Melvin A. Sarayba

Initial clinical evaluation of an intraocular femtosecond laser in cataract surgery.

PURPOSE To evaluate femtosecond laser lens fragmentation and anterior capsulotomy in cataract surgery. METHODS Anterior capsulotomy and phacofragmentation procedures performed with an intraocular femtosecond laser (LenSx Lasers Inc) were initially evaluated in ex vivo porcine eyes. These procedures were then performed in an initial series of nine patients undergoing cataract surgery. In addition to standard intraoperative assessments (including capsulotomy diameter accuracy and reproducibility), optical coherence tomography was used to evaluate human procedures. RESULTS For an intended 5-mm capsulorrhexis in porcine eyes, average achieved diameters were 5.88+/-0.73 mm using a standard manual technique and 5.02+/-0.04 mm using the femtosecond laser. Scanning electron microscopy revealed equally smooth cut edges of the capsulotomy with the femtosecond laser and manual technique. Compared to control porcine eyes, femtosecond laser phacofragmentation resulted in a 43% reduction in phacoemulsification power and a 51% decrease in phacoemulsification time. In a small series of human clinical procedures, femtosecond laser capsulotomies and phacofragmentation demonstrated similarly high levels of accuracy and effectiveness, with no operative complications. CONCLUSIONS Initial results with an intraocular femtosecond laser demonstrate higher precision of capsulorrhexis and reduced phacoemulsification power in porcine and human eyes.

Randomized prospective clinical study comparing induced aberrations with IntraLase and Hansatome flap creation in fellow eyes: Potential impact on wavefront-guided laser in situ keratomileusis

Purpose: To measure and compare the changes in objective wavefront aberration and subjective manifest refraction after laser in situ keratomileusis (LASIK) flap creation with a mechanical microkeratome and a femtosecond laser. Setting: Private practice refractive surgery center, Irvine, California, USA. Methods: This randomized prospective study comprised 9 patients (18 eyes) treated with a 2‐step LASIK procedure: lamellar keratectomy with a Hansatome microkeratome (Bausch & Lomb) or the IntraLase femtosecond laser in fellow eyes followed by non‐wavefront‐guided (standard) excimer laser treatment with the Technolas 217A (Bausch & Lomb) excimer laser 10 weeks later. Fellow eyes were matched to within 0.75 diopter (D) sphere and 0.50 D cylinder. Patients were followed for 3 months after excimer laser treatment. Preoperative and post‐flap creation wavefront aberrometry using a Hartmann‐Shack aberrometer and manifest refraction were compared between the 2 groups. The same tests were performed 3 months after excimer laser ablation. Results: Statistically significant changes were seen in defocus wavefront aberrations after Hansatome (P = .004) and IntraLase (P = .008) flap creation. A hyperopic shift in manifest refraction was noted in the Hansatome group after the creation of the corneal flap (P = .04); no statistically significant changes in manifest refraction were seen in the IntraLase group. Statistically significant changes in total higher‐order aberrations (HOAs) (trefoil and quadrafoil Zernike terms) were seen after flap creation in the Hansatome group (P = .02). No significant changes in HOAs were noted after flap creation in the IntraLase group. After the flap was relifted and standard excimer laser ablation was performed, a statistically significant increase in coma occurred in the Hansatome group (P = .008). Standard refractive outcomes in the 2 groups were similar. Conclusions: The creation of the LASIK flap alone can modify the eyes optical characteristics in low‐order aberrations and HOAs. A significant increase in HOAs was seen in the Hansatome group but not in the IntraLase group. This may have significant clinical implications in wavefront‐guided LASIK treatments, which are based on measurements made before flap creation.

Femtosecond laser-assisted cataract incisions: Architectural stability and reproducibility

There is considerable interest in the potential relationship between postoperative endophthalmitis and clear corneal tunnel incisions for cataract surgery. Earlier work from Ernest et al. clearly demonstrated that incisions that are square in surface architecture are significantly more resistant to deformation and leakage than those that are rectangular. The purpose of this preliminary investigation was to determine whether corneal tunnel incisions could be constructed with femtosecond laser technology and in a manner that would preclude deformation and leakage at any intraocular pressure (IOP).

Comparative study of stromal bed quality by using mechanical, IntraLase femtosecond laser 15- and 30-kHz microkeratomes.

Purpose: To evaluate corneal stromal bed quality of lamellar keratectomy in laser in situ keratomileusis (LASIK) procedures by using mechanical and femtosecond laser microkeratomes. Methods: LASIK corneal flaps were created in 9 fresh human globes not suitable for transplantation. We grouped the samples into 3 different groups of 3 globes each. Group 1 was the control group, in which the flaps were created using a Hansatome microkeratome with a 160-μm head. Groups 2 and 3 consisted of flaps created at the 110-μm flap thickness setting using the IntraLase 15- and 30-kHz femtosecond laser, respectively. All the flaps were removed, and the corneal stromal beds were prepared for scanning electron microscopy (SEM). Qualitative surface roughness (QlSR) of the SEM images was graded using a roughness grading scale from 1 to 5 by 3 masked observers. Quantitative surface roughness (QnSR) of the SEM images was also assessed using software designed for roughness analysis. Mann-Whitney nonparametric statistical analysis was performed to compare groups. Results: There was no statistically significant difference in QlSR and QnSR scores between group 2 and group 1 (brand-new blade only). Group 3 30-kHz IntraLase samples showed a smoother stromal bed compared with group 1 and 2 samples. This was a statistically significant difference for QlSR (QlSR = 1.1 ± 0.17, P < 0.001) and showed borderline significance for QnSR (QnSR = 24.4 ± 0.96, P = 0.05). Conclusions: The IntraLase 15-kHz femtosecond laser 110-μm flaps and the Hansatome 160-μm head using a new blade both produced smooth, good-quality, compact stromal beds as assessed qualitatively by masked observers and quantitatively by image analysis software. The 30-kHz femotsecond laser permits a tighter spot/line separation and lower energy per pulse, which creates smoother corneal stromal beds.

Femtosecond laser posterior lamellar keratoplasty: a laboratory model.

Purpose To evaluate feasibility of femtosecond laser application in posterior lamellar keratoplasty. Methods To evaluate the lasers effectiveness through opaque corneas, anterior corneal caps were resected from opaque corneas induced with 80% acetone solution. To evaluate the femtosecond laser posterior lamellar keratoplasty surgical procedure, human corneoscleral rims were mounted on an artificial anterior chamber. After corneal pachymetry, the femtosecond laser was used to create a 6-mm-diameter, 200-μm-thick endostromal lenticule. Access to the lenticule was provided by a small perilimbal surface opening, also created by the laser. The lenticule was removed using a pair of corneal forceps. A donor lenticule of similar dimensions was created, its endothelial surface coated with viscoelastic, inserted, and positioned on the recipient bed. Two sutures were placed to seal the small surface opening. Results The femtosecond laser produced an effective and smooth dissection through opaque corneas even at deeper settings. Graft transplantation was fairly simple and effective. Conclusion Femtosecond laser posterior lamellar keratoplasty is a procedure that may provide an alternative to penetrating keratoplasty or the technically challenging manual posterior lamellar keratoplasty.

A 60 kHz IntraLase Femtosecond Laser Creates a Smoother LASIK Stromal Bed Surface Compared to a Zyoptix XP Mechanical Microkeratome in Human Donor Eyes

PURPOSE To compare the stromal surfaces created by the latest mechanical microkeratome and femtosecond, laser technologies. METHODS Laser in situ keratomileusis (LASIK) flaps were created in six fresh human globes unsuitable for transplantation. The eyes were placed in one of two groups of three globes each. One group had LASIK flaps created with a Zyoptix XP microkeratome using a 120-microm head and a fresh blade for each eye. Another group had flaps created at an attempted 100-microm thickness using the 60 kHz IntraLase femtosecond laser. Immediately following flap creation, the stromal beds were prepared for scanning electron microscopy (SEM). Qualitative roughness of the SEM images was graded by masked observers. Quantitative roughness of the SEM images was assessed using computerized software designed for roughness analysis. Mann-Whitney non-parametric statistical analysis was performed to compare groups. RESULTS A statistically significant difference was noted in bed smoothness as measured by qualitative roughness and quantitative roughness scores. The IntraLase samples showed smoother stromal beds compared to the Zyoptix group (qualitative roughness = 2.0 +/- 0.7 pm vs 3.6 +/- 1.6 pm, P = .03; quantitative roughness = 20238 +/- 1869 pm vs 26368 +/- 8133 pm, P = .03). CONCLUSIONS The 60 kHz IntraLase femtosecond laser and the Zyoptix XP 120-microm head using a new blade produced smooth, good quality, compact stromal beds qualitatively and quantitatively. Because the 60 kHz femtosecond laser permits a tight spot/line separation using low energy, it creates a smoother corneal stromal bed compared to previous femtosecond laser engines.

Fluoroquinolone therapy in multiple-drug resistant staphylococcal keratitis after lamellar keratectomy in a rabbit model ☆

PURPOSE To assess the effectiveness of a fourth-generation fluoroquinolone for prophylaxis against multiple drug-resistant staphylococcal keratitis after lamellar keratectomy in a rabbit model. DESIGN Experimental study. METHODS Twenty-eight New Zealand white rabbits underwent unilateral lamellar keratectomy using a manual microkeratome followed by the placement of 1000 colony-forming units (CFUs) of log-phase Staphylococcus aureus bacteria under each flap. Eyes (seven in each group) were randomized and treated with one of the following agents: sterile balanced salt solution, gatifloxacin (0.3%), ciprofloxacin (0.3%) or levofloxacin (0.5%) immediately and 6, 12, and 18 hours after surgery. Inflammation was graded by two masked observers at 24 and 48 hours, and the presence or absence of infectious infiltrates was determined. The means and standard deviations were calculated, and differences among the groups were statistically analyzed. RESULTS There were no flap complications encountered during surgery. Eyes treated with ciprofloxacin, levofloxacin, and balanced salt solution developed infectious infiltrates in five of seven eyes per group. Gatifloxacin-treated eyes did not develop clinical infection and exhibited lower mean inflammation scores (P <.01 compared with the other groups). CONCLUSION The fourth-generation fluoroquinolone, gatifloxacin, is an effective prophylaxis against the development of keratitis after lamellar keratectomy in rabbits with an organism resistant to methicillin, levofloxacin, and ciprofloxacin.

Characterization of submicrojoule femtosecond laser corneal tissue dissection

PURPOSE: To document the acute morphologic features of laser of situ keratomileusis (LASIK) flaps created using an IntraLase femtosecond laser (IntraLase, Inc.) with a 60 kHz engine. SETTING: Laser suite in a clinical practice. METHODS: A LASIK flap was created in 4 human eye‐bank eyes using the 60 kHz IntraLase femtosecond laser with the following settings: 110 μm flap thickness, 9.0 mm flap diameter, 60‐degree hinge length, 65‐degree side cut, 0.4 μJ or 0.7 μJ raster energy, 7 μm × 7 μm or 9 μm × 9 μm spot/line separation, and 1 μJ side‐cut energy. Immediately after the laser pass and without the flap being lifted, the globes were placed in fixative and subsequently processed for light and transmission electron microscopy. RESULTS: All 4 procedures were completed without complications or the appearance of an opaque bubble layer. The flaps were of uniform thickness and equaled the attempted thickness. Some areas had a complete dissection; other areas had scattered, incomplete tissue bridges. The adjacent corneal stroma and keratocytes were uninjured. When the epithelium was removed, the stromal component of the flap was measured as the attempted thickness; when the epithelium was present, the total flap thickness approximated the attempted flap thickness. CONCLUSIONS: Laser in situ keratomileusis flaps were safely created using raster energies and laser spot separations below those being used clinically. This technique may allow creation of flaps that are reproducibly thinner than those currently being performed and thus confer the benefits of surface ablation and LASIK.

Corneal Response to Femtosecond Laser Photodisruption in the Rabbit

In this report we evaluated the effect of femtosecond laser energy on the development of corneal haze and keratocyte activation in rabbits following intra-stromal photodisruption to create LASIK flaps using a modified commercial femtosecond surgical laser. Three groups of flap parameters were studied: 1.5 microJ/pulse with 10 microm spot separation and complete side cut (Group 1); 3.5 microJ/pulse with 14 microm spot separation and complete side cut (Group 2); 3.5 microJ/pulse with 14 microm spot separation and partial (50 microm) side cut (Group 3). All flaps were left attached without lifting to avoid epithelial contamination. Rabbits were then evaluated pre- and post-operatively by quantitative in vivo and ex vivo confocal microscopy. The achieved flap thickness 1 week after surgery averaged 88.9+/-12.8, 90.8+/-6.9 and 86.5+/-6.8 microm for Groups 1-3 respectively (p=NS). Interface thickness was significantly greater (p<0.05) in the higher energy groups averaging 40.0+/-11.2 and 37.7+/-5.7 microm for Groups 2-3 compared to 28.6+/-4.5 microm for Group 1. Corneal haze was barely detectible and not significantly different between groups, although haze was detected in the region of the side-cuts in Groups 1 and 2. No clinically significant changes in stromal or epithelial thickness were noted. Laser confocal microscopy showed the presence of small diameter cells within the flap interface that resided within disrupted regions of the corneal collagen lamellae. Keratocyte activation was only detected in regions of the 100% side cut and not over the flap interface. In conclusion, the results of this study indicate that photodisruption of the corneal stroma alone without flap elevation regardless of laser energy does not induce significant corneal haze in the rabbit. However, a thicker stromal interface was seen with the higher energy suggesting greater stromal damage.

Fluoroquinolone therapy in Mycobacterium chelonae keratitis after lamellar keratectomy

Purpose: To characterize a rabbit model of Mycobacterium chelonae keratitis after lamellar keratectomy and assess the effectiveness of fluoroquinolone therapy. Setting: University Laboratory, University of California, Irvine, California, USA. Methods: Twenty‐eight New Zealand white rabbits had unilateral lamellar keratectomy with placement of 2.5 × 105 colony‐forming units of log‐phase M chelonae under each flap. Eyes (7 per group) were randomized and treated with sterile balanced salt solution, gatifloxacin 0.3%, ciprofloxacin 0.3%, or levofloxacin 0.5% 4 times daily. Two masked observers examined all eyes on days 2, 5, and 7 and weekly for 4 weeks. Severity of disease and bacterial culture results were the main outcomes measured. The means and standard deviations were calculated, and differences between the groups were statistically analyzed. Results: All eyes developed clinical disease. At the time the rabbits were killed, eyes treated with balanced salt solution, ciprofloxacin, levofloxacin, and gatifloxacin were culture positive in 6 (85.7%), 7 (100%), 6 (85.7%), and 3 (42.9%) of 7 eyes per group, respectively. Frequency of positive culture and the severity of clinical disease in gatifloxacin‐treated eyes were significantly less (P<.05) than in the other groups combined. Conclusions: The rabbit model of M chelonae keratitis was successfully developed in our study. A fourth‐generation quinolone (gatifloxacin) showed the best performance among the fluoroquinolones tested in our experimental approach. The fourth‐generation fluoroquinolone, gatifloxacin, could be effectively used for the treatment of mycobacterial keratitis.