Refractive Lens Exchange (Clear Lens Extraction) for Myopia Correction

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Background

Clear lens extraction (CLE), also called refractive lens exchange (RLE), is the removal of a noncataractous natural lens of the eye with or without intraocular lens placement as a refractive procedure.

History of the Procedure

This refractive procedure has been around for nearly a century, and, throughout that time, it has been in a sea of controversy. In the past 5-10 years, CLE has slowly become accepted as a viable alternative to other refractive procedures for selected patients.

Problem

CLE is usually reserved for patients with high myopia (>8 diopters [D]) that is not easily managed by other refractive procedures, such as laser in situ keratomileusis (LASIK) or photorefractive keratoplasty (PRK). However, CLE may be an even better choice for patients with high hyperopia (>4 D) than for patients with myopia because of the smaller risk of postoperative retinal detachment and the fewer modalities available to treat patients with high hyperopia.

Epidemiology

Frequency

CLE still accounts for probably less than 1% of refractive procedures.

Etiology

Myopia is believed to be a result of a genetic predisposition in combination with close work over an extended period.

Pathophysiology

Myopia is due to an axial length longer than the focal point of the refracting system of the eye or an overly powerful refracting system, a thick cornea, or a thick lens, or a combination of any or all of the above.

Presentation

Myopia usually develops in early or mid teens and stabilizes in early adulthood. It presents as blurry distant vision.

Indications

Optical or refractive indications for lens surgery are ametropia (ie, myopia, hyperopia, astigmatism), anisometropia, and presbyopia. These include all classic refractive states of the healthy adult eye, which is why this new indication for lens surgery is controversial; no true histopathology may exist in most of these eyes.

Some eyes, as in those with extreme axial myopia, may be at risk for true pathology following surgical intervention. In addition, historical development of spectacles and contact lenses antedates the development of modern lens surgery. For these reasons, a mind-set has been created among academics that inborn errors of refraction are not diseases; therefore, they are not conditions to be treated by medicine or surgery, especially if such treatment might unnecessarily endanger an eye or expose an otherwise healthy eye to undue risk. This argument is rapidly losing credence.

The global anterior segment ophthalmic surgical community has embarked on a new and enticing endeavor called human emmetropia worldwide. The process began as an "idea before its time" in the 1950s, with the failed attempts at endothelial radial keratotomy of Barraquer and others at phakic anterior chamber intraocular lens (IOL) implantation.

The ophthalmic surgical technical revolution that ensued over the following decades allowed a return to the concept of the surgical correction of refractive errors 30 years later in the 1980s, this time as an "idea whose time had come." Refinements in ocular anesthesia, incision technology, lensectomy techniques, viscoelastic tissue protection, and IOL manufacture and implantation resulted in a return to the concept of intraocular correction of refractive errors, which includes both clear lensectomy and phakic implantation[1] . All this, combined with the seeming multitude of new keratorefractive procedures, led to the development of a new bona fide ophthalmic surgical subspecialty, controversial as it may appear, called refractive surgery.

The basic needs of refractive surgery are accuracy, stability, safety, and quality of vision.

Regarding accuracy, ideally, a standard deviation of less than 0.25 D is wanted, yielding 20/25 (or better) uncorrected acuity in 95% of patients for all amounts of myopia, hyperopia, and astigmatism. Currently, no procedure produces this result, but the closest are still LASIK or PRK for patients with low or moderate myopia and LASIK for patients with mild hyperopia. Currently, A-scan measurements and IOL choice, even using the IOL Master, especially in patients with high hyperopia and those with myopia, yield an accuracy of significantly less than ± 0.25 D.

For stability, CLE is probably the most stable refractive procedure available, with ± 0.02 D per year reported over a 9-year observation period. PRK has a significantly higher risk of regression or progression, and, in addition, LASIK carries a risk of corneal ectasia.

Several studies have shown that, for quality of vision, an unoperated cornea is optically superior to an operated cornea. Any operation on the cornea creates abnormal contours, which, in turn, create optical aberrations. The greater the correction, the greater the amount of induced aberration and the concurrent decrease in quality of vision, especially in low-contrast situations (eg, driving at night). Clearly, CLE is an optically superior choice in some situations.

Safety is discussed more extensively below.

Without question, the consequences of some complications (eg, endophthalmitis, retinal detachment) of intraocular surgery are much graver than the worst complications (eg, flap loss, corneal scarring requiring corneal transplant) of other refractive procedures.

Almost all operable tissues and spaces of the eye, including the corneal surface, the corneal stroma, the anterior chamber, the pupil, the posterior chamber, the lens, and the sclera, have been investigated as locations for refractive surgical modulation. Therefore, among others, the lens assumes its role as a popular location for surgical refractive modulation for those who prefer a familiar procedure that not only spares the cornea but also saves the economic expense of an excimer. Those who decry the lenticular approach emphasize all potential intraoperative and postoperative complications attendant with invasive intraocular procedures.

Despite the controversy, clear lens replacement is a viable procedure for both myopia and hyperopia, and toric IOLs are now available for intraocular correction of astigmatism. Multifocal IOLs and accommodative IOLs are now being used by many surgeons for the intraocular correction of presbyopia. Other attempts at development of a truly accommodative pseudophakos include intracapsular injection of liquid silicone, intracapsular placement of high-water content poly-HEMA lenses, liquid silicone-filled intracapsular balloon, multiple IOL implantation, polypseudophakia, and intracapsular placement of a flexible, plate-haptic, foldable, accommodative IOL.

Once thought of as an "idea before its time," surgical restoration of accommodation is becoming more of a reality. In 2003, the US Food and Drug Administration (FDA) approved the intracapsular placement of a flexible, plate-haptic, foldable, accommodative IOL, called Crystalens, for patients with cataracts. Crystalens was the first IOL to allow patients to focus on objects both at near and at distance without the use of spectacles or contact lenses. Working much like the natural lens of the eye, Crystalens, with its hinged haptics, facilitates back and forth movement along the optical axis of the eye in response to pressure changes that result from ciliary muscle relaxation and contraction. Since that early Crystalens, newer and improved versions have come out, and competitive brands with different modalities, such as ReSTOR[2] and ReZoom, have also entered the marketplace.

The surgical reversal of presbyopia is refractive surgery's "final frontier." Clinicians are exploring different techniques to surgically treat/reverse presbyopia (see Surgical Reversal of Presbyopia: A Comprehensive Video Text).

Indications for CLE are currently seen as the following:

Relevant Anatomy

CLE is performed as any other cataract procedure; the only difference is the decreased use or absence of phacoemulsification power and the almost exclusive use of aspiration.[3]

Ideally, this procedure is performed using a clear cornea approach, making a 3-mm or smaller corneal incision, creating a regular capsulorrhexis, performing aspiration within the bag, and placing an IOL of choice in the bag.

Contraindications

Contraindications include retinal disease. With high myopia, a higher rate of retinal detachment exists than with other types of refractive errors.

Prognosis

The prognosis is excellent.

Laboratory Studies

The usual preoperative workup as for cataract extraction is recommended.

Protocol varies from facility to facility and may include a chest x-ray, an ECG for patients older than 40 years, glucose and electrolyte studies, and a CBC count.

If patients are on blood thinners, prothrombin time (PT)/active partial thromboplastin time (PTT) or bleeding time may also be ordered.

Imaging Studies

A-scan biometry and IOL Master are recommended to determine the best power of IOL to be placed.

Using indirect ophthalmoscopy, a detailed examination of the peripheral retina must be undertaken, especially in patients with high myopia, to look for abnormalities (eg, lattice, holes, tears).

Other Tests

See Lab Studies.

Medical Therapy

Essentially, most ophthalmologists should follow their standard protocol for cataract extraction.

Consideration should be given to antibiotic prophylaxis beforehand (eg, Ocuflox qid 1 day preoperatively).

Preoperative prophylactic treatment of the peripheral retina, especially in patients with preexisting abnormalities and in those with high myopia, should be considered. So far, published results on CLE have shown that prophylactic 360° laser therapy provides a lower incidence of postoperative detachment than direct treatment limited to the visible abnormalities, which shows little difference from no treatment at all.

Topical antibiotics and steroids, separately or in combination, should be used postoperatively.

Prednisolone acetate 1% (Pred Forte)

Sterile ophthalmic suspension that is a topical anti-inflammatory agent for treating steroid responsive inflammation of the palpebral and bulbar conjunctiva, corneal and anterior segment.

Adult dose: Instill 1-2 gtt 2-4 times/d into conjunctival sac; during initial 24-48 h, dosage may be increased in frequency prn; shake well prior to use; do not discontinue therapy prematurely

Pediatric dose: Not established

Contraindications: Documented hypersensitivity; contraindicated in most viral diseases of the cornea and the conjunctiva, including epithelial herpes simples keratitis (dendritic keratitis), vaccinia, and varicella, and also in mycobacterial infection of the eye and in fungal diseases of ocular structures; prolonged use may lead to glaucoma and cataracts

Pregnancy: Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus.

Precautions: Fungal infections of the cornea are prone to develop coincidentally with long-term local corticosteroid use; suspect fungal invasion in any persistent corneal ulceration where a corticosteroid has been used or is in use; obtain fungal cultures when appropriate; if used for 10 d or longer, monitor intraocular pressure.

Ciprofloxacin 0.3% (Ciloxan Ophthalmic, Cipro)

Adult dose: 1 gtt q30min for 12 doses, then 1 gtt qh for the first 24-48 h; gradually taper off according to the clinical course

Pediatric dose: Administer as in adults

Pregnancy: Fetal risk not revealed in controlled studies in humans.

Precautions: May inhibit reepithelialization by crystallizing over the epithelial defect

Surgical Therapy

Essentially, surgeons should follow their standard cataract procedure, making allowances for the softer lenses.

Preoperative Details

One standard procedure is as follows:

Intraoperative Details

CLE is similar to cataract surgery, except less ultrasound and more aspiration are used.

Postoperative Details

Consider Miochol or postoperative pilocarpine if not contraindicated.

Follow standard protocol for postoperative medication. One recommended protocol is as follows:

Follow-up

Postoperative follow-up care is arranged with patients on day 1, at 1 week, and at 1 month, at which point refraction may usually be performed.

Follow-up care is similar to that for cataract surgery, with attention given to the same possible complications. Patients and/or their caregivers are instructed to call the ophthalmologist if vision suddenly deteriorates instead of slowly improves, if pain occurs, or if the eye becomes red or inflamed.

Complications

Complications include the following:

The remaining complications are the same as for any cataract surgery; a detailed discussion can be found in Cataract, Senile.

Outcome and Prognosis

Visual outcome is usually excellent.

A 2008 retrospective study of 129 eyes showed CLE with posterior chamber IOL implantation to be safe, predictable, and effective. CLE was shown to achieve excellent visual acuity and refractive outcome with few complications.[4]

The latest reports with prophylactic 360° therapy of peripheral retina show a statistically lower rate of retinal detachment in those eyes than if they had not been subjected to prophylactic treatment.

Future and Controversies

CLE is becoming a more accepted procedure. Arguments in favor of CLE are as follows: predictability, stability, ease and cost with which a general surgeon can perform the technique, use of toric or multifocal lens technologies and small-incision surgery, and better optical quality vision. Arguments against CLE are as follows: seriousness of complications, rate of complications, and availability of other less invasive refractive procedures.

In a 2004 study comparing the 2 procedures, Arne believed that phakic IOL placement was a safer modality than CLE in the same selected group of patients that corneal refractive surgery cannot address.[5]

If clouding of the capsule can be eliminated and if a truly accommodating and adjustable lens can be achieved, CLE could become a much more prevalent refractive procedure.

The advent of the ReSTOR and ReZoom lenses in 2005 and 2006, respectively, increased the frequency of this procedure, and the advent of newer and better lenses continues to increase demand and quality of results.

Studies from 2010 show that CLE is a also a financially better and easier modality for treating high myopia in the developing world and that supracapsular phacoaspiration for clear lens extraction in correction of high myopia seems to present no risk for the posterior capsule, although there is a marginal risk to the endothelial cell count.[6, 7]

Author

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.

Coauthor(s)

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

Disclosure: Nothing to disclose.

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.

References

  1. Nanavaty MA, Daya SM. Refractive lens exchange versus phakic intraocular lenses. Curr Opin Ophthalmol. 2011 Nov 10. [View Abstract]
  2. Fernandez-Vega L, Alfonso JF, Montes-Mico R, et al. Visual acuity tolerance to residual refractive errors in patients with an apodized diffractive intraocular lens. J Cataract Refract Surg. 2008 Feb. 34(2):199-204. [View Abstract]
  3. El-Helw MA, Emarah AM. Assessment of phacoaspiration techniques in clear lens extraction for correction of high myopia. Clin Ophthalmol. 2010 Mar 24. 4:155-8. [View Abstract]
  4. Dúbravska Z, Rozsival P. [Refractive lensectomy--long-term results]. Cesk Slov Oftalmol. 2007 Jan. 63(1):28-35. [View Abstract]
  5. Arne JL. Phakic intraocular lens implantation versus clear lens extraction in highly myopic eyes of 30- to 50-year-old patients. J Cataract Refract Surg. 2004 Oct. 30(10):2092-6. [View Abstract]
  6. Emarah AM, El-Helw MA, Yassin HM. Comparison of clear lens extraction and collamer lens implantation in high myopia. Clin Ophthalmol. 2010 May 14. 4:447-54. [View Abstract]
  7. El-Helw MA, Emarah AM. Assessment of phacoaspiration techniques in clear lens extraction for correction of high myopia. Clin Ophthalmol. 2010 Mar 24. 4:155-8. [View Abstract]
  8. Colin J, Robinet A. Retinal detachment after clear lens extraction in 41 eyes with high axial myopia. Retina. 1997. 17(1):78-9. [View Abstract]
  9. Colin J, Robinet A, Cochener B. Retinal detachment after clear lens extraction for high myopia: seven-year follow-up. Ophthalmology. 1999 Dec. 106(12):2281-4; discussion 2285. [View Abstract]
  10. Dholakia SA, Vasavada AR, Singh R. Prospective evaluation of phacoemulsification in adults younger than 50 years. J Cataract Refract Surg. 2005 Jul. 31(7):1327-33. [View Abstract]
  11. Gris O, Guell JL, Manero F, et al. Clear lens extraction to correct high myopia. J Cataract Refract Surg. 1996 Jul-Aug. 22(6):686-9. [View Abstract]
  12. Jimenez-Alfaro I, Miguelez S, Bueno JL, et al. Clear lens extraction and implantation of negative-power posterior chamber intraocular lenses to correct extreme myopia. J Cataract Refract Surg. 1998 Oct. 24(10):1310-6. [View Abstract]
  13. John ME, Noblitt RL, Coots SD, et al. Clear lens extraction and intraocular lens implantation in a patient with bilateral anterior lenticonus secondary to Alport's syndrome. J Cataract Refract Surg. 1994 Nov. 20(6):652-5. [View Abstract]
  14. Kolahdouz-Isfahani AH, Rostamian K, Wallace D, et al. Clear lens extraction with intraocular lens implantation for hyperopia. J Refract Surg. 1999 May-Jun. 15(3):316-23. [View Abstract]
  15. Lee KH, Lee JH. Long-term results of clear lens extraction for severe myopia. J Cataract Refract Surg. 1996 Dec. 22(10):1411-5. [View Abstract]
  16. Lyle WA, Jin GJ. Clear lens extraction for the correction of high refractive error. J Cataract Refract Surg. 1994 May. 20(3):273-6. [View Abstract]
  17. Lyle WA, Jin GJ. Clear lens extraction to correct hyperopia. J Cataract Refract Surg. 1997 Sep. 23(7):1051-6. [View Abstract]
  18. Osher RH. Clear lens extraction. J Cataract Refract Surg. 1994 Nov. 20(6):674. [View Abstract]
  19. Ripandelli G, Billi B, Fedeli R, et al. Retinal detachment after clear lens extraction in 41 eyes with high axial myopia. Retina. 1996. 16(1):3-6. [View Abstract]
  20. Seiler T. Clear lens extraction in the 19th century--an early demonstration of premature dissemination. J Refract Surg. 1999 Jan-Feb. 15(1):70-3. [View Abstract]
  21. Siganos DS, Pallikaris IG. Clear lensectomy and intraocular lens implantation for hyperopia from +7 to +14 diopters. J Refract Surg. 1998 Mar-Apr. 14(2):105-13. [View Abstract]
  22. Sinskey RM. Clear lens extraction. J Cataract Refract Surg. 1994 Nov. 20(6):673-4. [View Abstract]
  23. Smith SE. Crystalens gains approval. Cataract & Refractive Surgery Today 2004 Jan;. 4(1):67-8.
  24. Wallace RB 3rd. Multifocal vision after cataract surgery. Curr Opin Ophthalmol. 1998 Feb. 9(1):66-70. [View Abstract]
  25. Werblin TP. Barraquer lecture 1998. Why should refractive surgeons be looking beyond the cornea?. J Refract Surg. 1999 May-Jun. 15(3):357-76. [View Abstract]

Comparison of published data on retinal detachment after clear lens extraction.

Comparison of published data on retinal detachment after clear lens extraction.