In pseudophakic pupillary block, the implanted intraocular lens (IOL) is partly or wholly involved in the obstruction of the aqueous flow through the pupil. This condition can develop days, weeks, months, or years after the lens implant surgery. If the condition is not recognized and treated early, it can lead to iris bombe, iridocorneal adhesion formation (starting at the periphery and extending toward the center), increasing intraocular pressure (IOP), and progressive damage to the optic nerve head.
The block is caused via mechanical closure of the pupil by the optic of the pseudophakos or by the development of synechiae between the iris and the artificial lens or remaining lens capsule. Pseudophakic pupillary block also can occur in patients with anterior chamber IOLs, either by direct blocking of the pupil by the optic or by the development of adhesions between the vitreous and the posterior iris. Closure of an existing peripheral iridectomy or an absence of a peripheral iridectomy may be a precipitating factor.
Pseudophakic pupillary block is shown in the image below.
Results after surgery of the patient above are shown in the following image.
Extracapsular surgery that precedes the insertion of the IOL creates the following conditions that are conducive to inflammatory, proliferative, and fibrotic reactions: retention of a large part of the anterior lens capsule, retained lens matter in the fornices of the capsular bag, a tear of the posterior capsule, and lens-vitreous mix. The inflammatory reactions produce adhesions between the artificial lens and the uveal tissues, particularly the iris.
The so-called sulcus-supported lenses have a tendency to erode the ciliary processes and the ciliary body. In the process, a breakdown of the blood-aqueous barrier occurs. The optics of the sulcus-supported lenses have a greater tendency to partial or complete pupillary capture. The fibrous reactions in the capsular bag also can push the optic out of the bag, a process that may lead to the pupil capture.
Either of the following can push the lens optic firmly against the pupil, effectively blocking the forward movement of the aqueous and causing partial or complete pupil capture: the shallowness of the anterior chamber due to a wound leakage or pooling of aqueous in the vitreous pushing the lens optic forward.
In pediatric patients, the aforementioned factors play a part with much greater severity than in adults. Fibrin formation is encountered more often in children. There is a greater tendency for the optic to come out of the small capsular bag and become captured by the pupil. In neonates and young infants, there is a tendency for the iridectomy opening to shrink (like shrinkage of a continuous curvilinear capsulorrhexis) and ultimately close.
The net result of all these processes is iris bombe, anterior synechiae formation, glaucoma, and an increased resistance to the forward movement of the aqueous. Pupillary block can occur if the peripheral iridectomy and the pupil close by the above factors and one of the following is used: an IOL in the anterior chamber, an angle-supported lens, or an iris claw (Artisan) lens. In the pupillary area, the initial adhesions are formed between the pupil and the posterior capsule. As iris bombe develops, adhesions form between the anterior surface of the iris and the optic and the haptic of the IOL. The iris bombe may involve the whole iris; more often, it is multiloculated.
Examples of pseudophakic pupillary block in a pediatric patient are shown in the images below.
Pseudophakic pupillary block is not an uncommon condition. The exact incidence is not known, but it occurs more frequently in pediatric patients, especially those who are very young.
Failure to relieve the pupillary block can lead to the development of chronic angle closure glaucoma and glaucomatous optic neuropathy.
No predominance in specific races exists; however, Nd:YAG laser iridotomy may be difficult to perform in dark-skinned people.
No sexual predilection exists.
The younger the patient, the greater the chance of a pseudophakic pupillary block. The space behind the iris contains the following reactive elements: anterior and equatorial lens capsular cells, remains of lens matter, ciliary processes and ciliary body, and posterior pigment epithelium of the iris. These elements can trigger inflammatory, proliferative, and fibrotic responses in the pupillary area and around the IOL. This ultimately can result in a pseudophakic pupillary block. Such reactions are uncommon in adults, especially after implantation in the bag. In the presence of an anterior chamber angle-supported lens or an iris claw lens, the absence or the closure of a peripheral iridectomy usually initiates the pupillary block.
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