Chapter 17 Weakened or missing zonules present a serious challenge to the cataract surgeon. Every step of the procedure from the capsulotomy to the final removal of the viscoelastic is more challenging due to the lack of zonular integrity. Intraoperative complications are more likely, such as vitreous loss and nucleus subluxation. Intraoperative centration of the intraocular lens (IOL) and its long-term stability are also of concern. Techniques that utilize the healthy zonules yet minimize the stress on the compromised zonules will decrease the risk of complications in these patients. The crystalline lens is described as dislocated or luxated when it lies outside the lens space (the patellar fossa), in the anterior chamber, in the posterior segment, or even on the retina. It is partially dislocated or subluxed when it remains within the lens space but is out of position. Table 17–1 lists the causes of lens dislocation.1 The most common cause is trauma.2 The second most common cause is pseudoexfoliation. As many as 5% of these patients have subluxation, although it may often be occult. Iridodonesis and phacodonesis may not be visible as the iris is infiltrated with pseudoexfoliative material, causing it to be stiff and immobile. The zonules are infiltrated with the pseudoexfoliative material, causing them to be fragile. They tend to break in the middle or at their attachment at the ciliary body. The few remaining common causes of lens dislocation are hereditary. They include Marfan’s syndrome, homocystinuria, and Weill-Marchesani syndrome. In Marfan’s, lens dislocation may be present at birth, remain stationary, or progress slowly up, or up and out. The zonules appear to be the cause of lens movement as they are thin and poorly aggregated. In homocystinuria the lens is spherophakic, with a crenated boarder. The zonules are weak and rupture at their midpoint. The lens may dislocate into the anterior chamber and precipitate glaucoma. Finally in Weill-Marchesani syndrome the lens tends to dislocate downward or centrally. Episodes of pupillary block are frequent as the small lens comes forward to occlude the pupil. In consideration of the above, trauma, pseudoexfoliation, and Marfan’s syndrome are the most common etiologies producing both cataracts and partial lens dislocation.1,3 A successful outcome is more likely when the surgery is preceded by a comprehensive preoperative examination. The surgeon should characterize and draw the zonular defect, describing the weakness in terms of degrees of loss, location of the defect, and presence or absence of vitreous within the anterior segment. He should make note of whether phacodonesis is present or absent. It is important to identify an angle recession and the existence of synechiae as implantation of an anterior chamber IOL may become necessary should capsular bag support become insufficient. Informed consent should be modified from that for the routine cataract. The patient should be specifically informed about the possibility of either a sutured posterior chamber IOL or a capsular tension ring.
CATARACT SURGERY IN
THE PRESENCE OF
COMPROMISED ZONULES
ANATOMIC AND ETIOLOGIC CONSIDERATIONS
PATIENT EVALUATION
Trauma, perforating, and nonperforating Secondary to ocular processes (“consecutive”) Staphylomas, ectasias Buphthalmias High myopia Hypermature cataract Syphilis, chronic uveitis Perforated corneal ulcer Displacement by tumors or contracting scars Unknown etiology, possibly hereditary Pseudoexfoliation syndrome | |
Primary hereditary systemic disease | Hereditary |
Marfan’s syndrome, inherited | AD |
Marfan variants | AD |
Congenital contractual arachnodactyly |
|
Asymmetric Marfan’s syndrome |
|
Homocystinuria | AR |
Weill–Marchesani (brachymorphia–spherophakia) | AR, AD |
Dominant spherophakia (McGavic type) | AD |
Simple ectopia lentis et pupillae | AR |
Hyperlysinemia | AR |
Sulfite oxidase deficiency | AR |
Primary hereditary systemic disease, infrequently associated with ectopia lentis |
|
Aniridia with microcornea |
|
Conradi’s syndrome |
|
Crouzon’s disease |
|
Dominantly inherited blepharoptosis, high myopia, and ectopia lentis |
|
Ehler–Danlos syndrome |
|
Familial pseudomarfanism |
|
Kniest syndrome Mandibulofacial |
|
dysostosis Megalophthalmos |
|
Oxycephaly |
|
Pfaundler syndrome |
|
Pierre Robin syndrome |
|
Proportional dwarfism and ectopia lentis |
|
Refsum’s syndrome |
|
Retinitis pigmentosa |
|
Sprengel’s deformity |
|
Sturge-Weber syndrome |
|
Wildervanck’s syndrome |
|
AD, Autosomal dominant; AR, autosomal recessive.
SURGICAL TECHNIQUE
It is of great importance not to overpressurize the eye at any time during the procedure, which might stress already weakened zonules, leading to unzipping of zonules and lens subluxation. Preoperatively, therefore, a Honan balloon or digital pressure should be gently applied after peri- or retrobulbar anesthesia administration.
In the operating room a number of surgical principles must be observed. Placing the incision away from the area of zonular weakness will reduce the stress caused by necessary movements of the phacoemulsification tip. An appropriate volume of highly retentive and cohesive viscoelastic material, or a reverse soft shell technique as described in Chapter 24
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