Corneal Inlays: A Surgical Correction of Presbyopia

As attention to quality-of-life issues among aging baby boomers grows, there is an increased interest in the development of new presbyopia treatments. Corneal implants, which have been on the backburner in ophthalmology for several years, are quickly becoming a safe and reversible treatment.

The Invue system (Biovision AG, Brüggs, Switzerland) was designed to improve near vision for emmetropic presbyopes, with minimal deterioration of distance vision. Francisco Sánchez León, MD, of Mexico City, and colleagues, conducted an informal study of 14 presbyopic patients who underwent surgical correction with the Invue. Patients were aged 45 to 58 years, and the refractive range was 2.25 D to 3.50 D for near vision. Preoperatively, near visual acuity for this patient set ranged from 20/40 to 20/200, including four patients who were 20/100. At 1 week, six patients achieved 20/20 uncorrected near vision. At 6 months, eight patients achieved 20/20 uncorrected near vision, and three patients achieved 20/25. Some patients noticed a minor loss of distance vision and loss of contrast sensitivity in the operated eye. None of the patients, however, noted changes in their binocular vision (data presented at the Mexican Congress of Ophthalmology in 2006).

SYSTEM SET-UP
The Invue system employs feedback-monitoring control to ensure high-precision corneal cutting and fixation (Figure 1). The water-permeable microlens is 15 µm to 20 µm thick and approximately 3 mm in diameter (Figure 2). Pocketblade cartridges are used to cut a precise corneal tunnel, and a lens-delivery instrument places the Invue intracorneal hydrogel refractive lens approximately 200 µm deep into the cornea of the nondominant eye (ie, corresponding to the visual axis) (Figure 3).

DATA ANALYSIS
Currently, we are collecting and analyzing the preliminary postoperative data of patients who underwent surgery with the Invue system at the University of Crete (Vardinoyiannion Eye Institute of Crete, Greece).

During wavefront analysis, we discovered an inlay effect when only the central 3-mm zone (corresponding to the inlay diameter) was analyzed. Interestingly, this was not the case when the central 6-mm zone was analyzed. We found, therefore, that the maximal inlay effect occurs during near vision without significantly disturbing distance vision. This is because as the pupil becomes smaller to accommodate for near vision, almost all the rays pass through the inlay. When the pupil becomes larger for distance vision, however, the rays pass through a larger zone. This differentiates the procedure from either a simple monovision with laser surgery or clear lens extraction, where the induced myopic effect is stable and independent of the pupil diameter.

We believe surgeons should consider intracorneal lenses as an effective treatment for emmetropic presbyopes aged 45- to 60-years-old; this patient group is considered too old for laser surgery and too young for clear lens extraction. Avoiding refractive surgery might prove beneficial for these patients in terms of safety, stability, and addressing dry eye. Because implantation of the Invue inlay is performed using a tunnel instead of creating a flap, the procedure might improve upon current corneal inlay stability and long-term results. Additionally, the transparent lens is not disturbed during ophthalmologic examinations, as we did not observe opacities after the first months of implantation. It is also biocompatible, making it friendly to the cornea. Clinical studies on the Invue are currently underway in Switzerland and will soon begin in Germany.

The easy implantation and reversibility of this procedure is appealing to patients and doctors alike. Further follow-up and a larger series of surgeries are necessary to prove the safety and efficacy of this new and promising surgical approach for presbyopia.

Dimitrios I. Bouzoukis, MD, is from the Department of Ophthalmology and Institute of Vision and Optics, University of Crete, in Greece. Dr. Bouzoukis states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +30 2810 371800; fax: +30 2810 394653; or Dbouzoukis@hotmail.com.

George D. Kymionis, MD, PhD, is from the Department of Ophthalmology and Institute of Vision and Optics, University of Crete, in Greece. Dr. Kymionis states that he has no financial interest in the products or companies mentioned. He may be reached at Kymionis@med.uoc.gr.

Ioannis G. Pallikaris, MD, PhD, is the Founder and Director of the Institute of Vision and Optics at Vardinoyannion Eye Institute of Crete, and the Chairman of the Department of Ophthalmology at the University of Crete, in Greece. Dr. Pallikaris states that he has no financial interest in the products or companies mentioned. He may be reached at pallikar@med.uoc.gr.