Brit . J . Ophthal . ( 1975 ) 59 , ' 4 ' Calcium deposition as a cause of spoilation of hydrophilic soft contact lenses

One of the commonest causes of soft lens spoilation is the formation of opacities within the matrix and/or on the surface of the lens. These opacities may develop after varying periods of wear and, at times, after as short as 48 hrs of continuous use. In addition to impairing the optical property of the lens, the opacities can be a cause of lens intolerance. Although aetiological factors, such as degenerative changes in the soft lens material, surface corrosion, bacterial and fungal infection, foreign body implantation, and mucoid encrustation, have been recognized in some cases (Tripathi and Ruben, I972; Milauskas, I972; Kaufman, 1972; Matas, Spencer, and Hayes, I972; Tragakis, Brown, and Pearce, I973; Filppi, Pfister, and Hill, 1973; Loran, 1973; Dohlman, Boruchoff, and Mobilia, I973; Sagan and Schwaderer, I974; Brown, Bloomfield, Pearce, and Tragakis, I974), the cause of the soft lens opacification remains obscure in most cases. In many of these lenses, the opacities manifest as discrete spots or as large areas of cloudiness, chalkwhite in appearance. Since similar opacities are known to occur in the cornea and conjunctiva of the eye in a variety of clinical conditions, and histochemical and electron probe microanalytical studies have shown the presence of calcium (Duke-Elder and Leigh, I965; Fishman and Sunderman, I966; Berlyne, I968; Berkow, Fine, and Zimmerman, I968; Doughman, Ingram and Bourne, I970; Harris, Cohn, Toyofuku, Lonergan, and Galin, I971), it seemed probable that calcium deposition might be implicated in the spoilation of soft lenses. In this paper, we report the histochemical, electron microscopical, electron probe microanalytical, x-ray diffraction, atomic absorption, spectrophotometric, and biochemical analyses of 75 spoilt soft lenses undertaken to identify the physical and chemical characteristics of the opacification, with special reference to the involvement of calcium.