Devices for Difficult Cataracts: Capsular Tension Rings, Cionni Rings, Segments, Malyugin Ring and Iris Hooks (Sizes and Use)
Last updated: November 2026
Weak zonules and small pupils are the two commonest reasons a routine cataract becomes difficult. A few devices make these cases much safer: capsular tension rings and their sutured versions for zonular weakness, and pupil expanders or iris hooks for small pupils. Knowing the sizes and when to use each lets you plan before the patient is on the table.
Capsular tension rings (CTR)
A CTR is an open PMMA ring placed in the capsular bag. It spreads force evenly around the equator, supports areas of weak zonules, keeps the bag round and reduces capsule contraction.
| Morcher model | Open diameter | Compressed in the bag | Usual choice |
|---|---|---|---|
| 14 | 12.3 mm | 10.0 mm | Smaller eyes |
| 14C | 13.0 mm | 11.0 mm | Average eyes; the most commonly used size |
| 14A | 14.5 mm | 12.0 mm | Large or highly myopic eyes |
| 13, 13A, 13B | Same sizes, blue PMMA, bent eyelet | — | Easier to see and position |
The ring should be larger than the capsular bag diameter. Other companies make similar rings; follow their size charts. Preloaded injectors are available.
- Indications: pseudoexfoliation, mild to moderate zonular weakness or dialysis (up to about 4 clock hours), trauma, high myopia, some toric IOL cases.
- Timing: after the capsulorhexis and hydrodissection; as late as possible (after nucleus removal) to make cortex removal easier, but early if the bag is unstable.
- Insertion: fill the bag with OVD; insert with an injector or forceps, guiding the leading eyelet along the equator; dial in the trailing eyelet.
- Contraindication: an incomplete capsulorhexis or posterior capsule tear (the ring can escape into the vitreous).
When a CTR is not enough
| Device | Zonular loss | How it works |
|---|---|---|
| Cionni ring (e.g. 1L, 2L) | More than about 4 clock hours (one eyelet) or 6 hours (two eyelets) | CTR with a hook-shaped eyelet that is sutured to the sclera (e.g. 9-0 polypropylene or Gore-Tex) |
| Capsular tension segment (Ahmed type, e.g. 6D) | Localised large dialysis; useful even with an incomplete rhexis | Partial ring (120°) placed in the fornix; can be hooked temporarily with an iris hook or sutured |
| Capsule hooks | Temporary support during surgery | Hook the rhexis edge through limbal stabs to hold the bag |
Severe zonular loss may need an anterior chamber, iris-fixated or scleral-fixated IOL instead.
Small pupil devices
| Device | Sizes | Notes |
|---|---|---|
| Malyugin ring | 6.25 mm and 7.0 mm | Square, single-use ring inserted through the main incision with its injector; scrolls hold the iris; quick to insert and remove |
| Iris hooks (flexible nylon or polypropylene) | Usually 4 (sometimes 5) hooks | Through limbal paracenteses in a square or diamond; the subincisional hook placed below the main incision ("diamond" configuration) keeps iris away from the phaco tip |
| Other expanders (e.g. Bhattacharjee ring, I-Ring) | Various | Similar principle |
Before devices: try preoperative dilating drops, intracameral adrenaline or Shugarcaine (see intracameral drugs), viscomydriasis with a cohesive or viscoadaptive OVD, and gentle iris stretching (avoid in floppy iris syndrome).
Who needs a device: pre-operative clues
- Pupil under about 5–6 mm after full dilation; tamsulosin or other alpha-blocker use (floppy iris).
- Pseudoexfoliation, phacodonesis, iridodonesis, lens subluxation, previous trauma or vitrectomy.
- Marfan syndrome, homocystinuria, high myopia.
- Have the devices opened or available in theatre before starting; see the pre-operative risk checklist.
Pearls
- 14C (13 mm open, 11 mm compressed) is the usual CTR size for an average eye.
- Never put a CTR in a bag with a torn rhexis or posterior capsule.
- Malyugin 6.25 mm fits most small pupils; 7.0 mm gives more room in larger eyes.
Common mistakes
- Inserting the CTR so the eyelet catches cortex or the rhexis edge.
- Iris hooks placed too tight, causing a permanently dilated pupil.
- Relying on a CTR alone for more than about 4 clock hours of zonular loss.
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Related: Cataract Pre-operative Risk Checklist: Spot the Difficult Case, Phacoemulsification Step by Step: A Beginner's Guide, Ophthalmic Viscosurgical Devices (OVDs): Cohesive, Dispersive, Viscoadaptive, Brands, Soft-Shell Technique and Removal, Posterior Capsule Opacification, Nd:YAG Capsulotomy and IOL Dislocation, IOL Injectors and Cartridges for Residents: Alcon A, B, C, D, Preloaded Systems, J&J Unfolder, Zeiss, Medicel and Indian Lenses.
Key sources
- Morcher GmbH. Capsular rings product information (types 14, 14C, 14A, Cionni rings, capsular segments)
- Cionni RJ, Osher RH. Management of profound zonular dialysis or weakness with a new endocapsular ring designed for scleral fixation. J Cataract Refract Surg. 1998;24:1299-1306
- Ahmed IIK, et al. Capsular tension segments for zonular weakness (J Cataract Refract Surg)
- Malyugin B. Small pupil phaco surgery: a new technique (Malyugin ring)
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