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Latest-generation femtosecond laser may offer new option for corneal presbyopia surgery
 Thomas John |
Surgical correction of presbyopia is used for the treatment of normal, age-related loss of near focusing ability that affects individuals older than 40 years of age. Surgery to correct presbyopia includes cornea-based procedures such as LASIK, PRK, conductive keratoplasty and corneal inlays, as well as lens-based procedures such as refractive cataract surgery and refractive lens exchange. Monovision is an option in which one eye is corrected for distance vision and the other eye for near vision, but there are other procedures that create a multifocal effect, such that both eyes are expected to see well for distance and near vision.
In this column, Dr. Sanchez-Leon describes using the IntraLase FS laser (Abbott Medical Optics) to correct presbyopia. Although this new technology appears to be promising in the arena of presbyopia-correcting surgery, continued long-term clinical and basic research will answer the questions of overall safety, reliability and reproducibility. This surgical technique has not been approved by the U.S. Food and Drug Administration.
Thomas John, MD
OSN Surgical Maneuvers Editor
At the NovaVision Center in Mexico City in 2008, we began an evaluation of presbyopia correction using the IntraLase FS femtosecond laser to create intrastromal rings. Our study has shown that we are able to reshape the tissue of the cornea and obtain the desired refractive effect (Figures 1 and 2). The exciting part of this project is that just as the IntraLase femtosecond technology has improved the safety and predictability of creating LASIK flaps, it has also improved the safety, predictability and control of corneal presbyopia surgery. The IntraLase FS can produce changes in the biomechanical forces of the cornea without disrupting the Descemet’s membrane or Bowman’s layer, and it retains the integrity of the corneal epithelium and endothelium with no apparent damage (Figure 3). The procedure produces steepening of the central portion of the cornea to improve near vision and maintain preoperative distance vision (Figures 4 and 5).
The IntraLase femtosecond laser creates intrastromal rings that are uniform in size and depth. The first step during the surgery is to mark the cornea on the Purkinje reflex; the treatment is centered based on that mark. To ensure biomechanical effect, a soft applanation technique is used to create a flat patient interface and is applied to the eye to compress collagen fiber and guarantee intrastromal effect. One of the advantages of using a flat interface is that this technique requires minimal energy and produces a straight incision. With the soft applanation technique, distortion in the centration of the eye is minimal to none. The software is also capable of assisting the surgeon in accurate centration as part of the last step before starting the procedure, if needed. A nomogram has been developed to utilize the technology and is customized to each patient according to age, refraction, keratometric values, corneal thickness and pupil diameter.
 Figure 1. Intrastromal rings are placed in the cornea using the IntraLase FS laser (Abbott Medical Optics). Photograph shows the corneal appearance 1 hour following the procedure. |
 Figure 2. Clinical photograph 1 day following surgery, showing the intrastromal rings placed in the cornea using the IntraLase FS laser. Images: Sanchez-Leon F |
 Figure 3. Photomicrograph showing the cross-sectional image of a cornea with areas of focal hyalinization (loss of organization) and occasional swirling of the collagen fibers in the stroma following intrastromal femtosecond laser ablation. |
 Figure 4. Orbscan topography showing steepening of the central portion of the cornea. Preoperatively vs. 1 month following surgery. |
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Study results
Encouraging early results were noted at 1 day, 1 week, 1 month and 3 months after surgery. There were 19 patients treated, with a mean age of 52.58 years. The uncorrected near visual acuity was equal to or less than 20/80, with a minimal near addition of +1.50 D for best corrected near visual acuity. The non-dominant eye was treated.
At 3 months’ follow-up, the mean monocular uncorrected near visual acuity improved from 20/80 (logMAR 0.56) to 20/30 (logMAR 0.23) in photopic and mesopic conditions. The mean distance corrected near visual acuity was 20/30 (J3) under photopic and mesopic conditions. The average best distance for near vision was 38 cm under mesopic and photopic conditions, with and without correction. The mean intermediate visual acuity was J3, with and without correction for distance. In addition, we observed no significant change in the monocular uncorrected distance visual acuity of 0.16 ± 0.19 D preoperatively to 0.14 ± 0.2 D postoperatively. The mean refractive cylinder remained unchanged. None of the patients reported nighttime glare, halos or severe visual symptoms at 1 month or 3 months.
The early results of this ongoing study demonstrate good distance and near vision with minimal risk of infection with monocular intrastromal ring treatment for presbyopia created by the IntraLase femtosecond laser.
References:
- Alió JL, Amparo F, Ortiz D, Moreno L. Corneal multifocality with excimer laser for presbyopia correction. Curr Opin Ophthalmol. 2009;20(4):264-71.
- Holzer MP, Mannsfeld A, Ehmer A, Auffarth GU. Early outcomes of INTRACOR femtosecond laser treatment for presbyopia. J Refract Surg. 2009;25(10):855-861.
- Ruiz LA, Cepeda LM, Fuentes VC. Intrastromal correction of presbyopia using a femtosecond laser system. J Refract Surg. 2009;25(10):847-854.
- Thomas John, MD, OSN Cornea/External Disease Board Member, is a clinical associate professor at Loyola University at Chicago and is in private practice in Tinley Park and Oak Lawn, Ill. He can be reached at 708-429-2223; fax: 708-429-2226; e-mail: tjcornea@gmail.com.
- Francisco Sanchez-Leon, MD, can be reached at Instituto Oftalmológico NovaVision, Director Médico y Científico, Av. Lomas Verdes 464, Piso 3, Naucalpan de Juárez, MEX, México; 52-55-53433595; e-mail: pacornea@yahoo.com. Dr. Sanchez-Leon has an unrestricted grant from Abbott Medical Optics.
