Refractive lens exchange (RLE), also called clear lens extraction, seeks to modify the focusing power of the eye by removing the clear or nearly clear (noncataractous) natural lens of the eye and replacing it with an intraocular lens (IOL).[26]
In refractive surgery, the properties of the cornea and/or lens can be surgically modified to better focus light onto the retina and decrease reliance on glasses or contacts.
Examples of refractive procedures targeting the cornea include:
Laser-assisted in situ keratomileusis (LASIK)
Photorefractive keratotomy (PRK)
Small incision lenticule extraction (SMILE)
Examples of refractive procedures targeting the lens include:
Phakic intraocular lenses (eg, with insertion of the Visian IOL lens implant between the posterior surface of the iris and anterior surface of the lens)[28]
Cataract surgery is removal of the lens that is sufficiently cloudy that it impairs quality of vision even with glasses and impacts quality of life. The procedure typically is eligible for insurance coverage.
Refractive lens exchange is removal of the clear or minimally cloudy lens to reduce or eliminate need for glasses and contact lenses. This is not eligible for insurance and is an out-of-pocket procedure.
It has become recognized that the crystalline lens of the individual over age 40 is “dysfunctional” in one or more ways. First, it becomes presbyopic, ie, loses the ability to accommodate, necessitating the use of reading or bifocal glasses or some other form of correction to provide near vision.[30] Second, the lens begins to develop some subtle but real clouding that can begin to impair quality of vision, even with optimal correction with glasses or contact lenses.[30] This has heightened interest in performing refractive lens exchange in patients before a “true “cataract forms, with a goal of improving sharpness and range of uncorrected vision.
In the United States, estimates of myopia prevalence range from 20-42%, with higher rates of nearsightedness observed among Asian and Hispanic ethnic groups and lower rates among African Americans and Caucasians.[31, 32] According to the World Health Organization, the prevalence of high myopia is projected to increase from 2.2% to roughly 10% of the world’s population by 2050.[33]
The etiology of myopia is complex. It is believed to be associated with a combination of both genetic and environmental factors such as prolonged near work, limited time spent outdoors, and diet.[34, 35, 36, 37, 38]
The cornea and the lens are the two optical components of the eye that are responsible for focusing light onto the retina. In hyperopia or farsightedness, the cornea-lens system is too weak relative to the axial length of the eye such that the image is focused behind the retina. In myopia or nearsightedness, the cornea-lens system is too powerful relative to the axial length of the eye, resulting in light being focused in front of the retina.[30]
The majority of patients with myopia have axial myopia, where the cause of their nearsightedness is increased axial length, sometimes accompanied by increased corneal power. Myopia can also be acquired through changes in lens or corneal shape (as seen in anterior lenticonus or keratoconus) or after surgeries that artificially induce elongation of the eye such as scleral buckles used for retinal detachment repairs.
Myopia typically develops in a progressive fashion through childhood or adolescence and stabilizes in early adulthood. It presents as blurry uncorrected distance vision.
The natural lens sits inside of a capsular bag behind the iris. The capsule is suspended in the eye through circumferential attachments to the ciliary body by zonular fibers. In RLE, the natural lens of the eye is replaced by an artificial IOL that is placed inside the capsule to provide the desired visual correction.
Broadly speaking, RLE is employed for correction of myopia, hyperopia, astigmatism, and/or presbyopia when alternative refractive options cannot sufficiently address the patient’s refractive error.
Most commonly, this would include patients over 45-50 with high myopia (> ~6 diopters [D]) or hyperopia (>~2 D) who may not be good candidates for corneal refractive procedures or the Visian ICL, or in whom early crystalline lens clouding is present.[39]
Reasons to consider RLE even in low myopia or hyperopia would be to:
Correct for presbyopia at the same time with the use of a multifocal lens, extended depth of focus (EDOF) lens, or monovision
Eliminate the need for cataract surgery in the future
Handle scenarios where corneal refractive surgery is less desirable (abnormal corneal anatomy, poor corneal healing, persistent dryness)
In patients with high myopia, there is a greater risk for retinal detachment after lens extraction.[41] If pre-existing areas of vulnerability are noted such as lattice degeneration or holes, breaks, or tears, patients should be evaluated by a vitreoretinal specialist prior to proceeding with RLE.
RLE may not be beneficial in eyes where visual potential is limited by other comorbidities.
There are three critical elements in counseling patients who are considering undergoing refractive lens exchange:
Lens implant choices can be grouped in these broad categories[42] :
Lens implant choices can be grouped in these broad categories[42] :
Monofocal (single-focus) designs that provide focus at one distance. These provide the sharpest vision, but, if the patient desires freedom from glasses, monovision (one eye for distance and one for near) is required. This can be tested preoperatively with a several-day trial of contact lenses to determine if the patient is a candidate for this option.
Extended depth of focus (EDOF) lenses. These provide vision at distance and intermediate range (eg, computer). Certain designs are relatively free from glare, whereas others provide higher contrast vision but create some glare and starburst that is most commonly seen at night around car headlights and streetlights. Patients implanted with these lenses typically will require glasses for reading at near.
Trifocal lenses provide uncorrected vision over the full range--distance, intermediate, and near--but again they create glare and starburst around lights. Sharpness of vision is slightly less than with the prior two lens designs.
A new option is lens implants whose power can be modified postoperatively to try to provide the patient with the maximal acceptable range of vision. These are monofocal designs, and hence some form of monovision is required for reducing or eliminating the need for reading glasses. The advantage is that patients can live with vision after one or more adjustments in order to ascertain the optimal balance of distance and near vision for each eye.
Possible need for additional postoperative procedures to refine the outcome: postoperative follow up is important to ensure that the refractive accuracy of the procedure is acceptable and that the patient’s visual goals have been met. A small percentage of patients might require corneal refractive surgery to treat any residual nearsightedness, farsightedness, and/or astigmatism.
Success and potential complications: RLE has a high success rate, greatly reducing or eliminating patients’ need for glasses and contact lenses postoperatively. That said, patients should be advised of the symptoms of postoperative complications (see below) that might occur and the importance of immediately contacting their physician if new visual symptoms arise.
Preoperative evaluation should include a thorough medical and ocular history. It is important to ask about medications, trauma, history of prior eye surgeries, as well as the patient’s refractive goals.
A full ophthalmic examination is performed. It is helpful to make note of the following factors as they may influence surgical approach:
Ocular surface disease
Extent of pupil dilation
Lens stability/zonular health
Presence or absence of posterior vitreous detachment (which is separation of the vitreous from the posterior retinal surface; if present, it reduces the risk of retinal detachment but is uncommon under age 60).
Detailed examination of the central retina to look for evidence of myopic degeneration and of the peripheral retina to look for vulnerabilities (eg, lattice, holes, tears, vitreous tufts) that increase the risk of postoperative retinal tears or detachment.
The procedure for prepping eyes for RLE is very similar to that used for routine cataract surgery. If performing a retrobulbar block in patients with high myopia, it is important to proceed with great caution due to increased risk for globe perforation in an elongated eye.
Surgery is conducted on an outpatient basis. RLE is performed in a similar fashion as routine cataract surgery, typically using topical anesthesia with some form of mild sedation, intravenous or oral. The main difference is the that the nucleus of the noncataractous lens is typically soft, requiring less ultrasonic energy to emulsify it.[43]
Topical antibiotics and steroids, separately or in combination, are prescribed to use for 3-4 weeks postoperatively. Most ophthalmologists follow their standard protocol for cataract extraction.
Postoperative follow-up care is arranged with patients on Day 1, as needed at 1 week, and at 3-4 weeks, at which point refraction may usually be performed to determine residual refractive error (which may require glasses, contact lenses, or eventually additional refractive surgery). A dilated fundus exam with careful attention to the retinal periphery should be performed.
Attention should be given to the same possible complications that follow cataract surgery. Patients and caregivers are instructed to call the ophthalmologist if vision suddenly deteriorates instead of slowly improving, if pain occurs, or if the eye becomes red or inflamed. Any new onset of flashes and floaters after cataract surgery should prompt immediate examination for the development of a posterior vitreous detachment, retinal tear, or retinal detachment.
High myopes have a higher lifetime risk for rhegmatogenous retinal detachment independent of any surgery. However, lens removal surgery can further increase this risk, particularly in patients under age 50 and in those who have not yet developed a posterior vitreous detachment (PVD).[42] In one study, over 75% of patients without a PVD prior to surgery developed a PVD after cataract extraction.[44] Studies report incidences of retinal detachment following RLE in myopic eyes of up to 3%.[41]
Other complications after RLE are similar to the complications experienced after cataract surgery, with an incidence of visual loss well below 5%.
Refractive lens exchange is an increasingly popular mode of providing patients with excellent uncorrected vision. Lens implant options and advances in surgical technique have made this an attractive option for presbyopic patients seeking to reduce their dependency on glasses and contact lenses.
Sanchay Gupta, MD, MBA, Resident Physician, Department of Ophthalmology, Baylor College of Medicine
Disclosure: Have a 5% or greater equity interest in: Umbulizer.
Coauthor(s)
Douglas D Koch, MD, Professor and Allen, Mosbacher, and Law Chair in Ophthalmology, Department of Ophthalmology, Baylor College of Medicine
Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Alcon; Carl Zeiss Meditec; Johnson & Johnson Surgical Vision.
Specialty Editors
Simon K Law, MD, PharmD, Clinical Professor of Health Sciences, Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine
Disclosure: Nothing to disclose.
Louis E Probst, MD, MD, Medical Director, TLC Laser Eye Centers
Disclosure: Nothing to disclose.
Chief Editor
Hampton Roy, Sr, MD, † Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences
Disclosure: Nothing to disclose.
Additional Contributors
Daniel S Durrie, MD, Director, Department of Ophthalmology, Division of Refractive Surgery, University of Kansas Medical Center
Disclosure: Received grant/research funds from Alcon Labs for independent contractor; Received grant/research funds from Abbott Medical Optics for independent contractor; Received ownership interest from Acufocus for consulting; Received ownership interest from WaveTec for consulting; Received grant/research funds from Topcon for independent contractor; Received grant/research funds from Avedro for independent contractor; Received grant/research funds from ReVitalVision for independent contractor.
Mounir Bashour, MD, PhD, CM, FRCSC, FACS, Assistant Professor of Ophthalmology, McGill University Faculty of Medicine; Clinical Assistant Professor of Ophthalmology, Sherbrooke University; Medical Director, Cornea Laser and Lasik MD
Disclosure: Nothing to disclose.
Pierre E Demers, MD, Regional Medical Director, Lasik MD Centers in Quebec; National Director of Professional Services, Lasik MD; Former Assistant Professor of Ophthalmology, University of Montreal, Canada
The impact of myopia and high myopia: Report of the joint World Health Organization-Brien Holden Vision Institute Global Scientific Meeting on Myopia. World Health Organization. 2015 Mar 18.
