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Today's Practice | Sep 2013

Presbyopia Correction on the Cornea

These solutions offer numerous advantages, including low rates of complications and reversibility.

Presbyopia, a common age-related condition, is a refractive defect in which the eye’s crystalline lens loses its ability to accommodate for near vision. Many surgical approaches have been developed in attempts to provide correction and eliminate the need for glasses or contact lenses for reading and other near-vision tasks. However, some of these procedures have disappeared from use for a number of reasons, including their associated complications, the progressive nature of presbyopia, and patients’ misunderstanding of or unrealistic expectations for visual outcomes.

Only two surgical options for presbyopia have to date survived the test of time. The first is surgery on the lens—refractive lens exchange or clear lens extraction (CLE)—which involves exchanging the patient’s natural lens for an accommodating, bifocal, trifocal, or multifocal IOL. The second option is surgery on the cornea, which can currently be performed in three types of procedure: (1) excimer laser ablation in the form of LASIK or surface ablation, (ie, presby-LASIK), (2) femtosecond laser intrastromal corneal surgery (Intracor; Bausch + Lomb Technolas), and (3) corneal inlay implantation.

Surveys of US trends in refractive surgery1-3 have illustrated that, for patients of precataract age, CLE is not a popular option among ophthalmologists. Companies are investing in the development of better systems for lens extraction, such as laser-assisted cataract surgery, in order to improve the safety of the procedure. Even with technical improvements, however, only 4% to 8% of survey respondents say they would prefer this option for the surgical correction of presbyopia.

The method most widely preferred by respondents to these surveys is excimer laser surgery, most often with a monovision strategy. Therefore, we can conclude that there is a place for corneal surgery, particularly in young presbyopes who have not developed cataracts and consider extraocular surgery a more attractive option than CLE. Even with the developments in lens surgery, the potential complications of CLE exceed those associated with corneal surgery, and the procedure is not reversible, making it an unlikely option when there is no cataract present.

Corneal surgery of any type, either excimer laser ablation or corneal inlay implantation, creates a multifocal cornea, as defined by topography and corneal aberrations. A multifocal cornea yields several problems, including decreased contrast visual acuity that returns to normal levels by 3 to 6 months postoperative and visual symptoms similar to those produced by multifocal IOLs, such as halos, glare, and night vision problems. However, in contrast to multifocal IOLs, multifocality created with programs such as the CustomVue presby-LASIK treatment (Abbott Medical Optics Inc.) is reversible.

EXCIMER LASER PRESBYO PIA SURGERY

Excimer laser surgery for presbyopia correction is based on the creation of corneal aberrations, mostly spherical aberration, and usually a combination of positive and negative. This increases depth of focus, thereby improving near vision and reducing spectacle dependence.

Presby-LASIK can utilize one of two patterns of ablation. Our center uses a peripheral corneal ablation pattern, in which the excimer creates distance vision in the center of the cornea and near vision in the periphery; this approach creates central positive spherical aberration (Z40) and peripheral negative spherical aberration (Z60), a combination that increases the depth of focus. Examples of this type of ablation are shown in Figures 1 and 2. A second approach is central ablation, in which a negative spherical aberration is created in the center and a positive spherical aberration in the periphery with the same overall effect as the other method.

To evaluate the efficacy of the peripheral ablation presby-LASIK approach, we analyzed 121 eyes of 66 patients (mean age, 51 years; range, 41–67 years) who were followed for a mean of 3 years. Preoperative sphere was 0.18 ±2.20 D (range, -5.00 to +5.00 D), and preoperative cylinder was -0.736 ±0.97 D (range, -6.50 to 0.00 D). Of the 66 patients, preoperatively, 57.9% were hyperopic, 31.4% were myopic, and 10.7% were emmetropic; 86.8% underwent LASIK with either femtosecond laser or microkeratome flap creation. There was a 9.9% rate of retreatment at 1 to 3 months.

At 32 months postoperative, 94% of eyes had 20/30 or better distance UCVA, and 95% had 20/25 or better near UCVA. All eyes achieved 20/25 or better BCVA for distance and near, and no loss of lines of BCVA was detected. When analyzed by refractive defect, myopic patients achieved better outcomes for distance and near compared with hyperopic patients. Overall, at 32 months follow-up, 92% of patients do not wear glasses under any condition, and all reported that they would recommend the surgery to a friend. However, 3.2% report that they do not drive at night due to visual symptoms.

As shown by these results, presby-LASIK can be a good option for young presbyopes (43–55 years of age), with the advantage of simultaneous correction of presbyopia and any accompanying refractive defect, including astigmatism. Additionally, excimer laser surgery is well known by patients and doctors alike, with a low rate of complications, none of which are sight-threatening. Finally, presby-LASIK is completely reversible, and the ability to provide custom ablation is a major difference from IOLs. The main disadvantage of presby-LASIK is that it is a temporary solution, with a 5-year mean duration of effect. However, it is also repeatable and may be followed by intraocular surgery when the patient is older.

CORNEAL INLAYS

Corneal inlays, the other corneal surgical approach for presbyopia, constitute another excellent option for young presbyopes who are not willing to undergo intraocular surgery. Currently three refractive inlays are commercially available: (1) the Raindrop Near Vision Inlay (ReVision Optics), (2) the Flexivue Microlens (Presbia Corp.), (3) and the Kamra inlay (AcuFocus, Inc.). These discs are inserted at different depths in the stroma, and each has a different mechanism of action. The inlay we currently use is the Flexivue Microlens.

All inlays are inserted into the patient’s nondominant eye only, producing controlled monovision without a major difference between eyes. Preoperatively, patients must be tested for tolerance of a small degree of monovision, such as 1.25 D in one eye and emmetropia in the other.

The surgical technique for implantation is easy with the help of the femtosecond laser, which is used to create the tunnel to insert the inlay. Centration on the Purkinje image is a crucial part of the procedure.

Currently, corneal inlays are used only for emmetropes, although several studies are under way to test their efficacy after treatment of other refractive defects with the excimer laser. The personal results of author Gustavo Tamayo, MD, with the inlay have been excellent, provided candidates were properly selected. Postoperatively, patients achieve 20/20 binocular distance UCVA; however, UCVA in the implanted eye is mean 20/50 at 1 month, reaching 20/30 at 6 months and stability after 1 year follow-up. For near UCVA, all eyes achieve 20/30 or better; this visual result is reached quickly during the first month and remains stable for the next year.

Corneal inlays are an excellent option for corneal surgery for presbyopia, but visual symptoms are similar to those produced by IOLs and presby-LASIK and include halos, glare, and night vision issues. A majority of patients adapt to these disturbances, and, with the surgery performed in only one eye, the symptoms become less bothersome over time. The main advantage of corneal inlays is their reversibility; the inlay can be removed, after which the eye returns to the previous state, or it can be exchanged for a more powerful inlay if mandated by the patient’s increasing loss of accommodation.

CONCLUSION

Corneal surgery for presbyopia is an excellent option for young presbyopes who are interested in decreasing or eliminating their use of glasses for near vision. Corneabased solutions offer many advantages, and, unlike with intraocular surgery, the associated complications are minor and not sight-threatening. The complete reversibility of the procedures is appreciated by patients who understand that they are temporary solutions that can be repeated or changed as needed.

Gustavo Tamayo, MD, is the Director of the Bogotá Laser Refractive Institute in Bogotá, Colombia. Dr. Tamayo states that he is a consultant to Abbott Medical Optics Inc. and Presbia, and he holds a patent for a method of presbyopic excimer laser ablation. He may be reached at e-mail: gtvotmy@ telecorp.net.

Claudia Castell, MD, is an attending ophthalmologist at the Bogotá Laser Refractive Institute in Bogotá, Colombia. Dr. Castell reports no financial interest in the products or companies mentioned. She may be reached at e-mail: claudiacastell@yahoo.com.

Pilar Vargas, MD, is an attending ophthalmologist at the Bogotá Laser Refractive Institute in Bogotá, Colombia. Dr. Vargas reports no financial interest in the products or companies mentioned. She may be reached at e-mail:pilar_vargas@hotmail.com.

  1. Duffey RJ, Leaming D. US trends in refractive surgery: 2003 ISRS/AAO survey. J Refract Surg. 2005;21(1):87-91.
  2. Duffey RJ, Leaming D. US trends in refractive surgery: 2004 ISRS/AAO survey. J Refract Surg. 2005;21(6):742-748.
  3. Duffey RJ, Leaming D. US trends in refractive surgery: 2010 ISRS Survey. Paper presented at: The AAO Annual Meeting; October 2010;Chicago.

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