The University of Iowa
Department of Ophthalmology and Visual Sciences
From antiquity to today, managing iris prolapse has long been a challenge for cataract surgeons, with its occurrence leading to increased risk of endophthalmitis, epithelial ingrowth, symptomatic glare, and several other postoperative complications. This tutorial will propose ten tips to prevent and treat iris prolapse. An accompanying article will discuss the history of iris prolapse as well as several mechanical and fluid dynamics-based theories believed to contribute to iris prolapse.
Recall that one of the primary factors driving iris prolapse is the distance from the iris to the internal opening of the wound. If you are concerned about the potential for iris prolapse, consider making a slightly longer clear corneal wound.
Beginning cataract surgeons often overfill with viscoelastic as it is easier to make the main wound in a firm eye, however this creates a larger pressure differential between the anterior and posterior chambers, and increases the risk of iris prolapse. In our experience, this seems to be an issue primarily with dispersive viscoelastic. A good rule of thumb is that if you are noticing considerable viscoelastic spilling out of the paracentesis, you may have overfilled the AC and should be weary of possible prolapse.
Hydrodissection poses the greatest risk of prolapse, and taking measures to prophylactically lower the anterior chamber pressure by removing viscoelastic is critical in preventing prolapse.
Before hydrodissection, use Balanced Salt Solution (BSS) to create a fluid tract for fluid to exit the eye. This tract prevents the situation where the BSS cannot leave the eye without taking viscoelastic with it, which could result in a rapid decrease in anterior chamber pressure - a main risk factor for prolapse.
Consider placing a single iris hook posterior to the main wound, or place several hooks in a diamond configuration with one of the hooks posterior to the main wound in a similar fashion. Alternatively, a Malyugin ring stabilizer can be used. Mechanically supporting the iris is particularly helpful if there is potential for intraoperative floppy iris syndrome.(1-3)
As soon as iris prolapse occurs, the knee-jerk reaction is to want to immediately push the iris back into the eye. It can be tough to overcome this urge, but realize that it is usually in repositing the prolapsed iris that pigment is permanently lost from the posterior iris. Also, manual reposition is rarely effective. Instead, the surgeon should immediately release trapped fluid or viscoelastic from the paracentesis to decompress the anterior chamber.
In order to resolve the prolapse, you must first decrease the force driving the iris to prolapse through the wound. This is typically due to an elevated anterior chamber pressure, often due to fluid from hydrodissection being trapped posteriorly behind the lens or unable to exit the eye due to impedance from viscoelastic. If fluid is trapped behind the lens, place a second instrument into the anterior chamber via the paracentesis and gently rock the lens to release the trapped fluid. If fluid is trapped by viscoelastic, burping or manually removing viscoelastic with a cannula will usually lower the pressure sufficiently to allow the iris to be easily reposited.
Use a hydrodissection cannula to gently stroke the cornea overlying the main wound. This technique is adopted from partial thickness endothelial keratoplasty, wherein stroking the cornea externally can cause internal movement of the endothelial graft, and also works well for releasing the prolapsed iris.
Once you have successfully reposited the iris, you should take measures to keep the iris from prolapsing again during the remainder of the case by stabilizing the fluidics. This can be done by lowering the intraocular pressure or bottle height and decreasing the aspiration flow rate/vacuum, which helps minimize large fluctuations in anterior chamber pressure and decreases the risk of repeat prolapse.
After prolapse, the iris architecture has been disrupted, and even a seemingly simple step like inserting the intraocular lens could catch the peripheral iris and cause an iridodialysis. Prior to IOL insertion, consider placing viscoelastic immediately posterior to the main wound to create more space for IOL insertion.
To learn more about the history of iris prolapse and theories explaining its causes, view the related tutorial: Iris Prolapse: The History of this Ancient (and Present) Surgical Challenge
To see more surgical videos describing these (and more) tips on iris prolapse, click on the links below:
Christiansen SM, Oetting TA. Ten Tips to Prevent and Treat Iris Prolapse. May 3, 2017; Available from: http://EyeRounds.org/tutorials/ten-tips-iris-prolapse.htm