Experimental intraocular lens implantation in the rabbit eye and in the mouse peritoneal space. Part V: Phagocytosis and nuclear patterns of giant cells observed on the implanted lens surface

Resident immune cells of the avascular lens: Mediators of the injury and fibrotic response of the lens

Tissues typically harbor subpopulations of resident immune cells that function as rapid responders to injury and whose activation leads to induction of an adaptive immune response, playing important roles in repair and protection. Since the lens is an avascular tissue, it was presumed that it was absent of resident immune cells. Our studies now show that resident immune cells are a shared feature of the human, mouse, and chicken lens epithelium. These resident immune cells function as immediate responders to injury and rapidly populate the wound edge following mock cataract surgery to function as leader cells. Many of these resident immune cells also express MHCII providing them with antigen presenting ability to engage an adaptive immune response. We provide evidence that during development immune cells migrate on the ciliary zonules and localize among the equatorial epithelial cells of the lens adjacent to where the ciliary zonules associate with the lens capsule. These findings suggest that the vasculature‐rich ciliary body is a source of lens resident immune cells. We identified a major role for these cells as rapid responders to wounding, quickly populating each wound were they can function as leaders of lens tissue repair. Our findings also show that lens resident immune cells are progenitors of myofibroblasts, which characteristically appear in response to lens cataract surgery injury, and therefore, are likely agents of lens pathologies to impair vision like fibrosis.

Membrane formation and cellular response on the surface of lenses implanted in rabbit eyes

PURPOSE

To study the pathogenesis of membrane formation and cellular response on the surface of posterior chamber intraocular lenses (IOLs) implanted in rabbits.

SETTING

Department of Histology and Embryology, Pathology, Ophthalmology. The First Military Medical University, Guangzhou, P.R. China.

METHODS

Thirty rabbits had extracapsular lens extraction and posterior chamber IOL implantation. The IOLs were removed 4, 7, 15, 30, and 90 days postoperatively. Membrane formation and cellular response on IOL surfaces were evaluated using light (n = 25), transmission (n = 5), and scanning electron (n = 5) microscopy.

RESULTS

On 30 IOLs, the incidence of cellular adhesion was 100%. Cellular components comprised macrophages, fibroblast-like cells, epithelioid cells, giant cells, ultralarge giant cells, and lymphocytes. A thin, proteinaceous film was also seen on the surface of the IOLs. The membrane of the IOL surface comprised fibrin, collagen fibrils, macrophages, fibroblast-like cells, giant cells, and fibroblasts.

CONCLUSION

The findings of this study might apply to humans because cellular elements and membranes have been reported in humans.

Natural history of cellular deposits on the anterior intraocular lens surface

Previous cytopathological studies have demonstrated the presence of cellular deposits on the poly(methyl methacrylate) (PMMA) intraocular lens (IOL) surface. In this prospective study, IOL surface specular microscopy was used to document the natural history of these deposits in the first year following PMMA IOL implantation. Intraocular lens surface specular microscopy was performed 1, 3, 6, and 12 months after endocapsular cataract surgery in 27 otherwise normal eyes. Postoperatively, IOLs were assessed for the presence of inflammatory cells, with the number of cells graded from 0 (none) to 4 (many). Two inflammatory cell types were visualized: small and giant cells. Small cells were found on 81.5% of IOLs at 1 month, 73.1% at 3 months, and 30.4% at 12 months. Small cells were found in only small numbers (peak mean cell score of 1.26 +/- 0.94 at 1 month). Giant cells were found on 59.3% of lenses at 1 month, 73.1% at 3 months, and 39.1% at 12 months. The number of giant cells on each lens peaked at 3 months (mean cell score 2.0 +/- 1.55), when 50% of lenses achieved a giant cell score of 3 or 4. Inflammatory cell deposits are, therefore, a normal occurrence on the PMMA IOL surface for up to 1 year after surgery. This cellular response consists of two distinct processes: a small cell response, which peaks by 1 month, and a later giant cell response, which peaks at 3 months.

In vivo documentation of cellular reactions on lens surfaces for assessing the biocompatibility of different intraocular implants

This prospective study was undertaken to assess the biocompatibility of different intraocular implants and to determine factors influencing cellular reactions on intraocular lenses (IOLs). Cellular reactions seen on the surface of 653 IOLs have been documented by specular microscopy. Various types of IOLs were used with different surgical procedures in humans. The 11 lens types used fall into five groups of materials: polymethylmethacrylate (PMMA), heparin surface-modified PMMA, surface-modified PMMA, poly Hema and silicone. Factors influencing the cellular reaction on intraocular implants were elaborated on in this study. Besides the foreign-body reaction itself, cellular reactions were influenced by an increased inflammatory disposition, surgical trauma, peri-operative treatment, implant positioning and lens style. A significant correlation was found between the development of posterior synechiae and the existence of giant cells on the anterior lens surface. The incidence of cellular reactions on IOLs revealed significant differences specific to lens and material. Hydrophilic surfaces show cellular reactions in a lower percentage of cases compared with hydrophobic surfaces. An accurate and individual selection of lens material and style is mandatory to guarantee optimal after surgery.