17 which have an even higher oxygen transmissibility than water, are polymers that contain silicon and oxygen. The use of silicone hydrogel enabled the invention of continuous-wear contact lenses, which can be worn overnight. However, silicone is a hydrophobic (water-repelling or lipid-loving) material so it is prone to problems like sticking to the eye surface which is covered by the tear film lipid layer [8]. After a few attempts to increase the hydrophilicity, bioengineers eventually solved the problem also by modifying the polymer. Contact Lens Solutions Contact lens solutions play a vital role in maintaining the cleanliness and functionality of contact lenses. They are specifically designed to disinfect, clean, and store the lenses, ensuring optimal comfort and vision for wearers. These solutions contain various chemical compounds that serve specific purposes. There are two main types of contact lens cleaning solutions: peroxide solutions and multi-purpose solutions [4, 9]. They differ by the way they disinfect. Peroxide solutions utilize hydrogen peroxide (H2O2) as a disinfectant, typically at a 3% concentration. To make them safe for the eyes when lenses are reinserted after disinfection, a neutralization catalyst, such as platinum, palladium, or silver, present in the contact lens case is used to speed up the degradation of peroxide into water and oxygen. Multi-purpose solutions commonly contain disinfection agents such as polyhexamethylene biguanide or polyquaternium-1 [4, 9]. These polymers possess optimal antimicrobial properties, and are derived from monomers with stronger antimicrobial activity but too harsh to be applied to the eyes before polymerization. It is speculated that polyhexamethylene biguanide works by selectively binding and condensing bacterial DNA, eventually blocking cell division [10, 11]. Polyquaternium-1 was found to cause leakage of cellular contents in ocular pathogens by disrupting the cell membrane [12, 13]. In addition to disinfection, contact lens solutions also include other compounds to maintain lens cleanliness and performance [4, 9]. Bisphosphonates help break down proteins that accumulate on the lens during wear, while moisturizing and conditioning chemicals ensure that the lenses remain in good condition while stored. There are also buffers to keep the pH gentle on the eyes, and preservatives to increase shelf life. Tried-and-True Techniques & Tips for Beginners For those who are new to contact lenses, the prospect of putting them on and taking them off can be quite intimidating. The thought of touching your eye or inserting a foreign object into it may seem daunting, but fear not! There are techniques that can make this process easier and potentially less frightening. Since most contact lenses sold today are hydrophilic, you should use a dry hand to put on contact lenses so that the lenses will not stick to your hand. When you remove contact lenses, using a wet hand will make the task easier, but always make sure you wash your hands thoroughly before handling contact lenses. It is advised not to use eyedrops when wearing contact lenses because that may cause problems with the lenses [14]. Nevertheless, you may consider Figure 1 Hydrophilic cross-linked polymer network in hydrogel.
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