Abstract
A frequent cause of the failure of various materials tested as artificial vitreous substitutes is their short retention in the vitreous humour of the eye. Previous techniques to monitor the residence time of the vitreous substitutes have been traditionally complicated and usually involved the chemical modification of the test fluids. Fourier transform infrared (FTIR) spectrometry is used in this study to determine the rate of disappearance of a crosslinked poly(l-vinyl-2-pyrrolidinone) (PVP) hydrogel after injection into the vitreous humour of rabbits. The fluid removed from the eye at various postoperative intervals of time (1 day, 1 week, and 1 month) was placed on a horizontal attenuated reflectance (ATR) unit, and the infrared spectrum from 700 to 3000 cm−1 was obtained directly. The absorption band at 1295cm−1 due to C-N stretching vibration does not overlap with bands of any other species (natural vitreous, blood) present in the test fluid. By estimating the intensity of this band, it was found that about 80% of the injected polymer was removed from the vitreous cavity within 1 month. This study shows that (1) FTIR spectrometry is a convenient method to assess the residence time of foreign materials in the vitreous humour, and (2) the PVP gel is unsuitable in this current form as a permanent vitreous substitute, regardless of the pathways of its removal, such as phagocytosis of fragments produced by the injection process, or enzymatic biodegradation.
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