EyeWorld journal club
Review of "Small-aperture corneal inlay for the correction of presbyopia: 3-year follow-up"

Mark D. Mifflin, M.D., program director, University of Utah, Salt Lake City

This month I asked the University of Utah residents to review this interesting study on 3-year results of refractive corneal inlays from the January issue of the Journal of Cataract and Refractive Surgery. —David F. Chang, M.D., chief medical editor

Figure 1

Despite the introduction of various surgical modalities in cataract and refractive surgery, the safe and effective correction of presbyopia remains an elusive goal. Current approaches include surgical reshaping of the cornea or replacement of the crystalline lens. Either modality may attempt to achieve good uncorrected distance and near acuity through "monovision" or "blended vision," or alternatively through induction of multifocality of each eye individually. Lens platforms offer the additional possibility of movement of optical elements or "pseudoaccommodation." In the January issue of JCRS, Seyeddain et al. present "Small-aperture corneal inlay for the correction of presbyopia: 3-year follow-up" as a longitudinal update on a cohort originally presented in 2010.1 This prospective, non-randomized, interventional cohort study followed 32 naturally emmetropic presbyopic patients in whom the AcuFocus Corneal Inlay (Irvine, Calif.) was implanted in the non-dominant eye. The AcuFocus Corneal Inlay is a ring-shaped implant designed to increase the depth of field by reducing the size of the optical aperture (the "pinhole effect"), an approach not currently utilized by other presbyopia-correction techniques. This implant received the CE mark for use in the European Union in 2005 and is currently under investigation in U.S. FDA trials. In this article, the authors prospectively collected a comprehensive set of pre- and post-op data points, including manifest and cycloplegic refraction, uncorrected near, intermediate, and distance visual acuities, corrected distance visual acuity, contrast sensitivity, visual fields, patient satisfaction via questionnaire, and performance of various diagnostic tools (fundus ophthalmoscopy, gonioscopy, OCT of the macula and retinal nerve fiber layer, and scanning laser polarimetry of the nerve fiber layer with the GDx VCC).
Analysis indicated that there was a significant improvement in the mean uncorrected near visual acuity (UNVA) in the surgical eye from J7/J8 pre-op to J1 at 36 months. Similarly, the mean uncorrected intermediate visual acuity (UIVA) in the surgical eye significantly improved from 20/40 pre-op to 20/25 at 1 month, remaining stable throughout the follow-up period. The objective gains reported are subjectively validated by inclusion of data from a manufacturer-designed patient questionnaire, where patients reported significantly better near and intermediate vision scores 36 months post-op, as well as significantly reduced spectacle dependency for near tasks at 36 months.
The mean uncorrected distance visual acuity (UDVA) in the surgical eye significantly decreased from 20/16 pre-op to 20/20 at 1 month, where it remained throughout the follow-up. However, the post-op mean binocular UDVA (perhaps a better indication of patients' functional status) was unchanged from the pre-op level. The questionnaire data show no change in distance vision while watching a movie but a worse score for distance vision while driving at night (the authors do not report whether this was statistically significant). The decrease in monocular UDVA and night driving distance vision in some patients can possibly be explained by a reduction in illumination due to the corneal inlay, which is suggested by the significant decrease in visual field indices (mean deviation and pattern standard deviation) during the follow-up period and the small loss of contrast sensitivity in the surgical eyes. The authors question the clinical significance of this finding even though seven patients reported moderate or severe symptoms while driving at night. Perhaps the most important outcome parameter reported is the questionnaire item that asked whether the patients would have the surgical treatment again. Of the patients, 84.5% answered yes, 12.5% were undecided, and 3.0% (1 patient) answered no. No amount of objective data can supplant this important measure of patient satisfaction. The only patient who answered no was one who had multiple subsequent procedures due to flap striae. In their previous publication,1 the authors reported that this patient's reason was a "subjectively insufficient improvement in UNVA," despite being J1 at last follow-up. Another potentially important issue not addressed by the study is the patient satisfaction with the cosmetic result of the procedure. Figure 1, although a slit lamp microscopic photo, indicates that the corneal inlay is likely to be readily visible externally, which may be important to some patients if their motivations for spectacle independence are cosmetic.
The data indicate no serious safety issues, with a statistically significant but clinically insignificant loss of endothelial cell density, no patients who required explantation, no evidence of inflammatory reactions or deposits, and clinically insignificant epithelial iron deposits in 56.2% of surgical eyes. A previous publication by Yilmaz, et al.2 reported three patients who required explantation of this same inlay; two were for refractive shift and one was for partial inlay extrusion due to an overlying presumed herpetic lesion.
A potentially significant issue that deserves more discussion by the authors is the loss of corrected distance visual acuity (CDVA) in some surgical eyes. Nine eyes (28.3%) lost 1 line of CDVA and one eye (3.1%) lost 3.8 lines. Although loss of 1 line of CDVA in the non-dominant eye may not be clinically significant, loss of 3.8 lines probably is. Likewise, the post-op refractive shifts in some patients, accompanied by a central flattening on corneal topography, seem to be unpredictable based on the pre-op data presented. A final consideration is the sensitivity of this procedure to decentration (a concept already familiar to modern cataract and refractive surgeons), as manifested by the two patients that required inlay recentration with resultant significant increases in their UNVA and UIVA.
We applaud the authors for including data regarding post-op ability to examine the surgical eyes with standard ophthalmic examination equipment. Funduscopic examination was not affected, although the authors reported only the use of the Goldmann 3-mirror contact lenses for peripheral retinal examination and not binocular indirect ophthalmoscopy. Furthermore, the use of the line scan instead of the volume scan on macula OCT likely contributed to the authors' assessment that there was only a "slight decrease in image quality at the edges." If the volume scan was used (as it often is in clinical practice), this decrease in image quality may have extended to include the majority of the paracentral lines superior and inferior to the foveal line scan.
This study had many strong points, including length of follow-up, high percentage of follow-up exams, conscientious and thorough design, and thoughtful outcome parameters. Meticulous inclusion and exclusion criteria contributed to their ability to avoid confounding ocular issues and maximize the chance of successful outcomes. Among this study's limitations are limited sample size, narrow age range (48-55 years), and the other issues mentioned above. It is worth noting that two authors have financial interests with AcuFocus, including one author who was involved in post-op patient examination and data collection. Masking of examiners was likely not possible due to the nature of the intervention. Nevertheless, we commend the authors for reporting further follow-up on this cohort, as the surgical correction of presbyopia is a very timely and relevant topic. This method promises to be relatively straightforward, requiring only the skills a competent LASIK surgeon already possesses, with no added nomograms or calculations. Although further studies are warranted (including the ongoing U.S. FDA trial), this study demonstrates that we continue to make progress toward the holy grail of presbyopia-correcting procedures—one that combines efficacy, safety, long-term stability, predictability, reversibility, and relative ease of use.

References
1. Seyeddain O, Riha W, Hohensinn M, et al. Refractive surgical correction of presbyopia with the AcuFocus small aperture corneal inlay: two-year follow-up. J Refract Surg 2010;26:707-715.
2. Yilmaz OF, Bayraktar S, Agca A, et al. Intracorneal inlay for the surgical correction of presbyopia. J Cataract Refract Surg 2008;34:1921-1927.

Contact information

Mifflin: mark.mifflin@hsc.utah.edu