Recognising zonular weakness before phaco

01 · Before surgery

Start with the anterior chamber.

I do not interpret anterior-chamber depth as a single isolated measurement. I compare the two eyes, then look for differences between quadrants within the same eye.

An anterior chamber shallower than 2 mm should prompt a closer look. So should a chamber that is unexpectedly deep, deeper than the fellow eye or uneven from one quadrant to another. None of these findings proves zonular weakness by itself. The asymmetry is the reason to examine the lens–capsule complex more carefully.

02 · Look for corroborating signs

Look at the capsule and anterior chamber.

A crumpled anterior capsule suggests that zonular tension is not being distributed evenly. An anterior subcapsular cataract and vitreous in the anterior chamber are other clues that alter how I approach the operation.

I examine the patient seated upright and again lying down. Changing position can reveal lens tilt into the mid-vitreous cavity that was not obvious during the first examination.

03 · Define the anatomy

Use UBM when it will change the plan.

Ultrasound biomicroscopy can show both direct and indirect evidence of zonulysis.

The direct signs described by Pavlin and colleagues include missing zonular fibres, stretched fibres and zonular remnants on the lens capsule. The indirect signs include increased curvature of the lens in the affected region, flattening of the ciliary body and an increased distance between the lens and ciliary body.

I use UBM to understand where the abnormality lies and how much of the circumference may be involved. It is not a perfect exclusion test: subtle weakness may still escape detection.

04 · In theatre

The first intraoperative clues may appear before the rhexis is established.

Sometimes the diagnosis becomes clearer as soon as viscoelastic is injected. The lens–bag complex may tilt, or the anterior capsule may wrinkle rather than remain stable.

Difficulty initiating the capsulorhexis is another early clue. If the capsule and bag move with the force applied to the flap, I stop treating the eye as a routine cataract. Pulling harder does not correct the underlying lack of support.

05 · Plan before control is lost

Decide whether the bag remains controllable.

The next question is not simply which capsular device to insert. I want to estimate how much support remains, where that support is located and whether the bag can still be controlled through cataract removal and IOL implantation.

If the bag appears salvageable, the operative plan should minimise further zonular stress and introduce support before control is lost. If there is a meaningful possibility that the bag cannot be preserved, I prepare a scleral-fixated IOL backup rather than improvise after the eye has already become unstable.

Preserving the bag is valuable only while it remains the safer and more controllable option.

06 · Common errors

Errors that make zonular weakness worse.

Failing to recognise the problem early

This is the mistake that makes the other mistakes more likely. An eye that has already shown anterior-chamber asymmetry, capsular wrinkling, lens tilt or vitreous in the anterior chamber should not be managed with the assumptions used for an uncomplicated cataract.

Increasing infusion pressure when the posterior capsule moves forward

When intraoperative aqueous misdirection develops, the anterior chamber may become shallower and the posterior capsule may move forwards. Increasing bottle height or infusion pressure in an attempt to push the chamber back can drive more fluid posteriorly and worsen the problem.

More infusion is not always the answer to a shallow chamber. The reason for the loss of space has to be understood first.

Catching vitreous and continuing phaco

Once vitreous has been caught, continuing phacoemulsification can transmit traction posteriorly and increase the risk of retinal detachment. The priority is to recognise what has happened and regain control, not to continue the original sequence as though nothing has changed.

Using rough phaco manoeuvres

Force applied to the nucleus is also transmitted to the remaining zonules. Rough rotation, manipulation or fragment removal can extend a limited area of weakness into a larger zonulysis.