Femtosecond lasers for eye surgery applications: historical overview and modern low pulse energy concepts

This review provides an overview of the historical development and modern applications of femtosecond (fs) lasers in ophthalmology, with a focus on the optical concepts involved. fs-Laser technology is unique because it allows very precise cutting inside the eye through optically transparent tissue, without a need for any mechanical openings. fs-Lasers were historically first used for refractive cornea surgery, later also for therapeutic cornea procedures and lens surgery. Further new areas of ophthalmic application are under development. The latest laser system concept is low pulse energy and high pulse frequency: by using larger numerical aperture focusing optics, the pulse energy required for optical breakdown decreases, and athermal tissue cutting with minimal side effects is enabled.

Comparative analysis of ultrasound biomicroscopy between femto-assisted and ultrasound cataract removal in case of lens subluxation

Purpose of the study to carry out a comparative analysis of the state of the zonular fibers before and after surgery on UBM between femtolaser assisted and classical ultrasound cataract removal. Material and methods. 19 patients (38 eyes) with age-related cataracts. 22 eyes were with pseudo-exfoliative syndrome. All patients were examined with grade 1 lens subluxation. The first group of 19 eyes underwent cataract femto-phacoemulsification. The second group included 19 eyes without using a femtolaser. The state of the fibers was determined on the UBM on the fifth day after the operation at the end of antibiotic therapy. Results. The data showed the presence of a statistically significant difference between the group with femto-assistance and the group without it. In the first group, UBM analysis showed that the state of the zonular fibers remained in the same state in 16 of 19 eyes. In the second group, 11 of 19 eyes required ring implantation with suturing to the sclera and 3 required IOL implantation with seamless fixation to the sclera and vitrectomy. Conclusions. The appropriate path to surgery depends on the most accurate objective assessment of the condition of the lens ligaments, since the position of the IOL is one of the main factors for a good result expected by the patient after surgery. Reducing the «trauma» of the eye with lens surgery has been a key success factor and femtolaser guidance provides valuable assistance in obtaining it. Key words: lens subluxation, femtosecond laser, UBM.

Distribution of preoperative angle alpha and angle kappa values in patients undergoing multifocal refractive lens surgery based on a positive contact lens test

Purpose To assess the preoperative objective angle alpha and angle kappa measurements of patients deciding to undergo multifocal refractive lens surgery based on a subjective positive multifocal contact lens test (MCLT). Methods Retrospective, consecutive case series. Alpha and kappa angles were measured using the iTrace aberrometer. All patients also performed a 1-week MCLT. Only patients with a positive MCLT underwent surgery. Visual outcome (UCVA) was obtained in the 1-year follow-up. We assessed the preoperative distribution of angle values within MCLT positive and negative patient groups. Results Two hundred seventeen eyes (111 patients) were included. Mean age was 56.4 years (SD 5.6) and 46.9% were female. In 71 eyes (38 patients), MCLT was positive. Of them, 12 eyes (17%) had an angle alpha and angle kappa ≥ 0.5mm. Of 146 eyes (73 patients) who refrained from surgery due to a negative MCLT, 71 eyes (48.6%) had both angles small (<0.5mm). In the 1-year follow-up, UCVA improved by 0.68 logMAR (SD 0.51; p<0.001) from baseline. Eyes with both small angle alpha and kappa sizes improved by 0.78 logMAR (SD 0.56), as did eyes with high (≥0.5mm) angle sizes (0.82 logMAR (SD 0.53). UCVA of eyes (n=24) with high alpha but low kappa sizes improved less (−0.31 logMAR (SD 0.13; p=0.019)). Conclusion Four out of five patients with a positive MCLT also had correspondingly small angle values. One-half of patients with low preoperative angle values refrained from surgery due to a negative MCLT result. One-year visual acuity improvement was substantial and independent from angle sizes.

Phacoemulsification and dexamethasone intravitreal implant in diabetic patients: A combined approach

Purpose: To analyse the morpho-functional outcomes of dexamethasone intravitreal implant (Ozurdex) injected after lens surgery in diabetic patients with coexisting cataract and macular oedema. Methods: This is a non-randomized, perspective, single-group study on 17 eyes with a diagnosis of cataract and early and advanced diabetic macular oedema. All eyes underwent combined phacoemulsification and Ozurdex injection at the end of surgery and morpho-functional outcomes were analysed in 3 months follow-up. Results: Foveal thickness decreased significantly from 349.6 ± 19.8 (95% CI) at baseline to 310.7 ± 17.5 (95% CI) 90 days after surgery ( p < 0.01). Mean BCVA (LogMAR) improved significantly from 0.38 ± 0.08 (95% CI) at baseline to 0.15 ± 0.06 (95% CI) after 90 days ( p < 0.01). Any ocular or systemic complications were observed during follow-up. Conclusions: Dexamethasone intravitreal implant combined with phacoemulsification may be safe and effective to improve morpho-functional outcomes in diabetic patients with coexisting cataract and macular oedema.

Aberrant TGF-β1 signaling activation by MAF underlies pathological lens growth in high myopia

High myopia is a leading cause of blindness worldwide. Myopia progression may lead to pathological changes of lens and affect the outcome of lens surgery, but the underlying mechanism remains unclear. Here, we find an increased lens size in highly myopic eyes associated with up-regulation of β/γ-crystallin expressions. Similar findings are replicated in two independent mouse models of high myopia. Mechanistic studies show that the transcription factor MAF plays an essential role in up-regulating β/γ-crystallins in high myopia, by direct activation of the crystallin gene promoters and by activation of TGF-β1-Smad signaling. Our results establish lens morphological and molecular changes as a characteristic feature of high myopia, and point to the dysregulation of the MAF-TGF-β1-crystallin axis as an underlying mechanism, providing an insight for therapeutic interventions.

Femtosecond Laser-assisted Lens Surgery with Low-energy Pulse versus Conventional Phacoemulsification for Presbyopia Correction: An Intraindividual Study

Background: Lens surgery with multifocal IOL implantation for presbyopia correction is performed by femtosecond laser-assisted lens surgery or conventional phacoemulsification. Objective: To compare the clinical results of femtosecond laser-assisted with low-energy pulse conventional phacoemulsification lens surgery for presbyopia correction intraindividually. Methods: Charts from patients who underwent Refractive Lens Exchange (RLE) for presbyopia correction in a single center, with Femtosecond Laser-Assisted Lens Surgery (FLALS) in one eye and Conventional Phacoemulsification (CP) in the other, were retrospectively reviewed. All eyes had the same multifocal Intraocular Lens (IOL) implanted. The clinical outcomes and the results of the level of satisfaction questionnaire were compared between the two groups according to the technique employed (FLALS vs. CP) for a period of up to four years. Stability, efficacy and safety indices were also assessed. Results: This study comprised a total of 56 eyes of 28 patients randomly assigned FLALS in one eye and CP in the other. No statistically significant difference was observed between the two techniques regarding postoperative visual acuities, duration of surgical procedure, efficacy or safety indexes (p>0.05). Refraction was stable in all FLALS eyes, whereas a change occurred in 2 eyes (7.1%) operated with CP upon 6 months postoperatively, but without statistical significance (p˃0.05). Satisfaction was slightly better with FLALS but not statistically significant (p=0.134). No immediate myosis or other adverse events after the femtosecond laser were registered. Conclusion: The parameters assessed showed no significant differences between the two techniques, in spite of a difference of refraction stability upon 6 months postoperatively.