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J. S. Mehta, K. Tan, R. Poh, V. A. Barathi,, A. Anshu, D. T. Tan, R. W. Beuerman, SERI-Stanford Study Group; Biocompatibility of a Novel Interpenetrating Hydrogel Polymer. Invest. Ophthalmol. Vis. Sci. 2009;50(13):592.
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Laser corneal surgery has been a successful modality to correct refractive errors. However, the corneal induced changes are irreversible and for certain patients there is a risk of iatrogenic keraectasia and regression. Refractive corneal inlays offer a reversible alternative but have had limited success due to issues with corneal biocompatibility. We have previously shown the high nutrient permeability and high mechanical strength of a novel interpenetrating (IPN) hydrogel polymer. The aim of this project was to examine the biocompatibility of this polymer.
Hydrogels consisting of poly(ethylene glycol)(PEG) interpenetrated by poly(acrylic acid)(PAA) were manufactured using a previously described technique. They were lathed to a 30 micron thickness. NZ white rabbits underwent corneal inlay surgery. Implants were inserted using a manual pocket incision. Rabbits (n=10) were followed up by anterior segment optical coherence tomography (ASOCT), slit lamp photography and keratometry. Rabbits were sacrificed at 2 months, 4 months and 6 months. Histological examination and electron microscopy was performed on the cornea.
Three animals were sacrificed at each of the above time points. Following surgery, ASOCT confirmed that the implants were placed at a mean depth of 75% of total corneal thickness. There was swelling of the anterior lamella which settled by one month postop. There was no thinning of the anterior lamella on ASOCT up to 6 months postop. There was no significant difference in mean keratometry compared to preoperative levels. Slit-lamp photography showed no stromal inflammation or implant vascularization. Histological examination showed normal stromal and epithelial architecture. Electron microscopy showed activated keratocytes at 2 months that settled by 4 months. Ultra-structural epithelial architecture was maintained throughout follow up.
This novel interpenetrating hydrogel polymer showed good biocompatibility in an animal model of corneal inlay surgery. There was no stromal thinning or inflammation up to 6 months follow up. IPN hydrogel polymers may be considered as a biomaterial for corneal inlays.
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