Can a Distorted Pupil Be Repaired? Pupilloplasty Explained

The pupil is the aperture of the eye. Its job is simple: let in the right amount of light and keep out the rest. When it’s the wrong shape, stuck wide open or missing altogether, the light that should have been blocked scatters across the retina instead. What patients notice is glare, a dislike of bright light, sometimes a ghost image, and an eye that looks different from the other one. Plenty of them have been told that nothing can be done. Usually that isn’t true. This post is about the two tools I use to fix a damaged pupil: a suturing technique called four-throw pupilloplasty and, for eyes with too little iris to repair, a custom-painted artificial iris.

Why a damaged pupil matters

The iris is the coloured curtain and the pupil is the hole in it. A healthy pupil is round, central and adjusts its size to the light. When part of the curtain is torn or absent, a few things go wrong at once:

• Glare and light sensitivity. Light enters through the edge of the lens, where the optics are worst, and scatters across the retina. Sunlight, oncoming headlights and screens all become harder to tolerate.
• Ghost images. A second, off-centre opening in the iris can throw a faint second image. Patients describe it as a shadow or a doubled edge in one eye.
• Appearance. A keyhole pupil, an oval pupil or one large black pupil is noticed by other people, and patients notice them noticing.
• Later surgery. An eye with a poor iris is harder to operate on. The edge of a lens implant may be visible through the gap, and some lens designs can’t be used at all.

What damages a pupil

Coloboma

A coloboma is a gap the eye is born with. Early in pregnancy the developing eye is a cup with a seam along its lower inner side, and that seam is meant to close. When it doesn’t close fully, the iris is left with a wedge missing at the lower, inner part of the pupil, which gives the classic keyhole shape. The rest of the iris is usually normal, which is exactly what makes a coloboma a good candidate for repair. Some colobomas also involve the retina or optic nerve at the back of the eye. Those parts can’t be sutured, but the iris component still can, and closing it still reduces the glare.

Trauma

A blunt injury from a ball, a fist, a cork or an airbag can tear the sphincter, the small ring of muscle that constricts the pupil. The pupil is left permanently large and often oval, a condition called traumatic mydriasis. A harder blow can tear the iris away from its root, leaving a second opening at the edge of the iris. Penetrating injuries and previous surgery can remove iris altogether. The iris has almost no ability to heal itself, so these defects are permanent unless they’re repaired.

Iris tumours

An iris melanoma or another iris lesion is sometimes treated by cutting out the wedge of iris it sits in. The tumour is gone, but a sector of iris goes with it, and the patient is left with a large, irregular pupil and the glare that comes with it.

Aniridia

Aniridia means the iris is essentially absent. It’s usually present from birth and usually affects both eyes, although a small rim of iris tissue is often there. Near-total loss of iris can also follow severe trauma. In these eyes there’s simply nothing to sew, and a different approach is needed.

Four-throw pupilloplasty: sewing the pupil back into shape

Pupilloplasty means reshaping the pupil with sutures placed inside the eye. Surgeons have tied knots inside the eye for decades, but the technique I use is the single-pass four-throw method described by Priya Narang and Amar Agarwal in 2017. Through tiny incisions, the two edges of the iris defect are picked up with a single pass of a needle. The end of the suture is then passed through its own loop four times, which forms a small helical knot that slides into the eye and locks itself as it tightens. There’s no second pass, no bulky knot left inside the eye, and the ends are trimmed flush. In their original series of 27 eyes, not one knot loosened over six months of follow-up, and none of the eyes developed inflammation from the suture.

The reason I like it is that it makes many different pupil defects repairable with the same, reliable stitch:

• closing a coloboma so the pupil becomes round
• shrinking a pupil that’s been stuck wide since an injury, with a series of sutures around the rim
• reshaping an oval or peaked pupil left by earlier surgery
• centring the pupil over a lens implant so its edge is hidden
• covering the edge of a lens implant that has become visible through a gap

An iris that has been torn from its root is repaired a little differently, by stitching it back to the wall of the eye, and that’s usually done at the same operation. The four-throw stitch has also found uses beyond appearance and glare. It’s used to pull the iris away from the drainage angle in some forms of angle-closure glaucoma, and to make the pupil smaller before a corneal transplant, because a small, intact pupil holds the air bubble that keeps a new endothelial graft in place. I’ve talked through the technique in this video:

When there isn’t enough iris to repair: the artificial iris

Suturing only works if there’s iris on both sides of the gap to bring together. When the missing area is too big, or there’s no iris at all, I use the CustomFlex ArtificialIris made by HumanOptics in Erlangen, Germany. It’s a thin, flexible disc of medical-grade silicone with a fixed central pupil, and every one is made to order. I send a clinical photograph of your other eye, and the front surface of the implant is hand painted to match it: the colour, the pattern and the fine radial lines. The aim is that the two eyes look like a pair. If both eyes are affected, the colour is chosen from a sample photograph instead.

Because the implant is foldable, it goes in through a small incision, unrolls inside the eye and is trimmed to size. It can be placed with a lens implant during cataract surgery, or, in a version reinforced with a fine fibre mesh, sutured to the remaining iris or to the wall of the eye when there’s nothing else to hold it. Where only a wedge of iris is missing, a matching segment can be cut from the disc rather than replacing the whole iris.

In 2018 the US Food and Drug Administration approved it as the first stand-alone artificial iris in the United States, for congenital aniridia and for iris defects caused by albinism, trauma or surgical removal, on the basis of a study showing less light sensitivity and glare and a better appearance of the eye. Those indications cover most of the patients I see it for: aniridia from birth, eyes where an injury has destroyed most of the iris, and eyes where a sector of iris was removed to treat a melanoma or another iris lesion. HumanOptics is clear that it’s a medical prosthesis rather than a way of changing the colour of a healthy eye, and I take the same view. Here’s a closer look at the implant itself:

Which repair suits which eye

The decision comes down to how much healthy iris is left:

• Enough iris on both sides of the defect: four-throw pupilloplasty. This covers most colobomas, most traumatic pupils and most surgical distortions.
• A large sector missing, or almost no iris: the artificial iris, either as a segment or a full disc.
• A bit of both: sutures to gather what remains, and a prosthesis for the rest.

Injuries that damage the iris often damage the lens too, and an artificial iris is designed to be implanted alongside a lens implant, so pupil repair is frequently done as part of cataract surgery or a lens exchange rather than as a separate operation. One anaesthetic, one recovery.

What the surgery is like

It’s a day procedure through the same small incisions used for cataract surgery. Most of my patients are asleep under sedation with the eye numbed by drops, the same arrangement I use for lens surgery. Afterwards there are drops for a few weeks and a handful of visits to check the pressure inside the eye, which any iris surgery can nudge up for a while.

There are two things I make sure people understand beforehand. First, a repaired pupil is fixed in size. A sutured pupil and an artificial iris both lose the ability to open and close with the light, and that’s the price of getting rid of the glare. I choose a size that blocks stray light but still allows your retina to be examined. Second, the goal is a natural-looking eye at conversational distance, not perfect symmetry under a microscope. Patients who go in with those expectations are consistently pleased.

The bottom line

A pupil that’s misshapen from birth, torn by an injury or left with a gap after tumour surgery is not something you have to live with. The four-throw technique makes most of these defects repairable with a few small stitches, and where there isn’t enough iris left, a hand-painted artificial iris can replace it and be matched to your other eye. If you’ve been told that glare from a damaged pupil is permanent, it’s worth a proper assessment.