As a lens-based option for the correction of refractive error, refractive lens exchange (RLE) has recently become an acceptable alternative to laser vision correction procedures, including LASIK and PRK, in presbyopic patients. RLE reduces or eliminates patients' dependence on postoperative optical correction. It may be the best surgical option for correction in patients with high refractive errors.1
In this cover focus, CRST Europe reviews and explores RLE techniques, considerations, and proper patient selection.
Alternatively called clear lens exchange, clear lens extraction, or refractive lens replacement, the RLE procedure removes the crystalline lens and replaces it with an IOL to correct hyperopia or myopia, and, increasingly, presbyopia.1 Although the surgical procedure for RLE parallels that of standard cataract surgery, patients undergoing RLE typically have higher expectations and do not easily accept anything less than excellent results.2,3 For this reason, IOL choice is paramount.
This first article features two surgeons—Charles Claoué, MA(Cantab), MD, DO, FRCS, FCROphth, FEBO, MAE, and Uday Devgan, MD, FACS—who share their respective processes for selecting the best IOL for each RLE patient.
CHARLES CLAOUÉ, MA(Cantab), MD, DO, FRCS, FRCOphth, FEBO, MAE
The vast majority of my RLE patients are presbyopic. The most important decision they make is whether to choose implantation of a monofocal or multifocal IOL for RLE. I do not create pseudophakic monovision unless the patient is already a happy monovision contact lens wearer.
Whichever IOL type the patient chooses, I guide them to the best IOL in that category. Because these patients do not have any media opacity, I suggest an IOL with a low posterior capsular opacification (PCO) rate. Unfortunately, all manufacturers claim to have the lowest PCO rate, and we must be critical of such claims. I am convinced from animal work4 and human research5 that the presence of a square-edge design is more important than the material of the IOL. Animal6 and human clinical data7 have also shown that it must be a 360° square-edge design to be efficient. If an IOL does not have a 360° square edge, it is an unacceptable choice for RLE.
A significant number of IOLs have square edges that do not cross the haptic-optic interface; I believe these IOLs should not be options for any RLE patient. Such IOL designs are also suboptimal choices for cataract surgery.
The IOL that I choose must address the patient's aspirations—most patients desire spectacle independence. My experience with accommodating IOLs has not been positive.8 Therefore, for RLE, I currently use multifocal IOLs with physiological optics that are well understood. I prefer an aspheric to a nonaspheric multifocal IOL, and I believe that zero asphericity models have some pseudoaccommodative advantage over negative aspheric versions.9,10
Significant corneal astigmatism has always been a significant contraindication for most patients considering RLE. Corneal incisions can address this,11 albeit with only medium predictability. Two European IOL manufacturers now make toric, aspheric, and multifocal IOLs: Carl Zeiss Meditec (Jena, Germany; formerly Acri.Tec GmbH) and Rayner Intraocular Lenses Ltd. (East Sussex, United Kingdom). Unfortunately, the former does not manufacture any IOLs with a 360° square-edge design. Both Carl Zeiss and Rayner manufacture true customized IOLs and must be preordered with the customized toric correction. Implantation is easy, and my experience is that patient satisfaction is high, as in most cases other surgeons have declined to perform laser vision correction in these patients. When choosing whether to implant an IOL with a +4.00 or a +3.00 D add at the IOL plane, I not only listen to my patient's requirements, but I also look critically at his morphology. It may seem too simple to state this, but shorter people have shorter arms; therefore, they are usually more comfortable with the shorter working distance of the +4.00 D add IOL.
The above explanation considers RLE in the phakic patient; however, pseudophakic patients also seek lens exchange for refractive reasons. Although these are not classically considered RLE patients, to me the conceptual simile is obvious. Exchanging the existing IOL for a new one may make sense in the immediate postoperative period; however, such patients may be several years postoperative before they request the lens exchange, making explantation hazardous and risking existing capsular support.
Although the existing IOL power may be known, it is often unavailable, or the IOL power may not be what was claimed on the box. In such cases, IOL exchange can result in a new and highly embarrassing refractive error. Therefore, I prefer piggybacking IOLs so that the adequate IOL power is reached by a simple vergence formula without knowing the existing IOL power.
Michael Amon, MD, Professor of Ophthalmology at the University of Vienna in Austria, recently described an IOL specifically designed for piggybacking.9-12 With rounded edges for uveal compatibility and a concave posterior surface to prevent IOL optic contact centrally, the Sulcoflex (Rayner Intraocular Lenses, Ltd.) is available with a toric, multifocal, or toric-multifocal option.
The future of RLE looks good to me.
UDAY DEVGAN, MD, FACS
The two main considerations for IOL selection in RLE surgery are the (1) patient's needs for vision and (2) his individual biometry and ocular status. For extreme myopes, I prefer a phakic IOL solution to RLE because I feel the risk of a retinal detachment is less when the human crystalline lens is retained. My principal lens exchange patients are hyperopes who fall outside the range of LASIK or PRK, which is 4.00 D or more.
For a spherical hyperope, many IOLs will be appropriate choices, with preference given to accommodating and multifocal lenses, which would also address presbyopia. To maximize UCVA after RLE, astigmatism must also be addressed. Because these patients tend to be younger than the average cataract patient, a limbal relaxing incision for astigmatism will be less effective. For 2.00 D or more of corneal astigmatism, a toric IOL would effectively address the cylinder.
Bioptics is sometimes the best approach to patients with extreme refractive errors. As the axial length of the eye gets shorter and hyperopia more severe, the IOL calculations become less accurate. The Hoffer-Q and Holladay 2 formulas tend to give better results; however, care should be taken to err on the side of residual myopia if a bioptics approach is planned. Excimer ablations for mild degrees of myopia is quite accurate.
The bottom line for RLE patients is addressing all of their refractive issues as accurately as possible. If the hyperopia, astigmatism, and presbyopia are all precisely corrected, the patient will be pleased with his resultant vision.
Charles Claoué, MA(Cantab), MD, DO, FRCS, FCROphth, FEBO, MAE, is a Consultant Ophthalmic Surgeon at The Queen's Hospital, BHR Hospitals NHS Trust, London, an Honorary Clinical Lecturer at the University of London, and Honorary Consultant Ophthalmologist at the Academic University of Pretoria. Dr. Claoué states that he is a consultant to and has a royalty agreement with Rayner Intraocular Lenses, Ltd. He may be reached at tel: +44 20 88 52 85 22; fax: +44 20 82 65 32 89; e-mail: email@example.com.
Uday Devgan, MD, FACS, practices at the Maloney Vision Institute, Los Angeles, and is Chief of Ophthalmology, Olive View-UCLA Medical Center. Dr. Devgan states that he is a consultant to Allergan, Advanced Medical Optics, Inc., Bausch & Lomb, Ista Pharmaceuticals, and STAAR Surgical, and has received award funds and travel support from Alcon Laboratories, Inc. He may be reached at tel: +1 310 208 3937; e-mail: firstname.lastname@example.org.