Dual Laser-Assisted Lamellar Anterior Keratoplasty With Top Hat Graft

Abstract

Objectives To develop a dual laser-assisted lamellar anterior keratoplasty (LALAK) technique, using excimer and femtosecond lasers to perform surgery on eye-bank eyes. Methods First we compared corneal stromal surfaces produced by (1) deep excimer ablation, (2) femtosecond lamellar cuts, and (3) manual dissection, and evaluated the effect of excimer laser smoothing with fluid masking on each surface. Masked observers graded scanning electron microscopy (SEM) images on a 5-point roughness scale. Then we performed a 6-mm diameter excimer laser phototherapeutic keratectomy (PTK) ablation to a residual bed thickness of 200μm, followed by laser smoothing. We used the femtosecond laser to cut donors in a modified top-hat design with a thin tapered brim, which fitted into a manually dissected circumferential pocket at the base of the recipient bed. Fourier-domain optical coherence tomography (OCT) was used to measure corneal pachymetry and evaluate graft fit. Results Deep excimer ablation with smoothing (n=4) produced a significantly (p<0.05) smoother surface (grade=3.5) than deep excimer alone (n=4, grade=3.8) or manual dissection with (n=1, grade=3.8) and without smoothing (n=1, grade=4.8). Deep femtosecond cuts (n=2) produced macroscopic concentric ridges on the stromal surface. Experimental LALAK was performed on 4 recipients prepared by deep excimer ablation and 4 donors cut with the femtosecond laser. After suturing good peripheral graft-host match was observed on FD-OCT imaging. Conclusion These preliminary studies show that the LALAK technique permits improved interface smoothness and graft edge matching. Clinical trials are needed to determine whether these improvements can translate to better vision.

Femtosecond laser deep lamellar keratoplasty

“…The 13 corneas that underwent resection with VisuMax FS laser yielded no perforations in DM, which can significantly improve the perforation percentages found in classical DALK procedure. [ 28 29 30 ] Previous evidence of posterior stromal irregularities and concentric peripheral rings that were seen with the high-energy FS laser settings[ 17 18 19 20 21 22 ] are not seen with the faster, lower-pulse energy settings. It is likely that visual performance with these smoother interface beds will be better, although human clinical trials will need to further assess this potential benefit.…”

“…Scanning electron microscopy (SEM) images of deep stromal cuts made by the FS laser have shown an irregular and rougher appearing surface with the appearance of concentric peripheral rings. [ 17 18 19 20 21 22 ] Additionally, there are controversial findings regarding endothelial damage with higher energy settings at deeper layers.…”

Femtosecond laser deep lamellar keratoplasty

“…The 13 corneas that underwent resection with VisuMax FS laser yielded no perforations in DM, which can significantly improve the perforation percentages found in classical DALK procedure. [ 28 29 30 ] Previous evidence of posterior stromal irregularities and concentric peripheral rings that were seen with the high-energy FS laser settings[ 17 18 19 20 21 22 ] are not seen with the faster, lower-pulse energy settings. It is likely that visual performance with these smoother interface beds will be better, although human clinical trials will need to further assess this potential benefit.…”

“…Scanning electron microscopy (SEM) images of deep stromal cuts made by the FS laser have shown an irregular and rougher appearing surface with the appearance of concentric peripheral rings. [ 17 18 19 20 21 22 ] Additionally, there are controversial findings regarding endothelial damage with higher energy settings at deeper layers.…”

Interface quality of different corneal lamellar–cut depths for femtosecond laser–assisted lamellar anterior keratoplasty

“…However, even with optimization of laser parameters, deeper lamellar cuts still create ridges that could interfere with visual outcomes. 3,20 In published studies, 21,22 anterior lamellar keratoplasty with a femtosecond laser lamellar cut produced only fair CDVA that averaged between 20/32 and 20/38 at a 12-month follow-up. The problem of laser lamellar–cut quality can be circumvented using the laser to make only the side cuts and then using the big-bubble technique 23-25 or the excimer laser 20 to prepare the lamellar bed.…”

Laboratory Evaluation of Femtosecond Laser Lamellar Cuts in Gamma-Irradiated Corneas

“…Deeper lamellar cuts could still create ridges that may interfere with visual outcome. 2, 7 Currently, the compromised approach was using femtosecond laser to make side cuts, and then using big-bubble technique, 14-16 or the excimer laser 7 to prepare the lamellar bed. Our previous laboratory observation on fresh cadaver corneas indicated that the interface ridge strongly correlated with cut depth.…”

Femtosecond laser deep lamellar keratoplasty

“…The 13 corneas that underwent resection with VisuMax FS laser yielded no perforations in DM, which can significantly improve the perforation percentages found in classical DALK procedure. [ 28 29 30 ] Previous evidence of posterior stromal irregularities and concentric peripheral rings that were seen with the high-energy FS laser settings[ 17 18 19 20 21 22 ] are not seen with the faster, lower-pulse energy settings. It is likely that visual performance with these smoother interface beds will be better, although human clinical trials will need to further assess this potential benefit.…”

“…Scanning electron microscopy (SEM) images of deep stromal cuts made by the FS laser have shown an irregular and rougher appearing surface with the appearance of concentric peripheral rings. [ 17 18 19 20 21 22 ] Additionally, there are controversial findings regarding endothelial damage with higher energy settings at deeper layers.…”

Interface quality of different corneal lamellar–cut depths for femtosecond laser–assisted lamellar anterior keratoplasty

“…However, even with optimization of laser parameters, deeper lamellar cuts still create ridges that could interfere with visual outcomes. 3,20 In published studies, 21,22 anterior lamellar keratoplasty with a femtosecond laser lamellar cut produced only fair CDVA that averaged between 20/32 and 20/38 at a 12-month follow-up. The problem of laser lamellar–cut quality can be circumvented using the laser to make only the side cuts and then using the big-bubble technique 23-25 or the excimer laser 20 to prepare the lamellar bed.…”

Laboratory Evaluation of Femtosecond Laser Lamellar Cuts in Gamma-Irradiated Corneas

“…Deeper lamellar cuts could still create ridges that may interfere with visual outcome. 2, 7 Currently, the compromised approach was using femtosecond laser to make side cuts, and then using big-bubble technique, 14-16 or the excimer laser 7 to prepare the lamellar bed. Our previous laboratory observation on fresh cadaver corneas indicated that the interface ridge strongly correlated with cut depth.…”

Femtosecond laser deep lamellar keratoplasty

“…The 13 corneas that underwent resection with VisuMax FS laser yielded no perforations in DM, which can significantly improve the perforation percentages found in classical DALK procedure. [ 28 29 30 ] Previous evidence of posterior stromal irregularities and concentric peripheral rings that were seen with the high-energy FS laser settings[ 17 18 19 20 21 22 ] are not seen with the faster, lower-pulse energy settings. It is likely that visual performance with these smoother interface beds will be better, although human clinical trials will need to further assess this potential benefit.…”

“…Scanning electron microscopy (SEM) images of deep stromal cuts made by the FS laser have shown an irregular and rougher appearing surface with the appearance of concentric peripheral rings. [ 17 18 19 20 21 22 ] Additionally, there are controversial findings regarding endothelial damage with higher energy settings at deeper layers.…”

Interface quality of different corneal lamellar–cut depths for femtosecond laser–assisted lamellar anterior keratoplasty

“…However, even with optimization of laser parameters, deeper lamellar cuts still create ridges that could interfere with visual outcomes. 3,20 In published studies, 21,22 anterior lamellar keratoplasty with a femtosecond laser lamellar cut produced only fair CDVA that averaged between 20/32 and 20/38 at a 12-month follow-up. The problem of laser lamellar–cut quality can be circumvented using the laser to make only the side cuts and then using the big-bubble technique 23-25 or the excimer laser 20 to prepare the lamellar bed.…”

Laboratory Evaluation of Femtosecond Laser Lamellar Cuts in Gamma-Irradiated Corneas

“…Deeper lamellar cuts could still create ridges that may interfere with visual outcome. 2, 7 Currently, the compromised approach was using femtosecond laser to make side cuts, and then using big-bubble technique, 14-16 or the excimer laser 7 to prepare the lamellar bed. Our previous laboratory observation on fresh cadaver corneas indicated that the interface ridge strongly correlated with cut depth.…”