Determination of calcium, sodium, potassium and magnesium concentrations in human senile cataractous lenses.

Cataractous lenses have been found to have a distribution of the intracellular ionic environment, the concentrations of potassium and magnesium decreasing and the concentrations of sodium and calcium increasing relative to the cytosol of most cells. This arises as a result of changes to lens membrane characteristics causing an increase in lens membrane permeability. These changes have been found to be initiated as a result of normal ageing of the human lens. In this study, total Ca2+, K+, Na+ and Mg2+ contents have been determined in human normal and cataractous lenses using atomic absorption and flame emission spectroscopy. The normal human lens Ca2+ is between 0.15 and 0.5 miromol g(-1) fresh lens weight; in senile cataracts the value increased up to 9.31 micromol g(-1) ( p < 0.0001). The normal levels of Na+, Mg2+ and K+ are 20, 5.5 and 60 micromol g(-1) respectively; these changed to 136.10, 3.60 and 9.33 micro mol g(-1), respectively in cataractous senile human lenses ( p < 0.002, p < 0.002 and p < 0.01). The remarkable differences in these elements may play some role in cataractogenesis.

Radial keratotomy for residual myopia after photorefractive keratectomy.

PURPOSE: To evaluate the safety, efficacy, and complications of radial keratotomy (RK) after photorefractive keratectomy (PRK) for myopia. SETTING: Laser Ultravision Institute. Montreal, Canada. METHODS: Surgically induced refractive and visual acuity changes were retrospectively evaluated in 14 eyes of 10 patients treated with RK after PRK. All patients had simple myopia or compound myopic astigmatism. Minimum follow-up was 6 months. RESULTS: Three eyes (21%) had one PRK, 7 (50%) had two treatments, and 4 (29%) had three. Eleven eyes (79%) required four-incision RK and 3 (21%), eight-incision RK. All patients had improved uncorrected visual acuity. Six months after the RK retreatment, there was a significant reduction in spherical equivalent of 2.93 diopters +/- 1.53 (SD) (P < .05). No intraoperative or postoperative complications occurred except overcorrection (two cases). CONCLUSION: Radial keratotomy is an effective, safe method for treating undercorrected myopia after PRK. Further study and analysis of this series of patients are planned.

A comparison of serological tests for detecting antibody to plague.

A study was undertaken of the relationship between the passive haemagglutination and haemagglutination inhibition tests used in serum surveys for specific plague antibodies. Both techniques gave similar titres for sera of albino Rattus norvegicus convalescent from plague infection. They appear to be equally suitable for plague surveillance and control programmes.