cortex.55
    • Anchored injector. An injector with a metal element holding the trailing eyelet was used in 50 eyes with lax zonules without intraoperative incidents.56

    7.3 Two warnings

    Watch the shape of the ring as it leaves the injector. In Miyake-Apple recordings of nine cadaver eyes with a surgically created four clock-hour dialysis, an S-shaped curve in the surgeon's view coincided with obstruction of the leading eyelet and stress on the zonules: S means stop.57 Then release the trailing end under the capsulorhexis edge. Released too early above it, the ring can spring sideways, push the bag in the opposite direction and extend the dialysis.50

    aUneventful insertionInjectorBag filled with viscoelasticSmooth arc along the equatorSuture on the leading eyeletbThe S-curveS-curve: leading eyelet obstructed,zonules under stressStopInjector
    Figure 3. Inserting a standard ring. (a) With the bag filled with viscoelastic, the ring leaves the injector and runs along the equator in a smooth arc; a suture on the leading eyelet lets the surgeon steer and retrieve it. (b) In cadaver eyes filmed with the Miyake-Apple technique, an S-curve in the surgeon's view coincided with obstruction of the leading eyelet and stress on the zonules: it is the signal to stop. Schematic, not to scale.

    8. Scleral Fixation of Sutured Devices

    Long-term success depends on what holds the device to the sclera. A closed-system technique described in 2001 preplaced 10-0 polypropylene sutures in the ciliary sulcus.58 In 90 eyes with congenital subluxation, a broken suture was recorded in 10%, and the authors recommended 9-0 polypropylene to reduce late breakage.21 9-0 can also fail: in a 52-year-old woman with Marfan syndrome, a 9-0 suture used to refixate a dislocated complex broke late despite knotless cow-hitch fixation, probably by chafing on the sharp edge of the ring eyelet.59

    Table 6. Fixation materials.
    MaterialEvidenceLimitations
    10-0 polypropyleneClosed-system technique of 200158Less resistant to breakage than Gore-Tex60
    9-0 polypropyleneRecommended to reduce late breakage;21 used in 16 of 19 paediatric eyes22One break at a ring eyelet in children;22 late break by chafing on the eyelet edge59
    Gore-Tex CV-8 (expanded polytetrafluoroethylene)Preferred for resistance to breakage;60 no late events with Gore-Tex against one polypropylene rupture, gauge not reported, in a series followed 6 to 80 months23Thick, overcurved needle that is risky inside the eye;60 off-label use61
    Double-flanged polypropylene, without sutures71 eyes, 173 flanges, mean follow-up 28 months; stable when the technique is followed62Flanges under Tenon 7.5%, exposure 2.9%, internalisation 2.3%; retinal detachment in 4.2% of eyes; problems with short tunnels and unburied flanges62

    Pass the suture at the sulcus, which anatomical studies place less than 1 mm behind the limbus. In 21 cadaver eyes, needles passed perpendicularly through the sclera reached the sulcus when they entered 0.83 mm behind the posterior surgical limbus in the vertical meridians and 0.46 mm in the horizontal ones;63 in 19 others, the mean distance from limbus to sulcus was 0.9 mm.12

    Optical axisLimbusLess than 1 mm behind the limbus(0.46 to 0.83 mm behind the posterior surgical limbus; 0.9 mm)CorneaScleraIrisCiliary bodyCapsular bagSuture through the sulcus to the scleraFixation eyelet in the ciliary sulcus,in front of the anterior capsuleRing at the equator
    Figure 4. Where a sutured device is fixed. Schematic section of the anterior segment at the meridian of the dialysis, optical axis at the bottom. The fixation element of a modified ring leaves the ring at the equator, wraps around the capsulorhexis edge without perforating the bag and ends in an eyelet in front of the anterior capsule, at the level of the ciliary sulcus; the suture passes through the sulcus and exits on the sclera. In cadaver eyes, the sulcus lay less than 1 mm behind the limbus. Not to scale.

    Access can go under a scleral flap or through a scleral pocket started from a peripheral clear corneal incision, which avoids conjunctival dissection and cautery and keeps the knot under the roof of the pocket.64 With Gore-Tex, a snare made from a short segment of the same suture on a 26-gauge needle retrieves the suture at the fixation site and avoids handling the original needle inside the eye;60 in deep-set eyes, a flexible loop instrument can lasso the suture.65 Sutureless techniques connect the segment or modified ring to a polypropylene haptic or suture whose ends are flanged with cautery and buried in the sclera,44,62 and a flanged iris hook through the segment eyelet has been described in a patient with a 180 degree dialysis.16

    In 15 eyes against 12 controls, a sutured segment did not seem to induce clinically significant tilt (vertical 2.20 against 1.97 degrees; horizontal 2.09 against 0.94, not significant), but the refractive error was larger: mean absolute errors near 1 D with four formulas against 0.3 to 0.4 D in controls, significant for two of the four.66

    9. Nucleus, Cortex, Lens and Refraction

    9.1 Nucleus

    Keep the work in the centre and off the zonules. A review of pseudoexfoliation lists phacoemulsification in the central zone, with minimal stress on the zonules, among the measures that keep most of these operations uneventful,32 and a review of subluxated lenses advises minimising sculpting and rotation of the nucleus.18 The hemi-flip, described for soft to moderate nuclei, removes each half of the nucleus in the iris plane after a single chop.67

    9.2 Cortex

    A ring inserted early traps cortex at the equator; in the prospective pseudoexfoliation comparison, cortex removal was significantly harder with early rings.39 Three tools help: a ring with eight 0.15 mm indentations designed to ease removal of lens material,27 a suture loop on the leading eyelet,55 and a flushing technique that lifts cortex trapped between the ring and the equator into the anterior chamber.68 In severe diffuse zonulopathy after the age of 90, central cortical clean-up without a ring was performed safely in a dozen eyes, with moderate capsular phimosis; its authors argue that the dogma of complete clean-up should give way to a clear visual axis with maximal preservation of the damaged zonules.35

    9.3 The lens

    A ring can be combined with common in-the-bag lenses,1 but the combination is not neutral. In a paired randomised study of trifocal lenses in eyes without zonular risk, decentration at 12 months was larger with a ring, and the laboratory arm showed that interference between the ring eyelets and the lens haptics increases decentration, a possible explanation.69 A practical inference, not tested in a trial, is to keep the haptics away from the eyelets. In a double-masked intraindividual trial of an 11 mm plate-haptic lens in eyes without zonular weakness, the ring did not improve rotation, and tilt was higher (6.7 against 5.6 degrees), with numerically higher decentration and posterior shift.70

    9.4 Refraction

    A meta-analysis of eight studies (407 eyes) found a pooled hyperopic shift with a ring of 0.16 D in the first month and 0.19 D after three months, with no difference in the high-myopia subgroup.71 Another found a deeper anterior chamber with plate-haptic lenses (0.11 mm) and noted that the hyperopic shift may require a target adjustment.72 In pseudoexfoliation, eyes without a ring showed a significant hyperopic shift and eyes with a ring did not; the authors suggest a slightly myopic target when no ring is used.73 In high myopia, a ring reduced the absolute error by 0.12 D without changing the mean error.74

    10. What the Evidence Shows

    The high-level evidence is modest. In eyes with zonular weakness there is one randomised trial, one multicentre device study and many case series; in eyes without it, several meta-analyses show small effects.

    Table 7. Outcomes in eyes with zonular weakness.
    SettingResultDesign
    Pseudoexfoliation, zonular separation during surgery0 against 12.8%; lens in the bag in 94.9% against 74.3%Randomised trial, 78 eyes19
    Dialysis below one third of the circumferenceLens centred in 98.8% immediately and 97.7% at 12 months; Nd:YAG capsulotomy in 12.8% at 12 monthsDevice study, 255 rings20
    Dialysis up to about 150 degreesSuccess in 90.5%; dialysis extended during surgery in 9.5%Prospective series, 21 eyes40
    Traumatic dialysis of 80 to 160 degreesNo decentration over a mean of 26 months, except after a new injuryProspective series, 17 eyes41
    Modified ring, congenital subluxation20/40 or better in 88.9%; late decentration 6.7%; broken suture 10%; posterior capsule opacification 20%Series, 90 eyes21
    Modified ring, traumatic subluxationNo decentration after surgery; vitrectomy needed in 50%Series, 22 eyes33
    At least six clock hours of traumatic zonulysisBag preserved in 38 of 41; 20/40 or better in 92.7%Series, 41 eyes45
    Paediatric ectopia lentis, sutured devicesAll lenses centred; 20/40 or better in 94.7%; posterior capsule opacification 57.9%Series, 19 eyes22
    Sutured segments, mean dialysis 142 degrees20/40 or better in 85.7%; one polypropylene rupture; no late events with Gore-TexSeries, 21 eyes23
    Pseudoexfoliation without signs of weaknessNo difference with or without a ring at 10 yearsRandomised data43

    10.1 Eyes without zonular weakness

    Here the effects are small and partly inconsistent (Figure 5). A 2025 meta-analysis of 11 randomised trials and 7 cohorts found 0.82 degrees less rotation and 1.04 degrees less tilt with a ring, the tilt benefit confined to high myopia, and a deeper chamber with plate-haptic lenses.72 A 2026 meta-analysis of 12 studies found no reduction in mean rotation with moderate certainty, and less misalignment only in very low certainty evidence.75 A second 2026 analysis by the same group, with 15 studies and a standardised metric, found less rotation with a ring, a larger effect in Asian populations and with plate-haptic lenses, and no difference in visual acuity, capsule opacification or intraocular pressure.76 For one plate-haptic toric lens, a propensity-matched cohort of 126 eyes per group found less rotation with a ring (4.6 against 10.9 degrees) and recommended it when lens thickness is 4.5 mm or more, white-to-white 11.6 mm or more, or the preoperative astigmatism is high.77 In pooled data, visual acuity did not improve beyond the first month.78

    OUTCOME AND SOURCEDEGREES (95% CI)RotationLin 2025 · 11 RCTs and 7 cohorts, 1,631 eyes−0.82 (−1.27 to −0.37)RotationLiu 2026 · 12 studies, 1,251 eyes, moderate certainty−0.40 (−1.20 to 0.39)Rotation, toric lensesMa 2023 · 5 studies, pooled−1.59 (−3.10 to −0.09)TiltLin 2025−1.04 (−2.05 to −0.03)Tilt, high myopiaLin 2025, subgroup−1.43 (−2.59 to −0.26)Misalignment, plate hapticLiu 2026 · very low certainty−3.18 (−6.29 to −0.08)−7−6−5−4−3−2−101favours the ringdegrees
    Figure 5. Effect of the ring on IOL position in comparative studies with and without a ring. Mean difference in degrees with its 95% confidence interval, as published in each meta-analysis; negative values favour the ring. This is not a new meta-analysis: each row reproduces one published estimate. Hollow square: very low certainty evidence. Sources:72,75,77

    10.2 Late dislocation

    A ring does not rule out late in-the-bag dislocation. Pseudoexfoliation was the main risk factor in 45 late dislocations, eight of which had a ring.7 Among 46 eyes exchanged for late in-the-bag dislocation, 34 had a ring, and those dislocated earlier (6.6 against 9.4 years); the study was not designed to compare eyes with and without a ring, and selection may explain the difference.79 In a region where pseudoexfoliation is uncommon, late subluxation of the ring, lens and bag complex occurred in 0.85% of eyes, a mean of 41 months after surgery; trauma and hypermature cataract were the commonest risks, and weakness of four clock hours or more was a risk factor.80 When it happens, the ring can serve as the handle for refixation: in one series all 11 complexes were repositioned, most with scleral suture loops around the ring through the bag (8 eyes) or with a segment (2 eyes).46

    10.3 Shrinkage and opacification

    The ring reduces bag shrinkage only slightly (Table 1),10 and a closed foldable equator ring did no better than a standard ring.30 A 2026 meta-analysis found no difference in posterior or anterior capsule opacification with a ring.76

    11. Special Situations

    11.1 Pseudoexfoliation

    Weak zonules, poor dilation and pronounced fibrotic shrinkage can lead to capsulorhexis phimosis and, years later, to spontaneous dislocation of the capsule and implant complex.81,32 In the 10-year Aravind data, capsular phimosis and a capsulorhexis that did not overlap the edge of the optic were independent risk factors for decentration and capsulotomy,43 which argues for a capsulorhexis that covers the optic edge. A ring before phacoemulsification reduced zonular separation in a trial of unselected pseudoexfoliation,19 while in eyes without phacodonesis, shallow chamber or small pupil a routine ring made no difference to decentration, capsulotomy or acuity at 10 years;43 reserving it for eyes with signs of weakness is an inference from the two trials.

    11.2 Trauma

    Traumatic dialysis is usually focal, but vitreous is common: in 22 traumatic subluxations treated with a modified ring, vitreous prolapse was present in 41% and vitrectomy was needed in half, and all lenses were centred after surgery.33 A standard ring worked up to about 160 degrees in one series,41 and fixated devices preserved the bag in all but total zonulysis.45

    11.3 Congenital ectopia lentis

    In Marfan syndrome, Weill-Marchesani syndrome and idiopathic ectopia lentis, the modified ring centred the bag in 90 eyes, with late decentration in 6.7%.21 In 19 paediatric eyes treated with a modified ring, a segment with a standard ring or, in two eyes, a segment alone, all lenses were centred at a median of 23 months, but posterior capsule opacification developed in 57.9% and 15.8% needed vitrectomy and posterior capsulotomy.22 Two-eyelet segments have been used in children with Marfan syndrome,24 and when the pupil dilates poorly, a pupil expansion ring can be sutured to the limbus to centre a laser capsulotomy over the displaced lens.82 Plan retinal follow-up: Marfan syndrome carries a high lifetime risk of retinal detachment, higher after lens removal in children when capsular remnants persist.83 The 2003 US labelling of the Morcher ring lists eyes still growing, in children aged 12 or younger, as a contraindication.6 Lens options without capsular support in children give similar acuity with different complication profiles.84

    11.4 Microspherophakia

    In a 35-year-old woman, a standard ring with two sutured segments kept the bag centred, but the complex moved forward over the years, the pressure rose and the left eye needed trabeculectomy in the fourth year.15

    11.5 High myopia

    The effects of a ring are small: absolute error 0.12 D lower and decentration 0.04 mm lower, with the same acuity. The authors suggest considering it when zonular weakness is suspected or the bag is large.74 The labelling reserves the 14.5 mm ring, with a safety suture, for eyes longer than 28 mm.6

    11.6 Angle closure and very advanced age

    Be alert to zonulopathy in primary angle-closure disease, where it was found in 7.3% of eyes without other risk factors.34 After the age of 90, central cortical clean-up without a ring has been described as safe in a dozen eyes with severe diffuse zonulopathy, without a comparison group (Section 9).35

    12. When the Bag Cannot Be Kept

    A torn or perforated capsule contraindicates the standard ring;6 when the zonules are also weak the lens may need support outside the bag, although a segment has been described even with a discontinuous capsulorhexis.49 Total zonular loss is the clearer limit: in the traumatic series, the bag could not be kept in the three eyes with total zonulysis, despite a segment in two of them.45

    Table 8. Options without the capsular bag, or after it dislocates.
    OptionEvidence
    Flanged intrascleral three-piece lens, double-needle technique100 eyes: tilt 3.4 ± 2.5 degrees; iris capture 8%; vitreous haemorrhage 5%; no retinal detachment, endophthalmitis or dislocation, with follow-up to 36 months85
    Scleral-sutured lens with Gore-TexPreferred over 10-0 polypropylene for resistance to breakage; off-label use60,61
    Exchange for an iris-claw anterior chamber lens65 eyes: pressure decompensation 26.2%, corneal decompensation in 7, central retinal vein occlusion in 5, endophthalmitis in 179
    Anterior chamber lens or scleral fixation for late dislocationSimilar final acuity with scleral fixation (20) and anterior chamber lenses (19) in a series of 457
    Trans-iris suture of a dislocated complex11 eyes stable at 16 months; oval pupil in all86
    Repositioning a complex that contains a ringAll 11 eyes repositioned46
    Ring dislocated into the vitreousExplanted with the ring inserter through a clear corneal incision in three cases87
    ChildrenSimilar acuity across techniques, different complication profiles84

    13. What Is Still Unknown

    • No randomised trial compares a standard ring, a segment and a modified ring at any extent of dialysis; the ranges in Section 4 come from series and labelling.
    • No sizing rule has been validated: the Vass regression explains 31% of the variance of the bag,8 and we found no study testing it as a selection rule.
    • We found no direct long-term comparison between Gore-Tex and flanged polypropylene.
    • No device has been shown to prevent late dislocation in pseudoexfoliation.7,43
    • Anchors, two-eyelet segments and new flanged techniques are reported in small series with months to a few years of follow-up.26,24,16,62
    • Two 2026 meta-analyses of rotation by the same group reached different conclusions with different study sets and metrics.75,76

    14. Checklist

    Before surgery

    • Note the risk factors in Section 3.
    • Examine with the pupil dilated for phacodonesis, decentration and vitreous; compare chamber depth between the eyes.
    • Ask for ultrasound biomicroscopy when the lens is visibly displaced.
    • Record the extent in clock hours and the course, static or progressive; choose the device and the size; plan the alternative without the bag.
    • Have rings in the sizes you need, segments or modified rings, capsular hooks or retractors, fixation suture, viscoelastic, vitrectomy and a three-piece lens available.
    • Discuss scleral fixation and the possibility of later surgery in the consent.

    During surgery

    • Make a good-sized, centred capsulorhexis, started away from the dialysis.
    • Minimise sculpting and rotation; work in the centre.
    • Use hooks or retractors if the bag moves during phacoemulsification.
    • Fill the bag before the ring, plan the first contact and consider a suture on the leading eyelet.
    • Stop if the ring forms an S-curve; release the trailing end under the capsulorhexis edge.
    • For a sutured device, pass the suture at the sulcus, less than 1 mm behind the limbus.
    • Keep the lens haptics away from the ring eyelets.

    After surgery

    • Check the pressure early: transient rises occurred in 12% to 14% of eyes in two series.40,31
    • Document centration and tilt.
    • Watch for capsular phimosis in pseudoexfoliation.43
    • Follow pseudoexfoliation and congenital cases for years: late decentration appeared a median of 18 months after surgery in congenital eyes and a mean of 41 months to 7 years in the other series cited.21,80,79
    • Inspect the conjunctiva over flanges and sutures.62,22

    15. Conclusion

    The capsular tension ring is a simple device with a narrow job: it holds the bag open and spreads stress around it. Two observations decide nearly everything, how much support is missing and whether the disease will keep taking more. A standard ring handles diffuse weakness and dialysis up to about a third of the circumference; sutured devices handle larger and progressive losses; and a ring adds little where the zonules are sound. Choose the size by axial length, insert as late as the bag allows, and fix sutured devices with materials that last.

    Calculate the lens for where it will sit. The MIOLO calculators are free: MIOLO Standard for a lens in the bag, and MIOLO Sulcus when a three-piece lens goes to the ciliary sulcus after posterior capsule rupture.

    MIOLO StandardMIOLO Sulcus

    About the author

    Bruno Miolo, MD, M.Sc, is an ophthalmologist and cataract surgeon and the developer of the MIOLO.AI platform.

    Conflicts of interest: Bruno Miolo is the developer of the MIOLO.AI platform. No external funding was received for this article.

    Methodological note: Every indexed reference was located on PubMed by its identifier in October 2026, and its authors, title, journal and year were checked against the record; the numbers in the text were checked against the abstract or the open full text of the cited study, and an independent review checked the claims again. Statements supported only by catalogues or websites were replaced by indexed sources or removed. Device sizes come from the 2003 US labelling of the Morcher rings; check the current labelling before use. Ranges without randomised evidence are presented as such. Figures 1 to 4 are schematic; Figure 5 reproduces published estimates.

    How to cite: Miolo BL. Capsular Tension Rings: An Evidence-Based Manual for Zonular Weakness in Cataract Surgery. MIOLO.AI Blog. October 2026. Available at: https://miolo.ai/article/capsular-tension-ring

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