Introduction

Phakic intraocular lenses (PIOLs) have been used for many years as a backup for patients who cannot have laser refractive surgery. There are three different types of PIOLs: the anterior chamber (AC) angle-supported PIOL, AC iris-fixated PIOL, and posterior chamber PIOLs. All three will have to be explanted at one point due to natural phacoesclerosis or to complications related to the PIOL. Depending on the cause of explantation and the patient’s age, they can be changed for either another PIOL or for a posterior chamber in-the-bag intraocular lens (IOL). The main causes of PIOL explantation are cataract formation, endothelial cell loss, corneal decompensation, IOL decentration, pupillary ovalization, high intraocular pressure (IOP), inadequate size or IOL power, and halos and glare ( Table 33.1 ).

Cataract Formation

Cataract formation is the principal cause of PIOL explantation ( Table 33.2 ).

The main causes of cataract formation are surgical trauma, high myopia, postoperative use of topical steroids, and inflammation secondary to the disruption of the blood-aqueous barrier. In posterior chamber PIOL, cataract formation may be secondary to intermittent trauma during accommodation, inadequate vaulting, lens trauma from preoperative yttrium-aluminum-garnet (Nd:YAG) laser iridotomy, and the use of dispersive viscoelastic, which can produce changes in the epithelial cells of the lens.

The incidence of cataract formation is higher with posterior chamber PIOLs than with AC PIOLs. This is due to the proximity between the IOL and the crystalline lens, which impairs the normal nutrition of the lens. Cataract formation is related to surgical trauma if it appears less than 3 months after surgery and to poor vault if it occurs 1 year after surgery. The anterior subcapsular cataract is the most common type of cataract after the implantation of a posterior chamber PIOL. It can be either diffuse or can have a focal dotlike appearance. The former causes glare and progresses slowly; the latter is asymptomatic and usually does not progress. In angle-supported PIOLs, nuclear cataract formation is the most common ( Fig. 33.1 ).

Nuclear cataract in a patient with an angle-supported Baikoff ZB5M PIOL.

Severe pupil ovalization with an angle-supported Baikoff PIOL.

The time between PIOL implantation and explantation will depend on the type of PIOL (see Table 33.3 ).

Endothelial Cell Loss

The main reasons for endothelial cell loss are an inadequate anatomy of the AC, PIOL design (acute endothelial cell loss is higher in angle-supported PIOLs than with iris-fixated PIOLs), PIOL intermittent contact with the posterior cornea, inflammatory mediators in the aqueous humor that are released owing to uveal trauma, and early postoperative high IOP.

The indications for PIOL explantation are

• 1.
  

  when the endothelial cell count is less than 1500 cells/ mm, ²

  
  
• 2.
  

  progressive loss of endothelial cells greater than 20% per year for 2 years regardless of the number of cells,

  
  
• 3.
  

  in AC PIOLs when distance between the endothelium and PIOL is <1.5 mm.

Decentration/Dislocation of PIOL

Decentration of PIOLs may induce visual symptoms (diplopia, glare ) or they may damage the structures of the AC, requiring its explantation. It is usually secondary to oversizing of the PIOL. In iris-fixated PIOLs, decentration happens if the enclavation of the haptic to the iris is not sufficient.

Dislocations can also be secondary to blunt ocular trauma.

Pupillary Ovalization

Pupillary ovalization mainly occurs in AC PIOLs; it is secondary to IOL oversizing and by a compression of the iris root vessels by the IOL haptics that causes ischemia of the iris root, inducing an iris retraction and atrophy. In iris-fixated PIOLs, pupillary ovalization is caused if the haptics are secured asymmetrically.

Explantation is required when the pupillary ovalization extends beyond the edge of the PIOL or when it causes glare and haloes that diminish the patients quality of vision. Caution should be taken during explantation surgery because of the formation of adhesions between the PIOL, AC, and iris.