Intereye comparison of femtosecond laser-assisted cataract surgery capsulotomy and manual capsulorhexis edge strength.

PURPOSE: To compare the breaking force required to tear the explanted capsule after femtosecond laser-assisted cataract surgery in the worse eye and manual cataract surgery in the contralateral eye. SETTING: Personaleyes, Sydney, Australia. DESIGN: Prospective nonrandomized case study. METHOD: Patients with bilateral cataract had femtosecond laser-assisted cataract surgery with the Lensx laser in the eye with worse vision and manual cataract surgery in the contralateral eye. Each explanted capsule was stretched mechanically, and the breaking force and strain in grams (g) were compared. When a large contralateral difference in capsule strength was found, scanning electron microscopy (SEM) was applied to determine whether morphologic imperfections were present in a case with a weak capsule. RESULTS: Paired samples of 78 eyes of 39 patients were tested. The mean breaking force was not significantly different between manual capsulorhexes (2.3 g ± 2.0 [SD]) and femtosecond laser capsulotomies (2.0 ± 2.2 g, P = .52). The breaking strain for the manual samples (33.8% ± 18.3%) and for the femtosecond laser samples (34.6% ± 18.6%) were also not significantly different (P = .81). In 5 patients, in the femtosecond group, the capsules required considerably less force to break than the capsules in the manual group. However, the SEM images of these samples did not show specific laser imperfections. CONCLUSION: In paired human eyes, the capsulotomies created by a femtosecond laser with a contact lens interface were as strong as manual capsulorhexes.

Transection and explantation of intraocular lenses using femtosecond lasers.

We present 2 cases in which a femtosecond laser was used in vitro to transect hydrophilic acrylic intraocular lenses (IOLs). At 8 µJ with 3 µm spot separation and 6 µm line separation, no charring occurred and there was no increase in total organic carbon. In vivo, the IOLs were successfully transected in the capsular bag (Case 1, opaque IOL) and the sulcus (Case 2, subluxated IOL post-pneumatic displacement of submacular hemorrhage) and explanted through a clear corneal incision (∼3.0 mm). At 3 months, in Case 1, the corrected distance visual acuity (CDVA) improved from 6/24 to 6/5, astigmatism improved by 0.23 diopters, and endothelial cell density (ECD) remained unchanged (1935 to 2210 cells/mm2); in Case 2, the CDVA was hand motion, astigmatism remained unchanged, and ECD decreased (1960 to 1600 cells/mm2), possibly as a result of complex surgery. Femtosecond IOL transection and explantation may be a clinically safe and feasible option for surgeons.

Factors affecting corneal incision position during femtosecond laser-assisted cataract surgery.

PURPOSE: To compare the expected versus actual position and dimension of corneal incisions during femtosecond laser-assisted cataract surgery. SETTING: Private Ophthalmic Clinic, Sydney, NSW, Australia. DESIGN: Retrospective case series. METHODS: Video recordings of femtosecond laser-assisted cataract surgery with a Lensx laser were reviewed. The deviation of the main and 2 secondary incisions from the expected position were correlated with globe tilt, globe displacement, and biometric data. The globe tilt was inferred from anterior capsule tilt. Globe displacement was measured. The Softfit contact lens thickness used in the patient interface was measured separately. RESULTS: The primary incision internal and external exits were within 142 µm ± 70 (SD) and 151 ± 75 µm of the planned position. The dimensions and position did not correlate with biometric variables. The superior secondary incision external exit was displaced centrally (321 ± 84 µm) and the internal exit was displaced peripherally (84 ± 102 µm). The inferior secondary incision external exit was displaced centrally (278 ± 142 µm) and the internal exit was displaced peripherally (190 ± 133 µm). Multivariate analysis showed that the external and internal exits of the superior (adjusted r2 = 0.36, P < .001; r2 = 0.15, P < .001) and inferior secondary incisions (r2 = 0.67, P < .001; r2 = 0.46, P < .001) correlated with globe tilt and displacement. CONCLUSIONS: The primary incisions were close to the expected dimensions. The secondary incision position was affected by eye tilt and eccentric docking. These could potentially be improved with optical coherence tomography guidance.

Intraocular Lens Fragmentation Using Femtosecond Laser: An In Vitro Study.

PURPOSE: To transect intraocular lenses (IOLs) using a femtosecond laser in cadaveric human eyes. To determine the optimal in vitro settings, to detect and characterize gasses or particles generated during this process. METHODS: A femtosecond laser was used to transect hydrophobic and hydrophilic acrylic lenses. The settings required to enable easy separation of the lens fragment were determined. The gasses and particles generated were analysed using gas chromatography mass spectrometer (GC-MS) and total organic carbon analyzer (TOC), respectively. RESULTS: In vitro the IOL fragments easily separated at the lowest commercially available energy setting of 1 µJ, 8-µm spot, and 2-µm line separation. No particles were detected in the 0.5- to 900-µm range. No significant gasses or other organic breakdown by products were detected at this setting. At much higher energy levels 12 µJ (4 × 6 µm spot and line separation) significant pyrolytic products were detected, which could be harmful to the eye. In cadaveric explanted IOL capsule complex the laser pulses could be applied through the capsule to the IOL and successfully fragment the IOL. CONCLUSION: IOL transection is feasible with femtosecond lasers. Further in vivo animal studies are required to confirm safety. TRANSLATIONAL RELEVANCE: In clinical practice there are a number of large intraocular lenses that can be difficult to explant. This in-vitro study examines the possibility of transecting the lasers quickly using femtosecond lasers. If in-vivo studies are successful, then this innovation could help ophthalmic surgeons in IOL explantation.

Electron microscopy of laser capsulotomy edge: Interplatform comparison.

PURPOSE: To perform a morphological comparison of capsulotomy edges generated by commercially available femtosecond lasers with manual capsulorhexis. SETTING: Private clinic. DESIGN: Experimental study. METHODS: Capsules were collected using the following laser platforms and software versions: Lensx pre-soft-fit (version 2.16), Lensx post-soft-fit (version 2.20), Victus I (version 2.5), Victus II (version 2.7SP2), Catalys (version 2.15.13), and 10 manual. Scanning electron microscopy images were analyzed for the coefficient of variation (CoV) of pixilation along the capsule edge and homogeneity using gray-level co-occurrence matrix analysis. A qualitative assessment for anomalies, such as tags, was also made. RESULTS: The mean CoV values from the regression analysis showed the manual edge (n = 10) (101.6% ± 0.6% [SD]) was smoother than the edges created with Lensx pre-soft-fit (105.2% ± 1.2%) (P<.001), Lensx post-soft-fit (102.7% ± 1.4%) (P=.04), Victus I (104.9% ± 0.9%) (P<.001), Catalys (104.5% ± 1.6%) (P<.001), and Victus II (104.7% ± 1.6%) platforms. All lasers (0.19 to 0.23) (P<.001) except the Lensx post-soft-fit (0.25 ± 0.03) (P=.23) generated less homogenous capsulotomies than the manual technique (0.27 ± 0.04). Tags occurred with Lensx pre-soft-fit (5/10), Lensx post-soft-fit (1/10), Victus I (1/4), and Victus II (3/10) platforms. Misdirected pulses were seen with the Catalys (4/10) and Victus II (4/10) platforms, which used fluid interfaces. CONCLUSIONS: Laser capsulotomies are approaching the smoothness of the manual capsulorhexis. The Lensx post-soft-fit platform showed the least anomalies and the smallest difference for the CoV and homogeneity metrics compared with the manual method. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Improvement in vision with inverted placement of an asymmetric refractive multifocal intraocular lens.

UNLABELLED: We report the case of a 73-year-old man who presented for bilateral cataract surgery. He was noted to have a 0.5 mm corneal scar inferonasally at the pupil margin in his right eye. Uneventful bilateral cataract surgery was performed. An asymmetric toric refractive multifocal intraocular lens (IOL) (LU-313MF30T, Lentis MPlus toric) was implanted in the right eye. Postoperatively, the uncorrected distance visual acuity (UDVA) in that eye was 6/6(-3), the uncorrected intermediate visual acuity at 60 cm was J4, and the uncorrected near visual acuity (UNVA) at 40 cm was J8. The patient was not satisfied with the UNVA. Corneal topography showed 3.0 diopters (D) of corneal flattening over the +3.00 D near segment. The IOL was rotated 180 degrees, which improved the UNVA to J1 while maintaining the UDVA. This study demonstrates that the Lentis Mplus can function even when the near segment is not positioned inferiorly. FINANCIAL DISCLOSURE: Neither author has a financial or proprietary interest in any material or method mentioned.