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Modelling the formation of calcific deposits in hydrophilic IOLs with hydrophobic surface

Poster Details


First Author: P.Gartaganis GREECE

Co Author(s): S. Alimisi   S. Gartaganis   P. Koutsoukos              

Abstract Details

Purpose:

Clinical findings show that hydrophilic IOLs with hydrophobic surface implanted during cataract surgery, opacify due to calcium phosphate mineral formation on the surface and in the interior of the implants. An in vitro study was performed to obtain better understanding of the mechanism leading to the calcification of hydrophilic intraocular lens (IOL) with hydrophobic surface. Experiments were done in special reactor simulating eye chamber including flow of synthetic aqueous humor, were combined with clinical findings and allowed for the suggestion of a viable mechanistic model.

Setting:

1. From the Department of Ophthalmology and 2. the Department of Chemical Engineering, Laboratory of Inorganic and Analytical Chemistry, University of Patras and FORTH-ICEHT, Greece

Methods:

The development of reliable and reproducible in vitro models, which simulate in vivo interactions, is of key importance for studying the underlying mechanisms for the kinetics of mineralization that control hydrophilic IOLs with hydrophobic surface calcification. According to that rationale, a special type of reactor, Eye Chamber Reactor, was constructed in which three IOL specimens were mounted and immersed in simulated aqueous humor at 37oC, pH 7.40, flowing at a rate of 0.2 mL/hr. Samples were withdrawn in 270 days intervals and were examined by optical, electron microscopic and spectroscopic analytical techniques to identify and/or quantify the calcification.

Results:

Examination of opacified IOLs showed crystalline deposits, formed more likely in their interior. The morphology of these deposits and the molar calcium:phosphorus ratios corresponded to hydroxyapatite (HAP). Thermostated reactors mimicking anterior chamber’s conditions and simulated aqueous humor, were used. Analysis of hydrophilic IOLs with hydrophobic surface confirmed the influence of factors other than supersaturation conditions, such as the hydrophilic or hydrophobic nature of the IOLs, on the calcification process. Explanted IOLs confirmed experimental results. According to the spatial and temporal development of deposits, it is believed that IOLs interior calcification was proliferated by the hydrophilic posterior surface.

Conclusions:

In vitro findings from reactors simulating eye chamber agreed with the results from in vivo investigations on opacified hydrophilic acrylic IOLs with hydrophobic surface. The formation of calcific deposits in the interior of the IOLs highlighted the significance of surface hydroxyl groups of the polyhydroxyl acrylic materials as a major factor that facilitates nucleation and growth of calcium phosphate. Hydrophilic surfaces, promote the formation of calcific deposits and allow for the easier diffusion in the interior, resulting in the accumulation of calcium and phosphate ions in the interior of the IOLs, which form clusters supersaturated with respect to calcium phosphates.

Financial Disclosure:

None

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