Effects of peptide ratios in nanofibre-based hydrogels for the prevention of capsular opacification.

PURPOSE: To moderate the capsular opacification (CO) response after lens surgery, an experimental study was performed in which nanofibre-based hydrogels (nanogels) with different ratios of attached peptides were applied to provide extracellular matrix-related cues for lens epithelial cells (LECs) in a porcine eye model. METHODS: The lens content was removed, and the capsules were refilled with nanogel. Lenses were divided into two groups, the first group (n = 34) was refilled with nanogels containing different ratios of two laminin-derived peptides (IKVAV + YIGSR), and the latter group (n = 26) was refilled with nanogel combinations of a fibronectin-derived and a type IV collagen-derived peptide (RGDS + DGEA). Two lenses were refilled with culture medium to investigate the effect of the medium on LECs. After refilling, lenses were extracted and cultured for 3 weeks. Lens epithelial cells (LECs) were assessed for morphology and alpha-smooth muscle actin (αSMA) expression using confocal laser scanning microscopy. RESULTS: Differences were seen in cell morphology between lenses refilled with nanogels with IKVAV + YIGSR and RGDS + DGEA peptides. In nanogels with IKVAV + YIGSR peptides, differences in LEC morphology were largest when ratios between the peptides were unequal, whereas LEC responses from the RGDS + DGEA refilled groups showed variation in LEC morphology dependent on the total quantity of mixed-in peptides. The culture medium did not induce proliferation or transformation of LECs. CONCLUSIONS: Ratios and concentrations of cell adhesion-mediating peptides both can direct the LEC response, depending on the adhesion molecules of origin, by influencing LEC proliferation and transformation. Nanogels with incorporated peptides may be tuned towards CO prevention.

Nanofiber-based hydrogels with extracellular matrix-based synthetic peptides for the prevention of capsular opacification.

Nanofiber-based hydrogels (nanogels) with different, covalently bound peptides were used as an extracellular environment for lens epithelial cells (LECs) in order to modulate the capsular opacification (CO) response after lens surgery in a porcine eye model. Lenses were divided into 15 groups (n = 4 per group), the lens content was removed and the empty capsules were refilled with nanogel without peptides and nanogels with 13 combinations of 5 different peptides: two laminin-derived, two fibronectin-derived, and one collagen IV-derived peptide representing cell adhesion motifs. A control group of 4 lenses was refilled with hyaluronan. After refilling, lenses were extracted from the porcine eye and cultured for three weeks. LECs were assessed for morphology and alpha smooth muscle actin (αSMA) expression using confocal laser scanning microscopy. Compared to hyaluronan controls, lenses filled with nanogel had less CO formation, indicated by a lower αSMA expression (P = 0.004). Microscopy showed differences in morphological cell response within the nanogel refilled groups. αSMA expression in these groups was highest in lenses refilled with nanogel without peptides (9.54 ± 11.29%). Overall, LEC transformation is reduced by the presence of nanogels and the response is improved even further by incorporation of extracellular matrix peptides representing adhesion motifs. Thus, nanomaterials targeting biological pathways, in our case interactions with integrin signaling, are a promising avenue toward reduction of CO. Further research is needed to optimize nanogel-peptide combinations that fully prevent CO.

Influence of stereoscopic vision on task performance with an operating microscope.

PURPOSE: To determine the extent to which stereoscopic depth perception influences the performance of tasks executed under an operating microscope. SETTING: Laboratory of Experimental Ophthalmology, University Medical Center Groningen, the Netherlands. DESIGN: Experimental study. METHODS: Medical students were assigned (on the basis of their stereoacuity) to a stereo-sufficient group (depth perception ≤240 seconds of arc [arcsec]) or stereo-deficient group (≥480 arcsec). They performed a bead-stringing task (a mockup surgical test) under an operating microscope or a task on a cataract surgery simulator. The stereo-sufficient subjects also performed the bead-stringing task under artificial stereo-deficient conditions (binocular and monocular viewing). RESULTS: The study comprised 77 medical students. The stereo-sufficient subjects performed both tasks faster than the stereo-deficient subjects and artificially stereo-deficient subjects (P ≤ .024). In addition, a within-group analysis established that the stereo-sufficient subjects were faster at the bead-stringing task with stereoscopic viewing than under artificial stereo-deficient conditions with binocular viewing (P ≤ .011). CONCLUSIONS: Having stereovision resulted in better initial performance on certain tasks involving the use of an operating microscope or cataract surgery simulator. However, this study did not show that stereo deficiency necessarily results in an inability to perform such tasks properly. Hence, it was not evident that for admission to an ophthalmology residency program, stereovision should be judged more stringently than other traits. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Prevention of posterior capsular opacification.

Posterior capsular opacification (PCO) is a common complication of cataract surgery. The development of PCO is due to a combination of the processes of proliferation, migration, and transdifferentiation of residual lens epithelial cells (LECs) on the lens capsule. In the past decades, various forms of PCO prevention have been examined, including adjustments of techniques and intraocular lens materials, pharmacological treatments, and prevention by interfering with biological processes in LECs. The only method so far that seems effective is the implantation of an intraocular lens with sharp edged optics to mechanically prevent PCO formation. In this review, current knowledge of the prevention of PCO will be described. We illustrate the biological pathways underlying PCO formation and the various approaches to interfere with the biological processes to prevent PCO. In this type of prevention, the use of nanotechnological advances can play a role.

Changes in lens stiffness due to capsular opacification in accommodative lens refilling.

Accommodation may be restored to presbyopic lenses by refilling the lens capsular bag with a soft polymer. After this accommodative lens refilling prevention of capsular opacification is a requirement, since capsular opacification leads to a decreased clarity of the refilled lens. It has been hypothesized that capsular fibrosis causing the capsular opacification results in increased stiffness of the lens capsular bag, therewith contributing to a decrease in accommodative amplitude of the lens. However, the change in viscoelastic properties of refilled lenses due to capsular fibrosis has never been measured directly. In this study we examined natural lenses from enucleated porcine eyes and refilled lenses directly after refilling and after three months of culturing, when capsular fibrosis had developed, and determined their viscoelastic properties with a low load compression tester. Control refilled lenses were included in which capsular opacification was prevented by treatment with actinomycin D. We related lens stiffening to the degree of capsular opacification, as derived from the microscopic images taken with a confocal laser scanning microscope. Overall, the refilled lenses directly after refilling were softer than refilled lenses after three months of culturing, and refilled lenses treated with actinomycin D were softer compared with untreated refilled lenses. The degree of capsular opacification as assessed by microscopy corresponds to an increase in lens stiffness. This indicates that the viscoelastic properties of the refilled lens are influenced by capsular fibrosis and modulated by treatment of the lens epithelium. In conclusion, this study shows that the development of capsular fibrosis negatively affects the viscoelastic properties of isolated, cultured refilled lenses.

Preservation of enucleated porcine eyes for use in a wet laboratory.

PURPOSE: To design a method to preserve enucleated porcine eyes for use in a wet laboratory. SETTING: Laboratory of Experimental Ophthalmology, University Medical Center Groningen, the Netherlands. DESIGN: Experimental study. METHODS: Porcine eyes were preserved using 15 methods including salt solutions, anterior chamber infusion fluids, tap water, mineral water, air, and topical glycerol on the cornea. The central corneal thickness (CCT) was measured by A-scan ultrasound over 3 days. Differences between increases in CCT were compared using repeated-measures multivariate analyses of variance. Also, lenses from eyes preserved in tap water were extracted and the lens epithelial cell morphology was studied. RESULTS: There was a significant interaction between the preservation method and CCT over 3 days (P<.001). Post hoc tests showed that the CCT in the sodium chloride (NaCl) 10.0% and tap-water groups increased significantly less than with 4 other preservation methods. However, preservation in NaCl 10.0% resulted in unusable shrunken coriaceous lenses. Addition of glycerol did not decrease the CCT. Lens epithelial cells from eyes preserved in tap water for 48 hours appeared to be intact but lost cell organization. CONCLUSIONS: Of the 15 tested methods to preserve porcine eyes, tap water (mineral content 1.79 mmol/L) resulted in the least corneal swelling. It is not necessary to use more expensive anterior chamber infusion fluids or other salt solutions. FINANCIAL DISCLOSURE: Neither author has a financial or proprietary interest in any material or method mentioned.