Surface quality and endothelial cell viability after femtosecond laser-assisted donor lenticule preparation for endothelial keratoplasty - An in-vitro study

Purpose

To compare surface quality and endothelial cell viability of descemet stripping automated endothelial keratoplasty (DSAEK) donor lenticules prepared with femtosecond laser (FSL) or microkeratome (MK).

Methods

Experimental ex-vivo evaluation of 15 DSAEK donor lenticules prepared from optical quality donor corneas using 200 KHz FSL (9 eyes) or MK (6 eyes). Surface quality and smoothness of the cut were assessed using atomic force microscopy and endothelial cell viability was assessed using transmission electron microscopy.

Results

Mean lenticule thickness was 121.89 ± 17.13 μm in FSL group and 112.67 ± 5.89 μm in MK group (P = 0.33). Average roughness of stromal surface (RMSavg) [FSL- 30.51 ± 4.55 nm, MK-22.37 ± 1.83 nm; P = 0.02] and root mean square roughness (RMSrough) [FSL-31.39 ± 5.75 nm, MK-23.08 ± 0.40 nm; P = 0.012] was significantly more in FSL group. Increased granular and linear irregularities were observed in the FSL group. Endothelial cell disruption was more in FSL group (FSL- 29.49 ± 6.91% MK-13.28 ± 3.62%; P < 0.001) with decreased mean nucleus length (FSL-5.56 ± 0.17 μm, MK-7.52 ± 0.65 μm; P < 0.001).

Conclusion

Automated MKs are still the standard of care for donor lenticule preparation and MK-assisted donor lenticules have smoother surface with less endothelial cell disruption than FSL. Further research is mandatory before FSL platforms can be considered a viable alternative to the MK.

Femtosecond Laser-Assisted Surgery for Implantation of Bioengineered Corneal Stroma to Promote Corneal Regeneration

The femtosecond laser has achieved widespread use in ophthalmology owing to its ability to deliver focused high energy that is rapidly dissipated and thereby does not damage surrounding tissue outside the precise focal region. Extremely accurate and smooth cuts can be made by the laser, enabling a range of applications in anterior segment surgery. Minimally invasive corneal surgical procedures can be performed using the femtosecond laser, and here we describe the application of such procedures to improve implantation of bioengineered materials into the cornea. Bioengineered corneal tissue, including the collagenous corneal stroma, promises to provide a virtually unlimited supply of biocompatible tissue for treating multiple causes of corneal blindness globally, thereby circumventing problems of donor tissue shortages and access to tissue banking infrastructure. Optimal implantation of bioengineered materials, however, is required, in order to facilitate postoperative wound healing for the maintenance of corneal transparency and avoidance of postoperative complications such as scarring, inflammation, and neovascularization. Moreover, the avoidance of a detrimental physiological physiological wound healing response is critical for facilitating the corneal stromal regeneration enabled by the bioengineered stroma. Without proper implantation, the tissue response will favor inflammation and pathologic processes instead of quiescent keratocyte migration and new collagen production. Here we describe several procedures for optimized biomaterial implantation into the corneal stroma, that facilitate rapid wound healing and regenerative restoration of corneal transparency without the use of human donor tissue. A step-by-step methodology is provided for the use of the femtosecond laser and associated techniques, to enable seamless integration of bioengineered materials into the corneal stroma.

Possible Risk Factors and Clinical Outcomes of Black Areas in Small-Incision Lenticule Extraction

PURPOSE

To investigate the possible risk factors and clinical effects of black areas in small-incision lenticule extraction.

METHODS

Thirty-one cases and 126 controls were enrolled in a case-control study from the database of a single center from September 2012 to July 2017. A retrospective analysis of surgical procedures with video and medical records was performed. Logistic regression analysis was used to assess the possible risk factors for black areas between cases with black areas and controls without black areas.

RESULTS

In the study, 19 eyes (61.3%) with black areas were associated with the presence of surface debris, 10 of which had repeated suction during docking and centration (P < 0.001). There was a significant difference in the energy of the femtosecond laser used for the cases (133 ± 4.04 nJ) and controls (138 ± 3.26 nJ) (P < 0.001). The odds ratio for the energy of the laser was 0.180 (95% confidence interval, 0.099-0.328, P < 0.001). Eyes with black areas had poorer uncorrected vision at 1 and 7 days and 1 month postoperatively (0.06, 0.01, and 0.00 logMAR, respectively) compared with controls (-0.01, -0.07, and -0.05 logMAR, respectively) (P < 0.005). At month 3, the safety index was lower in the cases (1.14 ± 0.47) compared with controls (1.36 ± 0.28) (P = 0.003). The postoperative spherical equivalent in the cases was more myopic than in controls (P = 0.036), except for month 3 (P = 0.183).

CONCLUSIONS

Black areas in small-incision lenticule extraction could be caused by repeated suction, presence of surface debris, and a lower energy of the femtosecond laser. These factors could result in rough dissection and slower recovery of visual acuity.

Femtosecond laser corneal refractive surgery for the correction of high myopic anisometropic amblyopia in juveniles

AIM

To evaluate the effects of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and small-incision lenticule extraction (SMILE) to correct high myopic anisometropic amblyopia in juvenile patients.

METHODS

From November 2013 to January 2015, 33 amblyopic patients with high myopic anisometropic amblyopia were studied. FS-LASIK (30 eyes) or SMILE (3 eyes) was performed in the amblyopic eyes. Visual acuity, refraction, contrast sensitivity, stereoacuity and complications were evaluated. Patients completed follow-up examinations at 3d, 1mo, 3mo and the last follow-up time (mean 8.17±3.23mo) after surgery.

RESULTS

The mean age at surgery was 9.04±3.04y (range 6-16y). The mean spherical equivalent in the amblyopic eyes was significantly decreased from -10.00±2.39 D preoperatively to -0.06±1.06 D at 1mo, -0.19±1.33 D at 3mo and -0.60±1.43 D at approximately 8mo postoperatively (P<0.05 for all). The mean myopic anisometropia was significantly decreased from -9.45±2.33 D preoperatively to +0.37±1.48 D at 1mo, -0.46±1.47 D at 3mo and -0.09±1.83 D at approximately 8mo (P<0.05 for all). The logarithm of the minimum angle of resolution (logMAR) for uncorrected and corrected distance visual acuity (UDVA and CDVA, respectively) of the amblyopic eye improved from 1.74±0.35 and 0.98±0.63 preoperatively to 0.45±0.31 and 0.41±0.33 at approximately 8mo after surgery, respectively. The logMAR CDVA at 3d, 1, 3 and 8mo postoperatively improved by means of 1.42, 2.22, 2.96, and 4.39 lines, and a gain of more than two lines accounted for 45%, 50%, 74% and 86% of all patients, respectively. The contrast sensitivity of both amblyopic eyes and dominant eyes at 0.5, 2, 8 cycles per degree was significantly improved postoperatively (P<0.05 for all). Of the 33 pediatric patients, no patients had near stereopsis preoperatively and seven patients (21.2%) recovered near stereopsis (400″ to 60″) at approximately 8mo after surgery. No intraoperative or postoperative complications occurred in any patient.

CONCLUSION

FS-LASIK or SMILE can be promising alternative methods to correct high myopic anisometropic amblyopia in juvenile patients who have failed with traditional approaches.

Second femtosecond laser treatment application for completion of partial capsulotomy caused by suction loss

PURPOSE

To describe a case of a second application of femtosecond laser-assisted capsulotomy to achieve a complete treatment pattern after an initial incomplete capsulotomy creation due to loss of suction.

METHODS

A 66-year-old woman presented with visually significant cataract in both eyes. She was scheduled to undergo femtosecond laser-assisted cataract surgery (FLACS) using the Victus platform. During FLACS capsulotomy of the right eye (capsulotomy diameter set at 5.0 mm), loss of suction occurred followed by laser treatment interruption, resulting in an incomplete, discontinuous capsulotomy treatment pattern. A second FLACS pretreatment was performed immediately after the first incomplete treatment, aiming for a capsulotomy diameter 0.1 mm larger than the previous (5.1 mm in diameter) and with placement of the capsulotomy treatment outside the prior incomplete capsulotomy.

RESULTS

A complete continuous treatment pattern was achieved for the capsulotomy after second application of FLACS pretreatment. No intraoperative complications were noticed.

CONCLUSION

A second application of femtosecond laser-assisted capsulotomy to achieve a complete treatment pattern after initial incomplete capsulotomy creation due to loss of suction is feasible during the same surgical setting.

Translational label-free nonlinear imaging biomarkers to classify the human corneal microstructure

Diseases that affect the cornea can lead to severe vision loss and have tremendous social impact. These diseases are associated to deviations from normal structural order and orientation of collagen fibril bundles. Unfortunately, resolving non-invasively the corneal collagen structure is not possible to date. In this work, polarization sensitive second harmonic generation (pSHG) microscopy is used to obtain information with molecular specificity on microstructure of human corneas. This information is used to develop a set of label-free imaging biomarkers that were generated by means of a novel methodology based on mathematical tensorial calculus. The method is proven to be highly sensitive and robust. The use of these biomarkers permits accurate characterization of the anisotropic, depth-dependent, structural organization of corneal collagen fibril bundles without any a priori information. The method can be valuable to improve understanding of microstructural pathophysiological changes of the human cornea close to in vivo conditions.

The 'Magic Light': A Discussion on Laser Ethics

Innovations in technology and science form novel fields that, although beneficial, introduce new bio-ethical issues. In their short history, lasers have greatly influenced our everyday lives, especially in medicine. This paper focuses particularly on medical and para-medical laser ethics and their origins, and presents the complex relationships within laser ethics through a three-dimensional matrix model. The term 'laser' and the myth of the 'magic light' can be identified as landmarks for laser related ethical issues. These ethical issues are divided into five major groups: (1) media, marketing, and advertising; (2) economic outcomes; (3) user training; (4) the user-patient/client relationship; and (5) other issues. In addition, issues arising from two of the most common applications of lasers, laser eye surgery and laser tattoo removal, are discussed. The aim of this paper is to demonstrate that the use of medical and para-medical lasers has so greatly influenced our lives that the scientific community must initiate an earnest discussion of medical laser ethics.