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We congratulate Mathur and Pai for their interesting article entitled, “Comparison of serum sodium and potassium levels in patients with senile cataract and age-matched individuals without cataract,” in which they noted significantly higher mean serum sodium levels in individuals above 50 years of age with cataract than in age-matched individuals without cataract; however, mean serum potassium levels were not significantly different. The authors concluded that a high level of serum sodium contributes to cataract formation and that diets with high sodium content could be a risk factor for senile cataract formation. We wish to offer a few comments:
The electrolyte composition of the lens resembles that of other human cells, with a high potassium and low sodium and chloride concentrations. The aqueous bathing the lens closely reflects the ionic composition of the plasma, with high concentrations of sodium and chloride but low levels of potassium. Potassium loss from the lens, which occurs during cataract formation, probably results from interruption of the ion pump within the cell membrane; potassium complexes thus break down and diffuse outward.
Interestingly, Consul et al. reported that although mean aqueous humor levels of sodium, potassium, and chloride were slightly lower in eyes with senile cataract than those in normal eyes, the differences were not statistically significant, leading them to suggest that this was “just another manifestation of senility.”
There are no conflicts of interest.