By now, most surgeons have heard of Intracor, an intrastromal treatment for presbyopia performed using the Technolas Femtosecond Workstation 520F (Technolas Perfect Vision GmbH, Munich, Germany). The procedure, which involves making five concentric rings within the stroma, avoids cutting the corneal epithelium or Bowman's membrane. The incisions within the stromal tissue cause localized biomechanical change, leading to slight steepening of the central cornea. This article provides an update of results with Intracor since Luiz Antonio Ruiz, MD, of Bogotá, Colombia, performed the first treatments in 2007.
Our clinic at the University of Heidelberg, Germany, is involved in a prospective, multicenter Conformité Européenne (CE) study. In addition to our center, the study is being conducted at three other sites in Germany (Duisburg, Mannheim, and Munich). Results thus far have led to CE approval of Intracor for the treatment of low hyperopic presbyopia in 2009.
Within our subgroup study site at Heidelberg, we have performed Intracor on 25 patients, treating the nondominant eye to induce a minimum near add of 2.00 D. Patient inclusion criteria were refractive error of 0.50 to 1.25 D, less than 0.50 D of cylinder, and a distance BCVA of at least 20/25. Eyes with diseases or those with a history of previous eye surgery were excluded. The mean patient age was 56.2 ±5.79 years.
A local anesthetic is administered before centering the eye using the patient's visual axis and marking the Purkinje reflex. The eye is then fixated to the laser via the uniquely curved patient interface, minimizing corneal deformation to allow more accurate treatment. Centration software can be used to make final centration adjustments after docking; optimal centration is essential for good outcomes.
The procedure is initiated once the vacuum setting is optimized, taking only 15 to 20 seconds to cut the rings. Following completion of the procedure, the patient undergoes slit-lamp examination, and the rings are visible owing to cavitation gas bubbles (Figure 1). The gas typically escapes within a few hours postoperatively, and only fine circular rings are visible at 1 day postoperative (Figure 2). Patients receive steroid eye drops in the initial few days postoperative.
To date at our center, results after Intracor are stable, and patients achieve marked improvement in near vision with minimal change in distance vision. At 3-month follow- up, near UCVA was 0.26 ±0.21 logMAR compared with 0.70 ±0.16 logMAR preoperatively.1 Patients gained an average of 4.42 lines of near vision, comparable with findings reported by Ruiz et al.2 Similar results were seen at 12- and 18-month follow-up, with improvement in near vision remaining stable in our patients. Minimal change in distance UCVA was observed.
Preoperative distance UCVA and BCVA were 0.11 ±0.11 and -0.06±0.06 logMAR, respectively. At 3 months postoperative, distance UCVA and BCVA were 0.05±0.10 and 0.00 ±0.07 logMAR, respectively, with a mean loss of 0.46 ±0.83 lines of BCVA. Patient satisfaction levels are generally high, and most patients report benefitting from good near and distance vision within the first day postoperative, once the cavitation bubbles have escaped. Slight visual disturbances may occur if the patient can see the rings; however, they do not affect the ability to perform activities. These side effects generally disappear after a few months.
BENEFITS AND KEYS TO SUCCESS
One of the key benefits of this presbyopic treatment is that Intracor is minimally invasive. Because no cuts are made to the corneal surface, risk of infection is minimized. Pre- and postoperative endothelial cell count and pachymetry measurements were similar, with no recorded change in pachymetry at the thinnest point.
Performing proper patient selection and managing patient expectations are the keys to success with Intracor. Thorough preliminary examinations should be performed, and patients with previous intraocular or corneal surgeries or ocular disease should be excluded. A minimum pachymetry of 500 µm is recommended to keep a safe distance from Descemet's and Bowman's membranes.
During preoperative consultation, patients should be advised of the early postoperative visual disturbances while driving at night (caused by the visibility of the rings) and the potential for a slight decrease in distance vision owing to the myopic shift of approximately -0.50 D. It is suggested that the treatment should initially be monocular, on the nondominant eye. The interval between surgeries should be around 4 weeks, and the second eye should be treated only if the patient demands this treatment and no significant loss of distance BCVA is observed in the first eye.
When the surgeon is transitioning to Intracor procedures, I recommend starting conservatively with patients whose spherical equivalents are between 0.50 and 1.00 D, to assess the myopic shift.
To date, the multicenter study outcomes indicate that Intracor is a safe and effective treatment for presbyopia, providing stable outcomes at 18 months. Longer-term follow- up data are required to ensure ongoing stability of the effect. The fact that the technique is minimally invasive and fast, providing almost immediate improvement in visual acuity, is a real advantage compared with other presbyopic solutions. The current treatment range is for low hyperopic presbyopes, but evaluations are currently under way to expand the indications to a broader patient group.
Mike P. Holzer, MD, is an Associate Professor and Director of Refractive Surgery, University of Heidelberg, Department of Ophthalmology, Heidelberg, Germany, and practices at the International Vision Correction Research Centre, Germany. Dr. Holzer states that he is a consultant to Technolas Perfect Vision. He may be reached at tel: +49 6221 566999; fax: +49 6221 568229; e-mail: email@example.com.