CHAPTER 31 Refractive lens exchange
History
Early in the year 1890, Fukala reported on refractive lens extraction in eyes with high myopia1. This procedure was subsequently abandoned due to the 10-fold increase of post-operative retinal detachment in comparison to unoperated myopic eyes. Since 1890, ophthalmic surgery has undergone steady changes by means of innovations in intraocular lens design, application of ophthalmic viscoelastics substances, and development of phacoemulsification and microincisional surgical techniques. These innovations improved the safety and efficacy of refractive lens exchange (RLE), making it an integral part of refractive surgery today.
Indications and patient selection
Indications for RLE are high myopia or hyperopia with coexistent presbyopia. The reason for the inclusion of presbyopia is the fact that RLE always leads to a complete loss of accommodation. Correction of underlying regular astigmatism in scope of RLE, which cannot be managed by corneal incisional techniques, is best accomplished by implantation of toric lens implants. Border indications for RLE are presbyopia without ametropia implying implantation of a multifocal lens implant, presbyopia with underlying astigmatism, and prepresbyopic patients with high hyperopia of from +5 to +10 D not amenable for keratorefractive surgery or phakic IOL due to shallow anterior chamber situation. Table 31.1 displays an overview over indications for RLE.
Preoperative calculation of IOL power
Exact calculation of IOL power is essential for a good postoperative outcome. It mainly depends on measurement of axial length, corneal power, and the IOL power calculation formula. In fourth-generation formulas, patients’ age, preoperative refraction, preoperative anterior chamber depth, lens thickness, and white to white measurement are also taken into consideration. In our own recent study, we assessed the predictive ability of third- (Hoffer Q and SRK/T) and fourth-generation (Holladay and Haigis) formulas in eyes with high ametropia2. All formulas tended to produce hyperopic surprises with the manufacturers’ lens constants in eyes having myopic RLE. With optimized lens constants, the Haigis formula performed best. In eyes with hyperopic RLE, all four formulas were almost equivalent2.
Complications in refractive lens exchange
Intraoperative complications
Myopic RLE may be difficult due to instability of the capsular bag. This bears an increased risk of tearing the capsule. Insertion of a capsular tension ring might alleviate the intraoperative situation, especially in cases of weak zonules or lysis of the zonules. In eyes with high axial length, the risk of an intraoperative subchoroidal hemorrhage is markedly increased as compared with that in normal eyes3. In eyes with an axial length of more than 25 mm rare capsular block syndrome appears more frequently4.
Hyperopic RLE surgery in eyes with an axial length below 21 mm is hampered by the narrow spatial situation and shallow anterior chamber. Compared with eyes with normal axial length, the risk of choroidal effusion syndrome (Fig. 31.1) is markedly increased5.
