Abstract
Purpose :
The purpose of this study is to create corneal lenticule incisions with ultralow pulse energy using a new femtosecond laser (NFS). The system is designed to produce tissue-bridge free incisions that require less surgical manipulation and mechanical disruption of the cornea during lenticule extraction.
Methods :
45 ex-vivo porcine eyes and 21 ex-vivo cadaver eyes were used to create corneal lenticule incisions with varying low pulse energies. The NFS lenticule was programmed to treat myopia with astigmatism, of which the refractive error was prescribed by a manifest sphere of -4.00D, manifest cylinder of -1.00D, and manifest cylinder axis of 180°. The measured energies to cut the posterior and anterior surfaces of the lenticule were programmed between 25-55nJ, with the lower limit set based on the glass burn threshold (GBT) of the femtosecond system. The ring and entry cut energies were tested between 28-65nJ. Lenticules were cut across optical zones of 6.0mm and 7.0mm for comparison of quality. Lenticule entry cut, edge quality, and removal ability were assessed by a subject matter expert (SME) on a scale of 1-4 (1: no lift, 2: some adhesions, 3: little adhesions, 4: no adhesions).
Results :
The lower threshold for anterior and posterior energies was 30nJ on porcine eyes and 36nJ on cadaver eyes using a femtosecond laser system with a GBT of 36nJ and across optical zones of 6-7mm. Ring and entry energies allowed a lower threshold of 26nJ and 30nJ on the same system, respectively. SME scores indicate that lenticule incisions on cadaver eyes result in poorer quality of the lenticule and its removal compared to porcine eyes, due to tissue quality and corneal structure. Larger optical zones also resulted in cuts with lower quality of lenticule incision due to larger “single pass” laser scan locations.
Conclusions :
The new femtosecond laser system has the capability to produce lenticule incisions of acceptable quality consistently and successfully at or lower than its glass burn threshold. Lenticule quality reflects the system design to produce tissue-bridge free incisions with ability to remove without disruptive surgical manipulation.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.