Lens-associated angle closure

occur gradually if it is age related or sudden if it is due to trauma. Those who are drug induced may have symptoms of blurred distant vision from acquired myopia due to lens swelling and a positive history of drug intake.

Ocular findings

There may be signs of acute angle closure attack with corneal oedema, shallow anterior chamber, mid dilated pupil, high IOP and closed angles (Fig. 1). However, the lens would be intumescent and swollen. At times liquefied lens matter may be visible within the lens capsule.

In cases where there is no view of the anterior chamber in the affected eye, a deep anterior chamber and open angles in the fellow eye would negate the diagnosis of primary angle closure.

Fig. 1. Anterior segment photograph showing lens intumescence causing secondary acute angle closure with circumciliary congestion, corneal oedema, shallow anterior chamber and intumescent cataract. (Courtesy of Prof. Robert Ritch, New York Eye and Ear Infirmary)

Management

The definitive management is surgical lens removal with or without implantation of intraocular lens.

The IOP should be controlled medically to a safe level prior to surgery. Topical corticosteroids should be given to reduce inflammation. Peripheral iridotomy and/or iridoplasty may be performed to relieve pupillary block and allow time to plan for surgery.7-9 However, PI may not relieve the angle closure if the mechanism is not due to pupillary block.

Miotics is not helpful as it may aggravate the pupillary block and may cause more inflammation. Surgical lens removal for this type of cases remains a challenge to the surgeon. The difficulty in lens removal could be due to poor visibility from corneal oedema, shallow anterior chamber, posterior synechiae, increased intralenticular pressure and liquefied cortex. The choice of cataract surgery, whether phacoemulsification10,11 or extracapsular cataract extraction,12 depends on the experience of the surgeon and on cornea clarity.

Ectopia lentis is defined as displacement or malposition of the crystalline lens from its normal central position within the posterior chamber. The lens is considered dislocated or luxated when all zonular attachments have been broken, although it may still remain behind the iris, it will normally be completely outside the lens patellar fossa. The dislocated lens may migrate anteriorly into the anterior chamber or posteriorly, freely floating in the vitreous or directly on the retina. The lens is described as subluxated when there are loosening or breakage of some of the zonules. The subluxated lens is partially displaced, but still remains partially or entirely within the pupillary space entirely behind the iris. Subluxation or dislocation of the lens can occur after trauma, as an isolated congenital anomaly,13,14 secondary to pseudoexfoliation15,16 or as part of the manifestation of systemic diseases such as Marfan’s syndrome,17-19 homocystinuria,17,20 microspherophakia,21 Weill-Marchesani syndrome,22-24 Ehler-Danlos syndrome25and hyperlysinemia.26 There are many other rare heritable conditions reported to be associated with ectopia lentis.27 Certain ocular conditions such as myopia, congenital glaucoma and aniridia may also cause lens subluxation.

Forward movement of the crystalline lens due to lax or absent zonules causes pupillary block and secondary angle closure, presentation of vitreous in the pupillary area can also cause pupillary block. The degree of zonular impairment determines the degree of lens displacement.

History taking

The patient may present with symptoms of acute angle-closure attack, which may be recurrent. There may be history of ocular trauma which can be recent or in the past. Patients can also present with a history of visual disturbances, including blurring of vision from myopia or astigmatism, reduced near vision from loss of accommodative power or monocular diplopia if the lens is significantly displaced. Uncorrectable poor visual acuity may lead to amblyopia in children and may be the most common cause of diminished visual acuity in patients with ectopia lentis.28 Those patients due to systemic diseases may have history of systemic problems such as cardiac or skeletal problems and a positive family history.

Ocular findings

Visual acuity varies with the degree of malpositioning of the lens and can be potentially debilitating and amblyogenic. A disparity between the degree of astigmatism found on refraction and that measured by keratometry, as well as a variable amount of astigmatism from one examination to another, should direct the ophthalmologist to consider early subluxation as its cause. The lens subluxation may be subtle with slight localized shallowing of the anterior chamber to gross phacodonesis with displacement of the lens (Figs. 2 and 3). In early stages of subluxation, wide pupillary dilation may be necessary to confirm asymmetry of lens position. Gonioscopy will show varying degrees of narrowing of the angles depending on the degree of lens subluxation (Fig. 4). Intraocular pressure may or may not be raised.

The clinician should be suspicious of microspherophakia when angle closure

Fig. 2. Anterior segment photograph showing anteriorly subluxated cataractous lens secondary to trauma, the anterior chamber is shallower inferiorly and some vitreous strand is vaguely seen inferiorly. The patient subsequently had intracapsular cataract extraction and scleral fixation of posterior chamber intraocular lens. (Courtesy of Dr S.K. Fang)

Fig. 3. Anterior segment photograph showing a patient with Marfans syndrome whose crystalline lens is bilaterally subluxated upwards and outwards, zonules are present but stretched, the inferior equator of the lens is clearly seen almost bisecting the pupil. This patient had phacoemulsification cataract surgery with insertion of a Cionni modified capsular tension ring to fix the capsular bag to the sclera and in-the-bag foldable intraocular lens. (Courtesy of Dr S.K. Fang)

occurs in a young myopic individual or the myopic individual has a shallow anterior chamber. One should be also suspicious when angle closure occurs in patients who have history of ocular trauma, and those with presence of other congenital anomalies.

Fig. 4. Anterior segment photographs of the same patient who had secondary angle closure from a subluxated lens. A: shallow anterior chamber with subtle bulge of the lens forward. B and C: gonioscopic photos, showing the forward bulge of the lens. The bulk of the lens is in contact primarily with the middle third of the iris, stretching it and creating a bulge that appears to it the contour of the lens. The patient subsequently had a laser peripheral iridotomy, which relieved the pupillary block and the secondary angle closure. (Courtesy of Dr S.K. Fang and Dr Michael Law)

Management

Medical management to reduce IOP should include the use of a hyperosmotic agent to shrink the vitreous which would allow the lens to move posteriorly. If the lens is caught in the pupil or anterior chamber, a weak mydriatic agent should be administered. If the zonules are known to be intact a cycloplegic drug may be used to pull the lens posteriorly. Putting the patient in a supine position may facilitate the lens to reposit itself in the posterior chamber. Once the lens is in the posterior chamber, the pupil is constricted with a miotic, and peripheral iridotomy is performed.

The definitive management in most cases is laser peripheral iridotomy, which is the treatment of choice especially when angle closure appears imminent. If the condition is bilateral, the fellow eye should receive laser iridotomy prophylacti-

cally. The patient is then treated with a miotic to prevent the forward migration of the lens.

There are a few situations in which surgical removal of the lens is necessary. This includes inability to reposit the lens (especially if dislocated anteriorly), raised IOP even after a successful PI, intolerable monocular diplopia, reduction of visual acuity related to cataract or high astigmatism and phacolytic glaucoma.

The possible surgical options for lens removal are:

1.Intracapsular cataract extraction, anterior vitrectomy with anterior chamber or scleral fixated intraocular lens implant.

2.Phacoemulsification with insertion of capsular tension ring and in-the-bag intraocular lens implant.29-32

3.Phacoemulsification with insertion of modified or Cionni type of capsular tension ring (scleral fixation of capsular bag) and in-the-bag intraocular lens implant.33

4.Phacoemulsification with small incision scleral fixation of intraocular lens implant in the ciliary sulcus in cases where the capsular support is inadequate.32

5.Phacofragmentation of dislocated lens in the vitreous cavity with anterior chamber or scleral fixated intraocular lens implant.34,35

6.Pars plana lensectomy with or without intraocular lens implant.36,37

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