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Across the Pond | Oct 2008

Capsular Block Syndrome: A Case Report

Capsular block syndrome (CBS) is a rare complication that may occur after continuous curvilinear capsulorrhexis (CCC) and in-the-bag implantation of a posterior chamber IOL. CBS is caused by circumferential adherence between the anterior capsular opening and the optic plate of the IOL or lens nucleus. Capsular bag distension occurs behind the IOL or lens nucleus.

CASE REPORT
We previously published a case of postoperative CBS1 describing the clinical features of an eye with late-postoperative CBS occurring 7 years after cataract surgery.

In October 2007, a 76-year-old man was referred to our clinic. The patient complained of blurred vision in his right eye, which had progressed over the previous month. Ocular history included uneventful cataract surgery in October 2000 with in-the-bag implantation of a 23.00 D AcrySof MA60 hydrophobic acrylic IOL (Alcon Laboratories, Inc., Fort Worth, Texas).

The eye examination revealed UCVA of counting fingers at 30 cm. Upon slit-lamp biomicroscopy evaluation, a fibrotic and thickened anterior capsular opening was seen, and a turbid, whitish fluid entrapped behind the IOL (Figure 1) had inflated the entire capsule and masked the view of the posterior capsule and posterior segment. Fibrosis was present along the entire circumference of the anterior capsular rim. The margin of the CCC was smaller than that of the IOL and covered its edges. No corneal abnormalities, shallowing of the anterior chamber, cells, or flare were observed. Examination of the retina and vitreous body was impractical. The intraocular pressure (IOP) was 15 mm Hg.

A late-onset CBS was diagnosed at the slit lamp. Subsequently, Nd:YAG laser posterior capsulotomy was performed, resulting in rapid movement of viscous fluid into the vitreous. The capsular bag distension disappeared. One week later, the patient's visual acuity improved to 20/20, and slit-lamp examination revealed a quiet eye; however, white aggregates were seen on the posterior surface of the IOL (Figure 2).

DISCUSSION
Miyake et al2 proposed a classification of CBS based on time of onset: intraoperative, early-postoperative, and late-postoperative. Recently, Kim et al3 classified postoperative CBS into groupings according its pathogenetic mechanism (ie, expected main cause, time of onset, and treatment): noncellular CBS, inflammatory CBS, and fibrotic CBS. The latter classification system partly overlaps with that of Miyake et al, but it differs because for the first time some cases of inflammatory CBS were described.

Intraoperative CBS. This type of CBS (Figure 3) results from a forceful hydrodissection and is characterized by an abrupt shallowing of the anterior chamber associated with luxation of the lens nucleus. In the worst cases, a posterior capsular rupture occurrs, and the lens nucleus luxates into the vitreous, further shifting the iris/lens-capsule diaphragm anteriorly. IOP also becomes elevated.

Intraoperative CBS is more commonly associated with axial lengths greater than 25 mm.

Early-postoperative CBS. Occurring 1 to several days after surgery, early-postoperative CBS (Figure 4) is defined as the presence of capsular bag distension due to the accumulation of liquid between the IOL and the posterior capsule. The IOL is displaced forward, causing a myopic shift. Additionally, elevated IOP results. The main pathogenetic mechanism is likely the retention of ophthalmic viscosurgical device (OVD) in the capsular bag.4 OVDs create an osmotic gradient across the capsule that works as a semipermeable membrane. Subsequently, aqueous humor moves into the capsular bag.

Early-postoperative CBS occurs more often when a one-piece PMMA IOL, larger optic IOL, or square-edged IOL is used because they create a bend-related capsular block.5 IOL implantation in the presence of a small (4.5–5 mm) anterior CCC is also a risk factor for early-postoperative CBS.6

This condition is generally self-limiting. The surgeon may elect to perform an anterior or posterior Nd:YAG laser capsulotomy or a surgical capsular disruption. Noncellular CBS has a pattern compatible with early-onset CBS. Inflammatory CBS, described by Kim et al,3 has features similar to the noncellular type. Moreover, it presents an inflammatory cellular anterior chamber reaction that is manageable with topical steroids. In this condition, the inflammation promotes adherence of the IOL to the capsular opening. Topical steroidal antiinflammatory medications resolve the capsular distension and restore visual acuity.

Late-postoperative CBS. This type of CBS usually occurs several years after cataract surgery (Figure 5). A transparent, homogeneous, milky-white fluid containing floating particles accumulates inside the distended capsular bag. The anterior chamber is deep, but the IOP does not increase. Fibrosis between the optic and anterior capsular opening is seen, along with moderate distension of the capsular bag.

Fibrotic CBS has a pattern suggesting a diagnosis of late-onset CBS.3 Late-postoperative CBS may likely result from capsular bag accumulation of collagen and extracellular matrix produced by residual proliferating lens epithelial cells and/or osmotic attraction of fluid due to the types of substances previously described.2

Our patient had all of the features of late-postoperative CBS/fibrotic CBS. He described being asymptomatic until 7 years after surgery, when progressive blurring of vision occurred. The patient's visual acuity could not be improved beyond counting fingers at 30 cm with correction because of the dense, whitish fluid inflating the capsular bag. An unexpected myopic refraction is the usual symptom of onset of early-postoperative CBS. The variable amount of myopic shift corresponds with a slight improvement in near vision; however, late-postoperative CBS often does not induce deterioration of vision, except in cases that exhibit greater amounts of milky-white substance between the posterior surface of the IOL and posterior capsule. In some cases, patients with late-onset CBS complain of intermittent blurred vision (worse in the morning and in the supine position), which is consistent with the material moving in the inflated capsular bag.7 Late-postoperative CBS presenting with a hyperopic shift has also been described.8

In CBS, the etiology of the accumulated substance inside the capsular bag, the symptomatology described by the patient, and the management of these conditions are specific to the form of CBS. Therapeutic options also vary according to type of CBS.

In inflammatory CBS, topical antiinflammatory medications are the main treatment strategy.

In early-postoperative CBS, it may be best to wait for a spontaneous resolution; however, if CBS persists over weeks, or if the patient is not willing to wait, remediation can be attempted with Nd:YAG laser capsulotomy, needle revision at the slit-lamp,9 or surgical lysis of adhesions between the IOL and the anterior capsule. If early-onset CBS is untreated, the eye may develop secondary angle-closure glaucoma, posterior synechiae, or posterior capsular opacification (PCO).

Anterior or posterior Nd:YAG capsulotomy promotes the flow of fluid into the anterior chamber or vitreous cavity, respectively, with instant deepening of the anterior chamber. Capsulotomy usually achieves an immediate resolution of CBS; however, it is not free from disadvantages. Anterior Nd:YAG capsulotomy is the preferred method to resolve the distension of the capsular bag in cases of early-postoperative CBS. Often, posterior capsulotomy does not relieve CBS because of a posteriorly dislocated posterior capsule. A careful global assessment of the possible sequelae, such as a sudden release of an OVD into the anterior chamber causing elevated IOP, the need for wide dilatation of the pupil, or the risk of hemorrhage or posterior synechia formation due to contact with the iris margin, is necessary.

Mardelli9 treated early-postoperative CBS patients by introducing a 30-gauge needle through the peripheral cornea and into the anterior chamber, pushing the IOL posteriorly into the capsular bag. This repositioning allows the fluid to move across the edge of the CCC into the anterior chamber. The procedure is repeated until the capsular bag is empty and the posterior capsule is in direct apposition to the IOL.

In late-onset CBS, posterior Nd:YAG capsulotomy is generally the chosen method to remove the PCO. Nevertheless, the surgeon must consider both the possibility of rhegmatogenous retinal detachment and the technical difficulty of reliably focusing the Nd:YAG laser on the posterior capsule due to the opaque fluid distending the capsular bag.

Preventive measures include complete removal of the OVD from the capsular bag after IOL implantation or by intraoperative peripheral anterior capsulotomy.10 There are published observations of CBS following extracapsular cataract extraction11 with a can-opener type capsulorrhexis, and reports of CBS were associated with IOL implantation in the sulcus (posterior surface of the IOL optic occludes the anterior capsule opening).12 Therefore, CBS can occur at any time during or after any type of cataract surgery; however, it is most often notable in cases following CCC and phacoemulsification.

Giovanni Alessio, MD, is an Associate Professor of Ophthalmology, Department of Ophthalmology and Otorhinolaryngology, University of Bari, Italy. Professor Alessio states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +39 0805592058; fax: +39 0805478918; e-mail: g.alessio@oftalmo.uniba.it.

Maria Gabriella La Tegola, MD, is a researcher in the Department of Ophthalmology and Otorhinolaryngology, University of Bari, Italy. Dr. La Tegola states that she has no financial interest in the products or companies mentioned. She may be reached at e-mail: mg.lategola@oftalmo.uniba.it.

Milena L'Abbate, MD, is a postgraduate medical doctor in the Department of Ophthalmology and Otorhinolaryngology, University of Bari, Italy. Dr. L'Abbate states that she has no financial interest in the products or companies mentioned. She may be reached at e-mail: labbate.mail@gmail.com.

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