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Subluxated Intraocular Lenses


Key Points

  • Detailed ocular examination in patients with subluxated IOLs is a must, including undilated gonioscopy and dilated slit lamp evaluation to reveal the status of the zonules, capsular bag, and any endocapsular device in situ.

  • Subluxated IOLs may result from missed systemic entities. Hence, complete evaluation including family history and general examination is a must in all cases.

  • It is important to rule out any trauma to the eye or ocular appendages in the remote past, which the patient might find trivial, because this helps anticipate various intraoperative challenges like zonular dialysis.

  • Subluxated IOLs may present with lenticular astigmatism, monocular diplopia, and glare and halos caused by IOL edge effect.

  • Investigations like anterior segment OCT (ASOCT), B scan, and ultrasound biomicroscopy (UBM) can help precisely localize a subluxated/ dislocated IOL or parts like missing haptic/ optic.

  • Subluxated IOLs can be classified as in-the-bag IOL subluxation and out-of-the-bag IOL subluxation.

  • In-the-bag IOL subluxation with intact capsular bag can be managed with endocapsular devices like capsular tension ring, glued capsular, hook and paperclip capsule stabilizer.

  • Out-of-the-bag IOL subluxation can be managed with various methods of scleral fixated IOLs like glued IOL.

  • Eyes with subluxated IOLs are more prone to develop complications like cystoid macular edema, pseudophakic bullous keratopathy, and secondary glaucoma.

Introduction

What is Subluxation of IOL?

Subluxation of intraocular lens (IOL) is defined as partial displacement of the IOL away from its physiologic position. It can be classified based on the capsular bag-IOL relation:

  • In-the-bag IOL subluxation : IOL is subluxated but still in the capsular bag ( Fig. 53.1 ). This is commonly seen in cases of zonular dehiscence for (e.g., pseudoexfoliation syndrome). It is important to make note of any previously implanted endocapsular devices that support the bag in such cases ( Figs. 53.2 and 53.3 )

    Fig. 53.1, In-the-bag IOL subluxation. IOL subluxation noted with fibrosed capsular bag.

    Fig. 53.2, In the bag IOL subluxation with capsular tension ring (CTR) in situ.

    Fig. 53.3, Subluxated sutured Ahmed segment with broken suture.

  • Out-of-the-bag IOL subluxation :

    • ■

      This can arise in two different situations:

    • 1.

      IOL is subluxated with haptic/optic or both parts lying out of the capsular bag . This is common in cases with posterior capsular compromise/tear. Fibrosed or shrunken capsular remnants may be seen ( Fig. 53.4 ).

      Fig. 53.4, Out-of-the-bag IOL subluxation with posterior capsular rent (PCR).

    • 2.

      IOL is subluxated with no/absent remnants of capsular bag . This is very rare and is usually seen in cases of nonphaco cataract surgeries (small-incision cataract surgery [SICS] or extracapsular cataract extraction [ECCE]) wherein the mature cataractous nucleus was accidentally delivered with the capsular bag around it or sometimes also after complicated phacoemulsification. In such cases, the primary IOL is usually an anterior chamber IOL/iris fixated IOL or scleral fixated IOL, which may subsequently get subluxated as a result of improper fixation/support.

What is Dislocation/Luxation of IOL?

Complete displacement of IOL from its physiologic position is known as dislocation or complete luxation of the lens. IOL can be dislocated in the following ways:

  • 1.

    Anteriorly: IOL may lie in the anterior chamber leading to iris chafing, glaucoma, and pseudophakic bullous keratopathy.

  • 2.

    Posteriorly: IOL may drop through a posterior capsular tear or may drop within the bag to lie in the vitreous or on the retina, causing vitreous traction and damage to the retina.

Incidence and Etiology

Subluxation and dislocation of IOL have an overall incidence of 0.05% to 3% of cataract surgeries.

The etiology can be classified as shown in Table 53.1 .

Table 53.1
Etiologic Classification of Subluxated/Dislocated IOL
Preoperative Intraoperative Postoperative
Primary causes: High myopia, Marfan’s syndrome, Ehlers Danlos syndrome, Weil Marchesani, homocystinuria, hyperlysinemia,aniridia, lens coloboma,familial ectopia lentis Damage to capsular bag or zonules during various steps of cataract surgery or vitreoretinal surgery. Capsular fibrosis and shrinkage caused by pseudoexfoliation, diabetes mellitus, uveitistrauma (unrelated to surgery). Suture disintegration of primarily suture fixated IOL
Secondary causes: Pseudoexfoliation, trauma, uveitis, angle closure glaucoma

Preoperative

Primary

This includes congenital causes predisposing to subluxation caused by zonular weakness/dehiscence/absence. These cases usually present with bilateral subluxated IOLs. Examination of the other eye and syndromic associations aid in diagnosis of such entities.

  • High myopia

  • Marfan’s syndrome

  • Weil-Marchesani

  • Ehlers Danlos syndrome

  • Homocystinuria

  • Hyperlysinemia

  • Aniridia

  • Familial ectopia lentis

  • Lens colobomas

Secondary

This includes acquired causes of zonular dehiscence/weakness.

  • Pseudoexfoliation

  • Trauma

  • Angle closure glaucoma

Intraoperative

Damage to zonules or capsular bag during various steps of cataract or vitreoretinal surgery can lead to immediate or late IOL subluxation/dislocation. Common causes include the following:

  • Incomplete hydrodissection of the nucleus leading to zonular damage while attempting to rotate the nucleus

  • Excessive stress on zonules while sculpting or chopping

  • Accidental capsular aspiration during aspiration of cortex causing traction on zonules

  • Posterior capsular rent / compromise at any step of surgery ( Fig. 53.5 )

    Fig. 53.5, Out-of-the-bag IOL subluxation with posterior capsular rent.

  • A large capsulotomy or rhexis runaways also increase the chance of compromise on zonules.

Postoperative

Intraoperative/secondary causes usually present as postoperative IOL subluxations.

  • Capsular shrinkage and fibrosis (in pseudoexfoliation, diabetes mellitus, and uveitis) ( Fig. 53.6 )

    Fig. 53.6, Capsular shrinkage causing stress on zonules and dehiscence. The capsule has anatomic attachment of the zonules, hence shrinking of the capsule causes stress on zonules, weakening them leading to zonular dehiscence and disruption and subluxation of the IOL.

  • Trauma to the eye with blunt objects/sports related injury.

  • Suture disintegration of sutured scleral fixated IOL

Symptoms and Signs

Patient with IOL subluxation may be asymptomatic or present with various complaints, symptoms being specific for various scenarios that may be associated with the entity.

  • Glare/halos exaggerated while observing lights in poor lighting : this is common in mild to moderate subluxated IOLs caused by the edge effect of the IOL rim. Astigmatism, along with prismatic and higher order aberrations, set in and induce halos/glare around a light.

  • Monocular diplopia is seen in moderate to severe cases because of double refraction of the light via the aphakic and pseudophakic area of the pupil. There can also be perception of shaky/ shaking images because of associated pseudophakodonesis.

  • Constant blurred vision may be caused by astigmatism or induced aberrations.

  • Metamorphopsia may be caused by associated cystoid macular edema.

  • Redness with pain and cloudy vision point toward early onset of pseudophakic bullous keratopathy, uveitis, or rise in intraocular pressure caused by secondary glaucoma.

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