Corneal calcification: chemical composition of calcified deposit.
BACKGROUND
The aim of this study was to quickly and quantitatively detect the chemical composition of the calcified deposit on the surface of a surgically excised cornea by using vibrational microspectroscopy.


METHODS
Both attenuated total reflection (ATR)/Fourier transform infrared (FTIR) and confocal Raman microspectroscopies were used to evaluate the chemical composition of the excised corneal calcified opaque deposit of a 50-year-old male patient. Hydroxyapatite (HA) was used as a reference.


RESULTS
Microscopic observations indicated that a whitish-grayish opaque plaquelike deposit was observed. A peak at 1020 cm(-1) assigned to the stretching vibration of phosphate of the poorly crystalline, immature and nonstoichiometric HA was observed from the IR spectrum of the corneal calcified deposit, as compared with the peak at 1030 cm(-1) of the mature, crystalline and stoichiometric HA reference sample. Higher contents of two IR spectral peaks at 871 cm(-1) due to the type-B carbonated apatite and at 866 cm(-1) corresponded to a labile carbonate were also evidenced in the corneal calcified deposit. The predominate peak at 959 cm(-1) due to the stretching mode of phosphate was also found in the Raman spectrum of corneal calcified deposit.


CONCLUSIONS
The corneal calcified deposit was evidenced to contain much poor crystalline and immature HA having higher content of the type-B carbonated apatite within the corneal collagen matrix. The process of corneal calcification still proceeds on the surface of this cornea.
Chen
Ko-Hua
KH
Department of Ophthalmology, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China.
Cheng
Wen-Ting
WT
Li
Mei-Jane
MJ
Lin
Shan-Yang
SY
D001031:Apatites / Q000032:analysis; D002114:Calcinosis / Q000378:metabolism* / Q000601:surgery; D003315:Cornea / Q000737:chemistry*; D003316:Corneal Diseases / Q000378:metabolism* / Q000601:surgery; D017886:Durapatite / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman
D001031:Apatites; D017886:Durapatite