Calcification of intraocular hydrogel lens: evidence of dystrophic calcification

The human lens is capable of trilineage differentiation towards osteo-, chondro-, and adipogenesis-a model for studying cataract pathogenesis

The potential for trilineage differentiation of cells in tissues represents a model for studying disease pathogenesis and regeneration pathways. Human lens trilineage differentiation has not yet been demonstrated, and so has calcification and osteogenic differentiation of human lens epithelial cells in the whole human lens. Such changes can pose a risk for complications during cataract surgery. Human lens capsules (n = 9) from cataract patients undergoing uneventful surgery were trilineage-differentiated toward osteogenesis, chondrogenesis, and adipogenesis. Furthermore, whole human healthy lenses (n = 3) collected from cadaveric eyes were differentiated into bone and characterized by immunohistochemistry. The cells in the human lens capsules were capable of undergoing trilineage differentiation, while the whole human healthy lenses could undergo osteogenesis differentiation, expressing osteocalcin, collagen I, and pigment epithelium-derived factor. We, hereby, show an ex vivo model for cataract formation through different stages of opacification, as well as provide in vivo evidence from patients undergoing calcified lens extraction with bone-like consistency.

Physicochemical Analysis of Sediments Formed on the Surface of Hydrophilic Intraocular Lens after Descemet's Stripping Endothelial Keratoplasty

An intraocular lens (IOL) is a synthetic, artificial lens placed inside the eye that replaces a natural lens that is surgically removed, usually as part of cataract surgery. The opacification of the artificial lens can be related to the formation of the sediments on its surface and could seriously impair vision. The physicochemical analysis was performed on an explanted hydrophilic IOL and compared to the unused one, considered as a reference IOL. The studies were carried out using surface sensitive techniques, which can contribute to a better understanding of the sedimentation process on hydrophilic IOLs’ surfaces. The microscopic studies allowed us to determine the morphology of sediments observed on explanted IOL. The photoelectron spectroscopy measurements revealed the presence of organic and inorganic compounds at the lens surface. Mass spectroscopy measurements confirmed the chemical composition of deposits and allowed for chemical imaging of the IOL surface. Applied techniques allowed to obtain a new set of information approximating the origin of the sediments’ formation on the surface of the hydrophilic IOLs after Descemet’s stripping endothelial keratoplasty.

Osteogenic differentiation of human lens epithelial cells might contribute to lens calcification

Calcification of the human lens has been described in senile cataracts and in young patients with congenital cataract or chronic uveitis. Lens calcification is also a major complication of cataract surgery and plays a role in the opacification of intraocular lenses. A cell-mediated process has been suggested in the background of lens calcification, but so far the exact mechanism remained unexplored. Lens calcification shares remarkable similarities with vascular calcification; in both pathological processes hydroxyapatite accumulates in the soft tissue. Vascular calcification is a regulated, cell-mediated process in which vascular cells undergo osteogenic differentiation. Our objective was to investigate whether human lens epithelial cells (HuLECs) can undergo osteogenic transition in vitro, and whether this process contributes to lens calcification. We used inorganic phosphate (Pi) and Ca to stimulate osteogenic differentiation of HuLECs. Osteogenic stimuli (2.5mmol/L Pi and 1.2mmol/L Ca) induced extracellular matrix mineralization and Ca deposition in HuLECs with the critical involvement of active Pi uptake. Osteogenic stimuli almost doubled mRNA expressions of osteo-/chondrogenic transcription factors Runx2 and Sox9, which was accompanied by a 1.9-fold increase in Runx2 and a 5.5-fold increase in Sox9 protein expressions. Osteogenic stimuli induced mRNA and protein expressions of alkaline phosphatase and osteocalcin in HuLEC. Ca content was higher in human cataractous lenses, compared to non-cataractous controls (n=10). Osteocalcin, an osteoblast-specific protein, was expressed in 2 out of 10 cataractous lenses. We conclude that osteogenic stimuli induce osteogenic differentiation of HuLECs and propose that this mechanism might play a role in lens calcification.

Experimental investigation on mechanism of hydrophilic acrylic intraocular lens calcification

PURPOSE

To construct a model simulating intraocular lens (IOL) opacification attributable to the formation of calcium phosphate deposits and to investigate the kinetics of deposit formation.

DESIGN

Prospective laboratory investigation.

METHODS

SETTING

Department of Ophthalmology, Medical School and Department of Chemical Engineering, Laboratory of Inorganic and Analytical Chemistry, University of Patras, Greece.

STUDY POPULATION

Three hydrophilic acrylic IOLs (26% water content) were placed inside a 10-mL double-walled thermostated reactor simulating the anterior chamber. Simulated aqueous humor was injected continuously into the reactor using a pump with variable speed.

OBSERVATION PROCEDURES

The observation of IOLs was carried out in situ daily by optical microscopy. Scanning electron microscopy and energy-dispersive radiographic spectroscopy were used for the identification of the morphologic features and the composition of the deposits.

RESULTS

The lenses were removed and inspected 5, 9, and 12 months after the initiation of the experiment. Investigation showed deposits of calcium phosphate crystallites in the interior of opacified IOLs. However, these deposits were not observed on the surface of the IOLs.

CONCLUSIONS

In agreement with earlier reports by our group and in the literature, IOL opacification is the result of calcification. It is suggested that the surface hydroxyl groups of the polyacrylic polymeric components of the IOLs are capable of inducing surface nucleation and crystal growth of calcium phosphates. However, most important is the finding that the calcification of IOLs is initiated from their interior through the development of sufficiently high local supersaturation, realized through the diffusion of calcium and phosphate ions.

Opacification of intraocular lenses implanted during infancy: a clinicopathologic study of 4 explanted intraocular lenses

OBJECTIVE

To report the clinicopathologic features of 4 opacified, single-piece, hydrophilic, acrylic intraocular lenses (IOLs) explanted from children who had undergone IOL implantation during infancy.

DESIGN

Observational case series.

PARTICIPANTS

Four IOLs explanted from 4 eyes of 3 children for visually significant opacification were included in the study.

METHODS

The clinical details of each case were obtained to look for possible risk factors for IOL opacification. The explanted IOLs were subjected to gross examination, staining by alizarin red 1% for calcium, scanning electron microscopy, and energy-dispersive x-ray spectroscopy (EDS). Levels of calcium and phosphorous were analyzed in the serum of all cases and in the aqueous humor of 1 case.

MAIN OUTCOME MEASURES

Morphologic features and composition of deposits.

RESULTS

Two cases had congenital cataract while one case was after bilateral lens sparing vitrectomy for retinopathy of prematurity. All underwent surgery during infancy with implantation of an IOL. The IOLs were explanted 8 months after surgery from 4 eyes of 3 children at the age of 17, 25, and 26. All the children received a single-piece hydrophilic acrylic IOL. The IOLs were in situ for an average duration of 13.86 months. The deposits were in the shape of a bicycle wheel on 3 IOLs and looked like fish eggs on 1 IOL. All deposits stained bright orange with alizarin red. On EDS, the deposits were found to be composed of calcium, phosphate, and silicone.

CONCLUSIONS

The morphologic features and composition of IOL deposits in 2 cases were similar to those of earlier reports in adults. The hydrophilic nature of the IOL material, sulcus implantation, and postoperative inflammation may be possible risk factors for opacification.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Spectral analysis and comparison of mineral deposits forming in opacified intraocular lens and senile cataractous lens

This preliminary report was attempted to compare the chemical components of mineral deposits on the surfaces of an opacified intraocular lens (IOL) and a calcified senile cataractous lens (SCL) by vibrational spectral diagnosis. An opacified intraocular lens (IOL) was obtained from a 65-year-old male patient who had a significant decrease in visual acuity 2-years after an ocular IOL implantation. Another SCL with grayish white calcified plaque on the subcapsular cortex was isolated from a 79-year-old male patient with complicated cataract after cataract surgery. Optical light microscope was used to observe both samples and gross pictures were taken. Fourier transform infrared (FT-IR) and Raman microspectroscopic techniques were employed to analyze the calcified deposits. The curve-fitting algorithm using the Gaussian function was also used to quantitatively estimate the chemical components in each deposit. The preliminary results of spectral diagnosis indicate that the opacified IOL mainly consisted of the poorly crystalline, immature non-stoichiometric hydroxyapatite (HA) with higher content of type B carbonated apatites. However, the calcified plaque deposited on the SCL was comprised of a mature crystalline stoichiometric HA having higher contents of type A and type B carbonate apatites. More case studies should be examined in future.

Opacification of hydrophilic acrylic intraocular lens attributable to calcification: investigation on mechanism

PURPOSE

To identify the nature and to investigate the biochemical mechanisms leading to late opacification of implanted hydrophilic acrylic intraocular lenses (IOLs).

DESIGN

Retrospective laboratory investigation.

METHODS

setting: Department of Ophthalmology, Medical School, Department of Chemical Engineering, Laboratory of Inorganic and Analytical Chemistry, University of Patras and FORTH-ICEHT, Greece. study population: Thirty IOLs were explanted one to 12 years postimplantation attributable to gradual opacification of the lens material. observation procedures: Materials analysis was done using scanning electron microscopy (SEM) equipped with a microanalysis probe (EDS), confocal microscopy, x-ray diffraction (XRD), and Fourier transform infrared (FTIR) for the identification of the substances involved in the opacified lenses.

RESULTS

SEM investigation showed plate-like as well as prismatic nanoparticle deposits of calcium phosphate crystallites on the surface and in the interior of opacified IOLs. The plate-like deposits exhibited morphology and particle size typical for octacalcium phosphate (OCP), while the respective characteristics of the prismatic nanocrystals were typical of hydroxyapatite (HAP). EDS analysis confirmed the chemical composition of the deposits. Aqueous humor analysis showed that the humor is supersaturated with respect to both OCP and HAP, favoring the formation of the thermodynamically more stable HAP, while the formation and kinetic stabilization of other transient phases is also very likely. In vitro experiments using polyacrylic materials confirmed the clinical findings.

CONCLUSIONS

Hydrophilic acrylic IOLs' opacification may be attributed to the deposition of calcium phosphate crystallites. HAP is the predominant crystalline phase of these crystallites. Surface hydroxyl groups of the polyacrylic materials facilitate surface nucleation and growth.