The potential calcification of octacalcium phosphate on intraocular lens surfaces

Development of a standardized in vitro model to reproduce hydrophilic acrylic intraocular lens calcification

Opacification through calcification of hydrophilic acrylic intraocular lenses (IOL) is a severe complication after cataract surgery. Causing symptoms that range from glare through to severe vision loss, the only effective therapy is explantation of the opacified IOL so far. Although IOL calcification is a well-described phenomenon, its pathogenesis is not fully understood yet. The purpose of the current study was to develop a laboratory model to replicate IOL calcification. Calcification could be reproduced using a horizontal electrophoresis and aqueous solutions of calcium chloride and disodium hydrogen phosphate. The analysis of the in vitro calcified IOLs was performed using light microscopy, Alizarin Red and Von Kossa staining, scanning electron microscopy, energy dispersive x-ray spectroscopy and electron crystallography using transmission electron microscopy and electron diffraction. The presented laboratory model could be used to identify hydrophilic IOLs that are at risk to develop calcification and to assess the influence of associated risk factors. In addition, it can serve as a research tool to further understand this pathology.

Clinical Features of Patients with Opacification of Hydrophilic Acrylic Intraocular Lens in Neovascular Glaucoma

Purpose: To report the clinical features of patients with opacification of hydrophilic acrylic intraocular lens (IOL) after cataract surgery in neovascular glaucoma.Methods: This retrospective case series included 11 eyes of 10 patients with IOL opacification and neovascular glaucoma (NVG) between January 2006 and December 2010. We included and analyzed cases with opacification of hydrophilic acrylic IOL. An IOL exchange was performed in three cases, and the explanted IOLs were examined grossly and evaluated by light microscopy. Sagittal sections of the optics of the IOLs were evaluated by Von Kossa staining, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX).Results: All 11 eyes of 10 patients were implanted with hydrophilic acrylic IOLs. In addition, there were no cases of hydrophobic acrylic IOL opacification. Nine patients of the 10 patients had diabetic retinopathy and one patient had central retinal artery occlusion. The mean period of IOL opacification after IOL implantation was 19.45 ± 8.52 months and the mean period of IOL opacification after the occurrence of NVG was 14.37 ± 8.51 months. The deposits of the explanted IOLs were shown to consist of calcium by von Kossa staining. The explanted IOLs showed fine whitish irregular granular deposits on the entire anterior surface of the optics by SEM and the presence of calcium deposition was confirmed by EDX analysis.Conclusions: Care is required when using hydrophilic acrylic IOLs in patients with risk of neovascular glaucoma, such as those with diabetic retinopathy or central retinal artery occlusion.

Microscopic Characteristics of Late Intraocular Lens Opacifications

CONTEXT.—

The increases in overall life expectancy and in lens surgeries performed on younger patients have resulted in a significant increase in the anticipated duration of artificial intraocular lenses (IOLs) in the eye. Thus, the physicochemical properties of the IOL become a critical issue, and several types of postoperative IOL opacifications have been reported.

OBJECTIVE.—

To describe the microscopic characteristics of opacified IOLs. Glistenings and subsurface nanoglistenings are fluid-related phenomena developing mainly in hydrophobic acrylic IOLs and are associated with aqueous influx into the IOL matrix. Calcification presents in hydrophilic acrylic or silicone IOLs as deposits of hydroxyapatite or other phases of calcium. Snowflake degeneration is less common, and it manifests in older polymethyl methacrylate IOLs.

DATA SOURCES.—

PubMed and ScienceDirect databases were searched for the following keywords: intraocular lens, IOL, cataract surgery, phacoemulsification, opacification, glistening, subsurface nanoglistenings, calcification, snowflake degeneration. English-language articles published up to October 15, 2019 were included in the study. The manuscript contains mainly a literature review; however, it was supplemented with original investigations from the David J. Apple International Laboratory for Ocular Pathology.

CONCLUSIONS.—

Glistenings and subsurface nanoglistenings should be evaluated in a hydrated state and at room temperature; they manifest as microvacuoles sized from 1.0 to greater than 25.0 μm and less than 200 nm, respectively. Calcification deposits are situated on or underneath the surface of the IOL and can be stained with a 1% alizarin red solution or with the von Kossa method. Snowflake degeneration manifests as "particles" or "crystals," causing whitish IOL discoloration. Scanning electron microscopy or energy dispersive X-ray spectroscopy may improve the diagnostic accuracy.

Delayed postoperative opacification of three hydrophobic acrylic intraocular lens: A scanning electron microscopic and energy dispersive spectroscopic study

Purpose:

The aim of this study was to report scanning electron microscopic (SEM) and energy dispersive spectroscopic (EDS) findings of three specimens of opaque hydrophobic acrylic intraocular lens (IOL) explanted in delayed postoperative period for visual indications.

Methods:

Clinical data and photographs from each subject were obtained. Explanted IOLs were examined under gross and light microscopy followed by SEM coupled with EDS.

Results:

All three subjects underwent IOL implantation following senile cataract extraction at an average age of 64.3 ± 0.3 years, and the IOLs were in situ for a duration of 11.3 ± 4.04 years. The IOL explantation and exchange were done due to late postoperative opacification of the IOL and significant visual deterioration. The milky iridescent opacity affected the full thickness of IOL optics in the first two specimens and in the third only two surfaces were involved. SEM detected surface cracks in the first specimen, typical conglumated surface, pores and accumulation of crystals with surface deposit of nano-particles on the second specimen and uneven surface erosion in the third specimen. SEM detected mainly sodium (Na) and chloride (Cl) spikes. All patients recovered normal vision following IOL exchange.

Conclusion:

SEM features of the IOL optics and absence of calcium and phosphate spikes in EDS and other findings were consistent and suggestive of hydrolytic biodegradation of hydrophobic acrylic IOL polymer in ocular media and was responsible for delayed postoperative opacification of the hydrophobic IOLs and visual loss.

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.

Intraocular lens dystrophic calcification after trans-scleral diode laser treatment for a cyclodialysis cleft

Purpose

To describe a case of intraocular lens (IOL) dystrophic calcification as a complication of trans-scleral diode laser successfully used to treat a post-trabeculectomy cyclodialysis cleft.

Observations

A 76-year-old male with primary open angle glaucoma and pseudophakia (+19.0D Akreos M160L, Bausch & Lomb) was evaluated for vision impairment 4 months post-trabeculectomy complicated by a cyclodialysis cleft of his right eye. The patient was successfully treated with trans-scleral diode laser. After this treatment IOL opacification developed. Slit lamp examination and color photography of the anterior segment was performed prior to exchange of the opacified IOL. The explanted IOL underwent star testing, macroscopic imaging, phase contrast and scanning electron microscopy in addition to energy dispersive x-ray spectroscopy.

Confluent IOL deposits developed 4 months after trans-scleral diode laser treatment requiring IOL exchange. Star optical testing of the explanted IOL showed disruption of the diffraction image. An asymmetric pattern of deposition was congruent with the laser treatment quadrant. The subsurface location and discrete nature of the deposits were seen on phase contrast and electron microscopy. Energy dispersive x-ray spectroscopy demonstrated a predominance of calcium/phosphate in the deposits. We are unaware of previous reports in the literature of IOL dystrophic calcification occurring as a complication of trans-scleral diode laser treatment for a post-trabeculectomy cyclodialysis cleft.

Conclusion and importance

Delayed postoperative IOL dystrophic calcification in our case may have been from a combination of IOL biomaterial susceptibility to diode laser energy; damaged IOL material providing a nidus for calcific nucleation; and blood ocular barrier breakdown altering aqueous composition. We suggest that pseudophakia should influence the consideration of diode laser as treatment of a cyclodialysis cleft.

Akreos Adapt AO Intraocular Lens Opacification: A Case Report

A 79-year-old hyperglycemic patient was referred to the 'Santa Maria delle Croci' Hospital, Ravenna, Italy. He presented with visual impairment in the right eye. Four years ago, he had had an uneventful cataract surgery in the right eye. We observed an opacification of the intraocular lens (IOL) causing significant visual disturbance. The IOL was exchanged. Unfortunately, pathologic analysis was not performed. Patient-related factors such as hyperglycemia and hypertension might have been responsible for the opacification. To our knowledge, there is only one previous report of opacification of the Akreos Adapt AO IOL.

Dynamics of Biomineralization and Biodemineralization

In order to understand the fundamental processes leading to biomineralization, this chapter focuses on the earliest events of homo/heterogeneous nucleation from an initial supersaturated solution phase and subsequent growth involving various possible precursor phases (amorphous or crystalline) to the final mineral phase by specific template and other influences. We also discuss how the combination of macroscopic constant composition and microscopic atomic force microscopy provides insights into the physical mechanisms of crystal growth and phase stability and the influences of proteins, peptides or other small molecules.Biodemineralization reactions of tooth enamel and bone may be inhibited or even suppressed when particle sizes fall into certain critical nanoscale levels. This phenomenon actually involves particle-size-dependent critical conditions of energetic control at the molecular level. Clearly, this dissolution termination is a kinetic phenomenon and cannot be attributed to reaction retardation as a result of surface modification by additives. Almost all biomineralized structures are highly hierarchical at many different length scales. At the lowest level they often consist of tiny crystals, typically tens to hundreds of nanometers. This size is not arbitrary; rather, it seems to give biominerals such as bone and tooth remarkable physical characteristics.