Abstract
Purpose: :
A number of peer–reviewed publications have described calcification of hydrophilic intraocular lenses (IOLs) clinically. However, they are often limited to case reports of a single patient or a single lens type. Calcification of ocular biomaterials can lead to the loss of visual acuity and subsequent IOL explantation. Using a rabbit model, This study uses a rabbit model to assess 3 classes of IOL materials (hydrophilic acrylic, hydrophobic acrylic, and silicone) for their propensity to calcify.
Methods: :
Commercial IOLs were implanted subcutaneously in New Zealand White rabbits (Buchen et. al., JCRS 2001) for 70+2 days. The IOLs included the hydrophilic IOLs Akreos Adapt and Fit, Acri.Smart, ThinOptX, Rayner 570C and Hydroview; the hydrophobic acrylic AR40e IOL; and the silicone Clariflex IOL. Upon explantation, half of the specimens in each IOL group were subjected to histological analysis and the other half, to scanning electron microscopy (SEM) (to determine surface morphology) and energy dispersive spectroscopy (EDX) (to determine elemental composition) at 3 to 5 randomly selected representative sites per sample.
Results: :
All three samples of the following IOLs exhibited signs of material degradation and pitting in SEM analysis: Akreos Adapt and Fit, Acri.Smart, ThinOptX, and Rayner 570C. These same samples showed distinct calcium and phosphorus peaks with EDX analysis. The AR40e and Clariflex IOLs did not exhibit any signs of material degradation or evidence of calcium or phosphorus. The Hydroview IOL was unusual, showing signs of material degradation and the presence of calcium and phosphorus in only 1 of the 3 samples. Macrophages and/or giant cells appeared more prevalent at the tissue–implant interface of the hydrophilic materials compared to the hydrophobic materials.
Conclusions: :
In the current study, 5 of 6 hydrophilic IOLs showed obvious signs of calcification as demonstrated by SEM and EDX analysis. In contrast, no signs of calcification were noted in the hydrophobic acrylic or silicone IOLs. Clinically, hydrophobic acrylic or silicone may be the ocular biomaterials of choice.
Keywords: intraocular lens • calcium • microscopy: electron microscopy