Soemmerring's Rings Developed around IOLs, in Human Donor Eyes, Can Present Internal Transparent Areas.

Soemmerring's rings consist of a ring of lens epithelial derived cells that grow along the periphery of an aphakic lens capsule, or around an intraocular lens. These rings when visualized frontally, appear opaque, however, in some cases the cells that compose these rings are organized in the same fashion as those in normal transparent adult lenses. Thus, our purpose was to test whether any part of the adult Soemmerring's ring could be transparent and how this related to morphological factors. To study this, 16 Soemmerring's rings were extracted from donor eye globes. After imaging, they were thickly sectioned sagittally in order to analyze the degrees of transparency of different areas. All samples were also histologically analyzed using alpha smooth muscle actin, Vimentin, wheat germ agglutinin and DAPI. Our results showed that many samples had some transparent areas, mostly towards the center of their cross-section. Of the factors that we analyzed, only lens fiber organization at the bow region and an increased area of mature lens fiber cells had a significant relation to the degree of transparency at the center. Thus, we can conclude that as Soemmerring's rings mature, they can develop organized and transparent areas of lens cells.

Müller glia fused with adult stem cells undergo neural differentiation in human retinal models.

BACKGROUND: Visual impairments are a critical medical hurdle to be addressed in modern society. Müller glia (MG) have regenerative potential in the retina in lower vertebrates, but not in mammals. However, in mice, in vivo cell fusion between MG and adult stem cells forms hybrids that can partially regenerate ablated neurons. METHODS: We used organotypic cultures of human retina and preparations of dissociated cells to test the hypothesis that cell fusion between human MG and adult stem cells can induce neuronal regeneration in human systems. Moreover, we established a microinjection system for transplanting human retinal organoids to demonstrate hybrid differentiation. FINDINGS: We first found that cell fusion occurs between MG and adult stem cells, in organotypic cultures of human retina as well as in cell cultures. Next, we showed that the resulting hybrids can differentiate and acquire a proto-neural electrophysiology profile when the Wnt/beta-catenin pathway is activated in the adult stem cells prior fusion. Finally, we demonstrated the engraftment and differentiation of these hybrids into human retinal organoids. INTERPRETATION: We show fusion between human MG and adult stem cells, and demonstrate that the resulting hybrid cells can differentiate towards neural fate in human model systems. Our results suggest that cell fusion-mediated therapy is a potential regenerative approach for treating human retinal dystrophies. FUNDING: This work was supported by La Caixa Health (HR17-00231), Velux Stiftung (976a) and the Ministerio de Ciencia e Innovación, (BFU2017-86760-P) (AEI/FEDER, UE), AGAUR (2017 SGR 689, 2017 SGR 926).

Deformations and Ruptures in Human Lenses With Cortical Cataract Subjected to Ex Vivo Simulated Accommodation.

Purpose: Human cortical opacities are most commonly accompanied by changes in lens fiber structure in the equatorial region at the lens nucleus-cortex interface. Cortex and nucleus have different elastic properties, which change with age. We therefore subjected ex vivo lenses to simulated accommodation and studied the internal deformations to better understand the mechanism of cortical cataract formation. Methods: Nine human donor lenses (33-88 years old) were tested using a bespoke radial stretching device for anterior eye segments. Seven of the lenses exhibited cortical cataracts. The other two lenses, without cataract, were used as controls. Frontal and cross-sectional images of the lens obtained during stretching facilitated measurements on equatorial lens diameter and central lens thickness in the stretched and unstretched states. Results: Stretching caused the lens equatorial diameter to increase in all cases. Conversely, the lens central thickness showed no systematic variation during stretching. For four of the lenses with cortical cataract, ruptures were observed during stretching at the nucleus-cortex boundary adjacent to the cortical cataracts. Ruptures were not observed in the control lenses or in the three other lenses with cortical cataract. Conclusions: Internal ruptures can occur in aged ex vivo lenses subjected to simulated disaccommodation. These ruptures occur at the nucleus-cortex interface; at this location, a significant stiffness discontinuity is expected to develop with age. It is hypothesized that ruptures occur in in vivo lenses during accommodation-or attempted accommodation.

Correction: Bacterial nanocellulose as a corneal bandage material: a comparison with amniotic membrane.

Correction for 'Bacterial nanocellulose as a corneal bandage material: a comparison with amniotic membrane' by Irene Anton-Sales et al., Biomater. Sci., 2020, 8, 2921-2930, DOI: .

Safety and visual outcomes following posterior chamber phakic intraocular lens bilensectomy.

BACKGROUND: To evaluate the safety, efficacy, refractive outcomes and causes for bilensectomy (phakic intraocular lens - pIOL - explantation with cataract surgery and pseudophakic intraocular lens implantation) in patients previously implanted with posterior chamber pIOLs. METHODS: This multi-center retrospective study included 87 eyes of 55 patients who underwent bilensectomy for posterior chamber pIOL with a follow up time of 12 months. The uncorrected and best corrected distance visual acuities (UDVA, CDVA), endothelial cell density before and after bilensectomy were assessed, as well as the cause of bilensectomy and intra or postoperative complications. RESULTS: There was a statistically significant improvement in uncorrected and best corrected visual acuities after bilensectomy (p = 0.00). The main reason for bilensectomy was cataract development (93.1% of the cases), followed by miscalculation of lens size, and corneal edema. The endothelial cell count remained stable without a statistically significant change after surgery (p = 0.67). The refractive efficacy index was 0.8, none of the patients lost lines of CDVA after surgery, 73% of the patients were within ±1 D (spherical equivalent) of the target refraction. Intraoperative complications were one posterior capsule rupture with the intraocular lens (IOL) implanted in the sulcus, and 3 eyes required the use of pupil expanders for adequate pupil dilation. Postoperatively, one eye developed retinal detachment. The three pIOLs models explanted were the Implantable Collamer Lens (ICL), Implantable Phakic Contact Lens (IPCL) and the Phakic Refractive Lens (PRL). CONCLUSIONS: Good safety and visual outcomes were observed 1 year after bilensectomy for posterior chamber phakic intraocular lenses (PC pIOLs). There were few intra and postoperative complications and there was no significant endothelial cell loss after the bilensectomy procedure.

Bacterial nanocellulose as a corneal bandage material: a comparison with amniotic membrane.

Corneal trauma and ulcerations are leading causes of corneal blindness around the world. These lesions require attentive medical monitoring since improper healing or infection has serious consequences in vision and quality of life. Amniotic membrane grafts represent the common solution to treat severe corneal wounds. However, amniotic membrane's availability remains limited by the dependency on donor tissues, its high price and short shelf life. Consequently, there is an active quest for biomaterials to treat injured corneal tissues. Nanocellulose synthetized by bacteria (BNC) is an emergent biopolymer with vast clinical potential for skin tissue regeneration. BNC also exhibits appealing characteristics to act as an alternative corneal bandage such as; high liquid holding capacity, biocompatibility, flexibility, natural - but animal free-origin and a myriad of functionalization opportunities. Here, we present an initial study aiming at testing the suitability of BNC as corneal bandage regarding preclinical requirements and using amniotic membrane as a benchmark. Bacterial nanocellulose exhibits higher mechanical resistance to sutures and slightly longer stability under in vitro and ex vivo simulated physiological conditions than amniotic membrane. Additionally, bacterial nanocellulose offers good conformability to the shape of the eye globe and easy manipulation in medical settings. These excellent attributes accompanied by the facts that bacterial nanocellulose is stable at room temperature for long periods, can be heat-sterilized and is easy to produce, reinforce the potential of bacterial nanocellulose as a more accessible ocular surface bandage.

Histological comparison of in vitro and in vivo development of peripheral posterior capsule opacification in human donor tissue.

In order to study the mechanisms involved in the development of posterior capsule opacification (PCO) we compared in vivo developed PCO with PCO formed in tissue culture with focus on the periphery of the lens capsule to evaluate lens regeneration potential. We studied three human tissue groups: Cultured lens capsules after mock cataract surgery (n = 6, 30 days), lens capsules from donors that had previously undergone cataract surgery (IOL capsules) (n = 12) and intact lenses (n = 6). All samples were stained with Vimentin, alpha Smooth Muscle Actin, Picro Sirius Red (for collagen) and Paired box protein (Pax6). We found that cultured capsules and less developed IOL capsules consisted mainly of monolayers of mesenchymal cells, while more developed IOL capsules, contained lens epithelial cells (LECs), globular cells and lens fiber cells. Many IOL capsule samples expressed collagen I and III in areas where cells were in contact with the IOL. Pax6 had a similar dispersed distribution in less developed IOL capsules and cultured capsules, while more developed IOL capsules and intact lenses, concentrated Pax6 in LECs at the equatorial lens bow. The similarities between cultured capsules and less developed IOL capsules indicate that our in vitro developed PCO is comparable to early in vivo developed PCO. The similar morphology of more developed IOL capsules and intact lenses seems to indicate an attempt at lens regeneration.

Prevention of posterior capsule opacification through intracapsular hydrogen peroxide or distilled water treatment in human donor tissue.

In order to determine whether posterior capsule opacification after cataract surgery, could be delayed or inhibited through the application of hydrogen peroxide (H2O2) or distilled water (H2Od),we extracted lens capsules from 25 human donor eye globes. Samples were treated for 5 min with either 30 mM H2O2 or H2Od or used as controls, and cultured for one month, during which dark field and tilt illumination photos were taken. These were used to observe and quantify, time until cellular growth and confluence on the posterior capsule. After culture, histological sections were stained for H&E, α-SMA, Ki-67 and vimentin and evaluated. We prevented cellular growth in 50% of H2Od and 58% H2O2 of treated samples. The overall prevention of cell growth compared to cultured controls was significant for both treatments while there was no significant difference between them. In the cases where cellular growth was not prevented, both treatments significantly delay cellular growth. Until day 28 none of the treated samples of either type that had shown growth reached total confluence. All cultured controls reached total confluence before treated samples (median = day 11.5). Also, histologically, there was a clear morphological difference between cultured controls and treated samples.

Anterior lens capsule strains during simulated accommodation in porcine eyes.

Experimental protocols have been developed to measure the spatial variation of the mechanical strains induced in the lens capsule during ex vivo lens stretching. The paper describes the application of these protocols to porcine lenses. The deformations and mechanical strains developed in the anterior capsule during each experiment were determined using full field digital image correlation techniques, by means of a speckle pattern applied to the lens surface. Several speckling techniques and illumination methods were assessed before a suitable combination was found. Additional data on the cross section shape of the anterior lens surface were obtained by Scheimpflug photography, to provide a means of correcting for lens curvature effects in the determination of the strains developed in the plane of the capsule. The capsule strains in porcine lenses exhibit non-linear behaviour, and hysteresis during loading and unloading. Peripheral regions experience higher magnitude strains than regions near the lens pole. The paper demonstrates the successful application of a procedure to make direct measurements of capsule strains simultaneously with ex vivo radial lens stretching. This experimental technique is applicable to future investigations on the mechanical characteristics of human lenses.

Validation of the Nuclear Cataract Grading System BCN 10.

PURPOSE: To evaluate a new nuclear cataract grading system which is intended as a surgical guidance system to predict lens hardness before cataract surgery. METHODS: The new BCN 10 grading system consists of frontal and cross-sectional slit-lamp images of human eye lenses, ranging from a completely transparent lens nucleus to a totally black nuclear cataract. Validation was done with 9 observers for 110 cases. Two modalities were applied, and observers were asked to use only whole digits and then half digits for grading. RESULTS: Repeatability with regard to test-retest differences showed a mean limit of agreement of 1.70 for whole digits and 1.32 for half digits. The absolute test-retest difference was close to zero for low as well high degrees of cataracts. Reliability for the entire group of 9 observers yielded an intraclass correlation coefficient which was within the same confidence interval, i.e., 0.991-0.995, for whole digits and half digits. CONCLUSIONS: BCN 10 grading repeatability was not affected by the severity of the cataract. It showed very good repeatability. Repeatability was significantly higher when the observers used half digits compared to whole digits. Reliability was found to be very good as well, independently of the use of whole or half digits.

Experimental protocols for ex vivo lens stretching tests to investigate the biomechanics of the human accommodation apparatus.

PURPOSE: To explore alternative experimental protocols to investigate the biomechanical behavior of the crystalline lens and zonules using ex vivo stretching. METHODS: Radial stretching tests were conducted on the anterior segment (consisting of lens, zonules, ciliary body, and sclera) of four pairs of presbyopic human donor eyes. A simple mechanical model is used to describe the behavior of the anterior segment when tested in this way. Each pair of samples was initially stretched with the ciliary body intact. One sample was retested after cutting the ciliary body radially, and the other sample was retested after removing the lens. RESULTS: The external forces needed to stretch the sample with the ciliary body intact were significantly greater than for the tests in which the ciliary body had been cut. The forces measured with the ciliary body intact and lens in situ were comparable to the sum of the forces measured in the tests in which the ciliary body had been cut (lens in situ) and the forces measured in the tests on the intact ciliary body with the lens removed. CONCLUSIONS: When stretching tests are conducted on the anterior segment, significant circumferential tensions develop in the ciliary body. This means that the forces applied to the lens and zonules cannot be related directly to the forces applied by the external loading system. If radial cuts are introduced in the ciliary body prior to testing, however, then this difficulty does not arise.