[Intraoperative Complications in Cataract Surgery]

Cataract surgery is frequently and successfully performed in the developed world. The indications for the operation have shifted on one hand towards healthier patients seeking freedom from glasses and on the other hand towards more complex cases. How should the patient be informed? What complications can occur intraoperatively, and what treatment options are available for these complications?This article offers a focus on conditions such as zonulopathy and pseudoexfoliation that can pose challenges to cataract surgery. It discusses the use of specialized tools such as capsular tension rings and capsular hooks and precise maneuvers to minimize stress on weakened zonules in order to ensure in-the-bag fixation of the IOL.Furthermore, the article addresses appropriate actions towards intraoperative complications such as anterior or posterior capsule ruptures and loss of nuclear fragments into the vitreous cavity.Exploring innovative advancements, this article presents the latest alternatives for intracapsular lens fixation, such as sutureless scleral fixation and emerging lens designs in cases where there is insufficient capsular support.Ultimately, the primary objective remains delivering optimal outcomes even for complex cases, and minimizing post-surgical issues. Numerous tools and techniques are available.

Comparative Analysis of Antibody Titers against the Spike Protein of SARS-CoV-2 Variants in Infected Patient Cohorts and Diverse Vaccination Regimes

The presence of neutralizing antibodies against SARS-CoV-2 correlates with protection against infection and severe COVID-19 disease courses. Understanding the dynamics of antibody development against the SARS-CoV-2 virus is important for recommendations on vaccination strategies and on control of the COVID-19 pandemic. This study investigates the dynamics and extent of α-Spike-Ab development by different vaccines manufactured by Johnson & Johnson, AstraZeneca, Pfizer-BioNTech and Moderna. On day 1 after vaccination, we observed a temporal low-grade inflammatory response. α-Spike-Ab titers were reduced after six months of vaccination with mRNA vaccines and increased 14 days after booster vaccinations to a maximum that exceeded titers from mild and critical COVID-19 and Long-COVID patients. Within the group of critical COVID-19 patients, we observed a trend for lower α-Spike-Ab titers in the group of patients who survived COVID-19. This trend accompanied higher numbers of pro-B cells, fewer mature B cells and a higher frequency of T follicular helper cells. Finally, we present data demonstrating that past infection with mild COVID-19 does not lead to long-term increased Ab titers and that even the group of previously infected SARS-CoV-2 patients benefit from a vaccination six months after the infection.

Perioperative pupil size in low-energy femtosecond laser-assisted cataract surgery

PURPOSE

To assess potential changes in pupil size during femtosecond laser-assisted cataract surgery (FLACS) using a low-energy laser system.

METHODS

The pupil sizes of eyes undergoing FLACS were measured using the Ziemer LDV Z8 by extracting images from the laser software after each of the following steps: application of suction, lens fragmentation, and capsulotomy. Furthermore, the pupil diameters were measured based on preoperative surgical microscope images and after releasing the suction. Paired t-test and the two one-sided tests (TOST) procedure were used for statistical analyses. The horizontal and vertical pupil diameters were compared in each of the steps with preoperative values.

RESULTS

Data were available for 52 eyes (52 patients, mean age 73.4 years, range 51-87 years). The equivalence between mean preoperative pupil size and status immediately after femtosecond laser treatment was confirmed (p<0.001; 95% confidence interval [-0.0637, 0.0287] for horizontal and p<0.001; 95% CI [-0.0158, 0.0859] for vertical diameter). There was statistically significant horizontal and vertical enlargement of pupil diameters between 0.15 and 0.24 mm during the laser treatment steps as compared with preoperative values (all p values <0.001).

CONCLUSIONS

No progressive pupil narrowing was observed using low-energy FLACS. Although a suction-induced, slight increase in pupil area became apparent, this effect was completely reversible after removing the laser interface.

Substitution of C-terminus of VEGFR-2 with VEGFR-1 promotes VEGFR-1 activation and endothelial cell proliferation

VEGFR-1 is devoid of ligand-dependent tyrosine autophosphorylation and its activation is not associated with proliferation of endothelial cells. The molecular mechanism responsible for this characteristic of VEGFR-1 is not known. In this study, we show that VEGFR-1 is devoid of ligand-dependent downregulation and failed to stimulate intracellular calcium release, cell migration and angiogenesis in vitro. To understand the molecular mechanisms responsible for the poor tyrosine autophosphorylation of VEGFR-1, we have either deleted the carboxyl terminus of VEGFR-1 or exchanged it with the carboxyl terminus of VEGFR-2. The deletion of carboxyl terminus of VEGFR-1 did not reverse its defective ligand-dependent autophosphorylation. The carboxyl terminus-swapped VEGFR-1, however, displayed ligand-dependent autophosphorylation, downregulation and also conveyed strong mitogenic responses. Thus, the carboxyl tail of VEGFR-1 restrains the ligand-dependent kinase activation and downregulation of VEGFR-1 and its ability to convey the angiogenic responses in endothelial cells.

Recruitment and activation of phospholipase Cgamma1 by vascular endothelial growth factor receptor-2 are required for tubulogenesis and differentiation of endothelial cells

Vascular endothelial growth factor-mediated angiogenic signal transduction relay is achieved by coordinated induction of endothelial cell proliferation, migration, and differentiation. These complex cellular processes are most likely controlled by activation of both cooperative and antagonistic signals by vascular endothelial growth factor receptors (VEGFRs). Here, we investigated the contribution of tyrosine-phosphorylated residues of VEGFR-2/fetal liver kinase-1 to endothelial cell proliferation and differentiation and activation of signaling proteins. Mutation of tyrosine 1006 of VEGFR-2 to phenylalanine severely impaired the ability of this receptor to stimulate endothelial cell differentiation and tubulogenesis. Paradoxically, the mutant receptor stimulated endothelial cell proliferation far better than the wild-type receptor. Further analysis showed that tyrosine 1006 is responsible for phospholipase Cgamma1 (PLCgamma1) activation and intracellular calcium release in endothelial cells. Activation of PLCgamma1 was selectively mediated by tyrosine 1006. Mutation of tyrosines 799, 820, 949, 994, 1080, 1173, and 1221 had no measurable effect on the ability of VEGFR-2 to stimulate PLCgamma1 activation. Association of VEGFR-2 with PLCgamma1 was mainly established between tyrosine 1006 and the C-terminal SH2 domain of PLCgamma1 in vitro and in vivo. Taken together, the results indicate that phosphorylation of tyrosine 1006 is essential for VEGFR-2-mediated PLCgamma1 activation, calcium flux, and cell differentiation. More importantly, VEGFR-2-mediated endothelial cell proliferation is inversely correlated with the ability of VEGFR-2 to associate with and activate PLCgamma1.

Alternative intracellular signaling mechanism involved in the inhibitory biological response of functionalized PMMA-based polymers

A PMMA-based polymer previously shown to inhibit cell proliferation was compared to untreated PMMA. Conformation of adsorbed proteins, cell adhesion, cytoskeleton formation, and integrin activation were examined. Fibronectin adsorbed in a different conformation on the PMMA-based polymer exposing a different balance of the heparin-binding domains. Fibroblasts attached in equal numbers to both surfaces over a 4-h period, but the integrins involved in the adhesion process elicited different intracellular signaling pathways. Cells attached to PMMA showed activation of FAK and MAP as they spread using an assembled actin cytoskeleton. Cells attached to the polymer showed early and strong MAP activity that resulted in nonassembly of the actin cytoskeleton and sub-optimal cell spreading. We conclude that the chemistry of the polymer surface dictated a different conformation of the adsorbed proteins that resulted in alternative cell signaling and diminished cell spreading. This accounted for the biological inhibition previously reported on the PMMA-based polymer.

Inhibition of lens epithelial cell proliferation by substituted PMMA intraocular lenses

BACKGROUND

Migration and proliferation of lens epithelial cells (LECs) are based on interactions between cellular integrins and extracellular matrix proteins (ECMs). We were able to design polymers substituted with COO- and SO3- groups that counteract LEC proliferation through modification of the integrin/ECM interaction. The objective of this study was to compare the cell proliferation-inhibiting properties of differently substituted copolymers with those of a homopolymer.

METHODS

Polymers were synthesized by radical polymerization and characterized by nuclear resonance spectroscopy. Second-passage rabbit LECs were cultured either on PMMA homopolymers (control) or on substituted PMMA copolymers. Cells were counted on days 2, 7, and 17. Cell vitality was evaluated by trypan blue staining. Experiments were run in quadruplicate. Statistical analysis was performed using the Wilcoxon test and the Mann-Whitney U-test.

RESULTS

Compared with control, cells cultured on copolymers grew to significantly lower cell numbers. The inhibitory effect became evident at day 2 after seeding and persisted throughout the experiment. Different ratios of COO-/SO3- substitutions yielded different grades of inhibition. No toxic effect was seen on rabbit LECs.

CONCLUSIONS

The tested copolymers inhibit cell proliferation and are nontoxic. Further evaluation could lead to the development of new intraocular lens materials that prevent secondary cataract.