Aphakic Pupillary Block: An Overview

Introduction:

Aphakia is a condition in which a crystalline lens is absent because of trauma, subluxation, or dislocation. It is a complication of cataract surgery (surgery to treat lens cloudiness). Pupillary block aphakia is a condition that occurs after round pupil cataract extraction. It can also happen due to iridectomy (iris resection procedure) when it is small and placed in the extreme periphery. Pupillary block is seen not only in older individuals but also in infants undergoing treatment for congenital cataracts. This condition leads to increased intraocular pressure, optic disc damage, and visual field defects. Chandler and Johnson are the first to describe glaucoma due to papillary block in aphakic eyes.

What Is the Pathophysiology of Aphakic Pupillary Block?

• Pupillary block is a method of angle closure after cataract extraction. The mechanism is of two broad types anterior and posterior pupillary block. The proximity between the pupillary margin and other surfaces anterior or posterior to the iris may lead to a pupillary block. The anterior hyaloid surface may hinder the pupillary aperture (opening of the iris that admits light into the eyes).

• Postoperative inflammation following an intracapsular cataract extraction may cause complete posterior synechiae (defined as the margin of the pupil where the iris is adherent to the anterior lens capsule and prevents dilation and making the cataract surgery challenging) between the iris and the intact anterior hyaloid membrane.

• A narrow or blocked anterior chamber favors the formation of the adhesions. Adhesions are present between the pupillary margin and the anterior hyaloid surface. Such an obstruction is characterized as an anterior pupillary block. The aqueous is accumulated between the vitreous and the iris and causes the peripheral iris to balloon forward. This mechanism occurs after extracapsular cataract extraction. There is postoperative inflammation seen because of the sensitivity to lenticular cortical material, leading to irido capsular adhesions. This occurs after the treatment of congenital cataract surgery.

• An accumulation of the aqueous humor between the iris-capsule diaphragm and the anterior hyaloid face is called the canal of Petit. Pressure is exerted from the aqueous and trapped in the posterior chamber, displacing the iris forward and is known as the posterior pupillary block. The block abrupts the forward movement of the aqueous to the anterior chamber leading to an iris bombe that prevents the aqueous humor from flowing from the posterior to the anterior chamber.

• The absence of an iridectomy (iris resection procedure) leads to the development of the pupillary block. It also occurs in eyes with a visible iridectomy if the iridectomy becomes occluded by irido capsular adhesions. The exact mechanism of the pupillary block is also seen with phacomorphic glaucoma (diagnosed by the presence of eye pain) and called anterior aqueous misdirection perilenticular. The aqueous humor is accumulated around and behind the crystalline lens and obstructs the aqueous movement.

What Are the Symptoms of Aphakic Pupillary Block?

• Pain in the eyes.

• Redness of the eyes.

• The blurring of vision.

• Decrease in vision.

• Headache.

• Nausea.

• Vomiting.

What Are the Causes of Aphakic Pupillary Block?

Aphakic pupillary block is seen following congenital cataract surgery in children. It also occurs following implantation of the lens with cataract surgery.

What Is the Treatment of Aphakic Pupillary Block?

The treatment of the pupillary block involves:

1) Early Recognition of the Condition: It is important to diagnose aphakic pupillary block at an early stage, so that treatment is done to treat the disorder.

2) Relief of the Pupillary Block: Relief of the pupillary block is done with the help of miotic drops and anti-glaucoma therapy.

3) Medical Treatment: Medical treatment consists of intensive cycloplegia (paralysis of ciliary muscles of the eyes), mydriasis (when the black center is enlarged than usual), and aqueous suppressants. If the cornea is hazy or when peripheral iridotomy cannot be performed immediately, then the following agents are used:

• Carbonic anhydrase inhibitors such as Acetazolamide.

• Mydriatic agents like Cyclopentolate and Phenylephrine.

• Topical beta-blockers such as Timolol.

• Topical alpha-agonists like Brimonidine or Apraclonidine.

• Vigorous use of strong mydriatics alone or with hyperosmotic agents such as glycerol or mannitol can be used.

4) Surgical Treatment:

• Surgical treatment also consists of peripheral iridotomy, peripheral iridectomy, or incision of the hyaloid membrane.

• Peripheral iridotomy is done, which relieves the block.

• Argon laser iridotomy can also help relieve pure pupillary obstruction by vitreous or other causes.

• Photomydriasis (pupilloplasty) is done using an argon laser.

• Nd: YAG laser is also used to perform peripheral iridotomy when inflammation of the eye is there.

What Are the Complications Associated With Aphakic Pupillary Block?

1. Iridectomy - It refers to the iris resection procedure.

• Hyphema is defined as accumulated red blood cells in the anterior chamber of the eyes.

• Corneoscleral wound infection is a sight-threatening complication.

2. Laser Iridotomy - It refers to the iris resection procedure done with the help of a laser. The complications are:

• Bleeding and inflammation at the laser site.

• Increase in eye pressure.

• Double vision.

What Is the Differential Diagnosis of Aphakic Pupillary block?

1. Choroidal Detachment: Hemorrhage in the suprachoroidal space or within the choroid because of the rupture of choroidal vessels. Aphakia and choroidal separation exhibit an extremely shallow or flat anterior chamber (choroidal detachment). The defining characteristic of choroidal separation is subnormal IOP, whereas the pupillary block has normal or increased IOP.

2. Malignant or Ciliary Block Glaucoma:

• Anterior chamber shallowness can induce the iris diaphragm to move forward and the ciliary body to rotate and thus misdirecting aqueous humor toward the vitreous, resulting in malignant or ciliary block glaucoma. It is an unusual side effect following trabeculectomy, triple glaucoma surgery, and cataract excision with or without IOL (Intraocular lens implantation).

• A vicious cycle of anterior chamber shallowing, anterior iris-capsular membrane displacement and aqueous misdirection, and more anterior chamber shallowing can result from hypotony brought on by free suturing of a corneoscleral lesion or hyperfiltration of a trabeculectomy.

• Early postoperative cycloplegic withdrawal can result in malignant or ciliary block glaucoma. One of the early steps in the spectrum of aqueous misdirection may be the absence of a functional iridectomy predisposing to relative pupillary obstruction.

3. Suprachoroidal Hemorrhage: Increased intraocular pressure, a shallow or flat anterior chamber, and abrupt onset of severe pain are the hallmarks of suprachoroidal hemorrhage. On an ultrasonography B-scan or during a fundoscopic examination, a dark, non-serous choroidal detachment can be noticed.

Conclusion:

Aphakic pupillary block is a life-threatening condition that results in irreversible blindness arising after treatment with cataract surgery. A pupillary block is an acute angle closure that requires emergency treatment. It leads to increased intraocular pressure and also causes optic nerve damage. Surgical therapy is often needed if it is not treated with medicinal treatment.