Comparing Near Visual Acuity vs. Functional Reading Ability as primary outcome measures after implantation of an intracorneal inlay for the surgical correction of presbyopia

Background: The AcuFocus KAMRA corneal inlay ACI7000 (AcuFocus Inc., Irvine, CA) represents an intracorneal inlay implanted in the non-dominant eye for the improvement of intermediate and near vision by increasing the depth of focus. Within this clinical trial binocular near visual acuity (NVA) and functional reading ability have been evaluated after monocular implantation of this pinhole optic. Material and methods: This prospective, non-randomized, non-comparative study comprised 32 naturally emmetropic, presbyopic patients. Binocular NVA (logMAR; viewing distance: 40 cm), as evaluated with the OPTEC 6500P vision tester, was compared with functional reading ability (logRAD; measured "at best subjective distance"), as evaluated in a standardized testing procedure using the Salzburg Reading Desk, have been compared over a postoperative follow-up of 36 months. Results: NVA values and reading acuity values were found to be very similar pre-operatively (0.39 +/- 0.12 logMAR vs. 0.38 +/- 0.13 logRAD, p = 0.78), and to increase up to -0.01 +/- 0.13 logMAR and 0.22 +/- 0.13 logRAD after 36 months (p < 0.001). In addition the Salzburg Reading Desk allowed to evaluate the changes in subjectively preferred reading distance (pre-op: 48.1 +/- 5.5 cm vs. 38.0 +/- 6.0 cm 36 month post-op, p < 0.001), as well as those of the smallest readable log-scaled sentence (mean improvement: 2.6 +/- 1.3 lines, p < 0.001) and the ones in reading speed (pre-op: 142 +/- 13 wpm vs. 152 +/- 35 wpm 36 month post-op, p = 0.029). Conclusions: The AcuFocus KAMRA Corneal Inlay ACI7000 improved all tested parameters of NVA and Functional Reading Ability in emmetropic presbyopic patients over a minimum follow-up period of 3 years. Nevertheless evaluating NVA with a fixed viewing distance seems to overestimate the effect of improvement in functional reading ability (logRAD) after presbyopic surgery by about 0.26 +/- 0.12 log-units.