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As results from the FDA IDE clinical trial are awaited, analyses of data from patients receiving earlier versions of an investigational presbyopia-correcting intracorneal inlay show that its efficacy for improving near vision remains stable for at least 3 years.
The inlay has an annular design (3.8-mm overall diameter with a 1.6-mm central aperture) and provides a pinhole effect to improve near vision by increasing depth of focus. The device being evaluated in the FDA clinical trial represents the third version of the inlay studied in the United States.
Visual acuity outcomes
Data on mean monocular corrected and uncorrected distance VA showed a very minor initial loss from the preoperative level, but with no further change over time. At month 36 for patients receiving inlay version 1, mean corrected distance VA was 20/20 and mean uncorrected distance VA was 20/25. At 30 months of follow-up for the version 2 cohort, mean corrected distance VA was 20/16 and mean uncorrected distance VA was 20/20.
"These data are remarkable considering that presbyopic patients will experience some deterioration in their near vision over a period of 3 years, and achievement of 20/20 near UCVA with 20/20 distance UCVA is also unique for a presbyopia-correcting modality," Dr. Durrie said.
"These findings can be explained by the fact that the inlay works on the principle of increasing depth of focus rather than as a refractive lens," he said. "By providing increased depth of focus, the inlay brings objects into focus from near to far and is able to compensate for loss of accommodation as patients become more presbyopic."
Dr. Durrie acknowledged that the data are from patients with earlier versions of the inlay, but the same stability of the near vision outcome is expected to be seen as follow-up continues in patients with the current model of the inlay.
"We already know that the third version of the intracorneal inlay offers better quality of vision because of its design modifications, but the mechanism for improving near vision is the same for all three versions," he said.
The design of the inlay has evolved since the development project began more than 7 years ago. The current version is 5 æm thick and features 8,400 randomly spaced, laser-etched microscopic holes that enable nutrient passage to the cornea and allow 5% light transmission.
"The present design dramatically improves quality of vision due to reduced light scatter while maintaining adequate nutrient flow for corneal health," Dr. Durrie said.
The pivotal study includes 504 presbyopic patients with emmetropia who had the inlay implanted under a LASIK-style flap in the non-dominant eye. Analyses of data from the 1-year visit are being completed and AcuFocus will be filing those data with the FDA.
Daniel S. Durrie, MD
Dr. Durrie has been a clinical investigator in studies evaluating all three U.S. versions of the inlay and is a consultant to AcuFocus. The Kamra inlay is commercially available in Europe and Asia.