Although the water uptake of Hard and GP lenses is much less compared to Soft (hydrophilic) contact lenses (between 38% for Daily Wear materials to 75% of the high water content materials), Hard lenses have an uptake of about 2%, while the uptake for GP lenses varies between 5% to 8% dependant upon the DK value of the material. The moisture thus absorbed can evaporate overnight, if the lenses are stored dry. As a result of evaporation, debris accumulates on the lens surfaces, making wetting more difficult and encouraging contaminant activity. In addition, when the lenses are cleaned before wearing, the debris will cause scratches on the lens surfaces.
Studies indicate that a further result of this hydration – dehydration (dry–wet–dry) cycle causes lesser or greater steepening or flattening of the lens curvature, causing discomfort at the beginning of each wearing period. It also causes changes in visual comfort due to changes in the power of the lens caused by the curvature change and changes in the tear lens. The discomfort can last for varying periods of time (3 to 20 minutes), dependant on the specifications of the lens, till the lens is fully hydrated by the tear fluid.
Subjecting lenses to cycles of dry–wet–dry, causing constant curvature changes of the lens, will eventually lead to lens distortion, rendering the lenses useless. This applies to an even greater extent to high DK value RGP lenses.
The conclusion is that even Hard and GP lenses should be stored wet after the wearing period. Lens cleaning should also take place at the end of the wearing period and lenses removed from storage and worn at the beginning of the wearing period. Lenses cleaned and stored in Soaking Solution or Multipurpose Solution, should ideally not need cleaning or rinsing before wearing as the solution will contain wetting ingredients in order to render the lens surface wettable.
Soft contact lenses offer the patient considerable advantages of comfort and ease of adaptation compared to Hard or RGP lenses, however soft lenses present totally different set of problems.
Soft lens materials (polymers) consist of a three-dimensional array of hydrophilic and hydrophobic monomer units. However, in all cases, hydration involves moisture being present in the structure. Usually 30% to 40% of the liquid in hydrated material is bound, the rest being free and it is mainly by gain or loss of pore moisture that a hydrophilic material comes to equilibrium with its environment. Free moisture is relatively mobile and is lost from the structure by changes in temperature, osmotic conditions and pH. It has been found that take-up and loss of moisture is a continuous process with hydrophilic materials, with the result that as the lens is taking up moisture, it is prone to taking up dirt or contaminants as well as organisms and deposit them on the surface of the lens. In order to maintain the integrity of the lens it is therefore important that the lens is thoroughly cleaned immediately on removal and not allow either growth or denaturation of the proteins deposited.
Effective contact lens solutions contain specific bacteriostatic agents, which efficaciously treat established infections and act as prophylactic agents to prevent the occurrence of infections.
AEC Contact Lens Solutions have been tried and tested over a prolonged period and conform to the highest standards, through stringent control, and ensure consistent performance.
The solutions are carefully prepared in sterile environment and packed aseptically in bottles, manufactured from specially selected pharmaceutical grade plastic, which are irradiated for sterility. As a matter of procedure a number of bottles are selected from each batch and sent to an independent, Government approved analytical laboratory, for a check on the sterility of the product, thus ensuring that the packed solutions are sterile.
GP-1 75 ml Hard & GP lens
GP-2 150 ml Hard & GP lens soaking and disinfecting solution
Sterilised isotonic preparations. The cleaning solution is formulated for daily cleaning, maintains lens surfaces free of deposits. The soaking solution maintains lenses free of bacterium during storage and renders the surfaces wettable.
Sterilised isotonic preparations. Combines Cleaning, Disinfecting, Rinsing & Storage functions in one. A single solution for all daily needs of lens maintenance. FREE OF THIOMERSAL and CHLORHEXIDINE GLUCONATE.
Combines COLD Cleaning, Disinfecting, Rinsing and Storage functions. A single solution for all daily needs of lens maintenance. FREE OF THIOMERSAL and CHLORHEXIDINE GLUCONATE.
Lens plus + 360 ml & 150 ml Multiuse Multipurpose solution
Sterilised isotonic preparation in buffered polymeric complex with Tyloxapol for removal of Muco-Proteins, Lipid Secretions and other naturally occurring deposits & HPMC ((Hydropropyl Methycellulose) to help maintain lens equilibrium and conditioning as well as forming a cushion of moisture which provides lubrication for greater comfort .
An amphoteric polymeric surfactant cleaner with wetting and chealating agents for periodic cleaning. Helps maintain lens surfaces by removing oleaginous, proteinaceous matter and debris. .