Question

Contact lens solution is described as a sterile, buffered, isotonic aqueous solution. Explain the importance of the adjectives buffered and isotonic to the person buying the solution

Answer 1

A contact lens is a lens placed on the cornea of the eye.

Importance of buffers in contact lens products:

Buffers: They aim to keep the pH of the solutions at values ​​between 6.6 and 7.8 in order to maintain the lens parameters and the effectiveness of the solutions. They are made by the combination of an acid and its sodium salt (phosphate and acetate for example). Borate and citrate buffers are used.

Importance of isotonicity in contact lens products:

The solution composed by isotonic saline solution.

Isotonia is expressed by osmolarity or cryoscopic lowering

- 0.236 to 0.446 mOsmoles / l (increases during the day)

- If the osmolarity of the mixture is different from that of the tears, it causes discomfort and irritation

• Increased tear secretion

• Increase the blink frequency

- If hypotonia, entry of water to the epithelial cells, if hypertonia: inverse

- Osmolarity restored 1 or 2 minutes after instillation