In India, cataract accounts for 80% of treatable blindness. Many factors such as ageing, altered blood electrolyte levels, diabetes mellitus, hypertension, nutrition and family history are involved in cataract genesis. Lens has a high content of potassium and low content of sodium. These two cations are in balance with each other due to Na+- K+-ATPase pump and lens capsular permeability. Normally to maintain lens membrane permeability, water electrolyte balance must be maintained intracellularly as well as extracellurly. Hence alteration in cation concentration of aqueous humors can be attributed to changes in the serum electrolytes, these ultimately affect lens metabolism leading to cataract formation. The composition of aqueous humour has been studied in various animals. Few human aqueous humour studies were conducted so far. An attempt is made here to establish a range for the electrolytes mentioned i.e. sodium, potassium, and chloride in the human aqueous humour in cataract patients and also compare it with serum electrolyte levels. It’s a case control study. Sample size includes 60. Aqueous humour and serum electrolytes (Na+, K+, Cl-) were estimated by ion selective electrode method. Sodium and Chloride levels were higher in serum compared to aqueous humour. Further sodium levels were increased from Grade I to Grade IV cataract. Biochemical parameters such as serum electrolytes can be used as marker to determine the risk involved in progression of cataract. This serum electrolytes measurement should be done as a routine screening investigation as it might help in predicting early development of senile cataract.