Accuracy and safety of partial thickness femtosecond laser radial and arcuate keratotomy incisions in porcine eyes.

BACKGROUND: To evaluate the accuracy and safety of micro radial and arcuate keratotomy incisions constructed by a femtosecond laser system with a curved contact patient interface in porcine eyes. METHODS: Partial thickness micro radial and arcuate keratotomy incisions were constructed in porcine eyes with a femtosecond laser system and evaluated for precision of depth, quality, and consistency. Optical coherence tomography was used to determine the accuracy and precision of incision depth. Corneal endothelial safety was assessed by a fluorescent live/dead cell viability assay to demonstrate laser-induced endothelial cell loss. Quality was evaluated by ease of opening and examination of interfaces. RESULTS: In two micro radial incision groups, intended incision depths of 50% and 80% resulted in mean achieved depths of 50.01% and 77.69%, respectively. In three arcuate incision groups, intended incision depths of 80%, 600 µm or 100 µm residual uncut bed thickness resulted in mean achieved depths of 80.16%, 603.03 µm and residual bed of 115 µm, respectively. No loss of endothelial cell density occurred when the residual corneal bed was maintained at a minimum of 85-116 µm. The incisions were easy to open, and interfaces were smooth. CONCLUSIONS: A femtosecond laser system with curved contact interface created precise and reproducible micro radial and arcuate keratotomy incisions. Accuracy and precision of the incision depth and preservation of endothelial cell density demonstrated the effectiveness and safety of the system.

Femtosecond laser-assisted capsulotomy with capsular marks for toric IOL alignment: Comparison of tensile strength with standard femtosecond laser capsulotomy.

PURPOSE: To compare the capsulotomy rim strength with capsular marks (CMs) to the rim strength without CMs in porcine eyes, and to demonstrate the practicality of CMs for intraoperative toric intraocular lens (IOL) alignment. SETTING: LENSAR facility, Orlando, Florida, USA. DESIGN: Laboratory study. METHODS: The biomechanical strength of the capsulotomy with CMs was tested under two different load orientations (orthogonal to or in-line with CMs). Thirty-six porcine eyes were randomly assigned to three treatment cohorts: (1) standard capsulotomy with no CMs, (2) capsulotomy with CMs for in-line tensile testing and (3) capsulotomy with CMs for orthogonal tensile testing. Study parameters were capsulotomy break force and maximum extensibility. The ease of using CMs for toric IOL alignment was also evaluated. RESULTS: There was no significant difference between the mean break force for standard capsulotomy (180.57 mN ± 22 [SD]), capsulotomy with CMs with orthogonal load (178.04 ± 20 mN, P = 1.000), and with in-line load (181.05 ± 15 mN, P = 1.000). Likewise, the mean extensibility at the break point for standard capsulotomy (6.47 ± 0.33 mm) was equivalent to the mean extensibility with CMs with orthogonal load (6.49 ± 0.45 mm, P = 1.000) and with in-line load (6.3 ± 0.47 mm, P = .960). In the implanted eyes, toric IOLs were found to be easily aligned with the CMs. CONCLUSION: The femtosecond laser capsulotomies with CMs were equivalent in tensile strength and extensibility to standard femtosecond laser capsulotomies and showed high potential for effective alignment of toric IOLs.

Defining the ideal femtosecond laser capsulotomy.

PURPOSE: We define the ideal anterior capsulotomy through consideration of capsular histology and biomechanics. Desirable qualities include preventing posterior capsular opacification (PCO), maintaining effective lens position (ELP) and optimising capsular strength. METHODS: Laboratory study of capsular biomechanics and literature review of histology and published clinical results. RESULTS: Parameters of ideal capsulotomy construction include complete overlap of the intraocular lens to prevent PCO, centration on the clinical approximation of the optical axis of the lens to ensure concentricity with the capsule equator, and maximal capsular thickness at the capsulotomy edge to maintain integrity. CONCLUSIONS: Constructing the capsulotomy centred on the clinical approximation of the optical axis of the lens with diameter 5.25 mm optimises prevention of PCO, consistency of ELP and capsular strength.

Sealability of ultrashort-pulse laser and manually generated full-thickness clear corneal incisions.

PURPOSE: To compare the sealability and geometry of full-thickness clear corneal incisions (CCIs) created manually or with an ultrashort-pulse laser. SETTING: Lensar, Inc., Orlando, Florida, USA. DESIGN: Experimental study. METHODS: Ex vivo human donor globes were randomly assigned to groups for the manual or laser-generated full-thickness CCIs. Standard 3-plane manual or laser incisions were made in 22 globes. Incision geometry was measured using an optical coherence tomographer. Sealability was assessed by inflating globes to physiologic intraocular pressure (IOP) and pressing a mechanical plunger into the globe to deform the globe and increase IOP until leakage was detected using the Seidel test. The test of sealability at lowered IOP was performed similarly; the anterior chamber was monitored for signs of ingress of a povidone-iodine 10% solution placed externally. RESULTS: The mean IOP elevation at which leakage occurred was higher for the laser than for manually generated full-thickness CCIs, indicating that the mean sealability was better for the laser. However, t tests showed that there was no statistically significant difference in the mean IOP elevation at which full-thickness incision leakage occurred between manual and laser full-thickness CCIs. Thus, the sealability of the manual and laser full-thickness CCIs were equivalent for the incision geometry tested. The laser full-thickness CCIs were statistically closer to target geometry and showed less variability than the manual full-thickness CCIs. CONCLUSIONS: The sealability of laser and manual full-thickness CCIs were statistically equivalent. The laser full-thickness CCIs were more consistent in geometry and closer to the target incision geometry.