Procedures such as presby-LASIK and conductive keratoplasty are viable options for the treatment of presbyopia; however, some patients desire reversible, less invasive options. Such alternatives include corneal inlays, scleral procedures, and IOL implantation. In each, the aim is spectacle independence.
The AcuFocus Corneal Inlay ACI 7000 (AcuFocus, Inc., Irvine, California), is an intracorneal inlay that takes fewer than 30 minutes to insert, from start to finish. Implantation and centration are achieved after a flap is made with either a microkeratome or a femtosecond laser. Implant depth, greater than 170 µm (Figure 1). The inlay is acceptable cosmetically, regardless of eye color (Figure 2).
In contrast to other optic devices used for presbyopia correction, the AcuFocus inlay does not compromise distance vision. It may be used in both emmetropic presbyopes and in patients with a history of cataract surgery with monofocal IOL implantation. Initial European results with the AcuFocus inlay were typically 20/20 and J1 at intermediate and near vision at 1 year. On the downside, some patients experienced a delay in visual recovery and mild halos. If the device is implanted only in one eye, the benefits, including increased depth of focus and 20/20 vision, appear to outweigh the few drawbacks.
HOW IT WORKS
The device resembles a black ring; the hollow center allows focused light into the eye, and the optical principle of small-diameter aperture optics significantly increase the depth of focus (Figure 3). The device is placed over the patient's pupil after the flap is created. Centration is crucial and can be easily corrected, even months after the first surgery, should visual acuity at distance and near not meet the patient's expectations. The ring has visible nutrition pores that are essential to keep the anterior epithelium and stroma healthy.
The original European investigators implanted the 10-µm AcuFocus in 70 patients. Investigators included Michael Knorz, MD, and Thomas Neuhann, MD, of Germany; Jorge L. Alió, MD, PhD, of Spain; and myself, in this series. Preoperatively, the mean distance and near UCVA was 20/16 and J7 to J8, respectively. At 12 months, results were available for 57 patients. Patients were 20/20 at distance and had J1 near UCVA (Figure 2).
We recently conducted an updated study, using the new 5-µm AcuFocus model. In this series, 47 patients received the implant; results for 33 patients were available after 3 months. Preoperatively, distance and near UCVA were the same as in the earlier study. At 3 months, all patients had 20/20 and J2 distance and near UCVA, respectively.
From these studies, we have concluded that implantation of the AcuFocus comes with few side effects, including possibly needing time to adapt to the modified monovision, slight decrease in distance UCVA, and difference in near UCVA between the implanted and nonimplanted eyes. The presence of halos and scatter due to the hole pattern are rare. In the case of decentration, the AcuFocus is easily recentered, and flap complications are easily avoidable.
Overall in the European study, we have found this device to be safe and effective, with the potential to provide correction for patients with post-LASIK presbyopia or pseudophakic. This minimally invasive procedure provides stable results and was well tolerated by our patient population. Its reversibility makes this device an attractive option for patients.
I have found that regardless of the surgical technique employed to treat presbyopia, the most important postoperative assessment is a standardized reading test. We suggest a logarithmic reading chart, such as the Minnesota Low Vision Reading test acuity charts or the Radner chart. These can be used to test reading acuity, maximum reading speed, and critical print size. The reading acuity may then be converted to Snellen visual acuity.
I also recommend the Salzburg Reading Desk (SRD), a computerized timing and data management system that calculates the automatic distance measurement and correction. (For more information on the SRD, see Evaluating Patients After Presbyopia Correction; October 2008; pages 34-36.) We recently tested the reading performance of 15 patients with the SRD after AcuFocus implantation. On average, patients experienced more than two lines of improvement (Radner test charts; 2.2 ±1.52). When patients' depth of field improved, we found that their reading scores also improved.
Günther Grabner, MD, is a Professor of Ophthalmology and Chairman at the University Eye Clinic, Paracelsus Medical University of Salzburg, Austria. Professor Grabner states that he received travel grants from AcuFocus and has a proprietary interest as a patent assignee of the SRD. He has also receive support for his research performed at the Austrian Fuchs Foundation for Research in Ophthalmology. He may be reached at tel: +43 662 4482 3701; fax: +43 662 4482 3724; e-mail: G.Grabner@salk.at.